R&D (FilterCavity)
YuhangZhao, EleonoraCapocasa - 23:02, Monday 15 January 2018 (626)
Recovery of the cavity lock after Christmas break
Today I and Eleonora have aligned and locked the cavity again. We found that the beam was pretty misaligned (not reaching any of the two in-vacuum targets) and the range of the optical levers was too small to recover the alignement. So we had to move PR picomotor to send the beam at 300 m and INPUT mirror picomotor to superpose the reflected beam on the incoming one.
After doing that we have put to zero the local control error signals and we have closed all the local controls loops. Then, we could fine tune the alignment with the local controls and lock the cavity stably.
We took pictures of each local control panel while the cavity was locked (See figure from 1 to 4: END, INPUT, BS, PR). The lock can last for more than 30 minutes (we had to unlock on purpose before going away). See figure 5 for the transmitted beam during the lock. We took photos of the oscilloscope showing the transmitted power just after achieving the lock (pic 6) and after 30 min of locking (pic 7). In the best alignment condition it is about 1 V.
Images attached to this report
626_20180115150135_em.jpg 626_20180115150145_im.jpg 626_20180115150159_bs.jpg 626_20180115150208_pr.jpg 626_20180115150217_locking.jpg 626_20180115150229_justafterlocking.jpg 626_20180115150240_after30min.jpg