Pub Date : 2024-04-22DOI: 10.1103/physrevaccelbeams.27.041303
M. J. Wu, D. Y. Li, T. Yang, Y. Z. Li, H. Cheng, Y. D. Xia, Y. Yan, Y. L. Fang, K. Zhu, M. J. Easton, C. Lin, X. Q. Yan
With the rapid development of high-gradient laser plasma acceleration, implementing it in practical applications has become a priority. However, to go from “acceleration” to “accelerator,” a beam line system is required to accurately control the beam parameters according to different irradiation requirements. The laser-accelerated proton beam is characterized by a micron-scale original source size and a small emittance as low as 0.004 mm mrad [T. E. Cowan et al., Phys. Rev. Lett.92, 204801 (2004)]. However, due to the broad energy spread and large divergence, its initial ultralow emittance will increase rapidly in the subsequent transmission process. This indicates that designing a beamline for laser-driven protons is challenging and differs significantly from that of a conventional accelerator. As a fundamental parameter for beam line design, we have theoretically derived the emittance growth law for laser-driven protons in both drift space and in a focusing element. The results demonstrate that the beam emittance deteriorates sharply with the energy spread and the square of the divergence angle. These theoretical calculations have been verified both in experiments and simulations. This work is helpful for designing subsequent beam lines that pursue high transmission efficiency and achromatic ability.
随着高梯度激光等离子体加速技术的快速发展，将其应用于实际应用已成为当务之急。然而，要实现从 "加速 "到 "加速器 "的转变，就需要有一套光束线系统来根据不同的辐照要求精确控制光束参数。激光加速质子束的特点是原始源尺寸为微米级，发射率低至 0.004 mm mrad [T. E. Cowan 等人，Phys. Rev. Lett.然而，由于能量分布广、发散大，其初始超低发射率会在随后的传输过程中迅速增加。这表明，激光驱动质子的光束线设计具有挑战性，与传统加速器有很大不同。作为光束线设计的基本参数，我们从理论上推导出了激光驱动质子在漂移空间和聚焦元件中的辐照度增长规律。结果表明，光束辐照度随着能量扩散和发散角的平方而急剧恶化。这些理论计算在实验和模拟中都得到了验证。这项工作有助于设计追求高传输效率和消色差能力的后续光束线。
{"title":"Emittance growth analysis of laser-driven broad energy spectral proton beams","authors":"M. J. Wu, D. Y. Li, T. Yang, Y. Z. Li, H. Cheng, Y. D. Xia, Y. Yan, Y. L. Fang, K. Zhu, M. J. Easton, C. Lin, X. Q. Yan","doi":"10.1103/physrevaccelbeams.27.041303","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.041303","url":null,"abstract":"With the rapid development of high-gradient laser plasma acceleration, implementing it in practical applications has become a priority. However, to go from “acceleration” to “accelerator,” a beam line system is required to accurately control the beam parameters according to different irradiation requirements. The laser-accelerated proton beam is characterized by a micron-scale original source size and a small emittance as low as 0.004 mm mrad [T. E. Cowan <i>et al.</i>, <span>Phys. Rev. Lett.</span> <b>92</b>, 204801 (2004)]. However, due to the broad energy spread and large divergence, its initial ultralow emittance will increase rapidly in the subsequent transmission process. This indicates that designing a beamline for laser-driven protons is challenging and differs significantly from that of a conventional accelerator. As a fundamental parameter for beam line design, we have theoretically derived the emittance growth law for laser-driven protons in both drift space and in a focusing element. The results demonstrate that the beam emittance deteriorates sharply with the energy spread and the square of the divergence angle. These theoretical calculations have been verified both in experiments and simulations. This work is helpful for designing subsequent beam lines that pursue high transmission efficiency and achromatic ability.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"99 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140635291","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 : 2024-04-18DOI: 10.1103/physrevaccelbeams.27.044001
Ki Moon Nam, Ji-Gwang Hwang, Young Dae Yoon, Yong Woon Parc
In electron storage rings, an accurate description of particle dynamics near third-integer resonance is crucial for various applications. The conventional approach is to extrapolate far-resonance dynamics to near resonance, but the difficulty arises because the nonlinear detuning parameter diverges at this critical point. Here we derive, via a suitable application of the canonical perturbation theory, a revised detuning parameter that is well behaved near resonance. The resultant theory accurately describes the morphology of resonance islands for a wide range of parameter space and facilitates its optimization.
