正负电子谱仪屏蔽方案的模拟优化设计

SIMULATION AND OPTIMIZATION DESIGN OF SHIELDING SCHEME FOR ELECTRON POSITRON AND ELECTRON POSITRON SPECTROMETER

超短超强激光通过尾波场加速产生的高能负电子束与金属靶相互作用可以获得高能正电子束。实验和计算均表明当高能负电子与较厚的靶相互作用时,产生的正负电子和X射线强度强、发散角大。针对这种情况,为了准确测量能谱,谱仪前方必须使用准直孔,让混合束通过准直孔后再进入大间隙的磁场区域内进行偏转和探测。应用FLUKA程序模拟表明,通过在谱仪外部添加准直孔,谱仪内部添加塑料(以下简称CH)屏蔽片的方式,可以实现谱仪能量分辨率的提高和对噪声的有效抑制,从而实现在混合场中对正电子束能谱进行更准确的诊断。

High energy electrons beams generated in the laser wake field acceleration process can be used to produce energetic positrons by interacting with the high Z targets.Both experiments and calculations show that when the high-energy negative electron interacts with the thicker target,the positive electron and negative electron and the X-ray produced have strong intensity and large divergence Angle.In this case,in order to accurately measure the energy spectrum,a collimation hole must be used in the front of the spectrometer to let the mixed beam pass through the collimating hole and then enter the magnetic field area with large gap for deflection and detection.Through the FLUKA code,the simulations shown that the energy resolution of the spectrometer can be improved and the noise can be effectively suppressed by adding collimation hole outside the spectrometer and a plastic(hereinafter referred to as CH)shield inside the spectrometer,so as to achieve more accurate diagnosis of positronbeam energy spectrum in the mixed field.