Pub Date : 2024-08-09DOI: 10.1103/physrevaccelbeams.27.084402
W. F. Bergan
Coherent electron cooling is a novel method to cool dense hadron beams on timescales of a few hours. This method uses a copropagating beam of electrons to pick up the density fluctuations within the hadron beam in one straight section and then provides corrective energy kicks to the hadrons in a downstream straight, cooling the beam. Microbunched electron cooling is an extension of this idea, which induces a microbunching instability in the electron beam as it travels between the two straights, amplifying the signal. However, initial noise in the electron bunch will also be amplified, providing random kicks to the hadrons downstream which tend to increase their emittance. In this paper, we develop an analytic estimate of the effect of the electron noise and benchmark it against simulations. We also discuss how this effect has impacted the cooler design.
{"title":"Electron diffusion in microbunched electron cooling","authors":"W. F. Bergan","doi":"10.1103/physrevaccelbeams.27.084402","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.084402","url":null,"abstract":"Coherent electron cooling is a novel method to cool dense hadron beams on timescales of a few hours. This method uses a copropagating beam of electrons to pick up the density fluctuations within the hadron beam in one straight section and then provides corrective energy kicks to the hadrons in a downstream straight, cooling the beam. Microbunched electron cooling is an extension of this idea, which induces a microbunching instability in the electron beam as it travels between the two straights, amplifying the signal. However, initial noise in the electron bunch will also be amplified, providing random kicks to the hadrons downstream which tend to increase their emittance. In this paper, we develop an analytic estimate of the effect of the electron noise and benchmark it against simulations. We also discuss how this effect has impacted the cooler design.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943783","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 : 2024-08-09DOI: 10.1103/physrevaccelbeams.27.084501
Aamna Khan, Gabriele Bassi, B. Kosciuk, Robert Todd, V. Smaluk, Belkacem Bacha, Paul Palecek, C. Hetzel
In this article, we summarize recent theoretical and experimental studies of the impedance and beam-induced heating of titanium-coated ceramic vacuum chambers used in the NSLS-II injection kickers. The impedance was calculated using the field matching theory assuming planar approximation and compared with the mpedanceake2 code. For the coating thickness of a few microns, we demonstrated that the beam-induced power is dissipated in the titanium coating and that the longitudinally averaged two-dimensional power density is approximated by an analytical expression, thus allowing the use of a simplified model of the power density as input for the code to simulate the temperature distribution with realistic nonuniform thickness of the Ti coating. For a few values of the NSLS-II beam current, we measured the beam-induced heating of two ceramic chambers using thermal sensors installed along the chamber and compared the measurement results with the simulations. Published by the American Physical Society 2024
{"title":"Simulation and measurement of beam-induced heating of ceramic vacuum chambers","authors":"Aamna Khan, Gabriele Bassi, B. Kosciuk, Robert Todd, V. Smaluk, Belkacem Bacha, Paul Palecek, C. Hetzel","doi":"10.1103/physrevaccelbeams.27.084501","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.084501","url":null,"abstract":"In this article, we summarize recent theoretical and experimental studies of the impedance and beam-induced heating of titanium-coated ceramic vacuum chambers used in the NSLS-II injection kickers. The impedance was calculated using the field matching theory assuming planar approximation and compared with the mpedanceake2 code. For the coating thickness of a few microns, we demonstrated that the beam-induced power is dissipated in the titanium coating and that the longitudinally averaged two-dimensional power density is approximated by an analytical expression, thus allowing the use of a simplified model of the power density as input for the code to simulate the temperature distribution with realistic nonuniform thickness of the Ti coating. For a few values of the NSLS-II beam current, we measured the beam-induced heating of two ceramic chambers using thermal sensors installed along the chamber and compared the measurement results with the simulations.\u0000 \u0000 \u0000 \u0000 \u0000 Published by the American Physical Society\u0000 2024\u0000 \u0000 \u0000","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141924633","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 : 2024-08-09DOI: 10.1103/physrevaccelbeams.27.081601
A. Zholents, C. Hall
The wiggler-based amplifier of the microbunching instability in the electron beam is considered and compared to a longitudinal space charge amplifier consisting of the drifts and chicanes. The gain in the magnitude of a seed perturbation of the electron beam density is evaluated analytically as a function of the period of the perturbation, the electron beam parameters, the wiggler parameters, and the amplifier lattice parameters. The theory is compared with the results of the numerical calculations of the gain based on simulations of the electron beam transport through the amplifier lattice. Published by the American Physical Society 2024
