Physical Review Accelerators and Beams最新文献

{"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>&lt;</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":"18 1","pages":""},"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}

{"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":"30 1","pages":""},"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}

{"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":"58 1","pages":""},"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}

{"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":"54 1","pages":""},"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}

{"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":"16 1","pages":""},"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}

{"title":"Numerical studies of collinear laser-assisted injection from a foil for plasma wakefield accelerators","authors":"T. C. Wilson, J. Farmer, A. Pukhov, Z.-M. Sheng, B. Hidding","doi":"10.1103/physrevaccelbeams.27.071301","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.071301","url":null,"abstract":"We present a laser-assisted electron injection scheme for beam-driven plasma wakefield acceleration. The laser is collinear with the driver and triggers the injection of hot electrons into the plasma wake by interaction with a thin solid target. We present a baseline case using the AWAKE Run 2 parameters and then perform variations on key parameters to explore the scheme. It is found that the trapped witness electron charge may be tuned by altering laser parameters, with a strong dependence on the phase of the wake upon injection. Normalized emittance settles at the order of micrometres and varies with witness charge. The scheme is robust to misalignment, with a 1/10th plasma skin-depth offset (<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>20</mn><mtext> </mtext><mtext> </mtext><mi mathvariant=\"normal\">μ</mi><mrow><mi mathvariant=\"normal\">m</mi></mrow></mrow></math> for the AWAKE case) having a negligible effect on the final beam. The final beam quality is better than similar existing schemes, and several avenues for further optimization are indicated. The constraints on the AWAKE experiment are very specific, but the general principles of this mechanism can be applied to future beam-driven plasma wakefield accelerator experiments.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"294 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141871910","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}

{"title":"Rotatorlike gantry optics","authors":"M. Pavlovič, M. T. F. Pivi, I. Strašík, V. Rizzoglio, M. G. Pullia, L. Adler, G. Guidoboni, C. Maderböck, D. Prokopovich, G. Kowarik","doi":"10.1103/physrevaccelbeams.27.073502","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.073502","url":null,"abstract":"Rotating gantries are commonly used in ion-therapy facilities to assist and support optimizing the dose distribution delivered to the patient. They are installed at the end of the beamlines and rotated mechanically in the treatment room. In synchrotron-based facilities, the gantries must be able to transport slowly extracted beams with essentially different emittance patterns in the two transverse planes. Such beams will be referred to as the asymmetric beams. A special device called rotator has been proposed as a possible solution. The worldwide first beamline with the rotator has been recently commissioned. The original rotator concept uses an “external” rotator that is a part (a module) of the beamline the gantry is connected to. In this paper, a novel gantry ion-optical concept integrating the rotator optics into the gantry optics is introduced. The first-order gantry transfer matrix satisfies the so-called sigma-matching ion-optical constraints, and—at the same time—it possesses the format of a rotator transfer matrix. The rotator-matching and the sigma-matching principles are combined in the gantry transfer matrix, which means that the sigma-matching gantry acts simultaneously as a rotator without the need for an extra rotator device. In addition, scattering in the gantry nozzle is used to balance the asymmetric beam emittances in the two transverse planes without an additional scattering foil. In this way, the presented ion-optical concept combines all three known matching techniques—the sigma matching, the rotator matching, and the scattering-foil matching—within the gantry beam transport system. Such a beam transport system provides the best matching result and full angular independence of the beam parameters at the gantry isocenter. It also makes it possible to optimize the beam parameters not only at the gantry isocenter but also at the beam monitors located in the gantry nozzle without increasing the number of gantry quadrupoles. There are two possible versions of such gantry optics: the point-to-point and the parallel-to-point optics. They both are presented in this paper. Theoretical calculations are supported by beam transport simulations performed with the <span>w</span>in<span>agile</span> code. Feasibility of the newly proposed ion-optical concept is demonstrated on the MedAustron proton gantry. However, it can be applied to any rotating gantry at any ion-therapy facility. The presented design is the first rotatorlike gantry ion-optical concept worldwide.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"74 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141774412","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}

