TUPB
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Tuesday Poster Session
27 Aug 2024, 16:00 -
18:00
TUPB001
Smith-Purcell radiation studies towards a compact high-resolution longitudinal diagnostic
320
A new longitudinal diagnostic has been proposed, the SPACEChip (Smith-Purcell ACcElerator Chip-based) diagnostic, which can infer information about the temporal profile of a particle bunch from the Smith-Purcell radiation spectrum generated when the bunch passes close to a dielectric grating. This is done using the bunch form factor after retrieving the phase. A simulated dielectric grating has been excited by Floquet modes to investigate the angular distribution of the Smith-Purcell radiation. Progress on the SPACEChip experimental campaign at the ARES linac at DESY will be reported, along with the expected photon yield from the structure with the ARES operational parameters.
Paper: TUPB001
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB001
About: Received: 20 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 29 Aug 2024 — Issue date: 23 Oct 2024
TUPB002
Limitations of the EuXFEL 3rd harmonic cryomodule in high duty cycle operation
324
Future High Duty Cycle (HDC) operation scenarios of the European X-ray Free Electron Laser (EuXFEL) promise increased bunch repetition rate and photon delivery, at the cost of changing system requirements and moving away from the current mode of Short Pulse (SP) operation. To assess whether the third harmonic cryomodule design is also suitable for Long Pulse (LP) and Continuous Wave (CW) operation, key parameters of the spare module are examined at the Accelerator Module Test Facility (AMTF). For Radio-Frequency (RF) related energy efficiency, the cavity resonance tuning precision and the loaded quality factor tuning range are investigated. As performance indicators, limitations on attainable cavity gradient and RF stability are quantified. The results show that the module in its current design is insufficient for LP at high duty cycles and CW at the required operating points. The installed 3-stub tuners only yield maximum loaded quality factors between 5.3e6 and 1.9e7, and the mechanical cavity tuner prohibits tuning precision within the intended cavity half bandwidth. Also, some higher order mode couplers do not allow CW operation at required gradients. Nevertheless, closed-loop RF stability measured in single cavity control is comparable to that of the third harmonic system of EuXFEL.
Paper: TUPB002
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB002
About: Received: 18 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB003
Reaching design electron energy at FLASH after linac upgrade
328
The FLASH 2020+ project at DESY includes, among other modernizations, an upgrade of the electron beam energy. Two accelerator modules were replaced and the RF distribution of the other modules was optimized. The limiting factors such as cavity quenching and field emissions are identified and measured at acceleration modules. At a later stage, based on those measurements, a high-power distribution adjustment scheme was proposed and the optimal operating point was demonstrated to achieve the design energy of 1.35 GeV with the nominal RF pulse length at FEL lasing conditions. After proper optimization and tuning of the low-level RF parameters, the linac successfully operated at maximum energy and delivered SASE-FEL radiation in the wavelength range below 3.2 nm. The measurement results as well as the achieved cavity gradients with energy gains are presented.
Paper: TUPB003
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB003
About: Received: 30 Jul 2024 — Revised: 26 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB004
Status of the L-band gun development at PITZ
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Gun5, the new generation of high-gradient normal conducting 1.3 GHz RF guns for linac driven free-electron lasers like FLASH and European XFEL is under development at the Photo Injector Test facility at DESY in Zeuthen (PITZ). Its improved cell geometry and cooling concept allow for RF pulse durations of up to 1 ms at 10 Hz repetition rate, at gradients of ~60 MV/m at the cathode. Gun5 is also equipped with an RF probe for measurements of the RF field inside the gun. The first gun of this type, Gun5.1, is in operation at PITZ since April 2022. Gun5.2 will be commissioned at the FALCO conditioning facility at DESY in Hamburg, starting in June 2024. This gun is equipped with a balanced (symmetric) RF waveguide feed to the coaxial power coupler to prevent a coupler kick and thus improve the beam quality delivered by the electron source. Further guns are currently in the manufacturing process. In parallel, studies towards a more reliable cathode spring design are ongoing, in order to overcome observed issues during the high duty cycle operation of Gun5.1. This article will give an overview on all those developments.
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUAA012
About: Received: 16 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
TUPB005
Influence of environmental parameters on calibration drift in superconducting RF cavities
331
Precisely calibrating RF superconducting radio-frequency linear accelerators is crucial for accurately assessing cavity bandwidth and detuning, which provides valuable insights into cavity performance, facilitates optimal accelerator operation, and enables effective fault detection and diagnosis. In practice, however, calibration of RF signals can present several challenges, with calibration drift being a significant issue, especially in settings prone to humidity and temperature fluctuations. In this paper, we delve into the effect of environmental factors on the calibration drift of superconducting RF cavities. Specifically, we examine long-term calibration drifts and explore how environmental variables such as humidity, temperature, and environmental noise affect this phenomenon. The results show that environmental factors, particularly relative humidity, significantly influence calibration drifts. Moreover, we observe and analyze the lag in their influence. By analyzing these correlations, appropriate compensation algorithms can be designed to mitigate and eliminate these effects, thus optimizing calibration accuracy and stability.
Paper: TUPB005
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB005
About: Received: 19 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
TUPB006
Machine learning-based non-destructive measurement of bunch length at FRIB
335
A machine learning-based virtual diagnostic method for measuring the longitudinal phase space is proposed. Utilizing multiple measurements of bunch length from the Facility for Rare Isotope Beams (FRIB) accelerator, beam parameters are fitted with a concrete simulation model. A neural network model is trained to learn the correlations between the signals from beam position monitors (BPMs) and the bunch length. This model enables the rapid prediction of bunch length at BPM locations without compromising beam quality.
Paper: TUPB006
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB006
About: Received: 18 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
TUPB007
Machine learning enabled model predictive control for the resonance frequency of the FRIB RFQ
338
Efficient control of frequency detuning for the radio-frequency quadrupole (RFQ) at the Facility for Rare Isotope Beams (FRIB) is still challenging. The transport delay and the complicated heat transfer process in the cooling water control system convolute the control problem. In this work, a long-short term memory (LSTM)-based Koopman model is proposed to deal with this time-delayed control problem. By learning the time-delayed correlations hidden in the historical data, this model can predict the behavior of RFQ frequency detuning with given control actions. With this model, a model predictive control (MPC) strategy is developed to pursue better control performance.
Paper: TUPB007
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB007
About: Received: 19 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
TUPB008
Cryomodule operation experience for the FRIB continuous-wave superconducting linac
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The superconducting (SC) driver linac for the Facility for Rare Isotope Beams (FRIB) includes 46 cryomodules for acceleration of heavy ions to 200 MeV per nucleon. FRIB cryomodules have been supporting sustainable and reliable delivery of high-power heavy ion beams, including 10 kW uranium beam, to the target for production of rare isotope beams to nuclear physics user experiments. The linac operates in continuous-wave mode for maximum utilization of beam from the ion source. A total of 104 quarter-wave resonators (QWRs; β=0.041 and 0.085; 80.5 MHz) equipped with stepper-motor frequency tuners and frictional mechanical dampers are operated at 4 K. A total of 220 half-wave resonators (HWRs; β=0.29 and 0.53; 322 MHz) equipped with pneumatic frequency tuners are operated at 2 K. We will present resonance control and phase stability performance as well as experience with tuner systems in linac operation. FRIB cavities are designed to be operated at a peak surface electric field of approximately 30 MV/m. We will present cavity field emission performance over the years of linac operation and discuss field emission reduction measures such as pulsed RF conditioning (presently in use) and plasma processing (in development). Automation of SC devices is a key aspect of efficient delivery of beams to users. We will present our experience with automation of SC devices such as start-up, shut-down, and fast recovery from an RF trip as well as performance tracking of linac SC devices.
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUAA006
About: Received: 21 Aug 2024 — Revised: 03 Sep 2024 — Accepted: 07 Sep 2024 — Issue date: 23 Oct 2024
TUPB009
Tomography development at ATLAS
341
Beam tomography is a method for reconstructing the higher-dimensional beam from its lower-dimensional projections. This provides an understanding of the beam's transverse phase space, enabling better modeling and predicting downstream beam loss. We will show methods of extrapolating confidence intervals of our reconstructed beam and explore a new beam tomography algorithms using Markov Chain Monte Carlo (MCMC). \end{abstract}
Paper: TUPB009
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB009
About: Received: 20 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB010
Simulations of field emitters and multipacting in PIP-II Single Spoke Resonator Type-2
345
It has been found in benchmark tests that some Single Spoke Resonator Type-2 (SSR2) cavities have early field emission onset as well as strong multipacting barriers. A longstanding hypothesis is that field-emitted electrons in the high electric field accelerating gap can migrate and ignite multipacting bands in the low electric field regions of the cavity periphery. In this study, we use simulation techniques to examine multipacting behavior in SSR2 cavities from electrons seeded in common field emitter locations. Additionally, we investigated seed locations for areas in SSR2 cavities which may have poor coverage during high pressure water rinsing and compared the multipacting behavior.
Paper: TUPB010
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB010
About: Received: 20 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB011
Feasibility study for dual higher-order-modes for plasma processing of FRIB superconducting coaxial resonators
348
In-situ plasma processing is a promising technique to reduce field emission in superconducting radio-frequency cavities and thus maintain maximum accelerator performance for long-term operation. Continuous-wave accelerators such as FRIB are more challenging than pulsed accelerators due to relatively weak coupling (Qext = 2E6 to 1E7 for FRIB) via the fundamental power coupler (FPC). This results in an unfavorable mismatch at room temperature and makes fundamental-mode plasma processing difficult. Hence we have investigated the use of higher-order-modes (HOMs) with less FPC mismatch. Several HOMs are promising for lower-mismatch plasma generation. However, HOMs often present a less favorable plasma distribution. To improve the plasma distribution, we are studying techniques to drive the plasma with two HOMs simultaneously. Plasma development results will be presented for FRIB beta = 0.085 quarter wave resonators, including ignition threshold measurements and plasma distribution assessments.
Paper: TUPB011
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB011
About: Received: 20 Aug 2024 — Revised: 26 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB012
Anomalous frequency shifts near Tc of fundamental and higher-order modes in medium-velocity 644 MHz superconducting elliptical cavities
352
Recent studies indicate the magnitude of an anomalous decrease in the resonant frequency, so-called frequency dip, near critical temperature of superconducting niobium cavities, Tc, correlates to the cavity quality factor, Q0, and impurities introduced into the superconducting niobium surfaces, such as nitrogen or oxygen. We measured frequency dips in both 644 MHz fundamental mode (FM) and 1.45 GHz higher-order mode (HOM) of single-cell elliptical cavities for FRIB energy upgrade (FRIB400) R&D. These measurements were performed in cavities with the following surface treatments: 1) electropolished (EP) only, 2) nitrogen-doped (N-doping), 3) medium-temperature (mid-T) baked and then hydrofluoric (HF) acid rinsed. We will present measured frequency dips and compare them to cavity Q0 performance in the FM. Frequency-dependent behavior of frequency dips with various surface treatments will also be discussed as our experimental setup has a unique feature compared to previous studies, which allows for measurement of frequency dips in different modes within the same cavity, in other word, on the same surfaces.
