  A methodology to measure Near Infrared (NIR) scintillations in gaseous and
liquid Ar, using Geiger-mode APDs (GAPDs) sensitive in the NIR and pulsed X-ray
irradiation, is described. This study has been triggered by the development of
Cryogenic Avalanche Detectors (CRADs) with optical readout in the NIR using
combined THGEM/GAPD multiplier, which may come to be in demand in coherent
neutrino-nucleus scattering and dark matter search experiments. A new approach
to measure the NIR scintillation yield at cryogenic temperatures has been
developed, namely using GAPDs in single photoelectron counting mode with time
resolution. The time structure of NIR scintillations and their light yield were
measured both for primary scintillations and that of secondary at moderate
electric fields (electroluminescence), in gaseous and liquid Ar.
