Reports until 19:47, Saturday 09 September 2017
H1 SUS (ISC, SUS)
thomas.vo@LIGO.ORG - posted 19:47, Saturday 09 September 2017 - last comment - 11:17, Monday 11 September 2017(38591)
ITMY VIolin Mode Rang Up

Hang, TVo

We were locked for about 3 hours before the ITMY Vioilin Mode 5 rang up.  The mode rang up pretty steadily but we were only alerted to it about 30 seconds before it broke lock so we didn't have enough time to change the damping loop.

Upon re-locking, we stopped at ENGAGE_SRC_ASC to look at the status of the violin modes and it seems that the phase has shifted from what is set by the guardian and what is reported in the Violin Mode Wiki.  There were no earthquakes at the time so we couldn't find any obvious environmental reason for this shift.

Here is the summary of the change we made to the ITMY Violin Mode 5 Damping:

Before After
[FM1, FM3, FM4] = ON, GAIN = +200 [FM1, FM4] = ON, GAIN = -200    

Effectively, this shifts the phase by -120 degrees.  I'm not exactly sure if these settings are the nominal ones but it gets the job done.  When the mode was damped sufficiently at nominal low noise, I tried to go back to the "Before" configuration and could see it ringing up so I'm updating the guardian gen state to reflec the "After" configuration.

Comments related to this report
thomas.vo@LIGO.ORG - 11:17, Monday 11 September 2017 (38600)

Changed the violin mode wiki and committed the ISC_GEN_STATES to SVN.