{"title":"Design of a large energy acceptance beamline using fixed field accelerator optics","authors":"A. F. Steinberg, R. B. Appleby, J. S. L. Yap, S. L. Sheehy","doi":"10.1103/physrevaccelbeams.27.071601","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.071601","url":null,"abstract":"Large energy acceptance arcs have been proposed for applications such as cancer therapy, muon accelerators, and recirculating linacs. The efficacy of hadron therapy can be improved by reducing the energy layer switching time, however this is currently limited by the small momentum acceptance of the beam delivery system (<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>&lt;</mo><mo>±</mo><mn>1</mn><mo>%</mo></mrow></math>). A “closed-dispersion arc” with a large momentum acceptance has the potential to remove this bottleneck, however such a beamline has not yet been constructed. We have developed a design methodology for large momentum acceptance arcs with Fixed Field Accelerator optics, applying it to a demonstrator beam delivery system for protons at 0.5–3.0 MeV (<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>±</mo><mn>42</mn><mo>%</mo></mrow></math> momentum acceptance) as part of the Technology for Ultra-Rapid Beam Operation project at the University of Melbourne. Using realistic magnetic fields, a beamline has been designed with zero dispersion at either end. An algorithm has been devised for the construction of permanent magnet Halbach arrays for this beamline with multipole error below one part in <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mn>10</mn><mn>4</mn></msup></math>, using commercially available magnets. The sensitivity to errors has been investigated, finding that the delivered beam is robust in realistic conditions. This study demonstrates that a closed-dispersion arc with fixed fields can achieve a large momentum acceptance, and we outline future work required to develop these ideas into a complete proof-of-principle beam delivery system that can be scaled up for a medical facility.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"116 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785204","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}

{"title":"First experimental evidence of a beam-beam long-range compensation using wires in the Large Hadron Collider","authors":"A. Poyet, A. Bertarelli, F. Carra, S. D. Fartoukh, N. Fuster-Martínez, N. Karastathis, Y. Papaphilippou, M. Pojer, S. Redaelli, A. Rossi, K. Skoufaris, M. Solfaroli Camillocci, G. Sterbini","doi":"10.1103/physrevaccelbeams.27.071003","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.071003","url":null,"abstract":"In high intensity and high energy colliders, such as the CERN Large Hadron Collider (LHC) and its future high-luminosity upgrade, interactions between the two beams around the different interaction points impose machine performance limitations. In fact, their effect reduces the beam lifetime, and therefore, the collider’s luminosity reach. Those interactions are called beam-beam long-range (BBLR) interactions, and a possible mitigation of their effect using dc wires was proposed for the first time in the early 2000’s. This solution is currently being studied as an option for enhancing the HL-LHC performance. In 2017 and 2018, four demonstrators of wire compensators have been installed in the LHC. A 2-yearlong experimental campaign followed in order to validate the possibility to mitigate the BBLR interactions in the LHC. During this campaign, a proof-of-concept was completed and motivated an additional set of experiments, successfully demonstrating the mitigation of BBLR interactions effects in beam conditions compatible with the operational configuration. This paper reports in detail the preparation of the experimental campaign, including the corresponding tracking simulations and the obtained results, and draws some perspectives for the future.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"48 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141774413","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}

{"title":"Mitigation of the microbunching instability through transverse Landau damping","authors":"A. D. Brynes, G. Perosa, C.-Y. Tsai, E. Allaria, L. Badano, G. De Ninno, E. Ferrari, D. Garzella, L. Giannessi, G. Penco, P. Rebernik Ribič, E. Roussel, S. Spampinati, C. Spezzani, M. Trovò, M. Veronese, S. Di Mitri","doi":"10.1103/physrevaccelbeams.27.074402","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.074402","url":null,"abstract":"The microbunching instability has been a long-standing issue for high-brightness free-electron lasers (FELs) and is a significant showstopper to achieve full longitudinal coherence in the x-ray regime. This paper reports the first experimental demonstration of microbunching instability mitigation through transverse Landau damping, based on linear optics control in a dispersive region. Analytical predictions for the microbunching content are supported by numerical calculations of the instability gain. The effect is confirmed through the experimental characterization of the spectral brightness of the FERMI FEL under different transverse optics configurations of the transfer line between the linear accelerator and the FEL.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"203 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141745031","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}