In the Fall of 2019, the NEWS-G experiment used its latest detector, a 140 cm diameter Spherical Proportional Counter (SPC) to search for low-mass dark matter at the Laboratoire souterrain de Modane (LSM) in France. The detector has then been moved to SNOLAB in Canada and has taken data since the Fall of 2022. SPCs are metallic spheres filled with gas, with a high-voltage anode at the centre that attracts and amplifies ionization charges from atomic recoils. Having the sphere filled with pure methane, hydrogen was used as the target to produce new limits on the proton spin-dependent cross-section around masses of 1 GeV.


This paper first introduces the NEWS-G experiment and describes the commissioning at the LSM with the shielding used, the SPC detection principle and the new multi-anode sensor. It then focuses on the calibrations using a UV laser and argon-37, as well as the background discrimination methods to remove alpha-particle induced events and spurious pulses. Then, it presents the profile likelihood ratio method that was used to derive constraints on WIMP mass and cross-section. Finally, it describes the status of the recent data taken at SNOLAB and mentions future projects.