Pub Date : 2024-04-05DOI: 10.1103/physrevaccelbeams.27.040101
Ali M. Almomani, Ulrich Ratzinger
The development of cross-bar H-type cavities (CH-DTL, mode) is ongoing to improve the technology of this attractive type of drift tube linac (DTL). In comparison with the conventional DTL, the H-type cavities can reach a higher effective field gradient and are competitive in shunt impedance at an energy range up to 100 A MeV. H-mode DTL’s profit in shunt impedance additionally when applying the KONUS beam dynamics. They are in use at research laboratories as well as at hospitals. This paper describes a new concept to approach the zero mode in CH-type cavities, by extending the cavity diameter at the tank ends in combination with tilted drift tube stems. RFQs of the four-vane type are operated as well in the mode and the strategy for voltage flattening can be partly applied there too if conventional vane undercuts are causing problems. Up to around 35 MeV, it is attractive to integrate one or more triplet lenses into each cavity, as one KONUS section is relatively short and would not exploit the full rf power of 3 MW klystrons which are available above 300 MHz. Such a cavity is denoted as a coupled CH-cavity CCH. Three possible arrangements of those internal triplet lenses are discussed and are compared to each other. The operating modes as well as higher modes are then compared with a lens-free CH cavity, where the lens position was filled by ordinary drift tubes. As a result, it is shown that the rf behavior and resonance frequency for the higher harmonics of the frequency band are very similar for all four investigated arrays. This means, that the tuning behavior of the CCH cavity can be simply deduced from the lens-free CH cavity by replacing an even number of ordinary drift tubes () with a lens-containing drift tube with adequate length and large outer diameter. This large drift tube itself oscillates like an Alvarez-type drift tube. rf simulations on a 30-gap CH cavity show that the reduction in shunt impedance is about 10% when installing a lens with length 2 beta lambda.
{"title":"Field flattening concepts for linac cavities of the cross-barHtype","authors":"Ali M. Almomani, Ulrich Ratzinger","doi":"10.1103/physrevaccelbeams.27.040101","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.040101","url":null,"abstract":"The development of cross-bar H-type cavities (CH-DTL, <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>H</mi><mn>21</mn></msub></mrow></math> mode) is ongoing to improve the technology of this attractive type of drift tube linac (DTL). In comparison with the conventional DTL, the H-type cavities can reach a higher effective field gradient and are competitive in shunt impedance at an energy range up to 100 A MeV. H-mode DTL’s profit in shunt impedance additionally when applying the KONUS beam dynamics. They are in use at research laboratories as well as at hospitals. This paper describes a new concept to approach the zero mode in CH-type cavities, by extending the cavity diameter at the tank ends in combination with tilted drift tube stems. RFQs of the four-vane type are operated as well in the <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">H</mi><mn>210</mn></msub></mrow></math> mode and the strategy for voltage flattening can be partly applied there too if conventional vane undercuts are causing problems. Up to around 35 MeV, it is attractive to integrate one or more triplet lenses into each cavity, as one KONUS section is relatively short and would not exploit the full rf power of 3 MW klystrons which are available above 300 MHz. Such a cavity is denoted as a coupled CH-cavity CCH. Three possible arrangements of those internal triplet lenses are discussed and are compared to each other. The operating modes as well as higher modes are then compared with a lens-free CH cavity, where the lens position was filled by ordinary drift tubes. As a result, it is shown that the rf behavior and resonance frequency for the higher harmonics of the frequency band are very similar for all four investigated arrays. This means, that the tuning behavior of the CCH cavity can be simply deduced from the lens-free CH cavity by replacing an even number of ordinary drift tubes (<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">n</mi><mi>β</mi><mi>λ</mi></mrow></math>) with a lens-containing drift tube with adequate length and large outer diameter. This large drift tube itself oscillates like an Alvarez-type drift tube. rf simulations on a 30-gap CH cavity show that the reduction in shunt impedance is about 10% when installing a lens with length 2 beta lambda.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"15 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140599561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-05DOI: 10.1103/physrevaccelbeams.27.044401
A. Al Marzouk, B. Erdélyi
The first section of any coherent electron cooling (CeC) system is the modulator, where the density of the electron beam is modulated by the copropagating ion beam. This density modulation is a result of Coulomb collisions between the individual particles of the two beams. The pairwise, stochastic part of the interactions impacts the overall performance of the CeC process. We present the first simulations of the density modulations of the electron beams from a collisional picture of the dynamics, considering the proof-of-principle CeC experiments at Brookhaven National Laboratory. These simulations were performed using PHAD, which is the first efficient, large-scale collisional numerical method in beam physics that we have previously developed and benchmarked. Realistic beam distributions and external fields have been optimized to provide strong modulation signals necessary for variations of coherent electron cooling systems. Cooling performance limits and potential collisionless simulation pitfalls are pointed out.