Paper: TUPB012
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB012
About: Received: 20 Aug 2024 — Revised: 06 Sep 2024 — Accepted: 11 Sep 2024 — Issue date: 23 Oct 2024
TUPB013
RF pulse conditioning to reduce field emission in FRIB SRF cryomodules
355
Field emission (FE) is a major contributor to degradation in the high-field performance of Superconducting Radio Frequency (SRF) cavities. The driver linac for the Facility for Rare Isotope Beams (FRIB) has been operating for user experiments since May 2022, using 104 quarter-wave resonators and 220 half-wave resonators in 46 cryomodules. We have used pulsed RF conditioning to mitigate the FE X-rays and maintain the cavities’ performance. During conditioning, we observe "electrical breakdown," a rapid (<1us) collapse of the field. We have found that the FE X-rays may be greatly reduced after a single to several electrical breakdown events, which are accompanied by a local discharge in the vacuum and burning out of the emitter on the cavity surface. On the other hand, when a slow (~ms) thermal breakdown (known as quench) is seen, it limits the field and hampers further FE conditioning. We have also investigated the field enhancement factor and the effective area of FE emitter, inferred by Fowler-Nordheim fitting of FE X-ray dose rate vs accelerating gradient. In this paper, we will present RF pulse conditioning results and analysis thereof for about 50 cavities in FRIB cryomodules.
Paper: TUPB013
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB013
About: Received: 22 Aug 2024 — Revised: 29 Aug 2024 — Accepted: 30 Aug 2024 — Issue date: 23 Oct 2024
TUPB014
Development of wet nitrogen doping to enhance Q performance of β=0.53 half-wave resonators
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FRIB is developing a new N-doping method with a simplified recipe. This recipe is called wet nitrogen doping, by adding nitric acid to the conventional EP acid. Nitrogen doping introduces impurities to the SRF surface, and reduces the BCS resistance by shortening the mean free path, which leads to a higher Qo. Conventional nitrogen doping, developed at FNAL and Jlab, requires a high-temperature treatment (900 ºC), and an additional light EP to remove the over-contaminated layer. This recipe produces a decreasing Qo at extremely low fields but successfully achieves high Qo performance up to 25 MV/m. The wet doping method does not require additional high-temperature baking and light EP afterwards, therefore it is superior in terms of processing steps. This method produced a high Qo of 8x10^10 at a low field of 0.5MV/m without the decreasing trend on FRIB beta=0.53 HWR. In this presentation, we will show the related R&D results generated from the FRIB 0.53 HWRs.
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUAA002
About: Received: 20 Aug 2024 — Revised: 07 Sep 2024 — Accepted: 07 Sep 2024 — Issue date: 23 Oct 2024
TUPB015
Development of Bi-Alkali antimonide photocathodes for a 1.3 GHz superconducting rf photo-injector
359
Superconducting Radio Frequency (SRF) photo-injectors offer the possibility of producing low-emittance electron beams in continuous wave operation. Among the various photo-emissive materials, bi-alkali antimonide is favored for its high quantum efficiency (QE) at visible light wavelengths. A development effort at FRIB is oriented toward the integration of advanced photocathodes into an SRF photo-injector. This paper describes improvements to the cathode preparation chamber, first cathode depositions, and characterization trials. A K2CsSb film was produced with a notably extended dark lifetime, albeit with a modest QE of approximately 5% at 530nm. Extensive spectral response analyses of the layer were conducted, along with thorough assessments of measurement procedures and hardware. This presentation offers insights into the factors contributing to the measured QE and describes plans for improving the cathode preparation chamber and the experimental procedures.
Paper: TUPB015
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB015
About: Received: 12 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
TUPB016
Beam Emittance and Twiss Parameters from Pepper-Pot Images using Physically Informed Neural Nets
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In the field of accelerator physics, the quality of a particle beam is a multifaceted concept, encompassing characteristics like energy, current, profile, and pulse duration. Among these, the emittance and Twiss parameters—defining the size, shape, and orientation of the beam in phase space—serve as important indicators of beam quality. Prior studies have shown that carefully calibrated statistical methods can extract emittance and Twiss parameters from pepper-pot emittance meter images. Our research aimed to retrieve these parameters with machine learning (ML) from a transverse image of the beam after its propagation through a pepper-pot grid and subsequent contact with a scintillating plate. We applied a Convolutional Neural Network (CNN) to extract the x and y emittances and Twiss parameters (α and β), producing a six-dimensional output by simply looking at the image without calibration information. The extraction of divergence-dependent parameters, such as α and emittance, from a single image presented a challenge, resulting in a large Symmetric Mean Absolute Percentage Error (SMAPE) of 30%. To mitigate this issue, our novel method that incorporated image data from two points along the particles' propagation path yielded promising results. β prediction achieved a low SMAPE of 3%, while α and emittance predictions were realized with a 15% SMAPE. Our findings suggest the potential for improvement in ML beam quality assessment through multi-point image data analysis.
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUAA005
About: Received: 20 Aug 2024 — Revised: 07 Sep 2024 — Accepted: 07 Sep 2024 — Issue date: 23 Oct 2024
TUPB019
A novel test cavity setup for surface conductivity measurements of additive manufacturing samples
363
Additive Manufacturing (AM) has the potential to increase the performance of radio frequency (rf) cavity resonators while cutting manufacturing costs. To leverage this potential, AM processes and potentially post-processing techniques must be tailored to cavity requirements. Additionally, conventional manufacturing's quality assurance methods must adapt to the AM case requiring numerous studies on additively manufactured test bodies. We introduce a compact rf cavity design, enabling cost-effective and precise studies of the surface conductivity of test bodies. The test body is mounted on a dielectric holder inside a cylindrical rf cavity made of aluminum. The geometry of the test body corresponds to a rod which allows simple and cost-effective production, post-processing and evaluation. The test body’s surface conductivity is extracted from a measurement of the quality factor (Q0) of the cavity. Depending on the geometry of the test body, Q0 values of over 10,000 can be achieved for copper test bodies. Thereby, the test body is responsible for up to two thirds of the total cavity loss. Studies will be presented demonstrating the precision of surface conductivity determination via Q-measurement and the impact of uncertainties in test body position and geometry.
Paper: TUPB019
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB019
About: Received: 19 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB020
Surface finishing of additive manufacturing parts for particle accelerators
367
Significant progress towards the suitability of Additive Manufacturing (AM) metal parts for the production of linear accelerator components has been made in recent years. One significant factor for the suitability of AM parts to produce linac rf structures is the surface quality of the parts. Due to the inherently higher surface roughness of AM metal parts, post-processing is necessary to reach surfaces suitable for rf operation. We present most recent results of surface post-processing trials with AM parts from stainless steel.
Paper: TUPB020
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB020
About: Received: 19 Aug 2024 — Revised: 26 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB021
Current status of beam commissioning at the Frankfurt Neutron Source
371
The Frankfurt Neutron Source FRANZ will be a compact accelerator driven neutron source utilizing the 7Li(p,n)7Be reaction with a 2 MeV proton beam. Follwoing successful beam commissioning of the 700 keV proton RFQ, further beam experiments including emittance measurements are currently ongoning. Preparations for conditioning and commissioning of the IH-DTL are running in parallel to the current beam measurement campaign. We report on the current status of commissioning towards a 2 MeV proton beam.
Paper: TUPB021
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB021
About: Received: 19 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB022
Development of a compact RF coupler utilizing additive manufacturing
375
Additive manufacturing (AM) has established itself as a powerful tool for rapid prototyping and the production of complex geometries. For use in a 433 MHz IH-DTL cavity, a CF-40 coupler is being developed that is manufactured from pure copper using a 3D printing process and has a water cooling concept that cannot be realized using conventional methods. The coupler consists of a ceramic window cooled on both sides, an outer conductor with spiral cooling channels and a cooled inner conductor. Thanks to its modular design, the individual components can be easily replaced. The ideal transmission is frequency-dependent and was adjusted by fine-tuning the inner conductor structure in CST-Simulations. A prototype made of aluminum was built for verification purposes.
Paper: TUPB022
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB022
About: Received: 19 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
TUPB023
A new RFQ for the carbon therapy injector at HIT Heidelberg
379
The tumor therapy facility HIT, Heidelberg, Germany is in operation with light ion beams up to carbon since 2009. The 7 A MeV, 216.8 MHz synchrotron injector linac with a total length of 5 m is designed for the ion C^(4+) from an ECR ion source. The RFQ accelerates the beam from 8 A keV up to 400 A keV and is at present a bottleneck in beam transmission. After a careful analysis of the beam quality along the RFQ it was decided by HIT to order a new RFQ from Bevatech with higher beam acceptance and with tight mechanical tolerances. Other features are optimized entrance and exit gaps by including longitudinal field components, which are characteristic for 4-Rod-RFQs. A complete dipole field compensation along the mini-vane electrodes is another improvement. This RFQ is scheduled to replace the old one in 2026.
Paper: TUPB023
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB023
About: Received: 20 Aug 2024 — Revised: 11 Sep 2024 — Accepted: 11 Sep 2024 — Issue date: 23 Oct 2024
TUPB025
Phase setting issues for the SPIRAL2 LINAC
383
The SPIRAL2 superconducting LINAC accelerates beams of different species, in a large energy range. During operation, the beam requested by the physics can change quite often and it is mandatory that beams that have been already tuned can be obtained again by simple application of the machine parameters already used. This reduces the accelerator retuning time and increases the machine availability for the physics experiences. Voltages and more particularly phases of all the cavities are among the crucial parameters for a quick retuning. Proper beam tuning is monitored via the Beam Position Monitors. This paper focuses on the phase issues, reminds the way the reference frequency distribution, the LLRF and the BPM works and are used in the tuning procedures, and summarizes the upgrade foreseen to improve the cavity phase setting reliability
Paper: TUPB025
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB025
About: Received: 20 Aug 2024 — Revised: 04 Sep 2024 — Accepted: 11 Sep 2024 — Issue date: 23 Oct 2024
TUPB026
Progress and status of the FAIR proton linac
387
The progress and status of the high intensity short pulse 325 MHz proton linac driver for the FAIR facility in Darmstadt is described. The proton linac is designed to deliver a beam current of 70 mA at an energy of 68 MeV. The design of the normal conductiong CCH cavities was carried out in collaboration with our partners at the IAP Frankfurt and industrial partners. First bead pull measurements have been successfully performed on the CCH prototype. This prototype cavity is intended for later final production and copper plating. The construction of the ladder RFQ has been completed together with first rf measurements at levels up to 400 W. The RFQ has been delivered to FAIR and high power rf tests are expected to be performed on site during the next year. The proton driver, along with the antiproton chain of the FAIR project, has been postponed due to a re-prioritisation of the project and is now in a frozen state. All delivered components need to be brought to a state that is consistent with the project objectives. This will allow a smooth re-launch in the future. The status of this process is described in this paper.
