Sensor Development and Testing for the NEWS-G Dark Matter Experiment

Abstract

The NEWS-G collaboration utilizes Spherical Proportional Counters (SPCs) in direct detection searches for low-mass dark matter. The detectors use gasses with a high voltage sensor in the centre to collect incoming electrons ionized from particle interactions in the gas. The experiment is currently running at SNOLAB and uses its low threshold requirements to search for Weakly Interacting Massive Particles (WIMPs) with sub-GeV mass. To support charge collection from greater distances within the SPC volume, the detector uses a multi-anode achinos sensor. This style of sensor uses a resistive support structure to hold the anodes in place and correct the electric field in the volume of the detector. Previous sensor versions used support structures made from Bakelite or were 3D printed with a Diamond-Like Carbon coating.
 I worked on further development of the achinos utilizing electrostatic discharge resin to directly 3D print the support structure, allowing for increased precision and production rates. This included adding internal guide tubes to support the wires, reducing pressure points that could cause damage to the wire. These structures were then tested with increasing voltages in an argon gas mixture while being observed for discharges. The sensors were further tested in 30cm diameter sphere to monitor the stability during data-taking runs, leading to design iterations to improve the stability of the sensors and increase the maximum usable voltage. Tests were conducted considering the resistive properties of alternative structure materials, including glass capillary tubes of varying thicknesses, but the resin was further developed for its easier applications to multi-anode structures.
 I also worked to implement new methods of attaching the metal anodes to insulated wire, including the use of silver conductive paste to strengthen the electrical connection. This was measured to have a resistance of about 10Ω, where previous methods had connections too weak to observe.