Further studies of two-phase avalanche detectors: Electron emission and gamma-ray detection properties

Characteristic properties of two-phase avalanche detectors are further studied. Such detectors are relevant in the field of coherent neutrino-nucleus scattering, dark matter search and positron emission tomography (PET). The detectors investigated comprised a liquid Ar, Ar+N2 or Xe layer followed by a multi-GEM multiplier with CsI photocathode operated in saturated vapor. It was found that doping of two-phase Ar with N2 removed the slow electron emission component, existing in two-phase Ar, and enhanced the fast component. The electron emission efficiency was close to 100% both in two-phase Ar and Ar+N2 even at lower electric fields. The detection of 511 keV gamma-ray induced signals was demonstrated in two-phase Ar (scintillation signals) and two-phase Xe (ionization signals) avalanche detectors, in connection with PET applications.