Advancements in Muon Collider Calorimetry: Design, Testing, and Radiation Resistance of the Crilin Calorimeter Prototype

¹ INFN, Laboratori Nazionali di Frascati, Via E. Fermi 54, 00044, Frascati, Italy
² ENEA Nuclear Dept, Casaccia R.C., Via Anguillarese 301, 00123, Rome, Italy
³ ENEA Nuclear Dept, Frascati R.C., Via Enrico Fermi 45, 00044, Frascati, Italy
⁴ INFN Sezione di Roma,Piazzale Aldo Moro 2, 00185, Rome, Italy
⁵ INFN Sezione di Padova, Via Francesco Marzolo 8, 35131, Padova, Italy
⁶ Università degli Studi di Padova, Via 8 Febbraio 2, 35122 Padova, Italy
⁷ INFN Sezione di Torino, Via Pietro Giuria 1, 10125, Turin, Italy
⁸ Donostia International Physics Center, Manuel Lardizabal Ibilbidea, 4, 20018 Donostia, Gipuzkoa, Spain
⁹ INFN, Sezione di Ferrara, Via Saragat 1I, 44122, Ferrara, Italy
¹⁰ INFN, Sezione di Roma Tre, Via della Vasca Navale 84, 00146, Rome, Italy

^* e-mail: ivano.sarra@lnf.infn.it

Published online: 7 March 2025

Abstract

The Crilin calorimeter is a semi-homogeneous calorimetric system that uses Lead Fluoride (PbF₂) crystals with UV-extended Silicon Photomultipliers (SiPMs). Proposed for the Muon Collider, it requires high granularity to distinguish signal particles and address substructures for jet identification. Anticipating substantial occupancy due to beam-induced backgrounds, simulations indicate a photon flux with an average energy of 1.7 MeV and approximately 4.5 MHz/cm² fluence rate. Prioritizing time-of-arrival measurements within the calorimeter is crucial for associating clusters with interaction vertices. The calorimeter’s energy resolution is vital for determining jet kinematics. Extensive radiation hardness studies confirm the system’s effectiveness when operating in a challenging radiation environment, with exposure up to 10 kGy/year total ionizing dose (TID) and a neutron fluence equivalent to 10¹⁴ neutrons 1 MeV/cm²/year.

Prototype (Proto-1), with two layers of 3×3 PbF₂ crystals, achieved a timing resolution below 50 ps for energy deposits exceeding 1 GeV during 2023 tests. A comprehensive overview, including mechanics, electronics, and test beam outcomes, is presented. Construction is underway for a larger 9 9 crystal matrix prototype with 5 layers, to be completed in 2024. Testing is scheduled for the summer of 2025.