Directional dark matter readout with a novel multi-mesh ThGEM for SF 6 negative ion operation

• Published in: Journal of instrumentation 2023-08, Vol.18 (8), p.P08021
• Main Authors: Eldridge, C., Spooner, N.J.C., McLean, A.G., Burns, J., Crane, T., Ezeribe, A.C., Marcelo Gregorio, R.R., Scarff, A.
• Format: Article
• Language: English
• ISSN: 1748-0221; 1748-0221
• DOI: 10.1088/1748-0221/18/08/P08021

Direct searches for Weakly Interacting Massive Particle (WIMP) dark matter could greatly benefit from directional measurement of the expected induced nuclear recoils. Gas-based Time Projection Chambers (TPCs) offer potential for this, opening the possibility of measuring WIMP signals below the so-called neutrino floor but also of directional measurement of recoils induced by neutrinos from the Sun, for instance as proposed by the CYGNUS collaboration. Presented here for the first time are results from a Multi-Mesh Thick Gas Electron Multiplier (MM-ThGEM) using negative ion gases for operation with such a directional dark matter TPC. Negative ion drift gases are favoured for directionality due to their low diffusion characteristics. The multiple internal mesh structure is designed to provide a high gain amplification stage when coupled to future large area Micromegas, strip or pixel charge readout planes. Experimental results and simulations are presented of MM-ThGEM gain and functionality using low pressure pure CF 4 , SF 6 and SF 6 :CF 4 mixtures irradiated with alpha particles and 55 Fe x-rays. The concept is found to work well, providing stable operation with gains over 10 3 in pure SF 6 .