Electron emission properties of two-phase Ar avalanche detectors are studied.The detectors investigated comprised a liquid Ar or Ar+N2 layer followed by amulti-GEM multiplier operated in the saturated vapour at 84 K. Two componentsof the electron emission through the liquid-gas interface were observed: fastand slow. In Ar, the slow emission component dominated even at higher fields,reaching 2 kV/cm. In Ar+N2 on the contrary, the fast emission componentdominated at higher fields, the slow component being disappeared. This isexplained by the electron backscattering effect in the gas phase. The slowcomponent decay time constant was inversely proportional to the electric field,which is compatible with thermionic emission model. The electron emissionefficiencies in two-phase Ar and Ar+N2 were estimated to be close to eachother.
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