神龙一号电子束束参数测量系统猝发式的精确触发方式研究

为了准确了解电子束随时间变化的性能, 在神龙一号直线感应加速器上进行电子束束参数测量时要求测量系统精确地同步于电子束的产生和输运. 其功率系统开关放电波形后沿幅度高达250kV, 下降时间约20ns, 并且从该下降沿到电子束打靶的时间有145ns, 抖动1—2ns, 非常稳定; 如果以陡峭的后沿作为测量时间基准, 则可以获得与其抖动相同量级的同步精度. 因此通过对其波形的下降沿进行微分来获取测量系统的触发信号, 选择合适的微分参数可以得到对应于下降沿 约ns级精度的测量时间基准, 通过采用光纤驱动电路完全消除了高压开关对低压测量系统的干扰, 保证测量系统正常工作. 该方法消除了传统触发方式因延时长、精度低、抖动大等对确定测量时间基准的不利影响, 满足了使用高速测量设备准确获取电子束不同时刻的束参数波形的精确触发要求.

Accurate Burst Trigger Mode for Dragon- Ⅰ Electron Beam Measurement System

The electron beam measurement system for Dragon-I must work synchronously with the beam production and transportation accurately in order to obtain correct data. The synchronization with about 1ns is important. The output waveform of Blumlein lines in pulsed-power system is of amplitude of about 250kV and 20ns active edge time(following edge). The electron beam will hit the conversion target in about 145ns later steadily and the jitter time is about 1-2ns. The synchronization precision with the same level of the jitter time will be reached if the sharp following edge of waveform is selected to be the time base. The synchronization trigger signal for measurement system can be obtained by the way of differentiating the following edge and the accuracy of about ns can also be reached with suitable circuit parameters. The optical fiber is also adopted to remove the interference on the measurement system from the high voltage system. This kind of burst trigger mode overcomes many disadvantages such as low accuracy, long delay time, large jitter in normal trigger mode and can provide the trigger time accurately. It can meet the need to measure the electron beam parameters at any required time.