{"title":"Revised Hamiltonian near third-integer resonance and implications for an electron storage ring","authors":"Ki Moon Nam, Ji-Gwang Hwang, Young Dae Yoon, Yong Woon Parc","doi":"10.1103/physrevaccelbeams.27.044001","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.044001","url":null,"abstract":"In electron storage rings, an accurate description of particle dynamics near third-integer resonance is crucial for various applications. The conventional approach is to extrapolate far-resonance dynamics to near resonance, but the difficulty arises because the nonlinear detuning parameter diverges at this critical point. Here we derive, via a suitable application of the canonical perturbation theory, a revised detuning parameter that is well behaved near resonance. The resultant theory accurately describes the morphology of resonance islands for a wide range of parameter space and facilitates its optimization.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"11 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140616648","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 : 2024-04-15DOI: 10.1103/physrevaccelbeams.27.042001
H. Gong, W. Fang, J. Tan, X. Huang, C. Wang, Y. Xu, Z. Zhao
Shanghai Synchrotron Radiation Facility/Shanghai Soft X-ray FEL Facility is currently developing an advanced variable polarization transverse deflecting structure TTDS (two-mode transverse deflecting structure) using a dual-mode rf structure concept. Driven by two different rf power sources, this novel TDS works using both the and modes for simultaneous vertical and horizontal deflections, consequently, it can provide a time-varying polarization of the electrical field at ultrafast speeds. It is capable of producing circular and elliptical polarizations as well as flexible vector combinations through amplitude and phase modulation from a low-level rf system. The work presented in this paper is focused on the analysis and design of the variable polarization TDS, consisting of dual-mode cells and two dual-mode couplers. Designing and optimizing for dual-mode design and optimization is complex; consequently, an advanced optimization procedure based on neural networks and multiobjective algorithms has been developed. This improves the accuracy and efficiency of the rf structure design process. Through iterations, the dual-mode cells in the final design are optimized for high impedance and other rf performance criteria for both the and modes. The two couplers for rf power input and output are also optimized. Based on the optimized design and rf sensitivity analysis, the mechanical design has been completed and is now ready for manufacture.
{"title":"Design of a dual-mode transverse deflecting structure using neural network and multiobjective algorithms","authors":"H. Gong, W. Fang, J. Tan, X. Huang, C. Wang, Y. Xu, Z. Zhao","doi":"10.1103/physrevaccelbeams.27.042001","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.042001","url":null,"abstract":"Shanghai Synchrotron Radiation Facility/Shanghai Soft X-ray FEL Facility is currently developing an advanced variable polarization transverse deflecting structure TTDS (two-mode transverse deflecting structure) using a dual-mode rf structure concept. Driven by two different rf power sources, this novel TDS works using both the <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>HEM</mi><mn>11</mn></msub></math> and <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>HEM</mi><mn>12</mn></msub></math> modes for simultaneous vertical and horizontal deflections, consequently, it can provide a time-varying polarization of the electrical field at ultrafast speeds. It is capable of producing circular and elliptical polarizations as well as flexible vector combinations through amplitude and phase modulation from a low-level rf system. The work presented in this paper is focused on the analysis and design of the variable polarization TDS, consisting of dual-mode cells and two dual-mode couplers. Designing and optimizing for dual-mode design and optimization is complex; consequently, an advanced optimization procedure based on neural networks and multiobjective algorithms has been developed. This improves the accuracy and efficiency of the rf structure design process. Through iterations, the dual-mode cells in the final design are optimized for high impedance and other rf performance criteria for both the <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>HEM</mi><mn>11</mn></msub></math> and <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>HEM</mi><mn>12</mn></msub></math> modes. The two couplers for rf power input and output are also optimized. Based on the optimized design and rf sensitivity analysis, the mechanical design has been completed and is now ready for manufacture.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"19 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140616641","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 : 2024-04-12DOI: 10.1103/physrevaccelbeams.27.044403
F. J. Cullinan, Å. Andersson, J. Breunlin, M. Brosi, P. F. Tavares