相干电子冷却（CeC）系统的第一部分是调制器，在这里电子束的密度受到共传播离子束的调制。这种密度调制是两束电子束中单个粒子之间库仑碰撞的结果。相互作用的成对、随机部分会影响 CeC 过程的整体性能。考虑到布鲁克海文国家实验室（Brookhaven National Laboratory）的原理验证 CeC 实验，我们首次从碰撞动力学的角度模拟了电子束的密度调制。这些模拟是使用 PHAD 进行的，PHAD 是我们之前开发和基准测试的首个高效、大规模碰撞数值方法。对真实的束流分布和外部场进行了优化，以提供相干电子冷却系统变化所需的强调制信号。指出了冷却性能的限制和潜在的无碰撞模拟陷阱。
{"title":"Collisional simulations of the modulator section in coherent electron cooling","authors":"A. Al Marzouk, B. Erdélyi","doi":"10.1103/physrevaccelbeams.27.044401","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.044401","url":null,"abstract":"The first section of any coherent electron cooling (CeC) system is the modulator, where the density of the electron beam is modulated by the copropagating ion beam. This density modulation is a result of Coulomb collisions between the individual particles of the two beams. The pairwise, stochastic part of the interactions impacts the overall performance of the CeC process. We present the first simulations of the density modulations of the electron beams from a collisional picture of the dynamics, considering the proof-of-principle CeC experiments at Brookhaven National Laboratory. These simulations were performed using PHAD, which is the first efficient, large-scale collisional numerical method in beam physics that we have previously developed and benchmarked. Realistic beam distributions and external fields have been optimized to provide strong modulation signals necessary for variations of coherent electron cooling systems. Cooling performance limits and potential collisionless simulation pitfalls are pointed out.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"79 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140598913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-03DOI: 10.1103/physrevaccelbeams.27.041602
E. W. Snedden, D. Angal-Kalinin, A. R. Bainbridge, A. D. Brynes, S. R. Buckley, D. J. Dunning, J. R. Henderson, J. K. Jones, K. J. Middleman, T. J. Overton, T. H. Pacey, A. E. Pollard, Y. M. Saveliev, B. J. A. Shepherd, P. H. Williams, M. I. Colling, B. D. Fell, G. Marshall
The compact linear accelerator for research and applications (CLARA) is a 250 MeV ultrabright electron beam test facility at STFC Daresbury Laboratory. A user beamline has been designed to maximize the exploitation of CLARA in a variety of fields, including novel acceleration and new modalities of radiotherapy. In this paper, we present the specification and design of this beamline for full energy beam exploitation. We outline the key elements that will provide users access to ultrashort, low emittance electron bunches in two large experiment chambers. The results of start-to-end simulations are reported that verify the expected beam parameters delivered to these chambers. Key technical systems are detailed, including those which facilitate a combination of electron bunches with high-power laser pulses.
