一维丝室气体探测器衍射像差的修正方法研究

一维位置灵敏单丝气体探测器采用单根镀金钨丝和200根阴极感应条的探测结构, X射线在阳极丝上产生的信号被多个阴极条感应, 利用重心法得到X射线的原初电离点的位置信息, 位置分辨率达到160 μm(半高全宽). 在同步辐射衍射实验中, X射线通过样品后会形成不同大小的衍射环, 本实验中测量得到11.148°和14.201°的两组衍射角位置信息; 通过平行移动一维探测器在衍射环范围内多次扫描, 可以重建得到二维衍射环. 由于一维探测器的气体厚度和入射窗宽度会给测量结果带来像差, 分析发现像差的影响大于一维探测器的位置分辨. 基于相应的物理分析对测量到的衍射位置进行修正, 修正后的衍射位置相比修正前的衍射位置的相对像差最大改善达到7%, 该方法实现了无像差二维衍射环的重建.

Modified method for diffraction aberration of one-dimensional wire chamber

The one-dimensional position sensitive wire gaseous detector is developed for the synchrotron radiation diffraction, which consists of a single wire of gold-plated tungsten and 200 cathode strips as the readout. The induced signal is produced by the several adjacent cathode strips when X-ray is incident on anode wire with high voltage. Using the center gravity method to analyze the adjacent signals in one dimension, the primary ionization position of the X-ray can be obtained and the position resolution is 160 μm (FWHM). In Beijing Synchrotron Radiation Facility, the diffraction test is done at the experimental station. When the X-ray irradiates the crystal sample of SiO₂, the different sizes of the diffraction rings can be produced. The diffraction angles are measured to be 11.148° and 14.201°, and the two-dimensional diffraction rings are reconstructed when the detector is moved and scanned with the several steps in the diffraction ring range. The diffraction aberration of one-dimensional wire chamber is very obvious. In the paper, the relevant influence factors of the detector construct are discussed. The thickness of the working gas and the width of active area window can give rise to the diffraction ring aberration. The theoretical calculation value of the diffraction aberration is larger than the position resolution value of the gaseous detector. The correction method is established based on the corresponding physical analysis, and by this method the value of the diffraction ring point is calculated. The relative aberration of diffraction position is improved by up to 7% with using the method, and the two-dimensional diffraction ring with no aberration can be reconstructed.