On the Design and Development of a Radon Progeny Recoil Veto Systemfor the DRIFT-IIb Dark Matter Detector

Abstract

Finding dark matter is a major goal in contemporary physics today. DRIFT II-b (Directional Recoil Identification from Tracks detector) was designed to detect a theorized particle known as the Weakly Interacting Massive Particle (WIMP). A large amount of background has prevented the detector from operating at the sensitivity level necessary to detect WIMPs. The background radiation comes from radon progeny recoil (RPR). In an RPR event, a radioactive Radon (²²²Rn) atom decays into ²¹⁸Po⁺. Feeling the force of the electric field in the detector, a newly formed ²¹⁸Po daughter atom will move toward and attach itself to the central cathode. When that ²¹⁸Po atom decays into a ²¹⁴Pb and an alpha particle, about 1/3 of the time the alpha particle buries itself in a wire, becoming invisible to the detector. The proposed RPR veto system replaces the current central cathode wires with an aluminum-coated plastic scintillator. A plastic scintillator will allow the light output from buried alpha particles to be observed and recorded. Observed RPR events can then be differentiated from potential WIMP interactions. The goal of this summer?s research project was to test the various properties characteristic to such a veto system, including testing aspects of the light guides.