DMTPC: A dark matter detector with directional sensitivity

By correlating nuclear recoil directions with the Earth’s direction of motion through the Galaxy, a directional dark matter detector can unambiguously detect Weakly Interacting Massive Particles (WIMPs), even in the presence of backgrounds. Here, we describe the Dark Matter Time‐Projection Chamber (DMTPC) detector, a TPC filled with CF4 gas at low pressure (0.1 atm). Using this detector, we have measured the vector direction (head‐tail) of nuclear recoils down to energies of 100 keV with an angular resolution of ≤15°. To study our detector backgrounds, we have operated in a basement laboratory on the MIT campus for several months. We are currently building a new, high‐radiopurity detector for deployment underground at the Waste Isolation Pilot Plant facility in New Mexico.