A two-phase argon avalanche detector operated in a single electron counting mode

Abstract

The performance of a two-phase Ar avalanche detector in a single electron counting mode was studied, with regard to potential application in coherent neutrino-nucleus scattering and dark matter search experiments. The detector comprised of a 1 cm thick liquid Ar layer and a triple-GEM multiplier operated in the saturated vapour above the liquid phase. Successful operation of the detector in single electron counting mode, in the gain range from 6000 to 40000, has for the first time been demonstrated.

Thick GEM versus thin GEM in two-phase argon avalanche detectors

“…It was also observed [18] that the amplitude spectra of GEM multipliers in two-phase Ar were exponential, N~exp(-A/<q>), with the curve's slope <q> characterizing the average charge recorded. In particular, in single-electron counting mode this charge is equal to one electron on average, if the amplitude is expressed in primary electrons.…”

“…3. The latter permitted to study the GEM-and THGEM-multiplier performance for detecting weak signals, induced by 2 to 50 primary electrons, similarly to that studied elsewhere for thin-GEMs [18]. This mode was also used to measure the noise of each of the multipliers investigated.…”

“…In order to study the THGEM performance with weak signals, we developed a technique of obtaining signals with small amplitudes, in the range of 2-50 primary electrons; it is similar to that presented in [18], where it permitted reaching single-electron counting in triple-GEM multipliers. A two-phase detector was irradiated with a pulsed X-ray tube, with a reversed electric field across the liquid Ar.…”

Recent results on the properties of two-phase argon avalanche detectors

“…Such detectors have potential applications in rare-event experiments and in the medical imaging field: in particular, in coherent neutrino-nucleus scattering [5], dark matter search [6,7,8] and Positron Emission Tomography [2]. Their performances in Ar, Kr and Xe were described elsewhere [9,10,11,12,13,14,15]. Most promising results were obtained for the two-phase Ar avalanche detectors: using triple-GEM multipliers, gains reaching 10 4 were obtained [12,13], permitting the operation in a single electron counting mode [13] and the detection of both primary scintillation and ionization signals using CsI photocathode [16].…”

“…Their performances in Ar, Kr and Xe were described elsewhere [9,10,11,12,13,14,15]. Most promising results were obtained for the two-phase Ar avalanche detectors: using triple-GEM multipliers, gains reaching 10 4 were obtained [12,13], permitting the operation in a single electron counting mode [13] and the detection of both primary scintillation and ionization signals using CsI photocathode [16]. High-gain operation of two-phase Ar avalanche detectors with a double-THGEM multiplier has also been recently demonstrated [17].…”