We present the analytical and simulated results of our study of the influence of the acceleration gradient in the velocity bunching process, which is a bunch compression scheme that uses a travelling wave accelerating...We present the analytical and simulated results of our study of the influence of the acceleration gradient in the velocity bunching process, which is a bunch compression scheme that uses a travelling wave accelerating structure as a compressor. Our study shows that the bunch compression application with low acceleration gradient is more tolerant to phase jitter and more successful in obtaining a compressed electron beam with symmetrical longitudinal distribution and low energy spread. We also present a transverse emittance compensation scheme to compensate the emittance growth caused by the increase of the space charge force in the compressing process, which is easy to adjust for different compression factors.展开更多
High brightness electron beam is one of the main goals of the research and development effort in RF photo-injectors.Compared with the normally used magnetic chicane,an alternative scheme,commonly known as 'velocit...High brightness electron beam is one of the main goals of the research and development effort in RF photo-injectors.Compared with the normally used magnetic chicane,an alternative scheme,commonly known as 'velocity bunching',has been proposed as a tool to compress electron beam pulses in modern high brightness photo-injector sources.This paper presents numerical optimization systematically and the first attempt to demonstrate the velocity bunching scheme on SDUV-FEL linac experimentally.The relationship between the degree of bunching and the off-crest phase of the accelerating structure is explored experimentally.Velocity bunching operating mode illustrates flexible performances with an intrinsic machine jitter,which agrees well with the theoretical prediction.展开更多
从机理上对基于阴影恢复形状技术(shape from shading,SFS)全极化SAR海浪谱反演方法的可行性进行了理论论证。结果表明,利用全极化SAR图像计算方位角漂移时,实际上隐含了速度聚束调制。除方位角处于90°附近很窄范围内的情形,流体...从机理上对基于阴影恢复形状技术(shape from shading,SFS)全极化SAR海浪谱反演方法的可行性进行了理论论证。结果表明,利用全极化SAR图像计算方位角漂移时,实际上隐含了速度聚束调制。除方位角处于90°附近很窄范围内的情形,流体动力学调制机制的影响可以忽略。通过对比不同极化模式数值模拟结果发现,将HH极化图像强度应用于SFS技术公式时,比采用VV极化图像强度所得的结果精度高,特别是在方位角ψ值较大时,采用HH极化SAR图像的优势更为明显。展开更多
基金Supported by National Natural Sciences Foundation of China(11205152,11375199)Fundamental Research Funds for the Central Universities(WK2310000042)Major State Basic Research Development Program of China(2011CB808301)
文摘We present the analytical and simulated results of our study of the influence of the acceleration gradient in the velocity bunching process, which is a bunch compression scheme that uses a travelling wave accelerating structure as a compressor. Our study shows that the bunch compression application with low acceleration gradient is more tolerant to phase jitter and more successful in obtaining a compressed electron beam with symmetrical longitudinal distribution and low energy spread. We also present a transverse emittance compensation scheme to compensate the emittance growth caused by the increase of the space charge force in the compressing process, which is easy to adjust for different compression factors.
基金Supported by Major State Basic Research Development Program of China (973 Program) (Grant No.2011CB808300)
文摘High brightness electron beam is one of the main goals of the research and development effort in RF photo-injectors.Compared with the normally used magnetic chicane,an alternative scheme,commonly known as 'velocity bunching',has been proposed as a tool to compress electron beam pulses in modern high brightness photo-injector sources.This paper presents numerical optimization systematically and the first attempt to demonstrate the velocity bunching scheme on SDUV-FEL linac experimentally.The relationship between the degree of bunching and the off-crest phase of the accelerating structure is explored experimentally.Velocity bunching operating mode illustrates flexible performances with an intrinsic machine jitter,which agrees well with the theoretical prediction.
文摘从机理上对基于阴影恢复形状技术(shape from shading,SFS)全极化SAR海浪谱反演方法的可行性进行了理论论证。结果表明,利用全极化SAR图像计算方位角漂移时,实际上隐含了速度聚束调制。除方位角处于90°附近很窄范围内的情形,流体动力学调制机制的影响可以忽略。通过对比不同极化模式数值模拟结果发现,将HH极化图像强度应用于SFS技术公式时,比采用VV极化图像强度所得的结果精度高,特别是在方位角ψ值较大时,采用HH极化SAR图像的优势更为明显。