Paper: TUPB026
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB026
About: Received: 20 Aug 2024 — Revised: 29 Aug 2024 — Accepted: 30 Aug 2024 — Issue date: 23 Oct 2024
TUPB027
High current machine campaign with various ion species at GSI UNILAC
390
After dedicated machine upgrade measures at the GSI UNILAC, a high current beam campaign has been performed recently. The presented results were accomplished - among other things - with newly installed electrodes for the superlens (short RFQ-type matching section), working completely fault free. Beam experiments have been conducted with high intensity proton beam (1.2 mA), carbon (1 mA 12C6+) and nitrogen beam (5.4 mA 14N7+) dedicated for pion production. A record argon beam intensity of 28 mA (40Ar11) has been obtained at gas stripper section. A sufficiently high stripping efficiency of 35% applying a pulsed N2 gas stripper target could be realized. By achieving high-current performance for medium-heavy ions, a further step has been taken towards fulfilling the FAIR requirements for high-current operation. In this contribution the results of machine experiments are summarized, in particular the performance enhancement at the High Current Injector section (HSI).
Paper: TUPB027
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB027
About: Received: 09 Aug 2024 — Revised: 29 Aug 2024 — Accepted: 29 Aug 2024 — Issue date: 23 Oct 2024
TUPB028
Update on the intense heavy ion DTL project Alvarez 2.0 at GSI
394
The Alvarez-type post-stripper DTL at GSI accelerates intense ion beams with A/q <= 8.5 from 1.4 to 11.4 MeV/u. After more than 45 years of operation it suffers from aging and its design does not meet the requirements of the upcoming FAIR project. Prototyping of a new 108 MHz Alvarez-type DTL has been completed and series components for the 55 m DTL are under production and have been delivered partially. This report summarizes the actual status of Alvarez 2.0 at GSI and sketches the future path to completion.
Paper: TUPB028
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB028
About: Received: 15 Aug 2024 — Revised: 25 Aug 2024 — Accepted: 25 Aug 2024 — Issue date: 23 Oct 2024
TUPB029
Considerations and findings on beam vorticity dynamics
397
Rotation of beams is usually quantified through its angular momentum rather than through its vorticity. However, the difference of the two transverse eigen-emittance is linked more strongly to vorticity as to angular momentum. It has been found that the dynamics of vorticity has remarkable similarity to the dynamics of the beam envelope along channels of solenoids and quadrupole triplets. Transport matrices of vorticity, corresponding phase advances and Twiss parameters look very similar and are partially even identical to their counterparts concerning envelopes. Corresponding to emittance, the quantity of vortissance, being a constant of motion, is defined. Unlike emittance, for vorticity-dominated beams, it may take imaginary values causing imaginary Twiss parameters and negative or zero phase advances along a finite beam line section.
Paper: TUPB029
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB029
About: Received: 11 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
TUPB030
High performance megawatt uranium beams at GSI UNILAC
400
The 50 years old GSI-UNILAC (Universal Linear Accelerator) as well as the heavy ion synchrotron SIS18 will serve as a high current heavy ion injector for the FAIR (Facility for Antiproton and Ion Research) synchrotron SIS100. The UNILAC together will provide for short and intense pulses. This contribution presents the results of the full performance high current uranium beam machine experiment campaign at UNILAC, conducted in the last three years. In order to determine the behavior of uranium beams, the transverse beam emittance at five selected measurement positions along the complete UNILAC have been measured for the first time in several machine investigation runs. A significant improvement in beam brilliance was achieved by using the pulsed hydrogen stripper at 1.4 MeV/u. It could be shown that extremely low horizontal emittances, i.e. very high brilliances, are achieved along the complete UNILAC up to the SIS injection. Besides high intense uranium beam with charge state 28+ also multi charge beam, comprising 27+, 28+, 29+ uranium ions, commonly recharged primarily to charge state 73+ using a carbon foil, were investigated and a record current of 3.6 emA has been achieved.
Paper: TUPB030
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB030
About: Received: 31 Jul 2024 — Revised: 29 Aug 2024 — Accepted: 30 Aug 2024 — Issue date: 23 Oct 2024
TUPB031
Modeling beam dynamics in the HELIAC Advanced Demonstrator
404
A crucial milestone towards the final expansion stage of the HELIAC (Helmholtz linear accelerator at HIM & GSI) is the commissioning of the first fully equipped cryomodule, the so-called Advanced Demonstrator. The cryomodule comprises three accelerating superconducting crossbar H-mode cavities, a buncher and two superconducting solenoids. For modelling the beam dynamics of the Advanced Demonstrator test setup, the actual 3D electromagnetic field distributions of the cavities and solenoids are used. The digital model was paired with beam-based measurements of the longitudinal and transverse beam density distribution to calculate the realistic beam propagation along the 20 m setup. The beam dynamics insights gained during the cryomodule commissioning are presented.
Paper: TUPB031
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB031
About: Received: 31 Jul 2024 — Revised: 27 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB032
Beam commissioning of the first HELIAC cryomodule
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The superconducting heavy ion HELmholtz LInear ACcelerator (HELIAC) is designed to meet the needs of the Super Heavy Element (SHE) research and material science user programs at GSI in Darmstadt. The beam energy can be varied smoothly between 3.5 and 7.3 MeV/u, with an average current of up to 1 emA and a duty cycle of 100 %. Recently, the first cryomodule CM1, was fully commissioned and tested. CM1 comprises three Crossbar H-mode (CH)-type accelerator cavities, a CH-rebuncher, and two superconducting solenoid lenses. Following the commissioning of the cryogenic supply- and RF-systems, a successful beam test was conducted at the end of 2023. A helium ion beam was successfully accelerated to the design energy of 2.7 MeV/u. The beam energy could be varied continuously between 1.3 and 3.1 MeV/u without any significant particle losses being measured in the cryomodule. This contribution covers the construction and commissioning of the first HELIAC cryomodule and the results of the beam test campaign.
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUAA004
About: Received: 20 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
Preliminary results of electromagnetic simulation for optimizing an SRF gun cavity to maximize the beam brightness
A high beam brightness is a crucial requirement for an electron linear accelerator, with the electron source setting the lower limit for the achievable brightness. A superconducting radio-frequency photoelectron injector (SRF gun) stands out as an advanced electron source capable of delivering beams with superior properties compared to other continuous-wave injectors. Currently, SRF guns are being reliably operated at various accelerators. However, the gun cavities are operated below its design gradient due to the field emission. This lower gradient reduces particle energy gain per cell and adversely affects beam quality by deviating from theoretical optima. To overcome these limitations, a new cavity design is being explored, with the peak surface electric field restricted to 30 MV/m, corresponding to the fields that have typically been achieved so far. This contribution will begin by examining the similarities between accelerator and injector cavity designs, followed by an examination of the specific requirements unique to the injector cavity. Subsequently, the design methodology being followed will be described. A mesh convergence study is then presented in a later section. Various alternative cavity shapes to the TESLA design have been proposed, and the figure of merits (FOM) achieved using these full-cell shapes in conjunction with the existing HZDR injector first cell will be presented. The future plans are outlined in the final section.
TUPB034
Photocathode study in SRF Gun-II at HZDR
408
HZDR’s SRF Gun-II is an excellent demonstration of SRF technology application in the field of electron sources operating in continuous wave mode. As well known, quality of the photocathode is crucial for op-erational stability and reliability of an SRF gun. In this contribution, various studies on Cs2Te cathodes, in-cluding cleaning, preparation, transport/insertion, RF and beam operation will be summariesed. We will look back at the achievements and open issues, and discuss possible improvements and further development.
Paper: TUPB034
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB034
About: Received: 20 Aug 2024 — Revised: 30 Aug 2024 — Accepted: 30 Aug 2024 — Issue date: 23 Oct 2024
TUPB035
Development of an integrated monitor system for real-time relative phase measurement between the cavity-RF and beam
411
In a linear accelerator, phase drift in upstream cavities can adversely affect downstream cavity synchronization, leading to beam degradation and potential loss. J-PARC LINAC employs different phase reference signals for beam monitoring and RF systems, hindering direct comparison. Recent observations revealed susceptibility of reference signals to environmental effects in the Klystron Gallery. Hence, a thorough observation of the relative phase between cavity-RF and beam is imperative. Addressing this, we took advantage of the newly developed MicroTCA.4-based monitor digitizers to meticulously analyze RF signals from cavity pick-up and beam signals from existing fast current transformers dedicated to measuring beam phase. Initial results show enhanced long-term stability in the relative phase with a shared RF reference. A beam study was also conducted wherein deliberate alterations were made to the cavity-RF phase settings via the LLRF system to detect their impact on the phase drift of downstream cavities. The system recorded downstream beam oscillations prompted by phase drift in upstream cavities. Our work elucidates a real-time monitoring strategy for relative phase detection.
Paper: TUPB035
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB035
About: Received: 19 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
Recent progress of Nb3Sn cavity development at KEK
Nb3Sn is one of the most promising materials for the next generation of superconducting RF (SRF) cavities. One reason is that Nb3Sn cavities can achieve high Q-values at 4 K, whereas conventional Nb cavities need to be cooled down to 2 K. This allows for the operation of SRF cavities with conduction cooling, eliminating the need for liquid helium, unlike conventional SRF cavities which require immersion cooling. KEK started Nb3Sn deposition tests on the single-cell cavity based on the Sn vapor diffusion method around 2019 and has steadily improved the cavity performance. In addition, a small deposition furnace for the sample study was constructed last year to investigate the relationship between Nb3Sn film quality and deposition parameters and to improve the throughput of the deposition study. We will report the results of deposition tests on samples and RF measurements of single-cell Nb3Sn cavities.
TUPB037
RF reference phase control system in the SuperKEKB injector LINAC
415
The RF reference phase in the SuperKEKB injector LINAC has been specially controlled for the stable beam injection to the main rings (HER/LER). The phase control system consists of three parts: MOFB, MOPS and SECT35PS. MOFB is the phase feedback system for drift compensation between the LINAC master oscillator (LMO) of 571.2 MHz and ring MO (RMO) of 508.9 MHz which has frequency ratio of 49/55 to the LMO. MOPS is the MO phase shifter. The LMO phase needs to be shifted smoothly depending on the injection phase for HER or LER rings in the repetition rate of 50 Hz. The laser system of the photocathode RF gun for HER beam, however, does not accept such fast phase changes. The MOPS module, therefore, has been developed to satisfy the requirement of the laser system and injection phase adjustment. SECT35PS is the phase shifter of 2856 MHz RF reference for downstream side of positron damping ring (DR) located in the middle of the LINAC. DR is operated with the same frequency as the main rings, 508.9 MHz. To increase the synchronization probability for the bucket selection of LER ring, the LINAC reference phase at the downstream of DR is changed pulse-to-pulse by the bucket selection system. This paper describes the RF reference phase control system.
