sheila.dwyer@LIGO.ORG - posted 12:07, Friday 02 October 2015 - last comment - 15:06, Friday 02 October 2015(22184)
ALS glitches in Y arm are back
Screenshot attached. We have fast glitches in the ALS Y arm transmission and control signals, which make lock acquisition difficult. In the past they have disapeared after a few hours. see alog 51242 and others referenceing it.
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Daniel,Jeff B and I went to the Y end to look into this, and found nothing conclusive. We watched several signals on the scope. We see no signs of any problems on the fiber servo signals, or the PDH error signal, but it is clear that something is wrong looking at the PDH control signal. It is not saturating.