In the long standing search for dark matter’s annual modulation with NaI(Tl) detectors, all current generation experiments are plagued with noise from the PMTs which is about an order of magnitude higher than the signal at the keV recoil energies of interest.

ASTAROTH is an R&D project financed by INFN and located at LASA (Laboratori Acceleratori e Superconduttività Applicata) near Milan (Italy). The aim is to replace PMTs with SiPM matrices on all faces of cubic crystals, to highly enhance the signal-to-noise in the region of interest and lower the detection threshold below 1 keV where potentially a large fraction of signal awaits undetected.

SiPMs offer several advantages in terms of efficiency of light conversion, radiopurity, compactness and especially noise, if operated at cryogenic temperatures.

ASTAROTH has developed an innovative cryostat where the 5-cm cubic crystals can be cooled gently in He atmosphere while the cooling power is provided by a liquid argon bath that will be instrumented and act as a veto detector.

Crystals will be encapsulated in epoxy resins to maintain the transparency on all sides, maximize light collection and allow for safe manipulation through the cooling cycles, a breakthrough for NaI crystals users.

Our cryogenic front-end electronics is based on discrete and integrated technologies with the ambition of providing a working solution that goes beyond our physics scope and could replace PMTs for low energy astroparticle applications in a wide community. We report about the 2024 run when we have successfully cooled down a crystal with two faces coupled to matrices of SiPM from two different vendors.