{"title":"Specification and design for full energy beam exploitation of the compact linear accelerator for research and applications","authors":"E. W. Snedden, D. Angal-Kalinin, A. R. Bainbridge, A. D. Brynes, S. R. Buckley, D. J. Dunning, J. R. Henderson, J. K. Jones, K. J. Middleman, T. J. Overton, T. H. Pacey, A. E. Pollard, Y. M. Saveliev, B. J. A. Shepherd, P. H. Williams, M. I. Colling, B. D. Fell, G. Marshall","doi":"10.1103/physrevaccelbeams.27.041602","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.041602","url":null,"abstract":"The compact linear accelerator for research and applications (CLARA) is a 250 MeV ultrabright electron beam test facility at STFC Daresbury Laboratory. A user beamline has been designed to maximize the exploitation of CLARA in a variety of fields, including novel acceleration and new modalities of radiotherapy. In this paper, we present the specification and design of this beamline for full energy beam exploitation. We outline the key elements that will provide users access to ultrashort, low emittance electron bunches in two large experiment chambers. The results of start-to-end simulations are reported that verify the expected beam parameters delivered to these chambers. Key technical systems are detailed, including those which facilitate a combination of electron bunches with high-power laser pulses.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"14 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140598943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-02DOI: 10.1103/physrevaccelbeams.27.041601
A. Gonzalez, A. Plastun, P. N. Ostroumov
An rf chopper system is being designed for the ReAccelerator (ReA) linac at the Facility for Rare Isotope Beams at Michigan State University. The 80.5 MHz ReA radio-frequency quadrupole accelerates prebunched 16.1 MHz beams, producing four satellite bunches for every main bunch. The chopper system includes an rf deflector that kicks every bunch vertically to spatially separate main and satellite bunches. A constant magnetic field superimposed with the chopper electric field biases the beam trajectory to ensure the high-intensity bunches do not experience a net deflection and are injected straight to the ReA6 cryomodule or sent for experiments. The kicked bunches are low in intensity and will be sent to a beam dump, resulting in a clean 16.1 MHz beam structure, which allows for a reliable time-of-flight separation of the isotopes.
{"title":"rf chopper for prebunched radioactive ion beams","authors":"A. Gonzalez, A. Plastun, P. N. Ostroumov","doi":"10.1103/physrevaccelbeams.27.041601","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.041601","url":null,"abstract":"An rf chopper system is being designed for the ReAccelerator (ReA) linac at the Facility for Rare Isotope Beams at Michigan State University. The 80.5 MHz ReA radio-frequency quadrupole accelerates prebunched 16.1 MHz beams, producing four satellite bunches for every main bunch. The chopper system includes an rf deflector that kicks every bunch vertically to spatially separate main and satellite bunches. A constant magnetic field superimposed with the chopper electric field biases the beam trajectory to ensure the high-intensity bunches do not experience a net deflection and are injected straight to the ReA6 cryomodule or sent for experiments. The kicked bunches are low in intensity and will be sent to a beam dump, resulting in a clean 16.1 MHz beam structure, which allows for a reliable time-of-flight separation of the isotopes.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"47 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140602105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-26DOI: 10.1103/physrevaccelbeams.27.031603
S. A. Bogaczet al.
Powerful ERL for experiments (PERLE) is a novel energy recovery linac (ERL) test facility [1], designed to validate choices for a 50 GeV ERL foreseen in the design of the Large Hadron Electron Collider and the Future Circular Collider and to host dedicated nuclear and particle physics experiments. Its main goal is to demonstrate the high current, continuous wave, multipass operation with superconducting cavities at 802 MHz. With very high beam power (10 MW), PERLE offers an opportunity for controllable study of every beam dynamic effect of interest in the next generation of ERLs and becomes a “stepping stone” between the present state-of-the-art 1 MW ERLs and the future 100 MW scale applications.
{"title":"Beam dynamics driven design of powerful energy recovery linac for experiments","authors":"S. A. Bogaczet al.","doi":"10.1103/physrevaccelbeams.27.031603","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.031603","url":null,"abstract":"Powerful ERL for experiments (PERLE) is a novel energy recovery linac (ERL) test facility [1], designed to validate choices for a 50 GeV ERL foreseen in the design of the Large Hadron Electron Collider and the Future Circular Collider and to host dedicated nuclear and particle physics experiments. Its main goal is to demonstrate the high current, continuous wave, multipass operation with superconducting cavities at 802 MHz. With very high beam power (10 MW), PERLE offers an opportunity for controllable study of every beam dynamic effect of interest in the next generation of ERLs and becomes a “stepping stone” between the present state-of-the-art 1 MW ERLs and the future 100 MW scale applications.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"45 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140302503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-21DOI: 10.1103/physrevaccelbeams.27.032001
Volker Ziemann
We describe a method that measures the unloaded quality factor , the external quality factor , and the cavity detuning with a recursive least-squares algorithm. It combines a large number of consecutive measurements to successively improve an estimate of fit parameters that asymptotically converges to the “real” values. Exploiting the large amount of data acquired by a digital low-level radio frequency system permits us to reach this asymptotic regime in a moderate time frame of seconds to minutes. Simulations show that the method works both for critically coupled and overcoupled cavities. A new calibration method addresses very tight tolerances of the method on system parameters.