Paper: TUPB037
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB037
About: Received: 20 Aug 2024 — Revised: 26 Aug 2024 — Accepted: 26 Aug 2024 — Issue date: 23 Oct 2024
TUPB038
Development of new pulse driver for high power pulsed magnet
418
The KEK injector linac injects high-charge electron and positron beams into the high-energy-ring and low-energy-ring of SuperKEKB respectively. The linac also injects electron beams to the two light source rings, PF ring and PF-AR. We operate simultaneous top-up injections into the four rings by using many pulsed magnets. We have been upgrading the linac to attain the higher-quality beam injections for the SuperKEKB rings. In the summer of 2023, large-aperture quadrupole pulsed magnets have been newly installed upstream of the linac and driven by new large-current pulse driver. The power of the new pulse driver is 600 A 400 V and is energy recovery type. We achieve high efficiency with simple pulse width control. I would like to introduce this high-power, high-efficiency pulse driver.
Paper: TUPB038
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB038
About: Received: 20 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
TUPB039
Circular modes for linacs
421
Circular mode beams are beams with non-zero angular momentum and strong inter-plane plane coupling. This coupling can be achieved in linear accelerators (linacs) through magnetization of electrons or ions at the source. Depending on the magnetization strength, the intrinsic eigenmode emittance ratio can be large, which produces intrinsic flatness. This flatness can either be converted to real plane flatness or can be maintained as round coupled beam through the system. In this paper, we discuss rotation invariant designs that allow circular modes to be transported through the lattice while accelerating and maintaining its circularity. We demonstrate that with rotation invariant designs the circularity of the mode can be preserved as round beam while maintaining intrinsic flatness to be converted to flat beam later or injected into a ring.
Paper: TUPB039
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB039
About: Received: 20 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
Dominance of particle resonances over parametric instabilities in high-intensity linacs
For high-intensity linear accelerators, space-charge halo mechanisms are largely classified into two families: particle resonances and parametric instabilities. The dominance between the fourth-order particle resonance and the envelope instability has been argued and studied. Our studies and previous literature indicate the dominance of particle resonances over parametric instabilities in high-intensity linear accelerators. Any counter evidence has not been found yet. Furthermore studies indicate that parametric instabilities except the envelope instability are unlikely to be observed in actual linear accelerators unless waterbag or KV distributions are generated. We propose a way to overcome the previous design rule to avoid the zero-current phase advance > 90° for the high-intensity linac. The interplay is presented of the envelope instability and the fourth-order parametric instability.
Physics applications for RAON linac commissioning
Physics applications have been developed and applied to the linac commissioning of the RAON injector and superconducting linac. Beam parameters obtained from the physics applications have been checked and validated during the beam commissioning using various ion beams.
Calibration of button-type beam position monitor based on low beta beam at RAON
RAON is a multi-purpose accelerator facility that can accelerate various heavy ion beams and rare isotope beams. The maximum energy of the uranium beam is 200 MeV/u. Sixty button beam position monitors were fabricated for use in SCL3, which accelerates the beam from 0.5 MeV/u to 18.5 MeV/u in a uranium case. BPM Electronics has developed position measurement using the IQ method for the 1st, 2nd, and 3rd harmonic frequencies of 81.25 MHz. Calibration factors for each frequency of the BPM were obtained on a wire test bench for the three frequency harmonic components. The position calibration factor obtained from the CST simulation had a beta dependence and differed from the measurements from the wire test bench. To measure the calibration factor using a beam, a moving stage equipped with a micrometer was prepared on the one-dimensional plane of the MEBT cross-section. We present the results of a beam-based calibration test of a button-type BPM for a low-beta heavy ion beam.
Analysis of beam characteristic variations in the 14.5 GHz ECR ion source at RAON
RAON (Rare isotope Accelerator complex for ON-line experiments) is a heavy ion accelerator under construction in Daejeon, South Korea. RAON plans to operate a 28 GHz Electron Cyclotron Resonance Ion Source (ECRIS) with a fully superconducting magnet and is currently operating a 14.5 GHz ECR ion source with a fully permanent magnet. The 14.5 GHz ECRIS was manufactured by PANTECHNIK and installed in our beamline in September 2020. The initial beam conditioning of RAON was conducted using the 14.5 GHz ECR ion source with 40Ar9+ and 40Ar8+ beams. Additionally, beam tests were performed with protons, 4He2+, and oxygen. During these experiments, an unusual phenomenon was observed: the characteristics of the beam changed despite no variations in the parameters. This was consistently noted during some of the beam tests. We hypothesized several potential causes for this phenomenon and analyzed them through experiments. In this paper, we discuss the results of these analyses.
TUPB045
Design update of the power couplers for the single-spoke resonators in Institute for Rare Isotope Science
425
A heavy-ion accelerator facility was constructed for the Rare Isotope Science Project (RISP) at the Institute for Rare Isotope Science (IRIS) in Daejeon, Korea. A cryomodule with quarter-wave resonators (QWRs) and half-wave resonators (HWRs) was installed in the SCL (Superconducting Linac) 3 tunnel,and the initial beam commissioning using argon beams has been completed. Additionally, a cryomodule with single-spoke resonators (SSRs), power couplers,and tuners is currently under development for the SCL2 project. The geometry of the power couplers for the SSRs is a coaxial capacitive type based on a conventional 3-1/8 inch Electronic Industries Alliance (EIA) coaxial transmission line with a single ceramic window. A multi-physics analysis, incorporating electromagnetic, thermal, and mechanical aspects, was conducted to evaluate the design of the power coupler for the SSRs. This paper presents the results of the multi-physics analysis and the current design status of the power coupler for the SSRs.
Paper: TUPB045
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB045
About: Received: 07 Aug 2024 — Revised: 30 Aug 2024 — Accepted: 30 Aug 2024 — Issue date: 23 Oct 2024
Status and performance of 150 kW RF solid state power amplifiers for the RFQ cavity
The RAON facility, under the Institute for Basic Science (IBS) in Daejeon, is an advanced accelerator complex designed for research involving rare isotopes. RAON uses different types of cavities to accelerate various ions. The 81.25 MHz RF superconducting Radio Frequency Quadrupole (RFQ) cavity plays a key role in the initial acceleration of the ion beam. Supplying RF power efficiently to this RFQ cavity requires a total of 150 kW of RF power from Solid State Power Amplifiers (SSPAs). To fulfill this requirement, the RF group initially developed a 20 kW SSPA. The developed 20 kW SSPA showed good performance in frequency stability, power amplification efficiency, and thermal management. Based on these good performance results, several 20 kW SSPAs were combined to make two 80 kW SSPAs, meeting the RF power requirements for the RFQ cavity. In this paper, we present the development process and performance results of the 80 kW RF SSPAs.
Development of 81.25 MHz and 162.5 MHz LDMOS-based solid-state power amplifiers for the heavy ion accelerator
Construction of a heavy ion accelerator facility to support various scientific studies is underway. The heavy ion accelerator facility is largely comprised of SCL3 for low-energy acceleration and SCL2 for high-energy acceleration. SCL3 consists of 22 quarter wave resonators (QWR) with a superconducting acceleration cavity frequency of 81.25 MHz and 102 half wave resonators (HWR) with a frequency of 162.5 MHz, and SCL3 consists of 213 single spoke resonators (SSR) with a frequency of 325 MHz. A low-energy superconducting linear accelerator consisting of an injector, QWR, and HWR was successfully commissioned. SCL3 superconducting accelerator tube can supply up to 4kW of RF power to the acceleration cavity using a solid-state power amplifier (SSPA) based on LDMOS (Lateral Double-Diffused Metal Oxide Semiconductor). The basic principle of the solid-state power amplifier applied to the acceleration cavity of 81.25 MHz and 162.5 MHz is the same, with differences in the location and quantity of components such as circulator and RF combiner. The main components of SSPA are the main transistor, a bidirectional coupler for RF input power monitoring, an attenuator, a limiter to prevent over-input, an ultra-short MMIC, a driving amplifier, a 4-way input power divider, a 4-way output power combiner, a circulator, and a dummy load.
TUPB048
Preliminary design of transverse deflecting structure systems for Shenzhen Superconducting Soft-X-ray Free Electron Laser
428
Transverse Deflecting Structures (TDS) are commonly used in Free Electron Laser (FEL) facilities for the measurement of longitudinal information of electron beam, including bunch length, temporal distribution, slice emittance, etc. Shenzhen Superconducting Soft-X-ray Free Electron Laser (S3FEL) is a high-repetition-rate FEL recently proposed for scientific research and applications. In S3FEL, TDSs that work at S-band (2997.222 MHz) and X-band (11988.889 MHz) will be utilized for the diagnosis and analysis of longitudinal phase space of electron bunches along the beamline. In this manuscript, we present the preliminary design of both S-band and X-band TDS systems of S3FEL, including system layout, deflecting structures, pulse compressors, RF distribution networks, etc. Additionally, we introduce a new parallel-coupled TDS cavity with variable polarization for multi-dimensional phase space diagnostics.
Paper: TUPB048
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB048
About: Received: 20 Aug 2024 — Revised: 23 Oct 2024 — Accepted: 23 Oct 2024 — Issue date: 23 Oct 2024
First beam commissioning and beam experiments of the CiADS Front end
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The China Initiative Accelerator Driven System (CiADS), a multi-purpose facility driven by a 500 MeV superconducting RF linac, is currently under construction in Huizhou, Guangdong. In order to ensure the stable operation of the superconducting linac, we conducted optimization research on the beam quality in the front-end section of CiADS. By using the point scraping method, part of the beam halo particles are removed in advance at the entrance of the LEBT, avoiding the generation of beam halo particles. On the other hand, since the beam extracted from the ECRIS contains a portion of $H^{2+}$ and $H^{3+}$particles, impurity particles may lead to a decrease in the transmission efficiency of downstream accelerators. By separating the mixed beam, it is possible to measure the proportion and phase space distribution of the mixed beam at the exit of the ion source, thereby achieving accurate measurement of the proton beam. This paper mainly outlines the first beam commissioning of CiADS Front end. Additionally, the effectiveness of the point scraping method has been verified through transverse emittance measurement, and the proportion and phase space distribution of the mixed beam was measured. Furthermore, the stability of the ion source was tested, and the centroid shift of the ion source extracted beam was measured.
