Simulation, calibration & exploitation of the DRIFT-II directional dark matter detector

• Main Author: Ghag, Chamkaur
• Published: University of Edinburgh 2006
• Subjects: 520
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.651408

Cold Dark Matter is believed to constitute almost a quarter of the Universe, most likely in the form of Weakly Interacting Massive Particles (WIMPs), predicted by supersymmetry. This thesis describes the simulation methods, analysis techniques, and results for the calibration of the DRIFT-IIA directional dark matter detector. This is the first module in an array of gas time projection chambers capable of searching for WIMPs with directional sensitivity, localised in the Boulby mine. Analysis of calibration data taken over a period of five months is compared to detailed Monte Carlo simulations using GEANT4, and a number of efficiencies calculated. After simulation and analysis of data taken during neutron source exposures, in a variety of configurations and separated over a number of months, the DRIFT-IIA detector is found to have an efficiency of 94±2(stat)±5(sys)% for the detection of neutron-induced nuclear recoils. This efficiency is reduced to 44±1(stat)±5(sys)% when measures are taken to remove background events from all data, and a remaining population of events from radon progeny recoils is discussed. The gamma ray rejection factor is determined to be better than 10^-5 following similar analysis of data taken during gamma ray source exposures. Neutron and gamma ray flux from rock surrounding the detector is calculated and interaction rates as a result of this radioactivity in an un-shielded DRIFT-IIA found to be 1.3 nuclear recoils per day and under 2.1 electron recoils per day, above detector threshold, with the nuclear recoil rate dropping to under 1 event per year for a shielded detector. Future operation, development and expansion of the DRIFT-II array will lead to increased potential for directional dark matter detection.