Landau cavities used to lengthen the bunches in storage rings necessarily constitute a significant impedance. Because of the particular phase of the field required for bunch lengthening, they are often detuned quite considerably from resonance, more so than the main cavities. As a result, their impedance can excite the first coupled-bunch mode such that it becomes unstable. This phenomenon has previously been predicted [M. Venturini, Phys. Rev. Accel. Beams21, 114404 (2018)] and characterized in simulations [T. He, Phys. Rev. Accel. Beams25, 024401 (2022)] but experimental observation is yet to be documented. In this paper, the experimental observation of coupled-bunch modes- excited by the Landau and main cavities in a fourth-generation light-source storage ring is presented. Features of the instability such as amplitude and coherent frequency at saturation have been measured and its dependency on the main rf voltage has been explored. The impact of a parked main cavity has also been investigated.
{"title":"Experimental observation of a mode-1 instability driven by Landau cavities in a storage ring","authors":"F. J. Cullinan, Å. Andersson, J. Breunlin, M. Brosi, P. F. Tavares","doi":"10.1103/physrevaccelbeams.27.044403","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.044403","url":null,"abstract":"Landau cavities used to lengthen the bunches in storage rings necessarily constitute a significant impedance. Because of the particular phase of the field required for bunch lengthening, they are often detuned quite considerably from resonance, more so than the main cavities. As a result, their impedance can excite the first coupled-bunch mode such that it becomes unstable. This phenomenon has previously been predicted [M. Venturini, <span>Phys. Rev. Accel. Beams</span> <b>21</b>, 114404 (2018)] and characterized in simulations [T. He, <span>Phys. Rev. Accel. Beams</span> <b>25</b>, 024401 (2022)] but experimental observation is yet to be documented. In this paper, the experimental observation of coupled-bunch modes-<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>±</mo><mn>1</mn></math> excited by the Landau and main cavities in a fourth-generation light-source storage ring is presented. Features of the instability such as amplitude and coherent frequency at saturation have been measured and its dependency on the main rf voltage has been explored. The impact of a parked main cavity has also been investigated.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"20 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140599085","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 : 2024-04-12DOI: 10.1103/physrevaccelbeams.27.043001
A. Romero Francia, A. Perillo Marcone, S. Pianese, K. Andersen, G. Arnau Izquierdo, J. A. Briz, D. Carbajo Perez, E. Carlier, T. Coiffet, L. S. Esposito, J. L. Grenard, D. Grenier, J. Humbert, K. Kershaw, J. Lendaro, A. Ortega Rolo, K. Scibor, D. Senajova, S. Sgobba, C. Sharp, D. Steyaert, F. M. Velotti, H. Vincke, V. Vlachoudis, M. Calviani
The Super Proton Synchrotron (SPS) is the last stage in the injector chain for CERN’s Large Hadron Collider, and it also provides proton and ion beams for several fixed-target experiments. The SPS has been in operation since 1976, and it has been upgraded over the years. For the SPS to operate safely, its internal beam dump must be able to repeatedly absorb the energy of the circulating beams without sustaining damage that would affect its function. The latest upgrades of the SPS led to the requirement for its beam dump to absorb proton beams with a momentum spectrum from 14 to and an average beam power of up to . This paper presents the technical details of a new design of the SPS beam dump that was installed in one of the long straight sections of the SPS during the 2019–2020 shutdown of CERN’s accelerator complex within the framework of the Large Hadron Collider Injectors Upgrade Project. This new beam dump has been in the operation since May 2021, and it is foreseen that it will operate with a lifetime of 20 years. The key challenges in the design of the beam dump were linked to the high levels of thermal energy to be dissipated—to avoid overheating and damage to the beam dump itself—and high induced levels of radiation, which have implications for personnel access to monitor the beam dump and repair any problems occurring during operation. The design process, therefore, included extensive thermomechanical finite-element simulations of the beam-dump core and its cooling system’s response to normal operation and worst-case scenarios for beam dumping. To ensure high thermal conductivity between the beam-dump core and its water-cooling system, hot isostatic pressing techniques were used in its manufacturing process. A comprehensive set of instrumentation was installed in the beam dump to monitor it during operation and to cross-check the numerical models with operational feedback. The beam dump and its infrastructure design were also optimized to ensure it can be maintained, repaired, or replaced while minimizing the radiation doses received by personnel.
