Speaker
Description
NEWS-G (New Experiments With Spheres-Gas) is a direct dark matter detection experiment using Spherical Proportional Counters (SPCs). Key advantages of SPCs for dark matter search and especially light mass DM particles are their low energy threshold -single ionisation electron- and the possibility to use various light target nuclei -Neon/Helium/CH4 gases-. Dark
matter limits were obtained in 2017 using Neon in the 60 cm prototype SEDINE at Laboratoire Souterrain de Modane (LSM).
R&D is ongoing within the collaboration to de?fine the best operating conditions in a larger 140 cm detector at SNOLAB. For this, we use two main
calibration tools: a gaseous 37Ar source, providing two monoenergetic peaks
at 280 eV and 2.8 keV, and a 213 nm UV laser, extracting photoelectrons from
the inner surface of the sphere. The laser allows us to study the response
of the detector to single electrons, to measure the drift time and di?usion
of electrons from the surface. On the other hand, the 37Ar source allows
to measure the energy resolution for events in the whole detector volume.
Finally, combining these two tools, we can extract the W-value of the gas
mixture from the single electron response and the position of monoenergetic
peaks.
