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AdV-ISC (Commissioning up to first full interferometer lock)
ruggi, capocasa, spinicelli - 1:57 Thursday 23 June 2022 (56232) Print this report
Input mirrors transversal position adjustment

Input mirrors have been moved in transversal directions (X and Y)  in order to zero the alignment error signals from the demodulation of the arm transmitted power at the LF angular dithering lines of the input mirrors. See pic 1.

The movement has been used to calibrate such errors in um. In fact, when centering loop and PR trasverse/BS steering loops are active, these error signals give a measurement of the distance between input beam and input mirror centers.

After the change the ITF has been relocked up to carm null twice. (see pic2) 

We didn't observe relevant change in the ITF behaviour during either lock acquisition and at carm null. The presence of occasional jumps was still spoiling the quality of the lock. 

During both locks the PR_TY  set point adjustment loop was automatically activated. While at the beginning it seems to work fine, it starts showing a strange behaviour after a while (in the case of the second lock the strange behaviour started in the same moment of a jump) (see pic3). The commands to automatically activate the loop are commented in metatron.

We also commented the SR angular loop engagement at carm null as in the past it was observed that the error signal is not reliable at the beginning of the lock.

We switched on CITF and let Ilaria switch PR RH on (fig 4). We left CITF locked for the night with the autorelock engaged.

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Comments to this report:
bersanetti - 3:04 Thursday 23 June 2022 (56233) Print this report

Tonight I found SDB1 totally off position, with its LC corrections saturated. The DRMI is currently locked but the Autorelock Failsafe was not engaged earlier tonight. I am not sure if it's a good idea to unlock now by hand, it's better to have experts decide about that. The DRMI already relocked once with SDB1 misplaced, but I would avoid realigning the PR mirror again in this condition, especially in case also the arms unlock. In any case, I engaged the Autorelock Failsafe with 0 max_lock_retries and 10 seconds max_trans_duration, so that in case of a natural unlock the ITF will be be brought down immediately in LOCKED_ARMS_IR.

Experts informed by mail.

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bersanetti - 11:58 Thursday 23 June 2022 (56239) Print this report

At 9:57 UTC I disabled the Autorelock Failsafe, because it was still on.

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