Saturday, February 16, 2013
Auditorium/Exhibit Hall C (Hynes Convention Center)
The Cryogenic Dark Matter Search (CDMS) uses high-purity Ge (HPGe) crystals to detect dark matter in the form of weakly interacting massive particles. There are several crystal diagnostics that would benefit from an energy deposition system with precise position control, which include measuring charge transport through the HPGe to take into account inter-valley scattering of the electron beam produced by particle collisions. An apparatus for such experiments was made using a micro-electromechanical system (MEMS) device that controls the 2-dimensional tilt of a mirror via electrostatic attractions, thereby scanning a pulsed laser beam across the HPGe crystals. Measurements of the laser and MEMS mirror setup were made using a checkerboard-like shadow mask in front of a photodetector in the HPGe crystal’s future housing at room and cryogenic temperatures. These data demonstrate that the mirror has a very precise, linear response that is exceptionally temperature independent and has a mechanical quality factor close to 106, which is indicative of extremely low mechanical losses. This is a work in progress since the cryostat wiring induces much higher losses and nonlinear behavior than the experiment itself. Nonetheless, this emphasizes how critical it is for the lab to further investigate and perfect this cryogenic laser-scanning system.