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
目的:探讨环指蛋白144B(ring finger protein 144B,RNF144B)在胃癌组织中的表达水平及其与胃癌患者临床预后的关系。方法:回顾性分析2013年1月-2014年1月在兰州大学第二医院确诊并行根治性手术治疗的胃癌患者的临床资料;我们的研究一共...目的:探讨环指蛋白144B(ring finger protein 144B,RNF144B)在胃癌组织中的表达水平及其与胃癌患者临床预后的关系。方法:回顾性分析2013年1月-2014年1月在兰州大学第二医院确诊并行根治性手术治疗的胃癌患者的临床资料;我们的研究一共纳入了105名患者,记录患者的TNM分期、肿瘤大小、分化水平、癌胚抗原(carcino-embryonic antigen,CEA)等指标并记录患者的总体生存时间(overall survival,OS);利用免疫组织化学染色(immunohistochemistry,IHC)检测RNF144B在胃癌及癌旁组织中的表达,并分析其与患者一般临床病理特征的联系;应用Cox回归模型评估患者术后总体生存时间的影响因素;使用Kaplan-Meier Plotter数据库对RNF144B进行生存相关性分析,随后利用临床数据进行验证。结果:RNF144B在胃癌组织中显著高表达(P=0.0039),RNF144B高表达组的患者CEA水平、Ki67阳性率、临床病理分期、T分期均显著高于低表达组,而分化程度差于低表达组(P<0.05);多因素分析显示RNF144B高表达、肿瘤分化程度低、临床病理分期高均是影响胃癌患者术后总体生存时间的独立因素(P<0.05);Kaplan-Meier法分析得RNF144B高表达组术后5年生存率(6.06%)低于低表达组(29.69%)(P<0.01)。结论:RNF144B在胃癌中高表达并标志着更差的临床预后。展开更多
By choosing parameters in the modulator, the dispersive section and the seed laser, the spatial bunching of the electron beam can be correlated to the n-th harmonic of the radiator radiation, instead of the fundamenta...By choosing parameters in the modulator, the dispersive section and the seed laser, the spatial bunching of the electron beam can be correlated to the n-th harmonic of the radiator radiation, instead of the fundamental radiation in conventional high-gain harmonic generation (HGHG). Thus, the radiator undulator is operated at high harmonic mode. In this paper, the possibility of harmonic operation of Shanghai deep ultraviolet (SDUV) free electron laser (FEL) is studied. Discussions on the principle of harmonic operation, the simulation code development, the simulation results, and the proposed experimental procedure for verification of harmonic operation at the SDUV FEL are also presented.展开更多
As a natural character of high gain flee electron laser (FEL),harmonic radiation is regarded as the natural extensions to short wavelengths.In high gain harmonic generation (HGHG) scheme,harmonic evolution may be attr...As a natural character of high gain flee electron laser (FEL),harmonic radiation is regarded as the natural extensions to short wavelengths.In high gain harmonic generation (HGHG) scheme,harmonic evolution may be attributed to the initial harmonic bunching,self amplification of the harmonic radiation,electron beam strongly bunched by the fundamental radiation,the faster longitudinal dynamics and the fundamental synchrotron oscillation.It is more complex than harmonic evolution in other FEL schemes.In this paper,via theoretical analyses and three dimensional simulations,a general description of different aspects of harmonic evolution in the HGHG process is presented.展开更多
Cascading stages of high-gain harmonic generation(HGHG) free electron laser(FEL) is a promising way to produce fully coherent X-ray radiation.As a test facility for modern FEL R&D,the Shanghai deep ultraviolet FEL...Cascading stages of high-gain harmonic generation(HGHG) free electron laser(FEL) is a promising way to produce fully coherent X-ray radiation.As a test facility for modern FEL R&D,the Shanghai deep ultraviolet FEL(SDUV-FEL) is now under upgrading for the cascading two stages of HGHG experiment.Since the energy of the electron beam is as low as about 185 MeV after upgrade,the total harmonic number of this two stages HGHG is only 2×2,and the wavelength of the final radiation is 196.5 nm which is the 4th harmonic of the 786 nm seed laser.With help of three-dimensional simulation codes,design studies on the FEL physics for the cascaded HGHG experiment are present based on the parameters of the upgraded SDUV-FEL facility.It is found from the simulation results that the part of the electron beam which has been used in the first stage can still generate powerful radiation in the radiator of the second stage,and this radiation will be difficult to be separated from the radiation generated by the fresh part of the electron beam.To overcome this problem,a novel method based on the energy spectrum of the electron beam is proposed in this paper to demonstrate the "fresh bunch" technique.展开更多
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.
基金Key Project for Promoting Fundamental Research in China (Grant No. 2002CB713600)
文摘By choosing parameters in the modulator, the dispersive section and the seed laser, the spatial bunching of the electron beam can be correlated to the n-th harmonic of the radiator radiation, instead of the fundamental radiation in conventional high-gain harmonic generation (HGHG). Thus, the radiator undulator is operated at high harmonic mode. In this paper, the possibility of harmonic operation of Shanghai deep ultraviolet (SDUV) free electron laser (FEL) is studied. Discussions on the principle of harmonic operation, the simulation code development, the simulation results, and the proposed experimental procedure for verification of harmonic operation at the SDUV FEL are also presented.
基金supported by the Key Project for Promoting Fundamental Research in China (Grant No.2002CB713600)
文摘As a natural character of high gain flee electron laser (FEL),harmonic radiation is regarded as the natural extensions to short wavelengths.In high gain harmonic generation (HGHG) scheme,harmonic evolution may be attributed to the initial harmonic bunching,self amplification of the harmonic radiation,electron beam strongly bunched by the fundamental radiation,the faster longitudinal dynamics and the fundamental synchrotron oscillation.It is more complex than harmonic evolution in other FEL schemes.In this paper,via theoretical analyses and three dimensional simulations,a general description of different aspects of harmonic evolution in the HGHG process is presented.
基金supported by the National Natural Science Foundation of China (10935011)the National Basic Research Program of China (2011CB808300)
文摘Cascading stages of high-gain harmonic generation(HGHG) free electron laser(FEL) is a promising way to produce fully coherent X-ray radiation.As a test facility for modern FEL R&D,the Shanghai deep ultraviolet FEL(SDUV-FEL) is now under upgrading for the cascading two stages of HGHG experiment.Since the energy of the electron beam is as low as about 185 MeV after upgrade,the total harmonic number of this two stages HGHG is only 2×2,and the wavelength of the final radiation is 196.5 nm which is the 4th harmonic of the 786 nm seed laser.With help of three-dimensional simulation codes,design studies on the FEL physics for the cascaded HGHG experiment are present based on the parameters of the upgraded SDUV-FEL facility.It is found from the simulation results that the part of the electron beam which has been used in the first stage can still generate powerful radiation in the radiator of the second stage,and this radiation will be difficult to be separated from the radiation generated by the fresh part of the electron beam.To overcome this problem,a novel method based on the energy spectrum of the electron beam is proposed in this paper to demonstrate the "fresh bunch" technique.
