A thermionic gun is endowed with a long bunch tail,which presents challenges for the compact terahertz free electron laser(FEL)facility at the Huazhong University of Science and Technology.Owing to a large energy spre...A thermionic gun is endowed with a long bunch tail,which presents challenges for the compact terahertz free electron laser(FEL)facility at the Huazhong University of Science and Technology.Owing to a large energy spread,the tail particles do not contribute to the radiation.In the original design,an x-direction slit is used in the dispersive section of the transport line to remove the tail particles.This paper presents an improved scheme to remove the tail by introducing an RF beam chopper system at the exit of the electron gun,to prevent a significant number of tail particles from entering the linac.The facility remains compact while effectively removing the tail of the bunch.The parameters of the beam chopper system are designed.Bunch parameters and radiation performance are analyzed via a start-to-end simulation.The findings indicate that 43%of the particles can pass through the beam chopper system for subsequent acceleration and transport,which saves the RF power,reduces beam loss in the linac,reduces background noise,and suppresses the sideband instability.Simultaneously,the beam chopper system causes an increase in beam emittance,energy spread,and an offset in the center of the bunch.These effects can be mitigated by a solenoid,linac,and steering coils.The simulation results for the FEL show that the micro-pulse energy is greater than 1.1μJ in the frequency range of 2.8-9.7 THz,and the maximum micro-pulse energy is 1.28μJ.展开更多
Background The beam chopper system of China Spallation Neutron Source(CSNS)is used to pulsed chop the negative hydrogen ion beam from ion source;in order to meet the beam time structure of rapid cycling synchrotron(RC...Background The beam chopper system of China Spallation Neutron Source(CSNS)is used to pulsed chop the negative hydrogen ion beam from ion source;in order to meet the beam time structure of rapid cycling synchrotron(RCS),it is the key to control emittance growth of low energy beam and decrease beam loss during the beam injection process from the linac to RCS.After beam chopped,the particle beam is required to deviate completely and then lose at entrance of radiofrequency quadrupole(RFQ)cavity;considering high duty cycle of ion source and beam high chop rate,the effect of deflected particles on RFQ is difficult to predict.Purpose A bipolar beam chopper pulse power supply is developed,which makes the beam spot at the entrance of RFQ twice that of unipolar beam chopper power supply,and reduces the damage of deflected particles to RFQ cavity and vacuum.Methods The beam chopper power supply provides a fast high voltage pulse source;two fast reversing switches are used to quickly change the polarity of the output high voltage pulse in 40 ms.Results and conclusion The power supply has been installed in the low beam energy transport line(LEBT),the output high voltage pulse is±6 kV,frequency is about 1 MHz,and the pulse edge is less than 10 ns.展开更多
In order to perform the studies on a pulsed beam generation system based on a high intensity cyclotron, a test beam line with a pulsed beam generation for a 10 MeV compact cyclotron (CYCIAE-10) has been designed and c...In order to perform the studies on a pulsed beam generation system based on a high intensity cyclotron, a test beam line with a pulsed beam generation for a 10 MeV compact cyclotron (CYCIAE-10) has been designed and constructed at China Institute of Atomic Energy (CIAE). A 70 MHz continuous H- beam can be pulsed to the pulse length of less than 10 ns with a repetition rate of 4.4 MHz. The sine waveform with a frequency of 2.2 MHz is adopted for the chopper and a mesh structure with single drift and dual gaps is used for the 70 MHz buncher. A helical resonator is designed and constructed based on simulations and experiments on the RF matching for the chopper. A helical inductance loop that is exceptionally large of its kind and equipped with water cooling for the resonator has been successfully wound and a 500 W solid RF amplifier has been manufactured. A special measuring device has been designed, which can be used to measure both the DC beam and the pulsed beam. The required pulsed beam was obtained after pulsed beam tuning.展开更多
针对应用于硼中子俘获治疗的加速器中子源的束流偏转问题,为其低能束流传输线部分设计了一套斩束器,通过理论计算与软件模拟,验证方案的可行性。为了解决斩波器电场强度不均匀问题,引入圆弧电极设计结构,微波工作室(CST Studio Suite)...针对应用于硼中子俘获治疗的加速器中子源的束流偏转问题,为其低能束流传输线部分设计了一套斩束器,通过理论计算与软件模拟,验证方案的可行性。为了解决斩波器电场强度不均匀问题,引入圆弧电极设计结构,微波工作室(CST Studio Suite)模拟仿真表明其具有更好的电场分布均匀性。发展了基于Python程序的CST与TraceWin联合束流动力学模拟,结果表明设计的斩波器能够高效率地实现束流偏转功能,设计方案具有良好的实际应用价值和意义。展开更多
The design of CSNS MEBT has two objectives：（1） to match the beam both in the transversal direction and the longitudinal direction from RFQ into DTL;（2） to further chop the beam into the required time structure as...The design of CSNS MEBT has two objectives：（1） to match the beam both in the transversal direction and the longitudinal direction from RFQ into DTL;（2） to further chop the beam into the required time structure asked by RCS. It is very diffcult and critical to control well the emittance growth and in the meantime to match and chop the beam. Firstly,the optical design is done and optimized,and the multi-particle simulations show that the maximum emittance growth is successfully controlled within 14%. Secondly,based on the different beam envelopes obtained by TRACE-3D and PARMELA,the least deflecting angle of the chopper is determined by TRACE-3D. At last,the field of steering magnet is determined through simulations.展开更多
基金supported by the National Natural Science Foundation of China(No.12175077).
