Vacuum-Compatible, Ultra-Thin-Wall Straw Tracker; Detector construction, Thinner straw R&D, and the brand-new graphite-straw development
Vacuum-Compatible, Ultra-Thin-Wall Straw Tracker; Detector construction, Thinner straw R&D, and the brand-new graphite-straw development
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真空兼容的超薄壁吸管追踪器；
DOI：
10.1016/j.nima.2022.167373
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Watanabe K.
中科院分区：
文献类型：
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作者：
Nishiguchi H.;Danielsson H.;Hamada E.;Hashimoto Y.;Kamei N.;Mihara S.;Osawa O.;Suzuki J.;Tsamalaidze Z.;Tsverava N.;Ueno K.;Volkov A.;Watanabe K.
J-PARC的COMET实验旨在寻找μ子原子中μ子到电子转换的轻子味违反过程，μ-e转换，其分支比灵敏度优于1 0− 16，比目前的极限高4个数量级，以探索标准模型之外的大多数理论模型所预测的参数区域。对这种高灵敏度的需求对探测器提出了几个严格的要求：（i）对于100 MeV/c电子，良好的动量分辨率<2%，这主要受到该动量区域的多次散射效应的限制;（ii）高速率能力，高达5× 109 μ−/s的μ子束由J-PARC实现。为了满足这一要求，设计了一种真空兼容的超薄壁吸管跟踪器，并采用超声波焊接技术研制了一种20 μ m厚、70 nm铝阴极的Mylar吸管。通过测试束实验对探测器的探测效率和本征空间分辨率等性能进行了研究，并证实其可用于COMET实验。COMET第一阶段的吸管跟踪器的建造已经完成。在建造现有跟踪器的同时，科索沃能源公司、联合核研究所和欧洲核研究组织还共同合作开发了一种12微米厚的更薄的吸管。在研发过程中，人们注意到，目前的技术无法实现直径远小于5 mm的管或壁厚远小于12 μ m的管。我们还启动了一个全新的项目，以实现石墨纺织吸管，这有可能实现极低的材料跟踪器。本文简要介绍了用现有的20 μ m厚吸管、12 μ m厚吸管和石墨吸管研制探测器的情况。
The COMET experiment at J-PARC aims to search for a lepton-flavour violating process of muon to electron conversion in a muonic atom, μ-e conversion, with a branching-ratio sensitivity better than 1 0− 16, 4 orders of magnitude better than the present limit, in order to explore the parameter region predicted by most well-motivated theoretical models beyond the Standard Model. The need for such an excellent sensitivity places several stringent requirements on the detector;(i) good momentum resolution,< 2%, for 100 MeV/c electron, which is primarily limited by multiple scattering effect for this momentum region; and (ii) high rate capability, up to 5× 1 0 9 μ−/s muon beam enabled by J-PARC. In order to fulfil such requirements a vacuum-compatible, ultra-thin-wall straw tracker has been designed, and a 20 μ m-thick Mylar straw with 70 nm Al cathode has been developed employing an ultrasonic-welding technique. The detector performances such as detection efficiency and intrinsic spatial resolutions were investigated with test-beam experiments and confirmed to be acceptable for the COMET experiment. The construction of the straw tracker for COMET Phase-I has been completed. In parallel to the construction of present tracker a thinner 12 μ m-thick straw has been developed with joint collaboration among KEK, JINR and CERN. During this R&D, it was noticed that the current technology cannot achieve tubes much smaller than 5 mm in diameter or walls much thinner than 12 μ m. We also launched a brand-new project to realize the graphite-textile straw which has a potential to realize an extremely low material tracker. In this article, a brief report on detector construction with a present 20 μ m-thick straw, R&D on a new 12 μ m-thick straw, and a brand-new graphite straw, is provided.