Pub Date : 2015-06-23DOI: 10.1103/PHYSREVSTAB.18.064401
V. Smaluk, I. Martin, R. Fielder, R. Bartolini
In an electron storage ring, the interaction between a single-bunch beam and a vacuum chamber impedance affects the beam parameters, which can be measured rather precisely. So we can develop beambased numerical models of longitudinal and transverse impedances. At the Diamond Light Source (DLS) to get the model parameters, a set of measured data has been used including current-dependent shift of betatron tunes and synchronous phase, chromatic damping rates, and bunch lengthening. A matlab code for multiparticle tracking has been developed. The tracking results and analytical estimations are quite consistent with the measured data. Since Diamond has the shortest natural bunch length among all light sources in standard operation, the studies of collective effects with short bunches are relevant to many facilities including next generation of light sources.
{"title":"Beam-based model of broad-band impedance of the Diamond Light Source","authors":"V. Smaluk, I. Martin, R. Fielder, R. Bartolini","doi":"10.1103/PHYSREVSTAB.18.064401","DOIUrl":"https://doi.org/10.1103/PHYSREVSTAB.18.064401","url":null,"abstract":"In an electron storage ring, the interaction between a single-bunch beam and a vacuum chamber impedance affects the beam parameters, which can be measured rather precisely. So we can develop beambased numerical models of longitudinal and transverse impedances. At the Diamond Light Source (DLS) to get the model parameters, a set of measured data has been used including current-dependent shift of betatron tunes and synchronous phase, chromatic damping rates, and bunch lengthening. A matlab code for multiparticle tracking has been developed. The tracking results and analytical estimations are quite consistent with the measured data. Since Diamond has the shortest natural bunch length among all light sources in standard operation, the studies of collective effects with short bunches are relevant to many facilities including next generation of light sources.","PeriodicalId":20072,"journal":{"name":"Physical Review Special Topics-accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86388350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-22DOI: 10.1103/PHYSREVSTAB.18.060704
Yuhui Li, B. Ketenoglu, J. Pflueger
In long gap tunable undulators, strong magnetic forces always lead to some amount of gap-dependent girder deformation and resulting gap-dependent phase errors. For the undulators for the European XFEL, this problem has been investigated thoroughly and quantitatively. Using the different gap dependencies of suitable shims and pole height tuning, a method is presented which can be applied to reduce the overall gap dependence of the phase error if needed. It is exemplified by tuning one of the undulator segments for the European X-Ray Free Electron Laser back to specs.
{"title":"Girder deformation related phase errors on the undulators for the European X-Ray Free Electron Laser","authors":"Yuhui Li, B. Ketenoglu, J. Pflueger","doi":"10.1103/PHYSREVSTAB.18.060704","DOIUrl":"https://doi.org/10.1103/PHYSREVSTAB.18.060704","url":null,"abstract":"In long gap tunable undulators, strong magnetic forces always lead to some amount of gap-dependent girder deformation and resulting gap-dependent phase errors. For the undulators for the European XFEL, this problem has been investigated thoroughly and quantitatively. Using the different gap dependencies of suitable shims and pole height tuning, a method is presented which can be applied to reduce the overall gap dependence of the phase error if needed. It is exemplified by tuning one of the undulator segments for the European X-Ray Free Electron Laser back to specs.","PeriodicalId":20072,"journal":{"name":"Physical Review Special Topics-accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79319358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-22DOI: 10.1103/PHYSREVSTAB.18.063401
E. Prat, S. Bettoni, H. Braun, M. Divall, T. Schietinger
Radio-frequency (rf) photoinjectors are used to generate high-brightness electron beams for a wide range of applications. Because of their outstanding beam quality, they are particularly well-suited as sources for X-ray free-electron lasers (FELs). The beam emittance, which is significantly influenced by the intrinsic emittance of the cathode, is fundamental for FELs, since it has a strong impact on the lasing performance and it defines the length and cost of the facility. In this paper we present measurements of the intrinsic emittance as a function of the rf field for a copper photocathode. Our measurements match with the theoretical expectations, showing that the intrinsic emittance can be reduced by decreasing the rf field at the cathode. We obtained normalized intrinsic emittances down to 350 nm = mm, the lowest values ever measured in a rf photoinjector.
