Development of a RICH detector for collider experiments using multi-layer aerogel radiator

我们利用多层气凝胶辐射体的新思想研制了一种环成像切伦科夫探测器。具有多层气凝胶辐射体的RICH利用了由两层或多层不同折射率气凝胶层组成的辐射体，这使得由于辐射体整体厚度的增加而增加了切伦科夫光子产率，同时避免了与发射点不确定性增加相关的单光子角分辨率的同时退化。本研究项目取得的主要成果如下：1。我们在KEK使用由2到4层气凝胶组成的散热器进行了光束测试。我们成功地证明，我们可以在不降低单光子角分辨率（约13mrad）的情况下，将切伦科夫光子产率提高1.5倍（从6 p.e.到9 p.e.）。我们还对折射率与气凝胶厚度的组合进行了优化研究。气凝胶散热器光学质量的改进研究了一种具有两层或三层不同折射率内层的单片气凝胶散热器的研制方法。我们发现有可能生产出这种具有类似单层气凝胶散热器光学质量的辐射体。本文设计了一种由盖革模式apd和光波导组成的新型光传感器。我们对“盖革模式APD”的量子效率、时间分辨率和噪声性能等基本特性进行了测量。然后，我们使用详细的蒙特卡罗模拟评估了带有这种光传感器的气凝胶- rich的性能。仿真结果表明，与传统位置敏感光电倍增管相比，所设计的光电传感器能够更有效地检测上游气凝胶层中产生的切伦科夫光子，切伦科夫光子产率的改善因子高达4。少

We have developed a Ring-Imaging Cherenkov (RICH) detector using a new novel idea of multi-layer aerogel radiator. A RICH with multi-layer aerogel radiator utilizes the radiator consisting of two or more aerogel layers of different refractive indices, which allows for an increase in Cherenkov photon yield on account of the increase in overall radiator thickness, while avoiding the simultaneous degradation in single photon angular resolution associated with the increased uncertainty of the emission point. The major achievements in this research program are the followings;1. Proof-of-principle by a beam testWe carried out a beam test at KEK using the radiator consisting of 2 to 4 aerogel layers. We successfully demonstrated that we can increase the Cherenkov photon yields by a factor of 1.5 (from 6 p.e. to 9 p.e.) without deteriorating the single photon angular resolution (about 13mrad). We also carried out a study on the optimization for the combination of refractive index and thickness … More of the aerogel layers.2. Improvement of optical quality of aerogel radiatorWe carried out a study on the method to develop monolithic aerogel radiator having two or three internal layers with varying refractive indices. We found that it is possible to produce such radiator having optical quality similar to a single layer aerogel radiator.3. Study on photodetectionWe designed a new photo-sensor consisting of so-called Geiger mode APDs and light-guides. We carried out measurements of some fundamental properties of the "Geiger-mode APD", such as the quantum efficiency, the time resolution and the noise performance. We then evaluated performance of a aerogel-RICH with such a photo-sensor using a detailed Monte Carlo simulation. The simulation indicated that, compared to conventional position-sensitive photomultiplier tubes, the designed photo-sensor can detect Cherenkov photons, produced in upstream aerogel layers, more effectively, and the improvement factor in the Cherenkov photon yield is as high as 4. Less