北京大学射频四极场加速器研究及创新实践

RFQ accelerator research and innovation practice at Peking University

北京大学射频四极场(radio frequency quadruple,RFQ)加速器课题组在陈佳洱院士带领下,先后于1994、1999年提出并研制出我国第一台重离子整体分离环300 keV N^(+)和1 Me V O^(+) RFQ加速器;为提高离子的加速效率,提出分离作用RFQ加速器结构,研制出结构样机并完成束流验证;提出用RFQ加速器同时加速同荷质比正负离子的新思想,并在两台已建成的RFQ加速器上完成束流验证,通过模拟再现了正负离子自动聚束和加速的过程,用同轴快靶成功观测到正负氧离子的微观束流波形;发展了RFQ均温束流传输的束流动力学设计思想,研制出国内首台基于RFQ的中子成像装置,该四杆型D^(+)RFQ加速器是国际上迄今为止运行频率最高的四杆型D+RFQ加速器;与中国科学院高能物理研究所、中国原子能科学研究院合作,研制了352 MHz质子RFQ工艺模型腔,有效地助推了中国首台质子加速器驱动次临界系统(accelerator driven sub-critical system,ADS)RFQ加速器的研制.北京大学与中国科学院近代物理研究所合作,设计、建造了高电荷态重离子^(238)U^(34+)连续波RFQ加速器,已成功加速元素周期表中诸多重离子束流,并已稳定运行8年之久;与中国科学院近代物理研究所合作研制出国际首台162.5 MHz开窗四翼型D+RFQ加速器,成功加速连续波H_(2)^(+)流强1.95 mA,传输效率90%;与核工业西南物理研究院合作,设计并调试了一台162.5 MHz D+四翼型RFQ加速器,成功加速1%H_(2)^(+)流强10 mA.

The radio frequency quadrupole(RFQ)accelerator is a common linear accelerator placed directly after the ion source for low energy ion acceleration.In 1994 and 1999,the RFQ research group of Peking University,led by Academician Chen Jiaer,first proposed and developed the heavy ion integral split ring(ISR)300 keV N^(+)and 1 MeV O^(+)RFQ accelerators.Because of the simultaneous transverse focusing and longitudinal bunching in a cavity,an RFQ accelerator is considered to be the most suitable linear accelerator for the acceleration of low energy and high current beams.However,a long RFQ cavity will decrease the efficiency of RF power.To improve the acceleration efficiency of ions,separated-function radio frequency quadrupole(SFRFQ)was proposed for the first time,and the prototype of the structure was developed and the beam experiments were completed.A new idea of accelerating positive and negative ions simultaneously using RFQ accelerators was proposed for the first time.The process of beam bunching and acceleration of positive and negative ions was simulated and the microscopic beam waveforms of positive and negative oxygen ions were observed successfully with a coaxial fast Faraday cup.Beam experiments were completed on two existing RFQ accelerators.The equipartitioned design scheme of RFQ is developed,and the first neutron imaging facility based on RFQ(Peking University Neutron Imaging Facility,PKUNIFTY)is developed in China.The four-rod D^(+)RFQ accelerator is the one with the highest frequency in the world so far.In cooperation with the Institute of High Energy Physics of the Chinese Academy of Sciences and the China Institute of Atomic Energy,the 352 MHz proton RFQ model cavity was developed,which effectively boosted the development of China's first proton ADS RFQ accelerator,and won the Beijing Science and Technology Achievement Award in 2008.Peking University and Institute of Modern Physics of the Chinese Academy of Sciences have designed and buita high charge state heavy ion^(238)U^(34+)CW RFQ accelerator,which has successfully accelerated many kinds of heavy ion beams and has been in stable operation for 8 years.In cooperation with Institute of Modern Physics of the Chinese Academy of Sciences,the world's first 162.5 MHz window-type RFQ accelerator was developed,and the CW H^(2+)current intensity was successfully accelerated to 1.95 mA,and the transmssion efficiency was 90%.In cooperation with Southwestern Institute of Physics,a 162.5 MHz D^(+)four-vane RFQ accelerator was designed and tested,beam experiments on the RFQ accelerator indicated that the maximum accelerated beam current could reach 10 mA with a duty factor of 1%.The development direction of RFQ accelerators in the future is the high power accelerators with high current intensity and high duty factor.The above work lays a good foundation for the development of high power RFQ accelerators.High current continuous wave radio quadrupole accelerator(CW RFQ)is widely used as an injector in many big science projects,such as accelerator driven sub-critical clean nuclear energy system(ADS),isotope separation online analysis,International Fusion Materials Irradiation Facility(IFMIF).The most common component of accelerating the low energy segment is also widely used as an independent accelerator application device,it has a very broad application prospect in neutron imaging,boron neutron capture for cancer treatment(BNCT)and other fields.