Shukla R A, Achanta V G, De Barbaro P, Dugad S R, Heering A, Gupta S K, Mirza I, Prabhu S S, Rumerio P
Department of High Energy Physics, Tata Institute of Fundamental Research, Mumbai, Maharashtra 400005, India.
Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai, Maharashtra 400005, India.
Rev Sci Instrum. 2019 Feb;90(2):023303. doi: 10.1063/1.5046465.
The Hybrid Photodetector (HPD) is a hybrid unit with a single accelerating gap between a common photocathode and an array of PIN diodes. Customised HPDs with 19 channels were used to detect scintillation light from hadron calorimeter in the Compact Muon Solenoid (CMS) experiment. In this paper, we present results on radiation damage studies carried out on the used HPDs in the outer hadron (HO) and the end-cap hadron (HE) calorimeter of the CMS experiment operating at CERN. The calorimeter is made of alternating layers of scintillating tiles and metals, such as brass or iron. The scintillating light was transmitted to the HPDs by means of optical fibres. Due to excessive exposure to scintillation light and ionising radiation during data taking at the Large Hadron Collider, the performance of the HPDs was expected to degrade significantly in the HE detector. Independent studies on radiation damage of these used photosensors were important to assess the degradation in the performance of the calorimeter. Microscopic scans of relative photon detection efficiencies for two HPDs (one each from HO and HE detector) were made using micron resolution optical scanner. The scanner was specially designed and built for microscopic characterisation of photosensors. Imprints of each fibre (∼1 mm in diameter) on the photocathode with varying damage within the same pixel of the HPD were observed. The localised damage of the photocathode was determined to vary with the amount of scintillation (or calibration) light transmitted by optical fibres to the HPD.
混合光电探测器（HPD）是一种混合装置，在公共光电阴极和PIN二极管阵列之间有一个单一的加速间隙。在紧凑型μ子螺线管（CMS）实验中，使用了定制的19通道HPD来检测强子量能器发出的闪烁光。在本文中，我们展示了对在欧洲核子研究中心（CERN）运行的CMS实验的外强子（HO）和端盖强子（HE）量能器中使用过的HPD进行辐射损伤研究的结果。量能器由闪烁体砖和金属（如黄铜或铁）的交替层组成。闪烁光通过光纤传输到HPD。由于在大型强子对撞机数据采集期间过度暴露于闪烁光和电离辐射，预计HPD在HE探测器中的性能会显著下降。对这些用过的光电传感器的辐射损伤进行独立研究对于评估量能器性能的下降很重要。使用微米分辨率光学扫描仪对两个HPD（一个来自HO探测器，一个来自HE探测器）的相对光子探测效率进行了微观扫描。该扫描仪是专门为光电传感器的微观表征而设计和制造的。在HPD同一像素内观察到每个光纤（直径约1毫米）在光电阴极上具有不同损伤的印记。确定光电阴极的局部损伤随通过光纤传输到HPD的闪烁（或校准）光量而变化。
