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Beam dynamics and RF design have been performed of a new type trapezoidal IH-RFQ operating at 104 MHz for acceleration of 14C+ in the framework of RFQ based 14C AMS facility at Peking University. Low energy spread RFQ beam dynamics design was approached by the method of internal discrete bunching. 14C+ will be accelerated from 40 keV to 500 keV with the length of about 1.1 m. The designed transmission efficiency is better than 95% and the energy spread is as low as 0.6%. Combining the beam dynamics design, a trapezoidal IH-RFQ structure was proposed, which can be cooled more easily and has better mechanical performance than traditional RFQ. Electromagnetic field distribution was simulated by using CST Microwave Studio (MWS). The specific shunt impedance and the quality factor were optimized primarily. 相似文献
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Danqing Zhou 《中国物理 B》2021,30(11):116106-116106
Laser-accelerated ion beams (LIBs) have been increasingly applied in the field of material irradiation in recent years due to the unique properties of ultra-short beam duration, extremely high beam current, etc. Here we explore an application of using laser-accelerated ion beams to prepare graphene. The pulsed LIBs produced a great instantaneous beam current and thermal effect on the SiC samples with a shooting frequency of 1 Hz. In the experiment, we controlled the deposition dose by adjusting the number of shootings and the irradiating current by adjusting the distance between the sample and the ion source. During annealing at 1100 ℃, we found that the 190 shots ion beams allowed more carbon atoms to self-assemble into graphene than the 10 shots case. By comparing with the controlled experiment based on ion beams from a traditional ion accelerator, we found that the laser-accelerated ion beams could cause greater damage in a very short time. Significant thermal effect was induced when the irradiation distance was reduced to less than 1 cm, which could make partial SiC self-annealing to prepare graphene dots directly. The special effects of LIBs indicate their vital role to change the structure of the irradiation sample. 相似文献
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采用常规透镜设计了适用于非真空环境中交叉偏振波(XPW)产生的双透镜聚焦系统,在相对较短的距离实现了长焦透镜聚焦的效果,并测量了聚焦后的激光脉冲,发现其没有显著的非线性相位积累,保证了激光光束质量.在非真空中采用双BaF_2晶体得到了XPW系统转换效率22%,光谱1.78倍展宽的净化脉冲输出,双透镜组合聚焦形式使得双BaF_2晶体间距在13—22 cm内可保证20%以上的XPW转换效率,双晶体间距的调节冗余度提高了两个量级,极大地降低了双晶转换效率对晶体间距的依赖.这种正负透镜组合聚焦的光路设计在非真空中实现了高效稳定的XPW输出,为后续的放大应用提供了高对比度、宽光谱的高质量种子源. 相似文献
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A compact laser plasma accelerator(CLAPA) is being built at Peking University, which is based on an RPA-PSA mechanism or other acceleration mechanisms. The beam produced by this laser accelerator has the characteristics of short duration, high pulse current, large divergence angle, and wide energy spectrum. The beam cannot be produced by a normal ion source and accelerator. The space charge field in the initial is very strong.According to the beam parameters from preparatory experiments and theoretical simulations, a compact beam line is preliminarily designed. The beam line mainly consists of common transport elements to deliver proton beam with the energy of 1–50 MeV, energy spread of 0–±1% and current of 0–108 proton per pulse to satisfy the requirement of different experiments. The simulation result of a 15 MeV proton beam with an energy spread of ±1%, current of 400 m A, and final spot radius of 9 mm is presented in this paper. 相似文献
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周泉丰陆元荣朱昆颜学庆刘戈郭之虞陈佳洱 《强激光与粒子束》2013,(B05):124-128
为了提高射频四极场加速器(RFQ)的束流传输效率,需要对纵向分布不均匀的极间电压进行补偿,并且准确测量束流实验中极间电压的绝对数值。考虑到极间电压分布不均匀是由于分布电容和端部效应造成的,而采用调谐块可以调节分布电感,通过电磁场数值模拟研究了调谐块对极间电压分布的影响,最终极间电压的平整度被调整到优于95%。在束流实验中,通过测量轫致辐射谱测定了极间电压的数值,通过束流动力学模拟研究了多能峰产生的原因,并最终标定了70kV极间电压对应的输入功率值284kW。 相似文献
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介绍一种使用闪烁体耦合电子倍增电荷耦合器件(EMCCD)的方式对离子进行记录的汤姆逊能谱仪,可实现对离子能谱的实时单发测量。同时,该谱仪利用倾斜电极板对离子进行偏转,可减少由于离子打在电极板上产生的电磁噪声,能够提高实验结果的信噪比。该谱仪在北京大学4.5 MV静电加速器和26 MV串列加速器上进行了标定实验,测量了闪烁体将离子转化成光子后的探测效率,实验结果也验证了该谱仪的可行性和稳定性。该汤姆逊谱仪将用于北京大学激光加速器CLAPA对离子束流的测量研究。 相似文献
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