The detection of low energy neutrons and γ-rays by superfluid 3He, a potential dark matter detector

We have demonstrated in a pilot study using an existing experiment that superfluid 3He at 100 μK can be used as a nuclear recoil detector sensitive to neutron and γ-ray interactions depositing energies down to a few hundred eV. The deposited energy is converted to 3He quasiparticles which are detected by their effect on a vibrating wire resonator in the liquid. The system can be calibrated independently using a second vibrating wire as a heater but a convenient fixed point is provided by the exothermic reaction n + 32He = p + 31H + 764 keV. Given the great potential for improvement we propose that the system might make a sensitive WIMP detector.