{"title":"Design and early operation of a new-generation internal beam dump for CERN’s Super Proton Synchrotron","authors":"A. Romero Francia, A. Perillo Marcone, S. Pianese, K. Andersen, G. Arnau Izquierdo, J. A. Briz, D. Carbajo Perez, E. Carlier, T. Coiffet, L. S. Esposito, J. L. Grenard, D. Grenier, J. Humbert, K. Kershaw, J. Lendaro, A. Ortega Rolo, K. Scibor, D. Senajova, S. Sgobba, C. Sharp, D. Steyaert, F. M. Velotti, H. Vincke, V. Vlachoudis, M. Calviani","doi":"10.1103/physrevaccelbeams.27.043001","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.043001","url":null,"abstract":"The Super Proton Synchrotron (SPS) is the last stage in the injector chain for CERN’s Large Hadron Collider, and it also provides proton and ion beams for several fixed-target experiments. The SPS has been in operation since 1976, and it has been upgraded over the years. For the SPS to operate safely, its internal beam dump must be able to repeatedly absorb the energy of the circulating beams without sustaining damage that would affect its function. The latest upgrades of the SPS led to the requirement for its beam dump to absorb proton beams with a momentum spectrum from 14 to <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>450</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi><mo>/</mo><mi>c</mi></mrow></math> and an average beam power of up to <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>∼</mo><mn>270</mn><mtext> </mtext><mtext> </mtext><mi>kW</mi></math>. This paper presents the technical details of a new design of the SPS beam dump that was installed in one of the long straight sections of the SPS during the 2019–2020 shutdown of CERN’s accelerator complex within the framework of the Large Hadron Collider Injectors Upgrade Project. This new beam dump has been in the operation since May 2021, and it is foreseen that it will operate with a lifetime of 20 years. The key challenges in the design of the beam dump were linked to the high levels of thermal energy to be dissipated—to avoid overheating and damage to the beam dump itself—and high induced levels of radiation, which have implications for personnel access to monitor the beam dump and repair any problems occurring during operation. The design process, therefore, included extensive thermomechanical finite-element simulations of the beam-dump core and its cooling system’s response to normal operation and worst-case scenarios for beam dumping. To ensure high thermal conductivity between the beam-dump core and its water-cooling system, hot isostatic pressing techniques were used in its manufacturing process. A comprehensive set of instrumentation was installed in the beam dump to monitor it during operation and to cross-check the numerical models with operational feedback. The beam dump and its infrastructure design were also optimized to ensure it can be maintained, repaired, or replaced while minimizing the radiation doses received by personnel.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"58 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140598945","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 : 2024-04-12DOI: 10.1103/physrevaccelbeams.27.042801
Sergey Tomin, Jan Kaiser, Nils Maris Lockmann, Torsten Wohlenberg, Igor Zagorodnov
Undulator tapering controls the resonance properties of the free-electron laser (FEL) amplification process. Wakefield energy losses in an undulator’s vacuum chamber are one of the factors that determine the undulator’s linear taper. While another contribution to energy losses, namely the losses due to spontaneous radiation, can be calculated analytically, estimating wakefield energy losses requires detailed knowledge of the chamber geometry and the electron beam current profile. We introduce a method for the automatic estimation of wakefield energy losses, which leverages noninvasive THz diagnostics, a current profile reconstruction algorithm enhanced with machine learning, and a recently developed analytical wakefield function for the European XFEL’s undulator beamline. The correctness of this method was validated by directly measuring wakefield-induced electron beam energy losses in the undulator section. This, in turn, enables the prediction of the optimal linear taper in the undulator.
