High pressure operation of the triple-GEM detector in pure Ne, Ar and Xe

We study the performance of the triple-GEM (Gas Electron Multiplier) detector in pure noble gases Ne, Ar and Xe, at different pressures varying from 1 to 10 atm. In Ar and Xe, the maximum attainable gain of the detector abruptly drops down for pressures exceeding 3 atm. In contrast, the maximum gain in Ne was found to increase with pressure, reaching a value of 100,000 at 7 atm. The results obtained are of particular interest for developing noble gas-based cryogenic particle detectors for solar neutrino and dark matter search.Comment: 7 pages, 4 figures. Submitted to Nucl. Instr. and Meth. A as a letter to the Edito

Photon emission and atomic collision processes in two-phase argon doped with xenon and nitrogen

We present a comprehensive analysis of photon emission and atomic collision processes in two-phase argon doped with xenon and nitrogen. The dopants are aimed to convert the VUV emission of pure Ar to the UV emission of the Xe dopant in the liquid phase and to the near UV emission of the N2 dopant in the gas phase. Such a mixture is relevant to two-phase dark matter and low energy neutrino detectors, with enhanced photon collection efficiency for primary and secondary scintillation signals. Based on this analysis, we show that the recently proposed hypothesis of the enhancement of the excitation transfer from Ar to N2 species in the two-phase mode is either incorrect or needs assumption about a new extreme mechanism of excitation transfer coming into force at lower temperatures, in particular that of the resonant excitation transfer via ArN2 compound (van der Waals molecule).Comment: 6 pages, 1 figure, 1 tabl

Study of ion feedback in multi-GEM structures

We study the feedback of positive ions in triple and quadruple Gas Electron Multiplier (GEM) detectors. The effects of GEM hole diameter, detector gain, applied voltages, number of GEMs and other parameters on ion feedback are investigated in detail. In particular, it was found that the ion feedback is independent of the gas mixture and the pressure. In the optimized multi-GEM structure, the ion feedback current can be suppressed down to 0.5% of the anode current, at a drift field of 0.1 kV/cm and gain of 10^4. A simple model of ion feedback in multi-GEM structures is suggested. The results obtained are relevant to the performance of time projection chambers and gas photomultipliers.Comment: 9 pages, 11 figures. Submitted to Nucl. Instr. and Meth.

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

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.Comment: 9 pages, 9 figures. Submitted to JINS

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

The characteristic properties of two-phase Ar avalanche detectors, including those obtained with CsI photocathode, are further studied. Such detectors are relevant in the field of coherent neutrino-nucleus scattering and dark matter search experiments. The detectors investigated comprised a 1 cm thick liquid Ar layer followed by a triple-GEM multiplier. In these detectors, typical gains reaching 10000 were obtained with good reproducibility and a stable operation for at least one day was demonstrated. Amplitude and pulse-shape characteristics are presented under irradiation with X-rays, gamma-rays and neutrons from different radioactive sources. The detection of both primary scintillation and ionization signals at higher gains, at a deposited energy of 60 keV, has been demonstrated.Comment: 6 pages, 11 figures. Presented at Xth Int. Conf. for Collid. Beam Phys., Feb 28 - March 6, 2008, Novosibirsk, to be published in Nucl. Instr. Meth.

Physics of multi-GEM structures

We show that physics of multi-GEM structures is rather complex, regarding the number of phenomena affecting detector performance. The high-pressure operation in noble gases and the ion feedback are considered in more detail. It is proposed that the dominant avalanche mechanism in He and Ne, at high pressures, is the associative ionization. Ion feedback effects related to the dependence on gas, pressure and gain and to possible avalanche extension outside the GEM holes are discussed.Comment: Presented at the 8th International Conference on Instrumentation for Colliding Beam Physics, Novosibirsk, Febuary 28 - March 6, 2002. To be published in Nucl. Instr. and Meth.