Calibration and monitoring of the highly segmented SoLid anti-neutrino detector

The SoLid experiment is currently taking physics data close to the BR2 reactor core at SCK·CEN, Belgium, exploring very short baseline anti-neutrino oscillations. It aims to resolve the reactor anti-neutrino anomaly by measuring both anti-neutrino rate and energy spectrum. The 1.6-tonne detector is based on a highly segmented dual scintillator technology, which enables to face the high background environment imposed by operating at less than 10 meters from the reactor core without significant overburden. One of the challenges is to ensure the homogeneity and performance of the 12800 5 cm cubic voxels, particularly concerning the design energy resolution of 14 % and the design detection efficiency of 40 % for respectively the positron and the neutron from the inverse beta decay. To this end, the individual detection cells were tested during construction, and regularly calibrated since then using an automated calibration system.