Timing performance of spark counters and photon feedback

It was shown experimentally that delayed signals from the spark counters (“tail problem”) could be connected with low-gain avalanches. The development of these avalanches is stopped by the anode electrode but they still have a chance to produce a delayed streamer by photon feedback. Good absorption characteristics of the gas mixture at wide photon energy range (starting from a cathode work function up to the X-ray region) and a high cathode work function value reduce the tail.