Single-electron spectra in RPWELL-based detectors

Single-electron avalanche distributions in gaseous multipliers affect their efficient detection and that of single UV-photons. In this work, we investigated the shape of single-photo-electron spectra in single- and double-stage Resistive Plate WELL (RPWELL) detector configurations, operated in $\mathrm{Ne/CH_{4}}$ and $\mathrm{Ar/CH_{4}}$. Discharge-free operation was reached over a broad dynamic range, with charge gains of \numrange[range-phrase = -]{e4}{e6}. Compared to the usual exponential ones, the observed Polya-like charge spectra pave the way towards higher single-electrons detection efficiencies. The latter were evaluated here, using experimental data combined with numerical simulations. The effects of the gas mixtures, electric field configuration and detector geometry on the Polya spectra and their related "$\theta$" parameter are presented.