Modelling of the thermal systematics produced by cosmic rays in a sub-K bolometric array in L2

The characterization of primordial B-mode polarization in the Cosmic Microwave Background (CMB) requires unprecedented control of instrumental systematic effects. One key effect are the thermal fluctuations induced by cosmic-ray (CR) interactions with cryogenic detectors. In this work, we present a numerical model designed to efficiently simulate the thermal response of cryogenic focal planes to fast energy-deposition events. The method models the focal plane as a set of thermally coupled two-dimensional layers, significantly reducing the computational cost with respect to full finite-element simulations while retaining an accurate description of the induced thermal fluctuations. We compare the proposed approach with COMSOL Multiphysics simulations for different thermal configurations and deposited energies, obtaining good agreement while achieving a substantial reduction in computational time.