Light Yield in DarkSide-10: a Prototype Two-phase Liquid Argon TPC for Dark Matter Searches

TL;DR

This paper reports the measurement of scintillation light yield in the DarkSide-10 liquid argon TPC prototype, crucial for background rejection in dark matter detection, achieving around 9 photoelectrons per keVee with purification.

Contribution

It provides the first detailed measurement of light yield in a DarkSide-10 prototype, demonstrating improved performance with additional purification.

Findings

Average light yield of 8.887 p.e./keVee for gamma energies 122-1275 keV

Increased light yield to 9.142 p.e./keVee after purification

Light yield measurement supports effective background discrimination

Abstract

As part of the DarkSide program of direct dark matter searches using liquid argon TPCs, a prototype detector with an active volume containing 10 kg of liquid argon, DarkSide-10, was built and operated underground in the Gran Sasso National Laboratory in Italy. A critically important parameter for such devices is the scintillation light yield, as photon statistics limits the rejection of electron-recoil backgrounds by pulse shape discrimination. We have measured the light yield of DarkSide-10 using the readily-identifiable full-absorption peaks from gamma ray sources combined with single-photoelectron calibrations using low-occupancy laser pulses. For gamma lines of energies in the range 122-1275 keV, we get consistent light yields averaging 8.887+-0.003(stat)+-0.444(sys) p.e./keVee. With additional purification, the light yield measured at 511 keV increased to 9.142+-0.006(stat) p.e./keVee.