Matthew Truch with Daniel Akerib
Performance of a Cryogenic Particle Detector for a WIMP Dark Matter Search
The nature of dark matter is currently one of the most important puzzles of Astrophysics. Big bang nucleosynthesis suggests that WB = 0 05 + 0 005, whereas WM is measured to be 0.35 + 0.1, where Wx is defined as the density of x divided by the critical mass density of the universe. Non-baryonic matter must make up the difference. Particle physics theories provide a couple of possible candidates, in the form of relic elementary particles left over from the big bang. One such candidate is a Weakly Interacting Massive Particle (WIMP) of mass between 50 and 500 GeV. The Cryogenic Dark Matter Search (CDMS) collaboration, which includes Prof Akerib’s group here at CWRU, has developed a novel technique for Earth-based detection of WIMPs from our own galactic halo. By simultaneously measuring the charge liberated and phonon energy deposited in a germanium detector when a particle interacts with the detector, one can distinguish between WIMP events (nuclear recoils) and electromagnetic background events (electron recoils). As the CDMS project shifts from development to fill production and fabrication of detectors, the detectors developed will have to be calibrated and have their performance fully characterized. This thesis will address one of the performance criteria for study, such as the detector response to a specific form of radiation, e.g., from a radioactive source.