Fig. 1. UV photon detector working in ST configuration.

Fig. 2. Transmission curve for chromium coated quartz.

Fig. 3. Schematic representation of the electronic chain used for recording the electron spectra from the UV photon detector.

Fig. 4. Electron pulses as seen in the oscilloscope for pin-hole aperture.

Fig. 5. Electron spectra for different multiplication voltages recorded with a MCA.

Fig. 6. Excess pulses due to photon feedback at different ΔVTHGEMs.

Fig. 7. Effect of drift field on photon feedback.