The SND@LHC neutron shielding

Journal of Instrumentation, vol. 20, pp. T12002

Abstract

Abstract This paper presents the design, construction, and simulation-based validation of the ColdBox, a combined neutron shielding and insulating enclosure for the Scattering and Neutrino Detector at the LHC (SND@LHC). The emulsion films in the detector's target region require protection from the intense neutron radiation background and a stable environment of 15 ± 1 °C and 50–55 % relative humidity for long-term stability. The ColdBox meets these requirements through a dual-layer structure: an external 5 cm plexiglass wall to moderate fast neutrons, and an internal 4 cm layer of borated polyethylene (with 35 % boron content) to capture thermal neutrons. The mechanical design, based on a robust aluminum frame, accommodates the constraints of the TI18 tunnel. FLUKA simulations were used to optimize the shielding configuration, showing a significant reduction in the neutron flux, with a simulated ratio of shielded to unshielded thermal neutron fluence of 2.3 × 10 -3 . This result is consistent with initial measurements from BatMon detectors. The design also provides a sealed volume for a cooling system to maintain the required temperature and humidity, ensuring the necessary conditions for the emulsion films' integrity.

Authors 2

1. Mariyan Bogomilov

   Sofia University "St. Kliment Ohridski"

   Affiliation as printed

   Faculty of Physics, Sofia University, Sofia, 1164, Bulgaria

2. H. Lacker

   Humboldt-Universität zu Berlin

   Affiliation as printed

   Humboldt-Universität zu Berlin, Berlin, 12489, Germany