Observation of the GeV gamma-rays by a balloon-borne instrument

我们一直在开发一种新型的伽马射线望远镜，可以用气球送入太空，以供未来的卫星实验使用。该望远镜由一个探测伽马射线对产生的跟踪系统和一个测量能量的量热计组成。采用闪烁光纤检测伽马射线诱发的链状粒子，用紧凑型16阳极光电倍增管读取每根光纤的信号。该量热计由厚度为8辐射长度的分段CSL晶体组成。模拟结果表明，与传统的探测火花室对子产生的望远镜相比，该望远镜具有更好的性能。预计该望远镜在探测效率、紧凑性和准备就绪的性能上将优于目前的CGRO上的白鹭望远镜。有可能在几乎与EGRET相同的重量下研制出有效面积比EGRET大十倍的望远镜。通过模拟对探测器各部分的性能进行了优化，并用加速器束进行了测试。核子研究所的电子束测试证实，该量热计在能量和位置分辨率方面具有预期的性能。由16根闪烁光纤(每根光纤的截面为2 mm)和16个阳极的光电倍增管组成的跟踪系统单元被照射到CERN-PS上的质子束上。它可以探测到最小的电离粒子，效率接近100%，位置分辨率为0.6 mm。由于该系统具有快速触发的功能，因此，通过探测出适合于强子对产生的命中模式，有望作为一种有效的反符合系统在强子背景下工作。我们将在开发出用于多通道读出的ADC系统并构建气球有效载荷支架后，在两年内进行气球观测。

We have been develping a new-type gamma-ray telescope to be lauched by balloon for future satellite experiment. The telescope is composed of a tracking system to detect pair-creation by gamma-ray and a calorimeter to measure the energy. Scintillating fibers are adopoted to detect the chareged particles induced by gamma-ray, and a compact-type 16-anodes PMT is to read the signals from each fiber. The calorimeter consists of segmented Csl crystals with a thickness of 8 radiation length. It is prdicted by simulations that the telescope has advantages to conventional one which detect the pair creation wiht a spark chamber. The telscope is expected to be superior to the current telescope, EGRET on CGRO,on the performance of detection efficiency, compactness and readiness. It is supposed to be possible to develop a telescope with a larger effective-area by ten times within nearly same weight to EGRET.Peformance of each part of the detector has been optimaized by simulations and tested by using accelerator beams. It was confirmed by the electron beam test at the ES of Institute of Nuclear Study that the calorimeter has an expected performance in the energy and positional resolution. A unit of the tracking system consisting of 16 scintillating fibers (2mm square cross-section for each) and the 16-anodes PMT was irradiated to the proton beams at the CERN-PS.It could detect a minimum ionizind particle with an efficiency of nearly 100 % and a positional resolution of 0.6 mm. Since the system can have function of fast trigger, it is expected to work as an efficient anti-conincidence system against the hadron backgrounds by detcting a hit pattern which is charcteresitic to the pair creation.We will carry out the balloon observation within two years after developing the ADC system for multi-channel read-out and constructing the balloon payload support.