Speaker
Description
This contribution presents the novel single-moderator neutron spectrometer, named "TetraBall", developed by INFN within the CMS BRIL project, aiming at characterizing the complex neutron field in the CMS experimental cavern for the High-Lumi LHC era. The TetraBall is a wide energy range neutron spectrometer condensing the functionality of several Bonner Spheres in a single moderator. It is equipped with 42 SiC radiation-hard detectors organized in a tetrahedral geometry. It is designed to work in a single exposure mode and to be insensitive to incident gammas and charged hadrons. Thanks to a lead insert, exploiting the (n,xn) reaction, it can respond up to several GeV. It is designed to fulfill the CMS BRIL neutron monitoring requirements for the High-Lumi LHC period and it will be fundamental in benchmarking the FLUKA Monte Carlo expectations in several locations inside the underground experimental cavern. The first TetraBall propotype has been installed and commissioned in June 2025 and it has been operated in CMS continuously during the 2025 and 2026 LHC running periods. The unfolded neutron energy spectra, together with the total and partial neutron fluences, measured by the TetraBall system in 2025 and 2026 in different CMS locations will be shown. The results allow the benchmarking of the FLUKA Monte Carlo expectations at the level of 5%.
| Topics | T4. Shielding and dosimetry |
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