stefan.ballmer@LIGO.ORG - posted 19:25, Tuesday 21 January 2014 - last comment - 01:05, Wednesday 22 January 2014(9412)
First PRMI locks
Kiwamu, Stefan We locked the PRMI on the sidebands today. The locks lasted for about 1min at a time. Lock acquisition is still slow, so more work is needed. The first lock started at UTC 2014 Jan 22, 01:59:42, and lasted until 02:00:25. There were several additional locks after that. Attached is a large screen shot with all relevant screens. We managed to get a preliminary OLG measurement for PRCL, the UGF seems to be around 55Hz (plot attached.) We were not successful with a MICH OLG measurement yet. Finally, attached is also a plot of error and control signals for the two loops.
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It seems that the pitch motion in PRM and PR2 is excited a lot during the acquisition and this prevents us from a smooth and quick lock.
In fact, when I enabled the LSC output after the pitch motion of PRM and PR2 settled down, it often locked within 5 sec. However, when their pitch rang up to more than 1 urad in RMS, locking became extremely difficult -- it catches a fringe approximately once per 5-10 minutes. Also, it seems to me that the unlock events were more or less initiated by the pitch fluctuation. See an example in the attached.
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