{"title":"Wiggler-based electron beam microbunching amplifier study","authors":"A. Zholents, C. Hall","doi":"10.1103/physrevaccelbeams.27.081601","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.081601","url":null,"abstract":"The wiggler-based amplifier of the microbunching instability in the electron beam is considered and compared to a longitudinal space charge amplifier consisting of the drifts and chicanes. The gain in the magnitude of a seed perturbation of the electron beam density is evaluated analytically as a function of the period of the perturbation, the electron beam parameters, the wiggler parameters, and the amplifier lattice parameters. The theory is compared with the results of the numerical calculations of the gain based on simulations of the electron beam transport through the amplifier lattice.\u0000 \u0000 \u0000 \u0000 \u0000 Published by the American Physical Society\u0000 2024\u0000 \u0000 \u0000","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141923593","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 : 2024-08-07DOI: 10.1103/physrevaccelbeams.27.083401
X. Wang, J. B. Li, V. Mironov, J. W. Guo, X. Z. Zhang, O. Tarvainen, Y. C. Feng, L. X. Li, J. D. Ma, Z. H. Zhang, W. Lu, S. Bogomolov, L. Sun, H. W. Zhao
Intense highly charged ion beam production is essential for high-power heavy ion accelerators. A novel movable Vlasov launcher for superconducting high charge state electron cyclotron resonance ion source has been devised that can affect the microwave power effectiveness by a factor of about 4 in terms of highly charged ion beam production. This approach based on a dedicated microwave launching system instead of the traditional coupling scheme has led to new insight on microwave-plasma interaction. With this new understanding, the world record highly charged xenon ion beam currents have been enhanced by up to a factor of 2, which could directly and significantly enhance the performance of heavy ion accelerators and provide many new research opportunities in nuclear physics, atomic physics, and other disciplines.
{"title":"Demonstration of high-efficiency microwave heating producing record highly charged xenon ion beams with superconducting electron cyclotron resonance ion sources","authors":"X. Wang, J. B. Li, V. Mironov, J. W. Guo, X. Z. Zhang, O. Tarvainen, Y. C. Feng, L. X. Li, J. D. Ma, Z. H. Zhang, W. Lu, S. Bogomolov, L. Sun, H. W. Zhao","doi":"10.1103/physrevaccelbeams.27.083401","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.083401","url":null,"abstract":"Intense highly charged ion beam production is essential for high-power heavy ion accelerators. A novel movable Vlasov launcher for superconducting high charge state electron cyclotron resonance ion source has been devised that can affect the microwave power effectiveness by a factor of about 4 in terms of highly charged ion beam production. This approach based on a dedicated microwave launching system instead of the traditional coupling scheme has led to new insight on microwave-plasma interaction. With this new understanding, the world record highly charged xenon ion beam currents have been enhanced by up to a factor of 2, which could directly and significantly enhance the performance of heavy ion accelerators and provide many new research opportunities in nuclear physics, atomic physics, and other disciplines.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943909","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 : 2024-08-06DOI: 10.1103/physrevaccelbeams.27.084801
Ryan Rousselet al.
Accelerator physics relies on numerical algorithms to solve optimization problems in online accelerator control and tasks such as experimental design and model calibration in simulations. The effectiveness of optimization algorithms in discovering ideal solutions for complex challenges with limited resources often determines the problem complexity these methods can address. The accelerator physics community has recognized the advantages of Bayesian optimization algorithms, which leverage statistical surrogate models of objective functions to effectively address complex optimization challenges, especially in the presence of noise during accelerator operation and in resource-intensive physics simulations. In this review article, we offer a conceptual overview of applying Bayesian optimization techniques toward solving optimization problems in accelerator physics. We begin by providing a straightforward explanation of the essential components that make up Bayesian optimization techniques. We then give an overview of current and previous work applying and modifying these techniques to solve accelerator physics challenges. Finally, we explore practical implementation strategies for Bayesian optimization algorithms to maximize their performance, enabling users to effectively address complex optimization challenges in real-time beam control and accelerator design.