我们介绍了一种用递归最小二乘算法测量空载品质因数 Q0、外部品质因数 QE 和腔体失谐 Δω 的方法。该算法结合大量连续测量结果，连续改进拟合参数的估计值，使其渐近收敛到 "真实 "值。利用数字低频射频系统获取的大量数据，我们可以在几秒到几分钟的中等时间内达到这一渐近机制。模拟结果表明，该方法适用于临界耦合和过耦合腔体。一种新的校准方法解决了该方法对系统参数的极小公差问题。
{"title":"New method to measure the unloaded quality factor of superconducting cavities","authors":"Volker Ziemann","doi":"10.1103/physrevaccelbeams.27.032001","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.032001","url":null,"abstract":"We describe a method that measures the unloaded quality factor <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>Q</mi><mn>0</mn></msub></math>, the external quality factor <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>Q</mi><mi>E</mi></msub></math>, and the cavity detuning <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi mathvariant=\"normal\">Δ</mi><mi>ω</mi></math> with a recursive least-squares algorithm. It combines a large number of consecutive measurements to successively improve an estimate of fit parameters that asymptotically converges to the “real” values. Exploiting the large amount of data acquired by a digital low-level radio frequency system permits us to reach this asymptotic regime in a moderate time frame of seconds to minutes. Simulations show that the method works both for critically coupled and overcoupled cavities. A new calibration method addresses very tight tolerances of the method on system parameters.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"164 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140203596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-20DOI: 10.1103/physrevaccelbeams.27.031602
C. Xiao, L. Groening
Imposing angular momentum to a particle beam increases its stability against perturbations from space charge [Y.-L. Cheon et al., Phys. Rev. Accel. Beams25, 064002 (2022)]. In order to fully explore this potential, proper matching of intense coupled beams along regular lattices is mandatory. Herein, a novel procedure assuring matched transport is described and benchmarked through simulations. The concept of matched transport along periodic lattices has been extended from uncoupled beams to those with considerable coupling between the two transverse degrees of freedom. For coupled beams, matching means the extension of cell-to-cell periodicity from just transverse envelopes to the coupled beam moments and to quantities being derived from these.
{"title":"Periodic four-dimensional solution for transport of intense and coupled coasting beams through quadrupole channels","authors":"C. Xiao, L. Groening","doi":"10.1103/physrevaccelbeams.27.031602","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.031602","url":null,"abstract":"Imposing angular momentum to a particle beam increases its stability against perturbations from space charge [Y.-L. Cheon <i>et al.</i>, <span>Phys. Rev. Accel. Beams</span> <b>25</b>, 064002 (2022)]. In order to fully explore this potential, proper matching of intense coupled beams along regular lattices is mandatory. Herein, a novel procedure assuring matched transport is described and benchmarked through simulations. The concept of matched transport along periodic lattices has been extended from uncoupled beams to those with considerable coupling between the two transverse degrees of freedom. For coupled beams, matching means the extension of cell-to-cell periodicity from just transverse envelopes to the coupled beam moments and to quantities being derived from these.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"20 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140168193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-19DOI: 10.1103/physrevaccelbeams.27.034201
Rajni Pande, Monika Phogat, Srinivas Krishnagopal
In high intensity proton accelerators, there are two main mechanisms that can cause beam degradation: incoherent and coherent effects due to nonlinear space charge forces. The incoherent effects represent the single particle dynamics while the coherent effects represent the collective response of the beam. Of particular interest is the region above a zero current phase advance () of 90° where the (coherent) second-order envelope instability and the (incoherent) fourth-order particle resonance are seen to lead to emittance growth. Large emittance growth is also seen below the envelope instability region as the full current beam phase advance () decreases. In the present study, we have studied the nonlinear effects in a high intensity beam propagating through a focusing-defocusing (FD) quadrupole channel for greater than 90°, both analytically, by studying the solutions of Kapchinsky-Vladimirsky (KV) equation and the particle core model, and through detailed particle-in-cell (PIC) simulations using the tracewin code. The KV envelope equation gives the collective response of the beam while the particle core model gives the contribution of the single particle effects. With pic simulations, which resemble the behavior of the real beams more closely as compared to envelope calculations or the particle core model, it is possible to study the evolution of the beam in a self-consistent manner. Our studies show, that it is possible to identify the specific process responsible for beam degradation in high intensity beams. It is also possible to identify which process dominates under different conditions. We further show that the width of the emittance increase stop band calculated from PIC simulations is wider than that calculated by the envelope equations and that the width depends on the length of the channel being studied.
