直接等离子体注入模式下激光离子源与RFQ匹配的模拟研究

Simulation Study on Matching of Laser Ion Source to RFQ Linac with Direct Plasma Injection Scheme

基于直接等离子体注入(Direct Plasma Injection Scheme,DPIS)的方法,设计并建造了一台低能段离子加速装置;目前实验上利用该方法成功地加速了峰值流强为11.28 m A,能量为593 ke V/u的C6+脉冲束流。考虑到激光离子源产生的束流为脉冲束,且具有能散大,强度高等特点,给低能传输线(LEBT)的设计带来很大的困难,而DPIS方法则简单易行,可有效地提高注入效率;因此该装置将激光离子源与RFQ直接连接在一起,将离子源产生的等离子体直接注入到RFQ,并没有采用传统的LEBT。并采用IGUN程序对该注入方法进行了模拟,计算确定了离子源引出的强流脉冲束的参数以及注入效率,模拟的结果与实验的测量值一致。

An accelerator with low injection energy has been designed and constructed based on direct plasma injection scheme (DPIS); a pulsed C6+ beam with peak current of 11.28 mA, energy of 593 keV/u has been successfully achieved after accelerated with DPIS method. It is because that the beam produced by laser ion source is a pulsed one with large energy spread, high intensity and the design of a low energy transport line (LEBT) is also complicated, while the DPIS method is simple to achieve and improve the injection e?ciency effectively;so, the laser ion source is directly connected to the RFQ without a LEBT in this equipment and then the laser produced plasma will be injected into RFQ with DPIS. In addition, the DPIS method is simulated by IGUN code and the parameters of extracted beam and its injection e?ciency are obtained from simulation, which is well agreed with the measured one in our experiment.