{"title":"Bayesian optimization algorithms for accelerator physics","authors":"Ryan Rousselet al.","doi":"10.1103/physrevaccelbeams.27.084801","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.084801","url":null,"abstract":"Accelerator physics relies on numerical algorithms to solve optimization problems in online accelerator control and tasks such as experimental design and model calibration in simulations. The effectiveness of optimization algorithms in discovering ideal solutions for complex challenges with limited resources often determines the problem complexity these methods can address. The accelerator physics community has recognized the advantages of Bayesian optimization algorithms, which leverage statistical surrogate models of objective functions to effectively address complex optimization challenges, especially in the presence of noise during accelerator operation and in resource-intensive physics simulations. In this review article, we offer a conceptual overview of applying Bayesian optimization techniques toward solving optimization problems in accelerator physics. We begin by providing a straightforward explanation of the essential components that make up Bayesian optimization techniques. We then give an overview of current and previous work applying and modifying these techniques to solve accelerator physics challenges. Finally, we explore practical implementation strategies for Bayesian optimization algorithms to maximize their performance, enabling users to effectively address complex optimization challenges in real-time beam control and accelerator design.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943784","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 : 2024-08-05DOI: 10.1103/physrevaccelbeams.27.084401
W. H. Li, A. C. Bartnik, A. Fukasawa, M. Kaemingk, G. Lawler, N. Majernik, J. B. Rosenzweig, J. M. Maxson
Achieving maximum electron beam brightness in photoinjectors requires detailed control of the 3D bunch shape and precise tuning of the beam focusing. Even in state-of-the-art designs, slice emittance growth due to nonlinear space charge forces and partial nonlaminarity often remains non-negligible. In this work, we introduce a new means to linearize the transverse slice phase space: a sacrificial portion of the bunch’s own charge distribution, formed into a wavebroken shock front by highly nonlinear space charge forces within the gun, whose downstream purpose is to dynamically linearize the desired bunch core. We show that linearization of an appropriately prepared bunch can be achieved via strongly nonlaminar focusing of the sacrificial shock front, while the inner core focuses laminarly. This leads to a natural spatial separation of the two distributions: a dense core surrounded by a diffuse halo of sacrificial charge that can be collimated. Multiobjective genetic algorithm optimizations of the ultracompact x-ray free electron laser injector employ this concept, and we interpret it with an analytic model that agrees well with the simulations. In simulation, we demonstrate a final bunch charge of 100 pC, peak current A, and a sacrificial charge of 150 pC (250 pC total emitted from cathode) with normalized emittance growth of due to space charge. This implies a maximum achievable brightness approximately an order of magnitude greater than existing free electron laser injector designs.
{"title":"Compensating slice emittance growth in high brightness photoinjectors using a sacrificial charge","authors":"W. H. Li, A. C. Bartnik, A. Fukasawa, M. Kaemingk, G. Lawler, N. Majernik, J. B. Rosenzweig, J. M. Maxson","doi":"10.1103/physrevaccelbeams.27.084401","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.084401","url":null,"abstract":"Achieving maximum electron beam brightness in photoinjectors requires detailed control of the 3D bunch shape and precise tuning of the beam focusing. Even in state-of-the-art designs, slice emittance growth due to nonlinear space charge forces and partial nonlaminarity often remains non-negligible. In this work, we introduce a new means to linearize the transverse slice phase space: a sacrificial portion of the bunch’s own charge distribution, formed into a wavebroken shock front by highly nonlinear space charge forces within the gun, whose downstream purpose is to dynamically linearize the desired bunch core. We show that linearization of an appropriately prepared bunch can be achieved via strongly nonlaminar focusing of the sacrificial shock front, while the inner core focuses laminarly. This leads to a natural spatial separation of the two distributions: a dense core surrounded by a diffuse halo of sacrificial charge that can be collimated. Multiobjective genetic algorithm optimizations of the ultracompact x-ray free electron laser injector employ this concept, and we interpret it with an analytic model that agrees well with the simulations. In simulation, we demonstrate a final bunch charge of 100 pC, peak current <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>∼</mo><mn>30</mn></math> A, and a sacrificial charge of 150 pC (250 pC total emitted from cathode) with normalized emittance growth of <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo><</mo><mn>20</mn><mtext> </mtext><mtext> </mtext><mi>nm</mi><mtext> </mtext><mi>rad</mi></mrow></math> due to space charge. This implies a maximum achievable brightness approximately an order of magnitude greater than existing free electron laser injector designs.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943864","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 : 2024-08-05DOI: 10.1103/physrevaccelbeams.27.082001
Zhicheng Huang, Yelong Wei, Zexin Cao, Li Sun, Guangyao Feng, David Alesini
Numerical optimizations on couplers of the traveling-wave (TW) accelerating structures usually require lots of calculation resources. This paper proposes a new technique for matching couplers to an accelerating structure in a more efficient and accurate way. It combines improved Kroll method with improved Kyhl method, thereby simplifying simulation process while achieving a high accuracy. This paper also presents the detailed design on couplers for a C-band constant-gradient (CG) accelerating structure based on this new technique. Such a new technique can be widely used for any TW accelerating structures working at different frequencies of S-band, C-band, and X-band including CG, constant-impedance (CI), and other structures with either electric couplers or magnetic couplers.
