This morning we performed some tests of the OMC slow shutter in order to investigate the issue faced yesterday afternoon.

Francesco put the ITF in single bounce mode. We put DET_MAIN in pause and tried to act on the OMC shutter from the SDB1_Rot process using the MOVELIMIT command. The first attempts of opening the shutter in this way failed. We also tried to close the shutter (in case the sign in the command was wrong), but this did not open the shutter neither.

Then we opened the shutter using the relative movement of 45000 steps. After this was done, we clicked on "Stop movement". After this, we tried to close the shutter using again the MOVELIMIT command, and this time it worked. We then performed a few cycles of opening/closing the shutter with MOVELIMIT which all worked fine.

We updated the DET_MAIN.py file in order to use the MOVELIMIT command instead of the relative motion. We put DET_MAIN back in exec and reloaded the node. We tested a couple of cycles of opening/closing using DET_MAIN and it worked fine.

We also updated the opening and closing durations set in the DET_MAIN.ini file, as the motion with the MOVELIMIT command is faster. Looking at an example of opening sequence (Fig.1) we can see that the opening takes between 25 and 30s. Therefore we set the opening duration to 45 s (we leave at least 15s of margin). For the closing (Fig.2), the duration is about 35 s. We set the closing time to 60s.

For the record previous values for the opening and closing durations were 80 and 100 s respectively.

These durations could be optimized further when we have more statistics.