[Adam M., Paul]

The IMC Guardian script can now be used to maintain the required state of the IMC.

This was achieved using the essentially the same scripts as in Livingston, but with some temporary local modifcations to account for the difference in the install state at the two sites (for example, ASC loops are not controlled by the guardian at LHO yet). The current state should be regarded as temporary, and if it's not required one can still of course lock the modecleaner in the way we have been doing up to now. (However, it may be useful for commissioning as we have already experienced the frustration of wondering where our signals have gone before realising the IMC was unlocked). The scripts can be found in /opt/rtcds/userapps/release/ioo/h1/scripts/imc

Some details:

Since we don't yet have a beam on MC2 trans QPD, we are using the MC_REFL_DC_OUTMON channel to verify the locked/unlocked state of the IMC. Currently, the threshold is set to 70 counts, because when aligned reasonably well the REFL_DC count is around 45. If the alignment state changes significantly, for example due to the change in PSL temperature or the upcoming vent, I recommend to lock manually first and realign to bring the locked REFL_DC counts back below 50 or so. If necessary, as an alternative the threshold can be changed in the imc_params.txt file. Of course if the laser power is changed significantly, the threshold should be adjusted.

The starting common mode gain is 0dB, which ramps up to 16dB upon lock acquisition. If there are problems to do with locking to bad modes, it may be necessary to reduce the starting gain. This can be edited on line 44 of the mcdown script. The locked gain can be edited on line 20 of the mcup script. Currently it takes two steps of 8dB from 0dB. If the starting gain is edited, this should also therefore be edited, or it could be rewritten to just make one step to the required gain.