Corrections to Signal Saturation on the DEAP-3600 Dark Matter Search

Abstract

Dark matter is currently a topic at the frontier of astroparticle physics research. Its discovery or refutation would have profound implications for particle physics, cosmology, and astrophysics. There are numerous experiments trying to detect potential dark matter interactions with ordinary matter. The experiment at the focus of this thesis is the Dark matter Experiment using Argon Pulse-shape discrimination (DEAP). The DEAP collaboration has built a tonne-scale detector, dubbed DEAP-3600, which is part-way through its three-year data acquisition run. The detector utilizes roughly 3300 kg of liquid argon as a scintillating medium in order to detect potential dark matter interactions, which are expected to be in the form of rare elastic collisions with argon nuclei. The detection instrumentation comprises an array of 255 photomultiplier tubes, which can turn trace amounts of light into measurable electrical signals. In addition to these devices which generate the signals, DEAP-3600 has a data acquisition stream which includes a signal shaping/amplification stage and a digitization stage. The signal generation and digitization stages are especially prone to saturation effects which are associated with large electrical currents. These effects manifest themselves in data to varying degrees, depending on event energy, position, and how "prompt" the light is. What follows is a detailed overview of an algorithm devised to correct signal saturation in all forms of data collected by the detector.