Direct observation of avalanche scintillations in a THGEM-based two-phase Ar avalanche detector using Geiger-mode APD

Abstract

A novel concept of optical signal recording in two-phase avalanche detectors, with Geiger-mode Avalanche Photodiodes (G-APD) is described. Avalanche-scintillation photons were measured in a thick Gas Electron Multiplier (THGEM) in view of potential applications in rare-event experiments. The effective detection of avalanche scintillations in THGEM holes has been demonstrated in two-phase Ar with a bare G-APD without wavelength shifter, i.e. insensitive to VUV emission of Ar. At gas-avalanche gain of 400 and under ±70º viewingangle, the G-APD yielded 640 photoelectrons (pe) per 60 keV X-ray converted in liquid Ar; this corresponds to 0.7 pe per initial (prior to multiplication) electron. The avalanche-scintillation light yield measured by the G-APD was about 0.7 pe per avalanche electron, extrapolated to 4π acceptance. The avalanche scintillations observed occurred presumably in the near infrared (NIR) where G-APDs may have high sensitivity. The measured scintillation yield is similar to that observed by others in the VUV. Other related topics discussed in this work are the G-APD's single-pixel and quenching resistor characteristics at cryogenic temperatures.

Performance degradation of Geiger-mode APDs at cryogenic temperatures

“…We suppose that the GAPD performance degradation at cryogenic temperatures results from the increase of the GAPD pixel recovery time = R Q C P , due to the increase of the pixel quenching resistor R Q at cryogenic temperatures; here C P is the pixel capacitance. It should be remarked that the increase of R Q at low temperatures was observed earlier [12].…”

“…A 3x3 matrix of GAPDs (MRS APD "CPTA 149-35" [24], production of 2012) was placed in the gas phase at a distance of 6.5 mm behind the second THGEM, electrically insulated from the latter by an acrylic plate, transparent in the NIR, and by a wire grid at ground potential. Each GAPD had a 2.1×2.1 mm 2 active area with 1764 pixels, a capacitance of 150 pF and a Photon Detection Efficiency (PDE) of about 15% at 800 nm [12], [24]. The gain-voltage and noise-rate characteristics of this particular GAPD type, at 87 K, were presented elsewhere [22].…”

“…In this case the contribution of noise signals was negligible. Other details of the experimental setup and procedures are provided elsewhere [7], [9], [12], [13].…”

Liquid noble gas detectors for low energy particle physics

“…The authors of [346] studied avalanche scintillation 12 in double-phase argon using a double THGEM multiplication structure and a 4.4 mm 2 SiPM (termed by the manufacturer G-APD -'Geiger APD') placed behind a glass window at a distance of 4 mm from the top THGEM. The G-APD was sensitive only in the visible and near infrared regions up to 950 nm with an average quantum efficiency of 15%.…”

MPPC versus MRS APD in two-phase Cryogenic Avalanche Detectors

“…The details of the experimental procedures regarding determination of the GAPD noise rate, gain and pixel resistance, can be found elsewhere [7], [16], [23]. In particular, the noise rate was measured by counting the noise pulses in a given time interval, the noise signals being recognized by their characteristic pulse-shapes.…”