After one week of work, I started up the system. The polarzation scheme is symmetric :
- MCP front : +1000 V ->1400 V
- MCP rear: -1000V
- Anode: -1350 V
During the morning the dp (difference of potential) was increased from 0 to 1000V then in the afternoon from 1000V to 2400V. At 2100V, there was no noise aound 5Hz of dark count. The current was some-what lower then before (1-2 micro A). The dark count increased smoothly from 5 Hz up to 30 Hz at 2400V. The image of the detector was homogenous (no real acquisition has been performed at this stage unfortunatelly), the hit distribution of the dark count was with 2-3 pixels at equal height.
This has been from 15h00-17h30, in good shape. Just we I intended to switched off the system, the dark count "explosed", and I switched of the system straight away.