Speaker
Description
BULLKID is a detector design to detect rare and low threshold events, based on a monolithic array of particle absorbers sensed by multiplexed Kinetic Inductance Detectors (KIDs). The goal of this approach is to provide background identification and rejection by creating a fully active segmented structure and by applying fiducialization techniques.
A 20 g prototype, consisting of 60 voxels 5.4x5.4x5 mm$^3$ in size diced from a 3'' silicon wafer, demonstrated the feasibility of this approach. Following its successful results, we present the first operation, in a surface laboratory equipped with a lead and copper radiation shield, of a 60 g demonstrator with 180 dice. This demonstrator acts as a proof of concept for the final 800 g array, by sharing the same cryogenic setup except for the higher background level. The recorded backgrounds are compared to Geant4 simulations performed by the collaboration.
Currently, the collaboration is focused on developing BULLKID-DM, a new experiment aimed at searching for WIMP-like Dark-Matter candidates with mass of 1 GeV or lower and expected cross-section with nucleons lower than 10$^{-41}$ cm$^2$. The final device will consist of an 800 g array of over 2000 silicon dice, achieved by stacking several BULLKID detectors to achieve mass scaling and 3D segmentation.
Aside from BULLKID-DM, several R&D activities are currently focused on enhancing energy resolution and adapting the detector technology to germanium substrates. On one hand, improving the baseline energy resolution is essential to increase sensitivity toward increasingly lower-mass dark matter candidates. To this end, we present a new KID design featuring integrated phonon collectors, which has demonstrated enhanced responsivity, potentially paving the way for further improvements in this direction. Concurrently, adapting the BULLKID technology to germanium substrates is imperative for a possible Coherent Elastic Neutrino on Nucleus Scattering (CE$\nu$NS) experiment, where a higher target mass is required. While promising initial results have already been achieved, we present here the studies on the potential of a germanium-based BULLKID array.
Finally, we present the foreseen timeline and commissioning of the BULLKID-DM experiment, which will be deployed in the Gran Sasso national laboratories.