The Mu2e experiment at Fermilab will search for the charged lepton flavor violating neutrino-less conversion of a negative muon into an electron in the field of an aluminum nucleus [1], [2]. The Mu2e detector is comprised of a tracker, an electromagnetic calorimeter, and an external veto for cosmic rays. The calorimeter plays an important role in providing excellent particle identification capabilities, a fast and online trigger filter while aiding the track reconstruction capabilities. The calorimeter requirements are to provide a large acceptance for 100-MeV electrons and reach: 1) a time resolution better than 0.5 ns at 100 MeV; 2) an energy resolution O(10%) at 100 MeV; and 3) a position resolution of about 1 cm. The calorimeter consists of two disks, each one made of 674 pure CsI crystals readout by two large-area $2 \times 3$ array of UV-extended silicon photomultipliers (Mu2e SiPMs) of $6\,\,\times6$ mm² dimensions. A large-scale prototype has been constructed with 51 preproduction crystals readout by 102 Mu2e SiPMs. It has been tested at the beam test facility in Frascati, demonstrating satisfying results compared to the Mu2e requirements. At the moment of writing, the crystals production phase is halfway through the work, while the SiPM production has been completed. An overview of the characterization tests is also reported, together with a description of the final calorimeter design.

中文翻译：

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Mu2e em 量热仪：晶体和 SiPM 生产状态

费米实验室的 Mu2e 实验将在铝核场中寻找带电轻子味，这违反了无中微子将负 μ 子转换为电子的过程 [1], [2]. Mu2e 探测器由跟踪器、电磁热量计和宇宙射线外部否决权组成。热量计在提供卓越的粒子识别能力、快速和在线触发过滤器，同时帮助轨迹重建能力方面发挥着重要作用。量热计的要求是为 100-MeV 电子提供较大的接受度，并达到：1) 在 100 MeV 下的时间分辨率优于 0.5 ns；2) 100 MeV 时的能量分辨率 O(10%)；3) 位置分辨率约为 1 cm。热量计由两个圆盘组成，每个圆盘由 674 个纯 CsI 晶体制成，由两个大面积读数 $2 \times 3$ 紫外扩展硅光电倍增管 (Mu2e SiPM) 阵列 $6\,\,\times6$ 毫米²尺寸。已经构建了一个大型原型，其中包含 51 个预生产晶体，由 102 个 Mu2e SiPM 读出。它已经在弗拉斯卡蒂的光束测试设施中进行了测试，与 Mu2e 要求相比，结果令人满意。在撰写本文时，晶体生产阶段已完成一半，而 SiPM 生产已完成。还报告了表征测试的概述，以及对最终量热计设计的描述。