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

研制了一种具有位置敏感探测器的波长色散晶体光谱仪系统，用于大气中高分辨率粒子诱导x射线发射实验。我们设计并构建了两个检测器来提高其计数效率：一个是多阳极PSPC（位置敏感比例计数器），另一个是堆叠PSPC组件。多阳极PSPC有七个碳纤维细丝用作电阻阳极。来自阳极的脉冲用512 × 7通道电荷分频分析仪转换成数字信号。在调整偏移通道和转换因子后，Visual Basic程序将该二维数据集转换为一维频谱。堆叠式PSPC组件是一种改进的PSPC组件，由5个单个PSPC组成。每个PSPC也有一个碳纤维阳极，根据入射x射线在探测器表面的弯曲分布，放置以获得最大的计数效率和最佳的空间分辨率。该探测器的光谱分辨率为0.5mm，比我们之前开发的单个PSPC系统的光谱分辨率略大，而计数效率是单个PSPC系统的5倍。我们也尝试用Kr气体代替一般使用的Ar作为反气体来分析P和S的特征x射线，因为在2keV范围内，Kr气体的计数效率大约是Ar的两倍。使用该系统可以在几秒到几分钟内分析各种Al、Si、P、S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.