Detector development for direction-sensitive dark matter research
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The existence of Dark Matter was first proposed by Fritz Zwicky in 1933, based on the observed velocity distribution of galaxies in the Coma Cluster. Subsequent studies of visible mass and velocity distributions in other galaxies have confirmed Zwicky's original observation; there is now little doubt that Dark Matter exists. However, due to the fact that Dark Matter interacts very weakly through non-gravitational forces, nothing is known about the nature of Dark Matter. It is believed that Dark Matter particles are streaming toward the Earth, in the Earth's rest frame, from the direction of the constellation Cygnus. Observation of this so-called Dark Matter 'wind' with a direction-sensitive dark matter particle detector would be compelling evidence that Dark Matter does consist of a gas of discrete particles as a new form of matter. The DMTPC collaboration is developing such a detector, and this thesis describes R&D work in support of that project. The DMTPC technique for looking for Dark Matter relies on Dark Matter particles interacting with atomic nuclei, causing the nuclei to recoil and to leave optical signals that can be detected. Since neutrons are electrically neutral and collide with nuclei, they can mimic Dark Matter signals. Therefore, the reduction of neutron background is critical to the successful detection and identification of Dark Matter particles. One important aspect of this thesis is to fully understand and quantify neutron interactions with our detector. In addition to providing information for understanding Dark Matter experiments, this work also allows us to understand how our device can be used as a neutron detector. We have been able to measure a number of neutron events in a variety of experimental runs both with and without neutron sources such as a neutron generator and 252 Cf. From these runs, we have obtained data for both elastic and inelastic interactions of neutrons of various energy ranges with detector gas nuclei. In this thesis, I will also discuss our current background data taking for the Dark Matter research and our plan for scaling up the detector to 100 m 3 for a competitive Dark Matter search.
Thesis (Ph.D.)--Boston University
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