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Development, construction and tests of the Mu2e electromagnetic calorimeter mechanical structures

Atanov, N. and Baranov, V. and Borrel, L. and Bloise, C. and Budagov, J. and Ceravolo, S. and Cervelli, F. and Colao, F. and Cordelli, M. and Corradi, G. and Davydov, Y. I. and Di Falco, S. and Diociaiuti, E. and Donati, S. and Donghia, R. and Echenard, B. and Ferrari, C. and Gioiosa, A. and Giovannella, S. and Giusti, V. and Glagolev, V. and Grancagnolo, F. and Hampai, D. and Happacher, F. and Hitlin, D. and Lin, D. and Marini, A. and Martini, M. and Middleton, S. and Miscetti, S. and Morescalchi, L. and Pasciuto, D. and Pedreschi, E. and Porter, F. and Raffaelli, F. and Saputi, A. and Sarra, I. and Spinella, F. and Taffara, A. and Tassielli, G. F. and Tereshchenko, V. and Usubov, Z. and Vasilyev, I. I. and Zanetti, A. and Zhu, R. Y. (2022) Development, construction and tests of the Mu2e electromagnetic calorimeter mechanical structures. Journal of Instrumentation, 17 (1). Art. No. C01007. ISSN 1748-0221. doi:10.1088/1748-0221/17/01/c01007.

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The "muon-to-electron conversion" (Mu2e) experiment at Fermilab will search for the charged lepton flavour violating neutrino-less coherent conversion of a muon into an electron in the field of an aluminum nucleus. The observation of this process would be the unambiguous evidence of the existence of physics beyond the standard model. Mu2e detectors comprise a straw-tracker, an electromagnetic calorimeter and an external veto for cosmic rays. In particular, the calorimeter provides excellent electron identification, a fast calorimetric online trigger, and complementary information to aid pattern recognition and track reconstruction. The detector has been designed as a state-of-the-art crystal calorimeter and employs 1348 pure Cesium Iodide (CsI) crystals readout by UV-extended silicon photosensors and fast front-end and digitization electronics. A design consisting of two identical annular matrices (named "disks") positioned at the relative distance of 70 cm downstream the aluminum target along the muon beamline satisfies the Mu2e physics requirements. The hostile Mu2e operational conditions, in terms of radiation levels (total expected ionizing dose of 12 krad and a neutron fluence of 5 × 10¹⁰ n/cm² @ 1 MeV_(eq) (Si)/y), magnetic field intensity (1 T) and vacuum level (10⁻⁴ Torr) have posed tight constraints on scintillating materials, sensors, electronics and on the design of the detector mechanical structures and material choice. The support structure of each 674 crystal matrix is composed of an aluminum hollow ring and parts made of open-cell vacuum-compatible carbon fiber. The photosensors and front-end electronics for the readout of each crystal are inserted in a machined copper holder and make a unique mechanical unit. The resulting 674 mechanical units are supported by a machined plate of vacuum-compatible plastic material. The plate also integrates the cooling system made of a network of copper lines flowing a low temperature radiation-hard fluid and placed in thermal contact with the copper holders to constitute a low resistance thermal bridge. The data acquisition electronics are hosted in aluminum custom crates positioned on the external lateral surface of the disks. The crates also integrate the electronics cooling system as lines running in parallel to the front-end system. In this paper we report on the calorimeter mechanical structure design, the mechanical and thermal simulations that have determined the design technological choices, and the status of component production, quality assurance tests and plans for assembly at Fermilab.

Item Type:Article
Related URLs:
URLURL TypeDescription
Borrel, L.0000-0003-1436-1248
Echenard, B.0000-0002-3866-9370
Hitlin, D.0000-0003-4028-6982
Middleton, S.0000-0003-3380-5908
Porter, F.0000-0003-1948-8889
Zhu, R. Y.0000-0003-3091-7461
Additional Information:© 2022 IOP Publishing Ltd and Sissa Medialab. Received 29 September 2021; Revised 2 November 2021; Accepted 14 November 2021; Published 5 January 2022.
Issue or Number:1
Record Number:CaltechAUTHORS:20220412-237068000
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Official Citation:N. Atanov et al 2022 JINST 17 C01007
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114235
Deposited By: Tony Diaz
Deposited On:12 Apr 2022 16:46
Last Modified:12 Apr 2022 16:46

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