Operation stability of a prototype for CYGNO experiment

CYGNO experiment is working at the construction of one cubic meter TPC, based on Optical Readout of Gas Electron Multipliers (GEMs), for Directional Dark Matter search. This kind of research demands for very long dataacquisition runs and thus for high operation stability and reliability. This is one of the key elements of INITIUM project (ERC-2018-COG). The performance of such an approach was studied with a 7 liter sensitive volume detector. The detector was kept operative for 10 days in the working conditions able to provide full detection efficiency while continuously monitoring voltages and currents. Even if a few times per day the current drawn by the detector started to increase, these events could be recovered by an automated high voltage cycle. Dead time introduced by these procedures was evaluated to be lesser than 6% and the operation of the detector did not show any deterioration during the 10 days of the test.