对行波（TW）加速结构的耦合器进行数值优化通常需要大量计算资源。本文提出了一种新技术，可以更高效、更准确地将耦合器与加速结构相匹配。它结合了改进的 Kroll 方法和改进的 Kyhl 方法，从而在实现高精度的同时简化了仿真过程。本文还介绍了基于这种新技术的 C 波段恒定梯度（CG）加速结构耦合器的详细设计。这种新技术可广泛应用于工作在 S 波段、C 波段和 X 波段不同频率的任何 TW 加速结构，包括 CG、恒定阻抗 (CI) 和其他具有电耦合器或磁耦合器的结构。
{"title":"New design techniques on matching couplers for traveling-wave accelerating structures","authors":"Zhicheng Huang, Yelong Wei, Zexin Cao, Li Sun, Guangyao Feng, David Alesini","doi":"10.1103/physrevaccelbeams.27.082001","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.082001","url":null,"abstract":"Numerical optimizations on couplers of the traveling-wave (TW) accelerating structures usually require lots of calculation resources. This paper proposes a new technique for matching couplers to an accelerating structure in a more efficient and accurate way. It combines improved Kroll method with improved Kyhl method, thereby simplifying simulation process while achieving a high accuracy. This paper also presents the detailed design on couplers for a C-band constant-gradient (CG) accelerating structure based on this new technique. Such a new technique can be widely used for any TW accelerating structures working at different frequencies of S-band, C-band, and X-band including CG, constant-impedance (CI), and other structures with either electric couplers or magnetic couplers.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943786","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 : 2024-08-05DOI: 10.1103/physrevaccelbeams.27.080401
Quan Zhou, Xinlei Zhu, Yaping Du
Nonuniform transmission lines (NTLs) are widely used in pulsed power accelerators because they provide an efficient way to achieve impedance matching and pulse shaping. Since designing and constructing these accelerators typically demands substantial effort, finding the optimal impedance profile to maximize the power transmission efficiencies of the NTLs is important. In this paper, a convenient numerical method to determine the optimal impedance profile is proposed. First, the output of the NTL with arbitrary parameters is theoretically analyzed under arbitrary input conditions. It was found that only four factors affect the power transmission efficiency: the ratio of output impedance to input impedance, the ratio of input pulse width to the NTL’s one-way transit time, the normalized impedance profile, and the normalized input pulse. Based on these findings, a method designed to minimize the reflected component within the working frequency range is proposed. Using this method, an impedance profile demonstrating superior power transmission efficiency compared to the traditional exponential profile is identified. This work can provide a rapid and effective method to determine the impedance profile of the NTL, undoubtedly benefiting the design process of pulsed power accelerators.
{"title":"Method to determine the optimal impedance profile of nonuniform transmission lines used for pulsed power accelerators","authors":"Quan Zhou, Xinlei Zhu, Yaping Du","doi":"10.1103/physrevaccelbeams.27.080401","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.080401","url":null,"abstract":"Nonuniform transmission lines (NTLs) are widely used in pulsed power accelerators because they provide an efficient way to achieve impedance matching and pulse shaping. Since designing and constructing these accelerators typically demands substantial effort, finding the optimal impedance profile to maximize the power transmission efficiencies of the NTLs is important. In this paper, a convenient numerical method to determine the optimal impedance profile is proposed. First, the output of the NTL with arbitrary parameters is theoretically analyzed under arbitrary input conditions. It was found that only four factors affect the power transmission efficiency: the ratio of output impedance to input impedance, the ratio of input pulse width to the NTL’s one-way transit time, the normalized impedance profile, and the normalized input pulse. Based on these findings, a method designed to minimize the reflected component within the working frequency range is proposed. Using this method, an impedance profile demonstrating superior power transmission efficiency compared to the traditional exponential profile is identified. This work can provide a rapid and effective method to determine the impedance profile of the NTL, undoubtedly benefiting the design process of pulsed power accelerators.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943785","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 : 2024-08-01DOI: 10.1103/physrevaccelbeams.27.081301
J. Y. Hua, X. B. Zhang, M. Chen, S. M. Weng, Y. P. Chen, Z. M. Sheng
A terahertz radiation enhancing scheme, in which a linearly polarized weakly relativistic laser pulse irradiates a target consisting of two parallel thin-solid layers with a certain gap, is proposed and studied by using two-dimensional particle-in-cell simulations. The radiation is known to be produced by laser-produced hot electrons via mechanisms such as coherent transition radiation at the target surfaces. Under optimized conditions, the energy conversion efficiency of terahertz radiation can be as high as 3.3%, which is nearly 1.5 times higher than that obtained with a single-layer target with the same drive laser. This is mainly due to the enhanced hot electron generation with moderate energy via multiple reflections of the laser pulse between the two target layers. The radiation has two peaks close to 30° from the target surface, which are more collimated than that with the single-layer target. The dependence of the terahertz radiation on a variety of target parameters is given, which can control the terahertz spectrum and radiation efficiency and thus provide guidance for experimental investigations. Moreover, both the coherent transition radiation and antenna radiation models are applied to explain the angular distributions of the terahertz emission found in the simulations.
