Gas VUV photosensors operating face to face

The operation of two CsI-Micro-Hole and Strip Plate (MHSP) photosensors in pure xenon is presented. The photosensors operate face to face having the xenon medium in between. To produce VUV scintillation photons, a cluster of 7 stainless-steel grids is placed in the xenon medium and voltage is applied between the grids to establish an electric field higher than the xenon excitation threshold. The scintillation is triggered by electrons produced in xenon following X- or γ-ray interactions. The depth of the interaction position of X- or γ-photons in the xenon gap can be determined by weighing the signal amplitude from both photosensors. Experimental studies of the interaction position along the xenon gap, in the direction perpendicular to the photosensors, as a function of the actual position will be presented.