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

我们开展了研制适用于未来B工厂等对撞机实验的高折射率气凝胶（气凝胶-RICH）环形成像切伦科夫探测器的研究，取得了以下进展. <Proof of principle>___- ;为了验证探测器的原理，用多阳极PMT（Hamamatsu R5900-M16）和“平板”PMT（Hamamatsu H8500）制作了一个测试计数器，并用宇宙射线和加速器束进行了测试。观察到气凝胶产生的切伦科夫辐射的清晰环形像。使用折射率为1.05、厚度为2cm的气凝胶，测得的切伦科夫角分辨率为15 mrad，对每个光速粒子的平均探测光子数约为8个。这将在4GeV/c.2处产生超过4σ K/π的分离。<Study of Photodetection>对用于单光子计数的混合型光子探测器（HPD或HAPD）的基本性能进行了测试。它已被证明，这种类型的设备具有足够好的单光子计数能力，为我们的应用3。<Improvement of aerogel radiator>___- ;高折射率气凝胶（n = 1.05）的光学透明度对于现有的生产方法是不够好的，现有的生产方法是针对相对低的折射率区域（n = 1.03）进行优化的。我们已经确定了原因，并成功地获得了2倍以上的气凝胶与n ≥ 1.05的传输长度。

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.