{"title":"Measurements of intrinsic emittance dependence on rf field for copper photocathodes","authors":"E. Prat, S. Bettoni, H. Braun, M. Divall, T. Schietinger","doi":"10.1103/PHYSREVSTAB.18.063401","DOIUrl":"https://doi.org/10.1103/PHYSREVSTAB.18.063401","url":null,"abstract":"Radio-frequency (rf) photoinjectors are used to generate high-brightness electron beams for a wide range of applications. Because of their outstanding beam quality, they are particularly well-suited as sources for X-ray free-electron lasers (FELs). The beam emittance, which is significantly influenced by the intrinsic emittance of the cathode, is fundamental for FELs, since it has a strong impact on the lasing performance and it defines the length and cost of the facility. In this paper we present measurements of the intrinsic emittance as a function of the rf field for a copper photocathode. Our measurements match with the theoretical expectations, showing that the intrinsic emittance can be reduced by decreasing the rf field at the cathode. We obtained normalized intrinsic emittances down to 350 nm = mm, the lowest values ever measured in a rf photoinjector.","PeriodicalId":20072,"journal":{"name":"Physical Review Special Topics-accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72655037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-22DOI: 10.1103/PHYSREVSTAB.18.061001
R. Bruce, R. Assmann, S. Redaelli
The first run of the Large Hadron Collider (LHC) at CERN was very successful and resulted in important physics discoveries. One way of increasing the luminosity in a collider, which gave a very significant contribution to the LHC performance in the first run and can be used even if the beam intensity cannot be increased, is to decrease the transverse beam size at the interaction points by reducing the optical function β . However, when doing so, the beam becomes larger in the final focusing system, which could expose its aperture to beam losses. For the LHC, which is designed to store beams with a total energy of 362 MJ, this is critical, since the loss of even a small fraction of the beam could cause a magnet quench or even damage. Therefore, the machine aperture has to be protected by the collimation system. The settings of the collimators constrain the maximum beam size that can be tolerated and therefore impose a lower limit on β . In this paper, we present calculations to determine safe collimator settings and the resulting limit on β , based on available aperture and operational stability of the machine. Our model was used to determine the LHC configurations in 2011 and 2012 and it was found that β could be decreased significantly compared to the conservative model used in 2010. The gain in luminosity resulting from the decreased margins between collimators was more than a factor 2, and a further contribution from the use of realistic aperture estimates based on measurements was almost as large. This has played an essential role in the rapid and successful accumulation of experimental data in the LHC.
{"title":"Calculations of safe collimator settings and β * at the CERN Large Hadron Collider","authors":"R. Bruce, R. Assmann, S. Redaelli","doi":"10.1103/PHYSREVSTAB.18.061001","DOIUrl":"https://doi.org/10.1103/PHYSREVSTAB.18.061001","url":null,"abstract":"The first run of the Large Hadron Collider (LHC) at CERN was very successful and resulted in important physics discoveries. One way of increasing the luminosity in a collider, which gave a very significant contribution to the LHC performance in the first run and can be used even if the beam intensity cannot be increased, is to decrease the transverse beam size at the interaction points by reducing the optical function β . However, when doing so, the beam becomes larger in the final focusing system, which could expose its aperture to beam losses. For the LHC, which is designed to store beams with a total energy of 362 MJ, this is critical, since the loss of even a small fraction of the beam could cause a magnet quench or even damage. Therefore, the machine aperture has to be protected by the collimation system. The settings of the collimators constrain the maximum beam size that can be tolerated and therefore impose a lower limit on β . In this paper, we present calculations to determine safe collimator settings and the resulting limit on β , based on available aperture and operational stability of the machine. Our model was used to determine the LHC configurations in 2011 and 2012 and it was found that β could be decreased significantly compared to the conservative model used in 2010. The gain in luminosity resulting from the decreased margins between collimators was more than a factor 2, and a further contribution from the use of realistic aperture estimates based on measurements was almost as large. This has played an essential role in the rapid and successful accumulation of experimental data in the LHC.","PeriodicalId":20072,"journal":{"name":"Physical Review Special Topics-accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73573800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-18DOI: 10.1103/PHYSREVSTAB.18.064801
K. Floettmann
In this paper, a detailed discussion of the rf-related beam dynamics in rf guns and accelerating cavities is presented. Other rf-gun-related aspects such as space charge and cathode physics are not treated. An effective start phase is introduced in order to yield a better description for the synchronous phase, the energy gain, and the bunch compression factor in gun cavities. Energy spread and longitudinal emittance are treated in a form applicable to guns as well as to accelerating cavities. Discussions on the transverse emittance include the chromatic emittance variation at high emission phases and effects of field asymmetries and combined solenoid-cavity sections.
