Speaker
Description
The RICOCHET experiment at the Institut Laue–Langevin (ILL) in Grenoble, France,
is a neutrino observatory targeting low-energy reactor antineutrinos (<10 MeV) via
nuclear recoils. Exploiting the coherent enhancement of the cross section, RICOCHET
opens a low-energy sensitivity frontier that enables searches for physics beyond the
Standard Model with modest exposure. RICOCHET has been operating at ILL since
early 2024 with an array of 42-g Ge detectors (CryoCube) instrumented for simultane-
ous heat and ionization readout. We focus on the complementary Q-Array detectors,
which uses superconducting crystals (13-g Al or 44-g Sn) as recoil targets and Mn-
doped Al transition-edge sensors (TESs) for calorimetric readout. We present recent
R&D results in two configurations of heat collection: a direct gold collection pad for
both phonons and quasiparticles, and a gold collection pad with a thin insulating layer
that blocks quasiparticles but allows phonons to pass through. We also present the-
oretical thermal and athermal models of quasiparticle and phonon dynamics in bulk
superconductors which models the transport process based on the Boltzmann trans-
port equation. Because robust rejection of electron-recoil backgrounds is essential for
sensitivity to sub-keVee coherent elastic neutrino-nucleus scattering (CEνNS) signals,
we use the model to investigate how prompt and delayed signal components can po-
tentially differentiate electronic recoils from nuclear recoils.