{"title":"Undulator linear taper control at the European X-Ray Free-Electron Laser facility","authors":"Sergey Tomin, Jan Kaiser, Nils Maris Lockmann, Torsten Wohlenberg, Igor Zagorodnov","doi":"10.1103/physrevaccelbeams.27.042801","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.042801","url":null,"abstract":"Undulator tapering controls the resonance properties of the free-electron laser (FEL) amplification process. Wakefield energy losses in an undulator’s vacuum chamber are one of the factors that determine the undulator’s linear taper. While another contribution to energy losses, namely the losses due to spontaneous radiation, can be calculated analytically, estimating wakefield energy losses requires detailed knowledge of the chamber geometry and the electron beam current profile. We introduce a method for the automatic estimation of wakefield energy losses, which leverages noninvasive THz diagnostics, a current profile reconstruction algorithm enhanced with machine learning, and a recently developed analytical wakefield function for the European XFEL’s undulator beamline. The correctness of this method was validated by directly measuring wakefield-induced electron beam energy losses in the undulator section. This, in turn, enables the prediction of the optimal linear taper in the undulator.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"244 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140599511","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 : 2024-04-12DOI: 10.1103/physrevaccelbeams.27.043201
C. Castro Sequeiro, M. Ady, G. Bregliozzi, N. Chatzigeorgiou, A. R. Churchman, R. Kersevan, T. Lefevre, S. Mazzoni, G. Pigny, A. Rossi, M. Sameed, G. Schneider, O. Sedlacek, K. Sidorowski, C. Vazquez Pelaez, R. Veness, L. Zygaropoulos, O. Stringer, A. Webber-Date, C. P. Welsch, H. Zhang, P. Forck, S. Udrea
A beam gas curtain (BGC) monitor has been designed to obtain information about the relative position between the LHC proton beam and the hollow electron lens electron beam through a minimally invasive process. Its working principle relies on intersecting the path of both beams with a supersonic gas curtain, introduced transversely into the LHC beamline, to produce a fluorescence signal. As an intermediate project stage (phase II), a preliminary version of the BGC monitor has been installed into the LHC beamline. To ensure the successful integration of the monitor and subsequent operation under LHC ultrahigh vacuum conditions, a series of vacuum studies have been performed. These can be classified as follows: An off-line laboratory test campaign, to assess BGC behavior during pump down and gas injections; simulations and analytical calculations, to evaluate BGC behavior and estimate the impact of its installation and operation in the LHC. This document will briefly present the off-line tests campaign, followed by a more extensive description of the simulations performed.
{"title":"Beam gas curtain monitor: Vacuum studies for LHC integration and operation","authors":"C. Castro Sequeiro, M. Ady, G. Bregliozzi, N. Chatzigeorgiou, A. R. Churchman, R. Kersevan, T. Lefevre, S. Mazzoni, G. Pigny, A. Rossi, M. Sameed, G. Schneider, O. Sedlacek, K. Sidorowski, C. Vazquez Pelaez, R. Veness, L. Zygaropoulos, O. Stringer, A. Webber-Date, C. P. Welsch, H. Zhang, P. Forck, S. Udrea","doi":"10.1103/physrevaccelbeams.27.043201","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.043201","url":null,"abstract":"A beam gas curtain (BGC) monitor has been designed to obtain information about the relative position between the LHC proton beam and the hollow electron lens electron beam through a minimally invasive process. Its working principle relies on intersecting the path of both beams with a supersonic gas curtain, introduced transversely into the LHC beamline, to produce a fluorescence signal. As an intermediate project stage (phase II), a preliminary version of the BGC monitor has been installed into the LHC beamline. To ensure the successful integration of the monitor and subsequent operation under LHC ultrahigh vacuum conditions, a series of vacuum studies have been performed. These can be classified as follows: An off-line laboratory test campaign, to assess BGC behavior during pump down and gas injections; simulations and analytical calculations, to evaluate BGC behavior and estimate the impact of its installation and operation in the LHC. This document will briefly present the off-line tests campaign, followed by a more extensive description of the simulations performed.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"14 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140598947","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 : 2024-04-11DOI: 10.1103/physrevaccelbeams.27.041302
Laurence J. R. Nix, Joseph T. Bradbury, Christopher T. Shaw, Morgan T. Hibberd, Darren M. Graham, Robert B. Appleby, Graeme Burt, Rosa Letizia, Steven P. Jamison
