【摘要】 采用束包络方程分析了单脉冲和多脉冲情况下回流离子对强流相对论电子束聚焦的影响。分析结果表明,单脉冲情况下通过缩短焦距,仍可以获得较小的积分焦斑,而在多脉冲情况下回流离子将导致电子束完全散焦。通过数值模拟和实验研究了利用薄膜阻挡回流离子的可行性,对不同薄膜在电子束作用下的温升及动力学行为的模拟结果表明,在1.06μs的时间尺度内,薄膜虽然发生了不同程度的膨胀,但是仍然有足够的材料可以阻挡离子回流。在神龙一号加速器上,通过法拉第筒测量了靶前放置和不放置薄膜情况下的离子信号,实验证实了薄膜至少能够将离子约束在薄膜和转换靶之间长达数十μs。更多还原

【Abstract】 Impacts of backstreaming ions on the focus of single-pulse and multi-pulse high-current relativistic electron beams were studied by solving the envelop equation.The result indicates that smaller integrated spot size could be achieved by shorten the focal distance in single pulse machine,while in multi-pulse machine,electron beam pulses would be disrupted after interaction with the long ion column.The feasibility of using foils to block the back streaming ions mechanically was also studied by both numerical simulation and experimental methods.Simulation of foil expansion after interaction with electron beam shows that although the expansion is considerable during a time scale of 1.06 μs,there is still enough material to stop the ions.Faraday cup experiment at Dragon Ⅰ linear induction accelerator indicates that a piece of 25 μm-thick Al/Teflon foil could prevent ions from backstreaming for more than dozens of microseconds.更多还原