TUPB050
Development of the superconducting HWR cavities for NICA project
431
Nuclotron-based Ion Collider fAcility (NICA) is an accelerator complex under construction in JINR, in which superconducting linac-injector can accelerate protons up to 20 MeV and light ions to 7.5 MeV/u. To achieve this design target, a 325 MHz, beta = 0.21 niobium half-wave resonator (HWR) called HWR1 was developed jointly by IMP and JINR. This paper optimizes the electromagnetic design of NICA cavity, designs the mechanical structure (including helium jacket) and gives the results of multi-physical studies. Simulation results show that Epk/Eacc = 6.29, the coefficients of df/dp and LFD are 4.96 Hz/mbar and -1.28 Hz/(MV/m)^2, respectively. In addition, the niobium cavity has been fabricated and vertically tested, the magnetic shield and helium jacket are in the process of electron beam welding, and the cryomodule will be assembled in the next 1~2 months.
Paper: TUPB050
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB050
About: Received: 20 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
The acceleration of high intensity heavy ion beams at IMP
The production of low energy high intensity heavy ion beams is challenging for the community. Several high intensity heavy ion beam accelerators for versatile purposes have been developed at IMP, such as LEAF, which is a low energy high intensity heavy ion accelerator complex for multidiscipline researches that features a superconducting ECR source, and a heavy ion beam linac. The major acceleration structure of LEAF is a 4-vane RFQ, which accelerates heavy ions with M/q from 2 to 7 to 0.5 MeV/u. With the support of the energy modulation system based on a DTL and two bunchers, this facility features high intensity heavy ion beam acceleration up to 1 emA, fine tuning of ion beam energy within 0.3 to 1.0 MeV/u with an energy spread of <0.25% (FWHM) that is favored by high precision experimental investigations such as C-C burning study in nuclear astrophysics. A 4-rod RFQ, which was fabricated 15 years ago, has been recently modified and adopted a laser ion beam source as primary ion beam injector to accelerate high intensity pulsed heavy ion beams, especially for refractory metal ions. In addition, a very compact IH RFQ with frequency of 81.25 MHz has been developed to accelerate H2+ ions with currents of several mA. The cavity outer diameter is only 266 mm, which makes it possible that the RFQ could be embedded into a cyclotron and acts as the axial injector of high intensity ion beams. This report will present the latest progress and challenges of the aforementioned work.
Design of 200 mA superconducting linear electron accelerator
Electron accelerators utilized for radiation processing demand high beam currents and power outputs to maximize processing rate. Compared to conventional room-temperature accelerators, superconducting linear accelerators offer the capability to accelerate high-intensity continuous-wave (CW) electron beams. Therefore, the Design of a compact, 200mA, 2-5MeV CW superconducting linear accelerator holds promising potential for broad industrial applications. The Institute of Modern Physics (IMP) has recently completed operational testing on a conduction-cooled 5-cell-βopt=0.82 Nb3Sn superconducting cavity, thereby demonstrating the technical feasibility of miniaturizing superconducting accelerators. However, beam losses within the superconducting cavity, caused by factors such as mismatch between the inlet beam velocity and the cavity's optimal beta value, are impermissible. This paper addresses these challenges by methodically optimizing the beam line, ensuring 100% transmission within the superconducting cavity while maintaining compactness. The detailed beam dynamic design and the multi-particle simulation results were presented in this paper.
TUPB054
Superconducting β=0.40 half-wave cavity design for CiADS
434
A 325 MHz, optimal beta = 0.40 niobium half-wave resonator (HWR) called HWR040 for the superconducting driver linac of the China initiative Accelerator-Driven subcritical System (CiADS) has been designed and analysed at the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS). The linac requires 60 HWR040s to accelerate protons from 45 MeV to 175 MeV. This paper mainly presents the multi-physics studies of the HWR040, include electromagnetic optimization, mechanical structure design and heat transfer simulation of the cavity, to predict the behaviour of the cavity under practical operating process.
Paper: TUPB054
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB054
About: Received: 20 Aug 2024 — Revised: 22 Oct 2024 — Accepted: 22 Oct 2024 — Issue date: 23 Oct 2024
Simulation and measurement studies of longitudinal acceptance based on the CAFe superconducting linac
The accurate measurement of longitudinal beam parameters is paramount for controlling beam losses in high-power superconducting linac accelerators, particularly for low-energy beams which are significantly affected by the compensative challenges of nonlinear effects and pronounced space charge effects. In this context, systematic simulation and experimental studies of longitudinal acceptance have been performed based on the CAFe linac, employing techniques of phase and energy scanning. This paper provides a detailed description of the principles of the longitudinal acceptance measurement and presents an analysis of preliminary experimental results obtained from the CAFe linac. It was observed that the experimental longitudinal acceptance of the accelerator was reduced compared to the simulation predictions. Key factors such as transverse orbit deviations and RF phase errors are examined, and a thorough analysis of these discrepancies is discussed in the paper.
Reinforcement learning-based beam tuning for CiADS room temperature front-end prototype
Achieving high-quality proton beams for accelerators hinges on effective beam tuning. However, the conventional "Monkey Jump" method, widely used for tuning, proves labor-intensive and inefficient. Through harnessing Reinforcement Learning (RL), a novel beam tuning strategy can swiftly emerge, making informed decisions based on the prevailing system status and control demands, offering a promising alternative for accelerator systems. We explore novel techniques RL-based beam tuning and applying it to the beam tuning process of the CiADS Front End accelerator currently, with the aim of significantly enhancing the efficiency of the tuning process. To achieve this, we will first establish an RL-compatible environment based on dynamic simulation software. Subsequently, the policy is trained under different initial conditions. Finally, the strategy successfully trained in the simulation environment will be tested on real accelerator to verify its effectiveness.
TUPB057
Maximum entropy phase space tomography under nonlinear beam transport
438
Obtaining the complete distribution of a beam in high-dimensional phase space is crucial for predicting and controlling beam evolution. Previous studies on tomographic phase space reconstruction often required linear beam optics in the relevant transport section. In this paper, we show that the method of maximum entropy tomography can be generalized to incorporate nonlinear transformations, thereby widening its scope to the case of nonlinear beam transport. The improved method is verified using simulation results and potential applications are discussed.
Paper: TUPB057
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB057
About: Received: 20 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
TUPB058
A comparison of RMS moments and statistical divergences as ways to quantify the difference between beam phase space distributions
442
Accurately assessing the difference between two beam distributions in high-dimensional phase space is crucial for interpreting experimental or simulation results. In this paper, we compare the common method of RMS moments and mismatch factors, and the method of statistical divergences that give the total contribution of differences at all points. We first show that, in the case of commonly used initial distributions, there is a one-to-one correspondence between mismatch factors and statistical divergences. This enables us to show how the values of several popular divergences vary with the mismatch factors, independent of the orientation of the phase space ellipsoid. We utilize these results to propose evaluation standards for these popular divergences, which will help interpret their values in the context of beam phase space distributions.
Paper: TUPB058
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB058
About: Received: 20 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
Beam dynamics design of the superconducting section of a 100 mA superconducting linac
A high-power superconducting linac with an energy of 30 MeV and a beam current of 100 mA has been proposed and designed. The primary challenge lies in beam loss control and a robust lattice structure to ensure stable operation. This paper discusses the physics design study, design principles, and simulation results considering machine errors. Extensive multiparticle simulations (a cumulative statistic of 1×10^5 macroparticles) demonstrated that this linac operating at 100 mA could maintain beam losses lower than 1 W/m in error scenarios.
TUPB060
Development of an X-band LLRF prototype for the EuPRAXIA@SPARC_LAB LINAC
446
EuPRAXIA stands for “European Plasma Research Accelerator with eXcellence In Applications". It's a next generation free-electron laser (FEL) aimed at developing a compact, cost-effective particle accelerator based on novel wake-field accelerator technology. Traditionally, high-energy physics requires higher acceleration voltages, so developing an X-band acceleration technology, enables the possibility to achieve high gradients with very compact structures. EuPRAXIA@SPARC_LAB LINAC injector features 1 S-band RF gun, 4 S-band and 16 X-band structures, achieving a max beam energy of 1 GeV. Low-Level Radio Frequency (LLRF) systems are crucial for RF station synchronization and machine stability at femtosecond precision. Currently, there are no commercially available X-band LLRF solutions, especially for pulse processing and control in the 100ns range. This project aims to develop an X-band LLRF prototype, in collaboration with INFN, tailored to meet EuPRAXIA@SPARC_LAB LINAC's demands. Once confirmed on a real testbench, the prototype will be used as a starting point for industrialization into a commercial instrument. This paper presents the prototype’s architecture and preliminary results.
Paper: TUPB060
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB060
About: Received: 19 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
Multipacting with space charge: stability and saturation of a non linear dynamic system
The phenomenon of multipacting happens when in an RF cavity or wave guide electrons, randomly generated on the surfaces mainly by secondary emission and accelerated by the RF field, find e periodic and stable condition able to sustain the discharge. It is particularly detrimental for long pulse operation as in high intensity hadron linacs. An original view point for the associated dynamical system is here developed, with focus on the definition of stability conditions and on the role of space charge in the saturation of the discharge intensity. Moreover in the case of a resonant cavity the electron "beam loading" effect is analyzed.
TUPB064
Anthem project, construction of a RFQ driven BNCT neutron source
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The project Anthem, funded within the Next Generation EU initiatives, foresees the realization of an innovative accelerator based BNCT (Boron Neutron Capture Therapy) facility at Caserta, Italy. The INFN (LNL, Pavia, Napoli, Torino) has in charge the design and construction of the epithermal neutron source, that will assure a flux of 10^9 n/(s cm2) with characteristics suited for deep tumors treatment. The driver is a cw RFQ, able to produce proton beam of 30 mA 5 mA. impinging on a beryllium target. Specific challenges are related to the medical application of the device. In the paper an overview of the project will be given.
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUAA003
About: Received: 20 Aug 2024 — Revised: 07 Sep 2024 — Accepted: 07 Sep 2024 — Issue date: 23 Oct 2024
TUPB065
Tuning of ESS DTLs
449
The normal conducting part of ESS LINAC in Lund (Sweden) uses 5 DTL cavities, provided by INFN LNL as in-kind partner, to accelerate 60 mA proton beam from 3.9 MeV to 90 MeV. DTL1 have been tuned, installed in the accelerator tunnel and RF conditioned in 2021, DTL2, 3 and 4 in 2022, while DTL5 has been tuned and installed in summer 2023, but not yet conditoned. All the DTLs were equiped with tuning elements like tuners and post couplers, but the challenges experienced during the tuning of the first DTL has resulted in a change of tuning strategy, which effectively reduced the timeframe to tune the other cavities from months to days. The aim of this paper is to give an overview of the the achieved results and tuning procedure performed on the DTLs.
