Development of a RICH detector with high index aerogel for collider experiments

我们研究开发了一种适用于未来b工厂等对撞机实验的高折射率气凝胶（aergel - rich）环状成像切伦科夫探测器，并取得了以下进展。<原理证明>___-；为了验证探测器原理，利用多阳极PMT （Hamamatsu R5900-M16）和“平板”PMT （Hamamatsu H8500）构建了测试计数器，并进行了宇宙射线和加速器束的测试。观察到气凝胶产生的切伦科夫辐射的清晰环状图像。采用折射率为1.05、厚度为2cm的气凝胶，测得切伦科夫角分辨率为15mrad，每个光速粒子平均可探测到8个光子。这将在4GeV/c下得到超过4σ K/π的分离。<光电检测研究>___-；对用于单光子计数的混合光子探测器（HPD或HAPD）的基本性能进行了测试。实验证明，这种器件具有良好的单光子计数能力，适合我们的应用。<气凝胶散热器>改进___-；现有生产方法对高折射率气凝胶（n ~ 1.05）的光学透明度不够好，对相对低折射率区域（n ~ 1.03）进行了优化。我们找到了原因，并成功地获得了n ~ 1.05时气凝胶的透射长度增加2倍以上。

We have carried out research to develop a ring imaging Cherenkov detector with high index aerogel (aerogel-RICH), suitable for collider experiments, such as future B-factories, and made the following progress.1. <Proof of principle>___- ; in order to prove the detector principle, a test counter has been constructed using multi-anode PMT (Hamamatsu R5900-M16) and also "flat panel" PMT (Hamamatsu H8500), and tested with cosmic ray and accelerator beam. A clear ring image of Cherenkov radiation produced from aerogel has been observed. Using aerogel with refractive index of 1.05 and thickness of 2cm, the measured Cherenkov angle resolution is 15mrad and the average number of detected photons is about 8 for each light velocity particle. This would give more than 4σ K/π separation at 4GeV/c.2. <Study of Photodetection>___- ; basic performance of hybrid photondetectors (HPD or HAPD) for single photon counting has been tested. It has been demonstrated that this type of device has good enough single photon counting capability for our application3. <Improvement of aerogel radiator>___- ; optical transparency of high index aerogel (n〜1.05) is not good enough with the existing production method, which was optimized for relatively low index, region (n〜1.03). We have identified the reason, and succeeded to obtain more than 2 times longer transpmission length for aerogel with n〜1.05.