{"title":"rf-induced beam dynamics in rf guns and accelerating cavities","authors":"K. Floettmann","doi":"10.1103/PHYSREVSTAB.18.064801","DOIUrl":"https://doi.org/10.1103/PHYSREVSTAB.18.064801","url":null,"abstract":"In this paper, a detailed discussion of the rf-related beam dynamics in rf guns and accelerating cavities is presented. Other rf-gun-related aspects such as space charge and cathode physics are not treated. An effective start phase is introduced in order to yield a better description for the synchronous phase, the energy gain, and the bunch compression factor in gun cavities. Energy spread and longitudinal emittance are treated in a form applicable to guns as well as to accelerating cavities. Discussions on the transverse emittance include the chromatic emittance variation at high emission phases and effects of field asymmetries and combined solenoid-cavity sections.","PeriodicalId":20072,"journal":{"name":"Physical Review Special Topics-accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79240063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-18DOI: 10.1103/PHYSREVSTAB.18.060703
G. Penn
Preliminary studies of harmonic lasing have shown significant promise as a method to produce radiation at higher photon energies for a given electron energy and for a given undulator. The basic idea is to suppress radiation at the fundamental resonant wavelength, and allow radiation at a specific harmonic to grow exponentially without being driven by nonlinear processes at the fundamental. This has several potential benefits: higher photon energies for the same undulator field, plus significantly more power and smaller bandwidth compared to extracting nonlinear radiation at the harmonic after the fundamental has reached saturation. In this paper, we use beam parameters from the current design of LCLS-II to take a critical look at the challenge of suppressing radiation at the fundamental wavelength and to evaluate how much of an improvement in terms of photon energy reach and brightness can be achieved through harmonic lasing. For undulators with adjustable magnetic fields, a scheme is presented which can delay the onset of saturation at the fundamental wavelength by a factor of 2. Performance characteristics and especially spectral brightness are compared to self-seeded beam lines as an alternative method to reduce bandwidth, as well as with more conventional SASE beam lines.
{"title":"Simple method to suppress the fundamental in a harmonic free electron laser","authors":"G. Penn","doi":"10.1103/PHYSREVSTAB.18.060703","DOIUrl":"https://doi.org/10.1103/PHYSREVSTAB.18.060703","url":null,"abstract":"Preliminary studies of harmonic lasing have shown significant promise as a method to produce radiation at higher photon energies for a given electron energy and for a given undulator. The basic idea is to suppress radiation at the fundamental resonant wavelength, and allow radiation at a specific harmonic to grow exponentially without being driven by nonlinear processes at the fundamental. This has several potential benefits: higher photon energies for the same undulator field, plus significantly more power and smaller bandwidth compared to extracting nonlinear radiation at the harmonic after the fundamental has reached saturation. In this paper, we use beam parameters from the current design of LCLS-II to take a critical look at the challenge of suppressing radiation at the fundamental wavelength and to evaluate how much of an improvement in terms of photon energy reach and brightness can be achieved through harmonic lasing. For undulators with adjustable magnetic fields, a scheme is presented which can delay the onset of saturation at the fundamental wavelength by a factor of 2. Performance characteristics and especially spectral brightness are compared to self-seeded beam lines as an alternative method to reduce bandwidth, as well as with more conventional SASE beam lines.","PeriodicalId":20072,"journal":{"name":"Physical Review Special Topics-accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83167698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-17DOI: 10.1103/PHYSREVSTAB.18.061301
E. Guillaume, A. Döpp, C. Thaury, A. Lifschitz, J. Goddet, A. Tafzi, F. Sylla, G. Iaquanello, T. Lefrou, P. Rousseau, K. T. Phuoc, V. Malka
While large efforts have been devoted to improving the quality of electron beams from laser plasma accelerators, often to the detriment of the charge, many applications do not require very high quality but high-charge beams. Despite this need, the acceleration of largely charged beams has been barely studied. Here we explore both experimentally and numerically the physics of highly loaded wakefield acceleration. We find that the shape of the electron spectra is strikingly independent of the laser energy, due to the emergence of a saturation effect induced by beamloading. A transition from quasi-Maxwellian spectra at high plasma densities to flatter spectra at lower densities is also found, which is shown to be produced by the wakefield driven by the electron bunch itself after the laser depletion.