{"title":"Analysis of single particle and collective beam effects in high intensity beams in a periodic quadrupole channel","authors":"Rajni Pande, Monika Phogat, Srinivas Krishnagopal","doi":"10.1103/physrevaccelbeams.27.034201","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.034201","url":null,"abstract":"In high intensity proton accelerators, there are two main mechanisms that can cause beam degradation: incoherent and coherent effects due to nonlinear space charge forces. The incoherent effects represent the single particle dynamics while the coherent effects represent the collective response of the beam. Of particular interest is the region above a zero current phase advance (<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>σ</mi><mn>0</mn></msub></mrow></math>) of 90° where the (coherent) second-order envelope instability and the (incoherent) fourth-order particle resonance are seen to lead to emittance growth. Large emittance growth is also seen below the envelope instability region as the full current beam phase advance (<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>σ</mi></mrow></math>) decreases. In the present study, we have studied the nonlinear effects in a high intensity beam propagating through a focusing-defocusing (FD) quadrupole channel for <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>σ</mi><mn>0</mn></msub></mrow></math> greater than 90°, both analytically, by studying the solutions of Kapchinsky-Vladimirsky (KV) equation and the particle core model, and through detailed particle-in-cell (PIC) simulations using the <span>tracewin</span> code. The KV envelope equation gives the collective response of the beam while the particle core model gives the contribution of the single particle effects. With pic simulations, which resemble the behavior of the real beams more closely as compared to envelope calculations or the particle core model, it is possible to study the evolution of the beam in a self-consistent manner. Our studies show, that it is possible to identify the specific process responsible for beam degradation in high intensity beams. It is also possible to identify which process dominates under different conditions. We further show that the width of the emittance increase stop band calculated from PIC simulations is wider than that calculated by the envelope equations and that the width depends on the length of the channel being studied.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"31 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140203578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-19DOI: 10.1103/physrevaccelbeams.27.030703
Takashi Tanaka
A simple method to reduce the numerical cost in free electron laser (FEL) simulations is presented, which is based on retrieving a spatially coherent component of microbunching to suppress artifact effects that can potentially overestimate the FEL gain; this significantly reduces the number of macroparticle to reach the numerical convergence and enables the computation of amplified radiation with semianalytical formulas. Examples of FEL simulations performed to demonstrate the proposed method show that the computation time to get a reliable result is reduced by 1–2 orders of magnitude depending on the simulation condition.
本文介绍了一种降低自由电子激光器（FEL）模拟中数值成本的简单方法，该方法基于检索微束的空间相干分量，以抑制可能高估 FEL 增益的伪影效应；这大大减少了达到数值收敛所需的大粒子数量，并能利用半解析公式计算放大辐射。为演示所建议的方法而进行的激光雷达模拟实例表明，获得可靠结果所需的计算时间可根据模拟条件减少 1-2 个数量级。
{"title":"Accelerating the convergence of free electron laser simulations by retrieving a spatially coherent component of microbunching","authors":"Takashi Tanaka","doi":"10.1103/physrevaccelbeams.27.030703","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.030703","url":null,"abstract":"A simple method to reduce the numerical cost in free electron laser (FEL) simulations is presented, which is based on retrieving a spatially coherent component of microbunching to suppress artifact effects that can potentially overestimate the FEL gain; this significantly reduces the number of macroparticle to reach the numerical convergence and enables the computation of amplified radiation with semianalytical formulas. Examples of FEL simulations performed to demonstrate the proposed method show that the computation time to get a reliable result is reduced by 1–2 orders of magnitude depending on the simulation condition.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"96 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140168198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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