A Highly Sensitive Nuclear Recoil Detector Based on Superfluid 3He-B

摘要

The excitations in superfluid3 He have a dispersion curve in which the ener-gy minimum does not coincide with the momentum minimum. As a result, when a mechanical resonator moves through a gas of such excitations, nor-mal and Andreev scattering processes introduce a large asymmetry into the momentum exchange and the mechanical resonator experiences a very large drag force. A gas of such excitations is thus very easy to detect even at very low densities. We have exploited this effect to monitor the increase in excitation density in a small volume caused by a particle interaction. The working volume is filled with superfluid 3He-B at around 100nK. A particle undergoing an interaction in the volume releases a shower of quasiparticle excitations which can be detected by the increase in damping on a vibrating wire resonator. A small hole in the container allows the excitations to leak oiit into the outside colder liquid to reset the working liquid to the resting state, Using an existing experiment we can detect nuclear recoil interactions depositing energies as low as 500 eV. Two simple modifications should allow us to detect interactions in the 10 eV range.