We investigate the use of tapered rectangular dielectric-lined waveguides (DLWs) for the acceleration of low-energy, subrelativistic, electron bunches by the interaction with multicycle narrowband terahertz (THz) pulses. A key challenge exists in this subrelativistic regime; the electron velocity changes significantly as energy is gained. To keep electrons in the accelerating phase, the phase velocity must also be increased to match. We present simulations which demonstrate that the dielectric thickness can be kept constant and the width of the dielectric lining can be tapered along the direction of travel to vary the phase velocity, an approach only possible by the use of a rectangular waveguide geometry. The properties of tapered DLWs are discussed and following this, a design process is presented to demonstrate that the way this tapering can be optimized for different pulse and beam parameters. The minimum accelerating gradient for electron bunch capture is derived and compared to simulations. As examples of this design process, designs are considered based on considerations of the THz source, incoming electron beam, and manufacturing tolerances. A maximum THz pulse energy of in the DLW was considered, which represents what is readily achievable using mJ-level regenerative amplifier laser systems together with optical-to-terahertz conversion in lithium niobate crystals. This will be more than double the energy of a 100 keV electron beam, increasing it to 205 keV. We describe the optimization process and present a detailed exploration of the beam dynamics, discussing how the performance will further improve with compressed bunches.
{"title":"Terahertz-driven acceleration of subrelativistic electron beams using tapered rectangular dielectric-lined waveguides","authors":"Laurence J. R. Nix, Joseph T. Bradbury, Christopher T. Shaw, Morgan T. Hibberd, Darren M. Graham, Robert B. Appleby, Graeme Burt, Rosa Letizia, Steven P. Jamison","doi":"10.1103/physrevaccelbeams.27.041302","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.041302","url":null,"abstract":"We investigate the use of tapered rectangular dielectric-lined waveguides (DLWs) for the acceleration of low-energy, subrelativistic, electron bunches by the interaction with multicycle narrowband terahertz (THz) pulses. A key challenge exists in this subrelativistic regime; the electron velocity changes significantly as energy is gained. To keep electrons in the accelerating phase, the phase velocity must also be increased to match. We present simulations which demonstrate that the dielectric thickness can be kept constant and the width of the dielectric lining can be tapered along the direction of travel to vary the phase velocity, an approach only possible by the use of a rectangular waveguide geometry. The properties of tapered DLWs are discussed and following this, a design process is presented to demonstrate that the way this tapering can be optimized for different pulse and beam parameters. The minimum accelerating gradient for electron bunch capture is derived and compared to simulations. As examples of this design process, designs are considered based on considerations of the THz source, incoming electron beam, and manufacturing tolerances. A maximum THz pulse energy of <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>22.5</mn><mtext> </mtext><mtext> </mtext><mi mathvariant=\"normal\">μ</mi><mi mathvariant=\"normal\">J</mi></mrow></math> in the DLW was considered, which represents what is readily achievable using mJ-level regenerative amplifier laser systems together with optical-to-terahertz conversion in lithium niobate crystals. This will be more than double the energy of a 100 keV electron beam, increasing it to 205 keV. We describe the optimization process and present a detailed exploration of the beam dynamics, discussing how the performance will further improve with compressed bunches.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"58 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140598914","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 : 2024-04-08DOI: 10.1103/physrevaccelbeams.27.041301
Dillon Merenich, Brendan Leung, Gaurab Rijal, Xueying Lu, Scott Doran, Gongxiaohui Chen, Wanming Liu, Chunguang Jing, John Power, Charles Whiteford, Eric Wisniewski
A new regime in radiofrequency (rf) breakdown, named the breakdown insensitive acceleration regime (BIAR), was observed in an 11.7 GHz metamaterial structure for wakefield acceleration driven by rf pulses with a duration of a few nanoseconds. In the BIAR, rf breakdown occurs without interrupting potential beam acceleration, resulting in greater resilience to breakdown. We have investigated the possibility that BIAR can support higher gradients by characterizing the breakdown in a high-power test. The peak gradient reached when the structure was powered by 6 ns long rf pulses with 115 MW peak power. The short rf pulses were extracted from 65 MeV electron bunch trains with a total charge of up to 210 nC. This work has revealed the benefits of short-pulse acceleration by characterizing rf breakdown in the previously unexplored parameter space.
