Development of a high-resolution PIXE spectrometer using a multiple position-sensitive detector

研制了一种用于大气中高分辨PIXE（粒子感生X射线发射）实验的位置灵敏波长色散晶体谱仪系统。为了提高其计数效率，我们设计并制作了两种探测器：一种是多阳极PSPC（位置敏感正比计数器），另一种是叠层PSPC组件。多阳极PSPC具有用作电阻性阳极的七根碳纤维丝。来自阳极的脉冲通过512 x 7通道电荷分割分析仪转换为数字信号。用Visual Basic编程，调整偏移通道和转换因子后，将二维数据转换为一维光谱。每个PSPC也有一个碳纤维阳极，并放置，以便获得最大的计数效率和最佳的空间分辨率，根据一个曲线分布的入射X射线在探测器表面。该探测器的光谱分辨率为0.5mm，比我们以前研制的单PSPC系统稍大，而计数效率比单PSPC系统高5倍，我们还尝试用Kr气体代替通常使用的Ar气体作为分析P、S特征X射线的计数气体。在2keV范围内，Kr气体的计数效率约为Ar气体的2倍。利用该系统，可在几秒到几分钟内分析Al、Si、P和S的各种化合物的化学键态。

A wavelength-dispersive crystal spectrometer system with a position-sensitive detector has been developed for high-resolution PIXE (Particle Induced X-ray Emission) experiments in atmospheric air. We have designed and constructed two detectors to improve its counting efficiency : one is a multianode PSPC (Position-Sensitive Proportional Counter) and the other is a stacked PSPC assembly. The multianode PSPC has seven carbon fiber filaments used as resistive anodes. Pulses from the anodes are converted into digital signals with a 512 x 7 channel charge-division analyzer. A Visual Basic program converts this 2D data set into a 1D spectrum after adjusting the offset channels and conversion factors.The stacked PSPC assembly is improved one and consists of five single PSPCs. Each PSPC has also a carbon fiber anode, and is placed so as to obtain the maximum counting efficiency and the best spatial resolution according to a curved distribution of the incident X-rays on the detector surface. The spectral resolution of this detector is 0.5mm which is somewhat larger than that of our single PSPC system previously developed, while its counting efficiency is five times higher than that of the single one.We have also tried to use Kr gas for analyzing the characteristic X-rays of P and S as the counter gas instead of Ar generally used, because the counting efficiency of Kr gas is about two times as large as that of Ar for the range of 2keV.The chemical bonding states of various compounds of Al, Si, P, and S can be analyzed within several seconds to several minutes by using this system.