文摘A thermionic gun is endowed with a long bunch tail,which presents challenges for the compact terahertz free electron laser(FEL)facility at the Huazhong University of Science and Technology.Owing to a large energy spread,the tail particles do not contribute to the radiation.In the original design,an x-direction slit is used in the dispersive section of the transport line to remove the tail particles.This paper presents an improved scheme to remove the tail by introducing an RF beam chopper system at the exit of the electron gun,to prevent a significant number of tail particles from entering the linac.The facility remains compact while effectively removing the tail of the bunch.The parameters of the beam chopper system are designed.Bunch parameters and radiation performance are analyzed via a start-to-end simulation.The findings indicate that 43%of the particles can pass through the beam chopper system for subsequent acceleration and transport,which saves the RF power,reduces beam loss in the linac,reduces background noise,and suppresses the sideband instability.Simultaneously,the beam chopper system causes an increase in beam emittance,energy spread,and an offset in the center of the bunch.These effects can be mitigated by a solenoid,linac,and steering coils.The simulation results for the FEL show that the micro-pulse energy is greater than 1.1μJ in the frequency range of 2.8-9.7 THz,and the maximum micro-pulse energy is 1.28μJ.
基金supported by Beijing Natural Science Foundation(Project Nos.3214065).
文摘Background The beam chopper system of China Spallation Neutron Source(CSNS)is used to pulsed chop the negative hydrogen ion beam from ion source;in order to meet the beam time structure of rapid cycling synchrotron(RCS),it is the key to control emittance growth of low energy beam and decrease beam loss during the beam injection process from the linac to RCS.After beam chopped,the particle beam is required to deviate completely and then lose at entrance of radiofrequency quadrupole(RFQ)cavity;considering high duty cycle of ion source and beam high chop rate,the effect of deflected particles on RFQ is difficult to predict.Purpose A bipolar beam chopper pulse power supply is developed,which makes the beam spot at the entrance of RFQ twice that of unipolar beam chopper power supply,and reduces the damage of deflected particles to RFQ cavity and vacuum.Methods The beam chopper power supply provides a fast high voltage pulse source;two fast reversing switches are used to quickly change the polarity of the output high voltage pulse in 40 ms.Results and conclusion The power supply has been installed in the low beam energy transport line(LEBT),the output high voltage pulse is±6 kV,frequency is about 1 MHz,and the pulse edge is less than 10 ns.
基金supported by the National Natural Science Foundation of China (Grant No. 10775186)
文摘In order to perform the studies on a pulsed beam generation system based on a high intensity cyclotron, a test beam line with a pulsed beam generation for a 10 MeV compact cyclotron (CYCIAE-10) has been designed and constructed at China Institute of Atomic Energy (CIAE). A 70 MHz continuous H- beam can be pulsed to the pulse length of less than 10 ns with a repetition rate of 4.4 MHz. The sine waveform with a frequency of 2.2 MHz is adopted for the chopper and a mesh structure with single drift and dual gaps is used for the 70 MHz buncher. A helical resonator is designed and constructed based on simulations and experiments on the RF matching for the chopper. A helical inductance loop that is exceptionally large of its kind and equipped with water cooling for the resonator has been successfully wound and a 500 W solid RF amplifier has been manufactured. A special measuring device has been designed, which can be used to measure both the DC beam and the pulsed beam. The required pulsed beam was obtained after pulsed beam tuning.
文摘针对应用于硼中子俘获治疗的加速器中子源的束流偏转问题,为其低能束流传输线部分设计了一套斩束器,通过理论计算与软件模拟,验证方案的可行性。为了解决斩波器电场强度不均匀问题,引入圆弧电极设计结构,微波工作室(CST Studio Suite)模拟仿真表明其具有更好的电场分布均匀性。发展了基于Python程序的CST与TraceWin联合束流动力学模拟,结果表明设计的斩波器能够高效率地实现束流偏转功能,设计方案具有良好的实际应用价值和意义。
文摘The design of CSNS MEBT has two objectives：（1） to match the beam both in the transversal direction and the longitudinal direction from RFQ into DTL;（2） to further chop the beam into the required time structure asked by RCS. It is very diffcult and critical to control well the emittance growth and in the meantime to match and chop the beam. Firstly,the optical design is done and optimized,and the multi-particle simulations show that the maximum emittance growth is successfully controlled within 14%. Secondly,based on the different beam envelopes obtained by TRACE-3D and PARMELA,the least deflecting angle of the chopper is determined by TRACE-3D. At last,the field of steering magnet is determined through simulations.
