脉冲慢正电子束流的直流化装置

A Device Used in Pulsed Slow Positron Beam's Stretching

在基于加速器的北京慢正电子强束流装置上,用Penning-Trap技术实现了脉冲慢正电子束流的存储和直流化．实验表明,系统的真空度对正电子的存储效率有严重影响,脉冲正电子的释放方式决定了直流化后束流的能量分散;改变释放级信号波形以及释放方式可以得到能量分散小于1eV的准直流化慢正电子束流．

A slow positron beam＇s stretching device has been designed and constructed on Beijing Slow Positron Beam, which based on a 1.3GeV linac. Positron was storage and stretching use Penning-Trap technique. Measurements show that the positron storage time strongly depends on the vacuum level in Penning Trap tube. Two modes was used to release the positrons from storage part, lowering Vc while VB kept constant and rising VB while Vc kept constant. This technique makes the pulsed positron beam to a quasi-continuous beam. The energy spread of positrons depend on in release mode. In the latter mode, we observe that the energy spread was reduced to a value less than 1.0eV. The time profile in user-defined waveform is more uniform. It is beneficial to reduce the probability of amplifier pileup especially in the case of measurement with high counting rate.