{"title":"Physics of fully-loaded laser-plasma accelerators","authors":"E. Guillaume, A. Döpp, C. Thaury, A. Lifschitz, J. Goddet, A. Tafzi, F. Sylla, G. Iaquanello, T. Lefrou, P. Rousseau, K. T. Phuoc, V. Malka","doi":"10.1103/PHYSREVSTAB.18.061301","DOIUrl":"https://doi.org/10.1103/PHYSREVSTAB.18.061301","url":null,"abstract":"While large efforts have been devoted to improving the quality of electron beams from laser plasma accelerators, often to the detriment of the charge, many applications do not require very high quality but high-charge beams. Despite this need, the acceleration of largely charged beams has been barely studied. \u0000Here we explore both experimentally and numerically the physics of highly loaded wakefield acceleration. We find that the shape of the electron spectra is strikingly independent of the laser energy, due to the emergence of a saturation effect induced by beamloading. A transition from quasi-Maxwellian spectra at high plasma densities to flatter spectra at lower densities is also found, which is shown to be produced by the wakefield driven by the electron bunch itself after the laser depletion.","PeriodicalId":20072,"journal":{"name":"Physical Review Special Topics-accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79483830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-17DOI: 10.1103/PHYSREVSTAB.18.060702
Y. Sakai, I. Pogorelsky, O. Williams, F. O’Shea, S. Barber, I. Gadjev, J. Duris, P. Musumeci, M. Fedurin, A. Korostyshevsky, B. Malone, C. Swinson, G. Stenby, K. Kusche, M. Babzien, M. Montemagno, P. Jacob, Z. Zhong, M. Polyanskiy, V. Yakimenko, J. Rosenzweig
Inverse Compton scattering of laser photons by ultrarelativistic electron beam provides polarized x- to $ensuremath{gamma}$-ray pulses due to the Doppler blueshifting. Nonlinear electrodynamics in the relativistically intense linearly polarized laser field changes the radiation kinetics established during the Compton interaction. These are due to the induced figure-8 motion, which introduces an overall redshift in the radiation spectrum, with the concomitant emission of higher order harmonics. To experimentally analyze the strong field physics associated with the nonlinear electron-laser interaction, clear modifications to the angular and wavelength distributions of x rays are observed. The relativistic photon wave field is provided by the ps ${mathrm{CO}}_{2}$ laser of peak normalized vector potential of $0.5l{a}_{L}l0.7$, which due to the quadratic dependence of the strength of nonlinear phenomena on ${a}_{L}$ permits sufficient effects not observed in past 2nd harmonic study with ${a}_{L}ensuremath{approx}0.3$ laser [, Phys. Rev. Lett. 96, 054802 (2006)]. The angular spectral characteristics are revealed using $K$-, $L$-edge, and high energy attenuation filters. The observation indicates existence of the electrons' longitudinal motion through frequency redshifting understood as the mass shift effect. Thus, the 3rd harmonic radiation has been observed containing on-axis x-ray component that is directly associated with the induced figure-8 motion. These are further supported by an initial evidence of off-axis 2nd harmonic radiation produced in a circularly polarized laser wave field. Total x-ray photon number per pulse, scattered by 65 MeV electron beam of 0.3 nC, at the interaction point is measured to be approximately ${10}^{9}$.
超相对论性电子束对激光光子的逆康普顿散射，由于多普勒蓝移，提供了偏振x射线到$ensuremath{gamma}$射线脉冲。在相对强的线偏振激光场中，非线性电动力学改变了康普顿相互作用中建立的辐射动力学。这是由于诱发的数字8运动，它在辐射光谱中引入了一个整体红移，伴随着高次谐波的发射。为了实验分析与非线性电子-激光相互作用相关的强场物理，观察到x射线的角度和波长分布的明显变化。相对论光子波场是由峰值归一化矢量势为$0.5l{a}_{L}l0.7$的ps ${mathrm{CO}}_{2}$激光器提供的，由于非线性现象强度与${a}_{L}$的二次依赖关系，使得${a}_{L}ensuremath{approx}0.3$激光器在过去的二次谐波研究中没有观察到足够的效应[，物理学]。Rev. Lett. 96, 054802(2006)]。利用$K$ -， $L$边缘和高能量衰减滤波器揭示了角光谱特性。观测结果表明，电子通过频率红移进行纵向运动，即质量位移效应。因此，已经观察到三次谐波辐射包含与诱导的8字形运动直接相关的轴上x射线分量。在圆偏振激光波场中产生的离轴二次谐波辐射的初步证据进一步支持了这些。经0.3 nC的65 MeV电子束散射，在相互作用点处的每脉冲x射线总光子数约为${10}^{9}$。
{"title":"Observation of redshifting and harmonic radiation in inverse Compton scattering","authors":"Y. Sakai, I. Pogorelsky, O. Williams, F. O’Shea, S. Barber, I. Gadjev, J. Duris, P. Musumeci, M. Fedurin, A. Korostyshevsky, B. Malone, C. Swinson, G. Stenby, K. Kusche, M. Babzien, M. Montemagno, P. Jacob, Z. Zhong, M. Polyanskiy, V. Yakimenko, J. Rosenzweig","doi":"10.1103/PHYSREVSTAB.18.060702","DOIUrl":"https://doi.org/10.1103/PHYSREVSTAB.18.060702","url":null,"abstract":"Inverse Compton scattering of laser photons by ultrarelativistic electron beam provides polarized x- to $ensuremath{gamma}$-ray pulses due to the Doppler blueshifting. Nonlinear electrodynamics in the relativistically intense linearly polarized laser field changes the radiation kinetics established during the Compton interaction. These are due to the induced figure-8 