{"title":"Enhanced terahertz radiation generated by intense laser interaction with a two-layer thin solid target","authors":"J. Y. Hua, X. B. Zhang, M. Chen, S. M. Weng, Y. P. Chen, Z. M. Sheng","doi":"10.1103/physrevaccelbeams.27.081301","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.081301","url":null,"abstract":"A terahertz radiation enhancing scheme, in which a linearly polarized weakly relativistic laser pulse irradiates a target consisting of two parallel thin-solid layers with a certain gap, is proposed and studied by using two-dimensional particle-in-cell simulations. The radiation is known to be produced by laser-produced hot electrons via mechanisms such as coherent transition radiation at the target surfaces. Under optimized conditions, the energy conversion efficiency of terahertz radiation can be as high as 3.3%, which is nearly 1.5 times higher than that obtained with a single-layer target with the same drive laser. This is mainly due to the enhanced hot electron generation with moderate energy via multiple reflections of the laser pulse between the two target layers. The radiation has two peaks close to 30° from the target surface, which are more collimated than that with the single-layer target. The dependence of the terahertz radiation on a variety of target parameters is given, which can control the terahertz spectrum and radiation efficiency and thus provide guidance for experimental investigations. Moreover, both the coherent transition radiation and antenna radiation models are applied to explain the angular distributions of the terahertz emission found in the simulations.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883741","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 : 2024-07-30DOI: 10.1103/physrevaccelbeams.27.074602
Thorsten Hellert, Tynan Ford, Simon C. Leemann, Hiroshi Nishimura, Marco Venturini, Andrea Pollastro
Past research at the Advanced Light Source (ALS) provided a proof-of-principle demonstration that deep learning methods could be effectively employed to compensate for the significant perturbations to the transverse electron beam size induced by user-controlled adjustments of the insertion devices. However, incorporating these methods into the ALS’ daily operations has faced notable challenges. The complexity of the system’s operational requirements and the significant upkeep demands has restricted their sustained application during user operation. Here, we introduce the development of a more robust neural network (NN)-based algorithm that utilizes a novel online fine-tuning approach and its systematic integration into the day-to-day machine operations. Our analysis emphasizes the process of NN model selection, demonstrates the superior performance of the NN-based method over traditional feedback methods, and examines the effectiveness and resilience of the new algorithm during user-operation scenarios.
过去在先进光源（ALS）进行的研究提供了一个原理性证明，即深度学习方法可以有效地用于补偿由用户控制的插入装置调整所引起的横向电子束尺寸的显著扰动。然而，将这些方法纳入 ALS 的日常运行却面临着显著的挑战。系统运行要求的复杂性和大量的维护需求限制了这些方法在用户运行期间的持续应用。在此，我们介绍了一种基于神经网络 (NN) 的更稳健算法的开发情况，该算法采用了一种新颖的在线微调方法，并将其系统地集成到机器的日常运行中。我们的分析强调了神经网络模型的选择过程，证明了基于神经网络的方法优于传统反馈方法的性能，并检验了新算法在用户操作场景中的有效性和适应性。
{"title":"Application of deep learning methods for beam size control during user operation at the Advanced Light Source","authors":"Thorsten Hellert, Tynan Ford, Simon C. Leemann, Hiroshi Nishimura, Marco Venturini, Andrea Pollastro","doi":"10.1103/physrevaccelbeams.27.074602","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.074602","url":null,"abstract":"Past research at the Advanced Light Source (ALS) provided a proof-of-principle demonstration that deep learning methods could be effectively employed to compensate for the significant perturbations to the transverse electron beam size induced by user-controlled adjustments of the insertion devices. However, incorporating these methods into the ALS’ daily operations has faced notable challenges. The complexity of the system’s operational requirements and the significant upkeep demands has restricted their sustained application during user operation. Here, we introduce the development of a more robust neural network (NN)-based algorithm that utilizes a novel online fine-tuning approach and its systematic integration into the day-to-day machine operations. Our analysis emphasizes the process of NN model selection, demonstrates the superior performance of the NN-based method over traditional feedback methods, and examines the effectiveness and resilience of the new algorithm during user-operation scenarios.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141871981","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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