The development of two-dimensional position-sensitive counter for high-energy X rays provided from synchrotron radiation facility

点击翻译按钮获取中文摘要

In this research, we have made basic studies for the development of two-dimensional position-sensitive detector for high energy X rays of 10 - 100keV range, being based on the drift chamber principle. Our achievements are as follows :1) Operational mechanism of high-pressure proportional counter in the region of limited proportionality (RLP) (a) Detailed analysis was performed for the halo effect due to characteristic X rays, and the response of proportional counter caused by this effect was fully explained. It was first found that, in RLP,the degree of gas amplification for the halo events is greater than that for the photo-peak events. From the practical view-point, this fact helps since a simple pulse-height selection is able to exclude the halo events which is known to deteriorate position resolution. The results are published in the article No. (1). (b) It was confirmed that the sudden change of avalanche mode due to structural change of primary-electron cloud exists in 7-atm Ar+3 … More 0% CH_4. (the article No. (2)) (c) The feasibility of our position-sensitive proportional counter (PSPC) was examined in charged-particle accelerator experiment. The result showed that high-energy (position) resolving power of the PSPC enables to analyze trace elements to be studied in PIXE.(the article No. (4)) The performance of the PSPC for 10-60 KeV high-energy photon beams was tested in KEK Photon Factory. Fairly good position resolution of 122mum (fwhm) for 20-keV X rays and 140mum for 35-keV X rays were obtained. A part of the results is given in the article No. (3).2) Fabrication of drift detector for X rays (a) A drift detector for X rays with a large sensitive area of 110 x 110 mm^2 was made. The drift space consists of field wires of 25 layrs in drift direction and 4 laryers in counter-depth direction. 4 anode wires are extended for the 4 layrs, the thicknesses of which are 2,4,6 and 8 mm, respectively. (b) The potential distribution was calculated and the adequate flat potential for the 6-mm layr is realized. It was found that the distribution of the potential near the anode wire is important to efficiently collect primary electrons. (c) Test experiments of the drift counter were carried out by using 5-7 Mev proton beams. Owing to the window materials such as Kapton films, fine collimation of the beam was not possible. The beam broadening is peculiar aspect for the charged particles, but not the case for X rays. Thus, it is hoped that, in the well-collimated photon beam experiment scheduled in this June, much better result can be obtained. Less