Detection of neutron-induced nuclear recoils in a low-pressure gaseous detector for particle dark matter searches

Recent neutron beam tests of a prototype detector to search for weakly interacting massive particles in the Galactic Halo are presented. The detector is an optically imaged time-projection chamber using various low-pressure gas mixtures. This technique potentially offers significant advantages for the detection of galactic dark matter in that it measures both the energy and direction of the nuclear recoil. In this paper we present measurements of ranges of neutron-induced nuclear recoils in different target gasses which are then used to determine the sensitivity of the device in a dark matter search. We also demonstrate the ability to accurately determine the direction of the recoil which can be used to discriminate signal from background using the expected diurnal modulation in the average recoil direction, which is unique to particle dark matter interactions.