motion, which introduces an overall redshift in the radiation spectrum, with the concomitant emission of higher order harmonics. To experimentally analyze the strong field physics associated with the nonlinear electron-laser interaction, clear modifications to the angular and wavelength distributions of x rays are observed. The relativistic photon wave field is provided by the ps ${mathrm{CO}}_{2}$ laser of peak normalized vector potential of $0.5l{a}_{L}l0.7$, which due to the quadratic dependence of the strength of nonlinear phenomena on ${a}_{L}$ permits sufficient effects not observed in past 2nd harmonic study with ${a}_{L}ensuremath{approx}0.3$ laser [, Phys. Rev. Lett. 96, 054802 (2006)]. The angular spectral characteristics are revealed using $K$-, $L$-edge, and high energy attenuation filters. The observation indicates existence of the electrons' longitudinal motion through frequency redshifting understood as the mass shift effect. Thus, the 3rd harmonic radiation has been observed containing on-axis x-ray component that is directly associated with the induced figure-8 motion. These are further supported by an initial evidence of off-axis 2nd harmonic radiation produced in a circularly polarized laser wave field. Total x-ray photon number per pulse, scattered by 65 MeV electron beam of 0.3 nC, at the interaction point is measured to be approximately ${10}^{9}$.","PeriodicalId":20072,"journal":{"name":"Physical Review Special Topics-accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83222365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-16DOI: 10.1103/PHYSREVSTAB.18.074001
A. Franchi, M. Giovannozzi
With a few exceptions, all on-axis injection and extraction schemes implemented in circular particle accelerators, synchrotrons, and storage rings, make use of magnetic and electrostatic septa with systems of slow-pulsing dipoles acting on tens of thousands of turns and fast-pulsing dipoles on just a few. The dipoles create a closed orbit deformation around the septa, usually referred to as an orbit bump. A new approach is presented which obviates the need for the septum deflectors. Fast-pulsing elements are still required, but their strength can be minimized by choosing appropriate local accelerator optics. This technique should increase the beam clearance and reduce the usually high radiation levels found around the septa and also reduce the machine impedance introduced by the fast-pulsing dipoles. The basis of the technique is the creation of stable islands around stable fixed points in horizontal phase space. The trajectories of these islands may then be adjusted to match the position and angle of the incoming or outgoing beam.
{"title":"Novel technique for injecting and extracting beams in a circular hadron accelerator without using septum magnets","authors":"A. Franchi, M. Giovannozzi","doi":"10.1103/PHYSREVSTAB.18.074001","DOIUrl":"https://doi.org/10.1103/PHYSREVSTAB.18.074001","url":null,"abstract":"With a few exceptions, all on-axis injection and extraction schemes implemented in circular particle accelerators, synchrotrons, and storage rings, make use of magnetic and electrostatic septa with systems of slow-pulsing dipoles acting on tens of thousands of turns and fast-pulsing dipoles on just a few. The dipoles create a closed orbit deformation around the septa, usually referred to as an orbit bump. A new approach is presented which obviates the need for the septum deflectors. Fast-pulsing elements are still required, but their strength can be minimized by choosing appropriate local accelerator optics. This technique should increase the beam clearance and reduce the usually high radiation levels found around the septa and also reduce the machine impedance introduced by the fast-pulsing dipoles. The basis of the technique is the creation of stable islands around stable fixed points in horizontal phase space. The trajectories of these islands may then be adjusted to match the position and angle of the incoming or outgoing beam.","PeriodicalId":20072,"journal":{"name":"Physical Review Special Topics-accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84940059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-05-29DOI: 10.1103/PHYSREVSTAB.18.053401
Zhe Zhang, Chuanxiang Tang
{"title":"Analytical study on emittance growth caused by roughness of a metallic photocathode","authors":"Zhe Zhang, Chuanxiang Tang","doi":"10.1103/PHYSREVSTAB.18.053401","DOIUrl":"https://doi.org/10.1103/PHYSREVSTAB.18.053401","url":null,"abstract":"","PeriodicalId":20072,"journal":{"name":"Physical Review Special Topics-accelerators and Beams","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75937536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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