Paper: TUPB065
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB065
About: Received: 16 Aug 2024 — Revised: 09 Sep 2024 — Accepted: 10 Sep 2024 — Issue date: 23 Oct 2024
TUPB066
INFN LASA in-kind contribution to ESS ERIC project
453
INFN Milano - LASA recently concluded its in-kind contribution to European Spallation Source Eric, providing the 36 Superconducting Medium Beta cavities that will allow boosting the proton beam energy from 216 Mev to 571 Mev. The performances of the last four cavities, treated with Electro-Polishing as main removal step, are presented and compared with the results obtained on the remaining cavities treated with Buffered Chemical Polishing. The overall performance of the 36 cavities and lessons learned during the cavities production stages are also discussed.
Paper: TUPB066
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB066
About: Received: 20 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB067
RF and multipacting analysis of the high-power couplers of IFMIF/EVEDA RFQ and ESS DTL
457
The performances and failure cases of the power couplers of the IFMIF/EVEDA RFQ and ESS DTLs have been analyzed with dedicated high-power test campaigns and multipacting simulation methods. The paper presents test and simulation methodology, results, and inputs for the next activities.
Paper: TUPB067
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB067
About: Received: 17 Aug 2024 — Revised: 29 Aug 2024 — Accepted: 29 Aug 2024 — Issue date: 23 Oct 2024
TUPB068
ESS DTL: final installation and first commissioning results up to 74 MeV
461
The Drift Tube Linac (DTL) for the European Spallation Source (ESS ERIC) will accelerate proton beam up to 62.5mA peak current from 3.62 to 90 MeV. The 5 cavities are now fully installed and tested in the linac tunnel. Moreover, in 2023 DTL1 to DTL4 have been RF conditioned to full power and beam commissioned with max peak current at short pulses. Relevant results of these activities are presented in this paper.
Paper: TUPB068
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB068
About: Received: 17 Aug 2024 — Revised: 29 Aug 2024 — Accepted: 29 Aug 2024 — Issue date: 23 Oct 2024
TUPB069
Design and optimization of a C-band RF Pulse Compressor for a VHEE LINAC for FLASH Radiotherapy
465
In this paper, the design of a compact C-band SLED RF Pulse Compressor for a Very High Electron Energy (VHEE) FLASH machine is presented. A spherical cavity RF pulse compressor - selected because of its compactness and relative ease of fabrication - is adopted to compress the 5 𝜇s RF pulse, down to 1 𝜇s obtaining a peak power gain greater than 5. Both the RF and thermo-mechanical design have been carried out, including a sensitivity study to evaluate the mechanical tolerances, possible tuning methods, and the cooling system. The main parameters of the full RF design (spherical storage cavity + mode converter/polarizer) and the final mechanical design of the structure are presented.
Paper: TUPB069
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB069
About: Received: 20 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 29 Aug 2024 — Issue date: 23 Oct 2024
TUPB070
R&D on SRF at INFN LASA
468
Sustainability and cost reduction are key factors for the development of future large particle accelerators. This motivated INFN LASA to initiate an INFN-funded R&D program dedicated to improve the performance of SRF Nb cavities in terms of quality factor (High-Q) and accelerating gradient (High-G). The R&D program will start by exploiting state-of-the-art surface treatments on 1.3 GHz single-cell prototypes, in view of a possible industrialization process for large-scale productions. Integrating part of this program is the upgrade of our vertical test facility to enable qualification of such high-performance cavities. Ongoing activities include the construction of a new dedicated cryostat, which minimizes Liquid Helium consumption, reduces the impact of trapped magnetic flux and provides a wide range of diagnostics for quench, field emission, and magnetic flux expulsion studies.
Paper: TUPB070
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB070
About: Received: 20 Aug 2024 — Revised: 30 Aug 2024 — Accepted: 30 Aug 2024 — Issue date: 23 Oct 2024
TUPB071
Design and test of C-band linac prototypes for electron flash radiotherapy
472
FLASH Therapy, a novel cancer treatment technique, aims to control the tumor-grown sparing the healthy tissue from radiation damage, increasing the therapeutic index. Translating FLASH therapy into clinical practice, especially for treating deep-seated tumors, necessitates achieving Very High Electron Energy (VHEE) levels within the 50-150 MeV range [2]. In the framework of the SAFEST project [3–7], Sapienza University, in collaboration with INFN, is actively developing a compact C-band linac demonstrator at the energy of 24 MeV (loaded) with a 100 mA peak current. This paper provides insights into the design strategy and electromagnetic characteristics, focusing on prototype testing and tuning conducted at the Sapienza Accelerator Laboratory. The progress of this innovative linac represents a step toward realizing an advanced FLASH VHEE source in cancer treatment.
Paper: TUPB071
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB071
About: Received: 22 Aug 2024 — Revised: 17 Sep 2024 — Accepted: 17 Sep 2024 — Issue date: 23 Oct 2024
TUPB073
Fast chopper line for DONES
476
The International Fusion Materials Irradiation Facility – DEMO-Oriented Neutron Early Source (IFMIF-DONES) will provide a deuteron beam of unprecedented intensity for irradiation and characterization of materials to be used in fusion reactors. In recent years, the possibility to use a small fraction of this beam for other applications in parasitic mode was discussed. This not only has the potential to enlarge the user community without perturbing the main operation, but also allows characterization measurements for beam quality management purposes. Considering various requirements and constraints, the most promising option for the extraction towards such a parasitic line involves the use of a meander-line travelling-pulse beam deflector at the start of the High Energy Beam Transfer (HEBT) line. This paper describes preliminary studies aiming at a first definition of the structure, materials and geometrical parameters of the meander-line deflector.
Paper: TUPB073
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB073
About: Received: 20 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB074
Status of the INFN LASA in-kind contribution to PIP-II project
480
The status of INFN LASA in-kind contribution to the PIP-II project at Fermilab is reported in this paper. The effort for the series production of the 38 INFN LASA designed, 5-cell cavities with beta 0.61 for the LB650 section of the linac commenced and the status of ongoing activities and major procurements is here conveyed. At the same time, preliminary tests on INFN LB650 cavity prototypes are progressing in order to optimize the complete preparation and qualification cycle. All cavities will be produced, and surface treated in industry to reach the unprecedented performances required, qualified through vertical cold test at state-of-the art infrastructures and delivered as installation ready at the string assembly site.
Paper: TUPB074
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB074
About: Received: 18 Aug 2024 — Revised: 28 Aug 2024 — Accepted: 29 Aug 2024 — Issue date: 23 Oct 2024
TUPB075
Advanced algorithms for linear accelerator design and operation
484
In this paper, we investigate the usage of advanced algorithms adapted for optimizing the design and operation of different linear accelerators (LINACs), notably the superconducting linac ALPI at INFN-LNL and the ANTHEM BNCT facility to be constructed at Caserta, Italy. Utilizing various intelligent algorithms and machine learning techniques such as Bayesian optimization, genetic algorithms, particle swarm optimization, and surrogate modeling with artificial neural networks, we aim to enhance the design efficiency, operational reliability and adaptability of linear accelerators. Through simulations and case studies, we demonstrate the effectiveness and practical implications of these algorithms for optimizing LINAC performances across diverse applications.
Paper: TUPB075
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB075
About: Received: 14 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 28 Aug 2024 — Issue date: 23 Oct 2024
TUPB076
Beam transient studies for the JAEA-ADS LEBT
488
The Japan Atomic Energy Agency (JAEA) is designing a 30-MW CW proton linear accelerator (linac) for nuclear waste transmutation. Space-charge is the primary challenge in achieving low losses and high beam quality for high-power accelerators, especially at low energy levels where space-charge forces are greater. To counteract the space-charge effects, the low-energy beam transport (LEBT) uses a magnetostatic design to enable the neutralization of the beam charge, the so-called space charge compensation. The neutralization is an accumulation process that reaches a charge balance between the main beam and the opposite ionized particles. However, this equilibrium is destroyed by the chopper system used during beam ramping. During those transient regimes, the beam optics conditions are not optimal for the beam, producing considerable degradation that can end in serious damage to the accelerator. Thus, analysis of beam behavior at these periods is essential to develop a robust design and an efficient operation of the JAEA-ADS linac. This study presents the beam dynamics of neutralization build-up and chopper operation for the JAEA-ADS LEBT.
Paper: TUPB076
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB076
About: Received: 16 Aug 2024 — Revised: 27 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB077
The LINACs simulation framework
492
LINACs is a simulation framework for designing optics and beam dynamics of charged particles in particle accelerators. LINACs is an open-source software that enables the user complete control over all design and simulation parameters of RFQs. This includes beam-driven design, fully 3D simulation using precise quadrupolar symmetry, and rigorous Poisson solution for external and space charge fields. The code can handle simultaneous particle beams with analytical input distributions and allows input beam scans. The software offers a relatively short running time and provides extensive analysis techniques. This work provides a historical overview of the code, presents results from RFQ models, and discusses future developments.
Paper: TUPB077
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB077
About: Received: 16 Aug 2024 — Revised: 26 Aug 2024 — Accepted: 26 Aug 2024 — Issue date: 23 Oct 2024
TUPB078
Progress of the spoke cavity prototyping for the JAEA-ADS linac
496
The Japan Atomic Energy Agency (JAEA) has been proposing an accelerator-driven nuclear transmutation system (ADS) as a future nuclear system. In preparation for the actual design of the CW proton linac for the JAEA-ADS, we are now prototyping a low-beta (around 0.2) single-spoke cavity. The cavity fabrication started in 2020. Most of the cavity parts were shaped in fiscal year 2020 by press-forming and machining. In 2021, we started welding the shaped cavity parts together. By preliminarily investigating the optimum welding conditions using mock-up test pieces, each cavity part was joined together with smooth welding beads. So far, we have fabricated the body section and the two end-plate sections. By measuring the resonant frequency of the temporarily assembled cavity, it was confirmed that there were no significant problems with the cavity fabrication.
Paper: TUPB078
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB078
About: Received: 14 Aug 2024 — Revised: 29 Aug 2024 — Accepted: 29 Aug 2024 — Issue date: 23 Oct 2024
CEBAF operations, performance, and future plans
CEBAF has been providing electron beams for nuclear physics experiments for almost 30 years. Ten years ago, it went through a major upgrade to increase the beam energy from 6 to 12 GeV. This paper summarizes the status of the CEBAF 12 GeV operations. We discuss the performance of the machine, limitations, and performance enhancements. Also, the paper discusses future upgrade plans.
Injector status in NICA project
Nuclotron based Ion Collider fAcility (NICA) project is being realized in JINR, Dubna.The main goal of new collider facility is investigations of the heavy ions collisions with center-of-mass energy up to 11 GeV/u.Two injectors will provide the beams as for colliding and for extracted beam experiments.One of them is Heavy Ions Linear Accelerator (HILAC) intended to inject heavy ions produced with the ESIS ion source into accumulating synchrotron Booster following by Nuclotron. Another one is Light Ions Linear accelerator has to inject light polarized ions produced by source of polarized ions SPI directly to Nuclotron. Status of both injectors and accelerating runs are presented.
