Reports until 10:10, Friday 10 October 2014
H1 ISC
kiwamu.izumi@LIGO.ORG - posted 10:10, Friday 10 October 2014 (14402)
a strange lock loss understood

Keita, Sheila, Kiwamu,

Keita pointed out yesterday that there was a strange lock loss event of the DRMI in which the guardian seemed to have switched the state to a unlocked state even though the  PRC and SRC build-up were still sufficiently high. This is now understood and fixed.

We found out that this was due to our bad coding in the guardian. The "WFS_CENTERING" state had a unwated command (I don't exactly know what part was it) which brings the state to "DOWN" immediately. So every time when we requested the "WFS_CENTERING", it then shut down the lock. Sheila edited the code and now it does not show a funny lock loss any more.

The attached is time series from a second example of the funny lock loss. You can see that PRCL cut its input at t = 1.2 sec even though POP_RF18 and AS_RF90 were high. This was actually initiated by our request for the guardian to go to "WFS_CENTERING". Then it immediately transitioned to a wrong state DOWN, which shuts all the LSC control loops. Of course, this resulted in lock loss.

Images attached to this report