{"title":"Breakdown insensitive acceleration regime in a metamaterial accelerating structure","authors":"Dillon Merenich, Brendan Leung, Gaurab Rijal, Xueying Lu, Scott Doran, Gongxiaohui Chen, Wanming Liu, Chunguang Jing, John Power, Charles Whiteford, Eric Wisniewski","doi":"10.1103/physrevaccelbeams.27.041301","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.041301","url":null,"abstract":"A new regime in radiofrequency (rf) breakdown, named the breakdown insensitive acceleration regime (BIAR), was observed in an 11.7 GHz metamaterial structure for wakefield acceleration driven by rf pulses with a duration of a few nanoseconds. In the BIAR, rf breakdown occurs without interrupting potential beam acceleration, resulting in greater resilience to breakdown. We have investigated the possibility that BIAR can support higher gradients by characterizing the breakdown in a high-power test. The peak gradient reached <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>190</mn><mtext> </mtext><mtext> </mtext><mi>MV</mi><mo>/</mo><mi mathvariant=\"normal\">m</mi></mrow></math> when the structure was powered by 6 ns long rf pulses with 115 MW peak power. The short rf pulses were extracted from 65 MeV electron bunch trains with a total charge of up to 210 nC. This work has revealed the benefits of short-pulse acceleration by characterizing rf breakdown in the previously unexplored parameter space.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"94 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140599387","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}
We present a novel concept of longitudinal bunch train compression that can manipulate a relativistic electron beam across hundreds of meters. This concept holds the potential to compress the electron beam produced by a conditional linear accelerator at a high ratio, elevating its power to a level comparable with large induction accelerators. The method employs the spiral motion of electrons in a uniform magnetic field to fold hundreds-of-meters-long trajectories into a compact setup. The interval between bunches can be fine-tuned by modulating their spiral movement. We explore this method with the particle dynamic simulation. Compared to setups of similar size, such as a chicane, our method can compress bunches at considerably larger scales. Consequently, it opens up new possibilities for generating high-power beams using compact devices at lower costs.
{"title":"Longitudinal compression of a macrorelativistic electron beam","authors":"An Li, Jiaru Shi, Hao Zha, Qiang Gao, Liuyuan Zhou, Huaibi Chen","doi":"10.1103/physrevaccelbeams.27.044402","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.27.044402","url":null,"abstract":"We present a novel concept of longitudinal bunch train compression that can manipulate a relativistic electron beam across hundreds of meters. This concept holds the potential to compress the electron beam produced by a conditional linear accelerator at a high ratio, elevating its power to a level comparable with large induction accelerators. The method employs the spiral motion of electrons in a uniform magnetic field to fold hundreds-of-meters-long trajectories into a compact setup. The interval between bunches can be fine-tuned by modulating their spiral movement. We explore this method with the particle dynamic simulation. Compared to setups of similar size, such as a chicane, our method can compress bunches at considerably larger scales. Consequently, it opens up new possibilities for generating high-power beams using compact devices at lower costs.","PeriodicalId":54297,"journal":{"name":"Physical Review Accelerators and Beams","volume":"71 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140598921","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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