TUPB081
New 3-MeV RFQ design and fabrication for KOMAC
499
Since the second half of 2013, Korea Multi-purpose Accelerator Complex (KOMAC) has been supporting user beam service by using a 100-MeV proton linac. As the operation period of the proton accelerator exceeds 10 years and the cumulative operating time surpasses 33,000 hours, we judge that it is an opportune time to establish a long-term plan to prepare for the aging of the accelerator. To replace the currently operating RFQ, which shows degradation in performance (especially the reduced beam transmission), we designed a new RFQ with some modifications. We removed a resonant coupling structure, located in the middle of the old RFQ, for simple design and easy tuning. In addition, we increased the length of RFQ from 3,266 mm to 3,537 mm for better beam transmission efficiency in high current mode. Error study on the new structure showed that the design is robust to the various error sources. The details of the RFQ design along with fabrication status will be given in this presentation.
Paper: TUPB081
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB081
About: Received: 20 Aug 2024 — Revised: 04 Sep 2024 — Accepted: 11 Sep 2024 — Issue date: 23 Oct 2024
Development status of solid-state switches for thyratron replacement
This paper describes the development status of solid-state switches for thyratron replacement. A 50 kV, 10 kA solid-state switch has been developed based on IGBT series stacking technologies, including voltage balancing and synchronous driving. The proposed stacking structure minimizes internal inductance and provides a fast current rising time of up to 7 kA/us. Additionally, the developed switch has achieved low jitter of less than 1 ns. Owing to the modular structure of developed switch, it was implemented with various specifications for different applications. By implementing a 15 kV, 10 kA, 10 Hz switch, the solid-state kicker modulator was developed and successfully demonstrated in at Pohang Accelerator Laboratory(PAL). Furthermore, a 20 kV, 2 kA, 250 Hz switch has also been implemented and is currently used to operate a 6-MeV C-band electron linear accelerator (LINAC) at the Dongnam Institute of Radiological & Medical Sciences (DIRAMS). Additionally, a 50 kV, 10 kA switch is now ready for the klystron modulator. By sharing the development status of solid-state switches in Korea, it is hopefully expected to share our developed switch and technology and have the chance to discover its shortcomings together, so that we can work on improving them collaboratively.
Energy upgrade options of KOMAC 100 MeV linac
An energy upgrade of the existing 100 MeV proton linear accelerator is considered at Korea Multi-purpose Accelerator Complex (KOMAC). 1 GeV proton linac for spallation neutron source is planned through 200 MeV linac upgrade as a near term project. Two options are considered for 200 MeV linac structure, one is a superconducting linac based on the half-wave resonator (HWR) and the other is a normal conducting linac based on separate drift tube linac (SDTL). In this paper, two options are presented and compared.
TUPB084
Preliminary measurement of 4D beam phase space distribution using a slit emittance meter system
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Conventional beam diagnostics generally measure 2D projections of the phase space in x-x', y-y' and z-z'. To estimate a 6D beam phase space distribution for simulations, these 2D projections are multiplied without any correlations between them. It is true only if their degrees of freedom are independent. Recent studies show that there exists correlation across conjugate pairs. This correlation can affect beam dynamics and cause beam loss. In our study, we sought to measure 4D beam phase space distribution with possible correlations across conjugate pairs. For this purpose, we used a direct method of measuring the 4D phase space distribution using slits. A set of 4 slits is used to slice the beam into a specific volume of the 4D phase space, and the charge inside each volume is measured. KOMAC has a test bench called BTS (Beam Test Stand) which consists of a microwave ion source, LEBT, a 200 MHz RFQ and two beamlines. At one of the beamlines, we have just installed slit emittance meter system to measure 4D beam phase space distribution. This paper presents design and fabrication of a slit emittance meter system and shows preliminary experimental results thereof.
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUAA010
About: Received: 20 Aug 2024 — Revised: 26 Aug 2024 — Accepted: 26 Aug 2024 — Issue date: 23 Oct 2024
Design and optimization of a compact electron linac for iIndustrial applications using Bayesian optimization
This work presents the design and optimization of a compact electron linear accelerator capable of achieving an energy less than 5 MeV, specifically tailored for industrial applications. The innovative design incorporates a Superconducting RF photoinjector. A significant focus has been placed on optimizing the geometry of the SRF photoinjector cavity to accelerate high-charge and small-emittance electron beams. Utilizing Bayesian optimization, the linac configuration has been refined to enhance both the geometry and performance of the photoinjector, leading to improved beam quality and energy efficiency. Our findings demonstrate that the optimized linac meets the stringent requirements of industrial applications and significantly enhances beam dynamics and operational stability.
TUPB087
Evaluating beam neutralization and transport dynamics in laser-driven ion accelerators
502
We are developing a laser-driven ion accelerator aimed at downsizing heavy ion therapy devices. The ion beam produced by this accelerator exhibits low emittance(transverse emittance is approximately 10-3 π mm-mrad and longitudinal emittance is approximately 10-5 eV・s), with a very short pulse width (about picoseconds). As a result, the peak current reaches the kA level. However, explosive beam divergence is mitigated by co-moving electrons that neutralize the beam’s space charge in the high-density region immediately following acceleration. This study involved acceleration calculations and transport calculations of proton beams over 40 cm (up to just before the quadrupole magnet) using the Par-ticle-in-Cell (PIC) simulation code to assess the ion beam's space charge neutralization characteristics. This presentation will show the results of our simulations using the PIC code, which analyzed the degree of neutralization by co-moving electrons. The results suggest the potential for optimizing target thickness when utilizing of specific energy ions produced by laser-driven ion acceleration. The results suggest confirmation of the space charge neutralization phenomenon in the laser-accelerated ion beam.
Paper: TUPB087
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB087
About: Received: 26 Aug 2024 — Revised: 23 Sep 2024 — Accepted: 23 Sep 2024 — Issue date: 23 Oct 2024
TUPB089
Analysis of redundancy design and reliability estimation of 60 kW CW RF HPA for ALS-U project at LBNL
506
The 60 kW CW AR RF HPA is critical major equipment in new RF system for ALS-U project at LBNL and so it has been designed & built with a modular redundant topology having large array of 96 RF final PA modules (each delivering ~ 700 W RF output) that are combined in parallel, and large 30 DC PS modules (each ~ 5 kW DC power) operating in parallel for achieving very high reliability (MTBF ~ 135,000 hours) & availability (~ 99.997 %) of RF HPA which is essential for continuous 24/7 beam operations. The redundancy design to modules failures is such that in the event upto 10% failures of RF PA modules and simultaneously upto 15 % failures of DC PS modules the HPA still can generate minimum 48 kW CW RF output that is needed for full beam power and so RF power headroom of 12 kW is built in. The operating power levels & temperatures of all components in HPA are well below to their maximum ratings for high reliability. The MBTF values of subsystems in HPA has been estimated based on components with high failures rates. The reliability probabilities having exponential distribution parameterized on failure rate were determined and the binomial distribution used for modules having redundancy. This paper presents such redundancy design analysis of HPA to such modules failures to achieve such minimum output power. Also the Availability (~99.997%) and the Reliability (MTBF ~ 135,000 hours) Estimation analysis of the overall HPA with such redundancy to modules failures is presented.
Paper: TUPB089
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB089
About: Received: 18 Aug 2024 — Revised: 07 Sep 2024 — Accepted: 07 Sep 2024 — Issue date: 23 Oct 2024
TUPB090
IMPACTX space charge modeling of high intensity linacs with mesh refinement
509
High intensity linacs pose a challenge to efficient beam dynamics modeling due to the high numerical resolution required for accurate prediction of beam halo and losses. The code ImpactX represents the next generation of the particle-in-cell code IMPACT-Z, featuring s-based symplectic tracking with 3D space charge, parallelism with GPU acceleration, adaptive mesh-refinement, modernized language features, and automated testing. While the code contains features that support the modeling of both linear and circular accelerators, we describe recent code development relevant to the modeling of high-intensity linacs (such as beam transport for the Fermilab PIP-II linac), with a focus on space charge benchmarking and the impact of novel code capabilities such as mesh refinement.
Paper: TUPB090
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB090
About: Received: 20 Aug 2024 — Revised: 17 Sep 2024 — Accepted: 17 Sep 2024 — Issue date: 23 Oct 2024
TUPB091
On the life expectance of high-power CW magnetrons for SRF accelerators
513
Modern CW or pulsed Superconducting RF (SRF) accelerators require efficient RF sources controllable in phase and power with a reduced cost. Therefore, utilization of the high-power CW magnetrons as RF sources in SRF accelerator projects was proposed in a number of works. But typically, the CW magnetrons are designed as RF sources for industrial heating, and the lifetime of the tubes is not the first priority as it is required for high-energy accelerators. The high-power industrial CW magnetrons use the cathodes made of pure tungsten. The emission properties of the tungsten cathodes are not deteriorated much by electron and ion bombardments, but the latter causes sputtering of the cathode in the magnetron crossed fields. The sputtered cathode material covers the magnetron interior. That lead to sparks and discharges limiting magnetrons lifetime. We considered an analysis of magnetron failure modes vs. output power, developed a model of ionization of the residual gas in the magnetrons interaction space and simulated the spattering of the cathode in 100 kW CW magnetrons to estimate the life expectancy. Basing on results we proposed ways to increase the CW magnetrons longevity for SRF accelerators.
Paper: TUPB091
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB091
About: Received: 23 Aug 2024 — Revised: 14 Sep 2024 — Accepted: 14 Sep 2024 — Issue date: 23 Oct 2024
TUPB092
On forced RF generation of CW magnetrons for SRF accelerators
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CW magnetrons, initially developed for industrial RF heaters, were suggested to power RF cavities of superconducting accelerators due to their higher efficiency and lower cost than traditionally used klystrons, IOTs or solid-state amplifiers. RF amplifiers driven by a master oscillator serve as coherent RF sources. CW magnetrons are regenerative RF generators with a huge regenerative gain. This causes regenerative instability with a large noise when a magnetron operates with the anode voltage above the threshold of self-excitation. Traditionally for stabilization of magnetrons is used injection locking by a quite small signal. Then the magnetron except the injection locked oscillations may generate noise. This may preclude use of standard CW magnetrons in some SRF accelerators. Recently we developed briefly described below a mode for forced RF generation of CW magnetrons when the magnetron startup is provided by the injected forcing signal and the regenerative noise is suppressed. The mode is most suitable for powering high Q-factor SRF cavities.
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUAA009
About: Received: 23 Aug 2024 — Revised: 07 Sep 2024 — Accepted: 07 Sep 2024 — Issue date: 23 Oct 2024
Compact CW 1-15 MeV 10-100 kW Electron Accelerators
Muons, Inc is developing Compact Electron Linacs to meet the increasing demand for modern solutions to address diverse applications including Co60 replacement, isotope production, industrial uses, and sterilization of medical devices, food and water. The designs employ the Muons, Inc. – Richardson Electronics Limited 1497 MHz magnetrons that were designed, built, and being tested to replace the klystrons at the Jefferson Lab CEBAF superconducting RF recirculating Linac. The key features of the new designs are a single Linac that is powered by a high efficiency magnetron and permanent magnet systems that recirculate the beam through the Linac to enable compactness and efficiency. Future directions include integrating Nb3Sn-based superconducting cavities with cryocoolers for higher beam energies and scalability. We believe that these Compact Electron Linacs offer a cost-effective, versatile solution to revolutionize electron beam applications across industries.
Decrease of H- ion beam emittance with increased frequency in RF discharge
In recent years significant progress in increase intensity of H- beam in RF surface plasma sources. H- beam intensity in RF SPS of J-Parc was increased up to 145 mA.Intensity of H- in RF SPS of SNS was increased up to 110 mA, which is enough for European spallation source storage ring. Reduction of beamlet divergence in RF negative ion source for NBI is one of high-priority targets to be solved. Minimum beamlet 1/e divergence in RF H- ion sources with low RF frequency (2-4 MHz), much higher than in ion sources with DC discharge. - min. q div(FA) ≤ 5 mrad (obtained at NIFS and QST with DC discharge) - min. q div(RF) ≤ 12 mrad (obtained at IPP and RFX RF ion sources) - max. q div(ITER NB) < 7 mrad.In RF H- ion sources In H- ion sources with low RF frequency (2-4 MHz) is observed significant modulation of beam intensity at first and second harmonic. This should lead for vibration of the meniscus shape and increase angle spread. Work with higher RF frequency (13,56 MHz) should decrease intensity modulation and decrease emittance to two times. RF SPS with a frequency 13.56 MHz could be a good solution for a European spallation source with a storage ring.
TUPB095
Development of phase locked oscillator FEL for high repetition mid-infrared frequency combs
516
The mid-Infrared region (2-5 um) is currently a frontier of laser science with short durations, where many molecular absorbing spectrums exist. The oscillator free electron lasers have advantages against solid-state laser systems, that include the fundamental generations of high-intensity mid-IR pulses with femto-seconds scale short duration, continuous variations of the central wavelength, and the high-repetitions of pulses due to RF accelerations of electron bunches. Especially, the coexistence of high-intensities and high-repetitions at GHz scales is important for the development of mid-IR frequency combs that may open up a new direction of molecule nonlinear reactions. In this presentation, we report on the importance of phase-locking between FEL pulses that grow up independently due to shot noises for the mid-IR frequency combs, and the states of development of a test phase-locking system, and introduce possible applications of the mid-IR frequency combs.
Paper: TUPB095
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB095
About: Received: 20 Aug 2024 — Revised: 26 Aug 2024 — Accepted: 27 Aug 2024 — Issue date: 23 Oct 2024
TUPB096
First-principle beam-dynamics simulations of alpha magnets for bunch compression of bright beams
519
Producing bright electron beams is crucial for coherent light sources, where increasing the peak current is typically accomplished through bunch compression in magnetic chicanes. Alpha magnets, with their unique phase-space manipulation capabilities, have emerged as an attractive choice for compressing sub-10 MeV electron beams generated by radio frequency photoinjectors. This paper presents detailed numerical modeling of the beam dynamics of high-charge, bright bunches undergoing compression within an alpha magnet. The model incorporates space-charge effects and coherent synchrotron radiation, providing a comprehensive understanding of the complex interactions and behaviors of the electron beams during the compression process.
Paper: TUPB096
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB096
About: Received: 06 Sep 2024 — Revised: 24 Sep 2024 — Accepted: 27 Sep 2024 — Issue date: 23 Oct 2024
A significant step towards robust table-top XUV-FEL
Our recent experiments achieved EUV range undulator radiation amplification based on the stable electron beam obtained from laser wakefield accelerator (LWFA). The experiments were conducted on the LWFA platform in RIKEN Spring-8 center supported by ImPACT and JST MIRAI project. By optimizing the driving laser system and gas target, the reproducibility of the acceleration process has been significantly improved. The electron beam with central energy of 380 MeV can be steadily generated with an energy spread less than 1% and a pointing instability less than 0.5 mrad in RMS. The typical electron beams with an average charge of 15 pC were focused by three permanent magnetic quadrupoles and four electromagnetic quadrupoles to the undulators located 6.5 meters downstream to the target. The amplified undulator radiation centered at 45 nm has been detected and the maximum gain of the radiation power is approximately 14-fold. Such the demonstration is not only the first time in Japan but also one of the world leading results. Based on our current achievements, we anticipate a navigable road from EUV to X-ray wavelengths.
TUPB099
Engineering design of 402 MHz normal conducting coaxial window
522
RadiaBeam is fabricating a novel RF vacuum window for use with the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The window features a coaxial ceramic window between two waveguides, brazed as a single assembly. Unlike traditional pillbox window designs, this approach allows the outer diameter of the ceramic to decrease and the added benefit of water cooling the inner diameter of the ceramic. This paper covers the engineering design including details of key features, the impact of the unique RF design on manufacturability, and mechanical simulations. A status update on the fabrication is also provided with emphasis on the ceramic TiN coating and brazing process.
Paper: TUPB099
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB099
About: Received: 20 Aug 2024 — Revised: 21 Sep 2024 — Accepted: 21 Sep 2024 — Issue date: 23 Oct 2024
TUPB100
Design of a 25 kW fundamental power coupler for conduction cooled Nb3Sn industrial linac
526
RadiaBeam is designing a 915 MHz, 25 kW CW Fundamental Power Coupler (FPC) to power a Nb3Sn coated superconducting radio-frequency (SRF) cavity. Unlike traditional FPCs for SRF cavities, the device relies only on conductive cooling by cryocoolers. The baseline design was adapted from the liquid helium cooled 805 MHz SNS FPC with the notable addition of an intermediate 50 K thermal intercept and associated RF shield. Engineering design details to address the thermomechanical, manufacturability, and structural challenges will be presented. Particular emphasis will be placed on static and dynamic heat load management along with finite element analysis to validate mechanical stability. Additionally, initial manufacturing studies of the coaxial window brazing will be discussed along with full device manufacturing and integration plans.
Paper: TUPB100
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUPB100
About: Received: 20 Aug 2024 — Revised: 13 Sep 2024 — Accepted: 13 Sep 2024 — Issue date: 23 Oct 2024
S-band RF pulse compressor for high-gradient carbon therapy linac
Novel hadron radiotherapy accelerator-based systems require a fast-imaging capability, synchronized with the hadron beam, to allow positioning and treating the tumor practically at the same time. Such systems must operate at high repetition rates (~1,000 pulses per second) to provide reasonable treatment times. Currently, Argonne and RadiaBeam are collaborating on a high-gradient carbon therapy linac project, ACCIL, based on 40 MV/m S-band accelerating structures. In order to operate at repetition rates, the structures must be powered by the 5 MW klystrons. However, high gradient operation requires quadruple of this power. Therefore, we developed a compact S-band RF pulse compressor based on an E-plane polarizer and a spherical cavity operating at 2856 MHz. It incorporates features such as a cut-off circular port opposite to the circular waveguide to facilitate vacuum pumping, along with cooling channels distributed around the cavity and polarizer to manage the thermal loads. The RF pulse compressor is expected to generate a flat 18 MW 300 ns flat-top RF pulse with a 62% efficiency. We will present the mechanical design and fabrication status of the device.
Test results of an improved multi-dimensional Bunch Shape Monitor
RadiaBeam has developed and built a Bunch Shape Monitor (BSM) prototype for measuring the longitudinal bunch distribution in hadron linear accelerators. The device has been designed to operate at 402.5 MHz and it incorporates three main innovations to improve its performance: a focusing field between the target wire and the entrance slit for better collection efficiency, a novel design of the RF deflector to enhance beam linearity, and a moving mechanism that allows shifting both the wire and deflector cavity to enable transverse profile measurements. The BSM prototype has been installed at the Beam Test Facility at the Spallation Neutron Source and is currently under testing for characterization. In this paper, we will present the design, fabrication, and first test results of the BSM prototype.
TUPB103
Evaluation of wakefield mitigation for upgrading the ATF final focus beamline
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The KEK-ATF (Accelerator Test Facility) is an R&D facility for the final focus system to develop the nanometer beam technology required for the International Linear Collider. ATF is the best research environment for the study of wakefield effects on the nanometer small beam. The vertical beam size growth as a function of the bunch intensity was observed at the virtual interaction point (IP), which is mainly caused by wakefield. The evaluation results of wakefield effects show that wakefield sources installed in the high beta function section of the ATF final focus (FF) beamline, such as cavity BPM and vacuum flange, have strong effects on the small beam. We will upgrade the ATF-FF beamline to mitigate wakefield effects on the small beam. To confirm mitigation effects, internal shield parts were inserted into the vacuum flange, which is one of the strong wakefield source. The mitigation effect is evaluated based on the orbit response and IP vertical beam size. This report shows the evaluation results of the mitigation of the wakefild effects and the progress and current status of the work to upgrade the beamlines to reduce the effects of the wakefield.
DOI: reference for this paper: 10.18429/JACoW-LINAC2024-TUAA007
About: Received: 20 Aug 2024 — Revised: 20 Sep 2024 — Accepted: 20 Sep 2024 — Issue date: 23 Oct 2024
2D material integration with cathodes for accelerators
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The studies commissioned by the U.S. Department of Energy have repeatedly identified electron sources as critical risk area for development of future accelerators including LINAC. To address this challenge, we initiated an effort of integrating 2D materials with cathodes in 2013. The aim was to protect environmentally susceptible but high performing alkali antimonide semiconductor photocathodes with atomically thin two-dimensional (2D) materials such as graphene. The concept behind the effort was to decouple the competing mechanisms of high quantum efficiency and long lifetime. Our team succeeded in demonstration of the concept on metal photocathodes in 2017, won R&D 100 Award in 2019 and recently succeeded in demonstrating graphene encapsulated potassium caesium antimonide photocathodes to remain active in 3 orders of magnitude higher pressure compared to non-protected counterpart. The breadth of possibilities of 2D material integration with cathodes for accelerators will also be covered based on our findings during past decade such as graphene as reusable substrates for alkali antimonide photocathodes, prevention of alloying between substrate material and alkali antimonide photocathode by graphene coating, demonstration of no detectable emittance increase on metal single crystal photocathodes by graphene coating, and work function lowering of thermionic- and photo-cathodes by monolayer hexagonal boron nitride coating.