evan.hall@LIGO.ORG - posted 20:14, Tuesday 08 December 2015 - last comment - 21:49, Sunday 13 December 2015(24063)
Violin mode damping turned off
I have edited the ISC_LOCK guardian so that it now turns violin mode damping off before the interferometer reaches nominal low noise. This will hopefully allow us to collect ringdown data on the violin mode fundamentals.
Violin mode damping is still turned on as usual in BOUNCE_VIOLIN_MODE_DAMPING, but it now is turned off in the COIL_DRIVERS state. Thus the modes will still receive a few minutes of damping before DARM is switched to dc readout.
If this behavior needs to be reverted, there is a flag in the main() function of COIL_DRIVERS called self.turnOffViolinDamping which can be set to False.
Violin mode damping in full lock will be re-enabled once sufficient data have been collected.
Are there any observable results from this? For example, does this mean we will now see these on the running power spectrum on nuc3? And is this the reason we now have the red boxes on the violin mode medm on nuc0? I hadn't noticed the latter before, so I was wondering why these were flashing red.
Since turning the damping off, the violin mode fundamentals seem to appear on the DARM FOM at the level of 10−16 m/Hz1/2 or so. Before turning the damping off, they would eventually damp down below 10−18 m/Hz1/2 after a few hours.
I'm guessing this is why the violin mode monitors are red, but I don't know what Nutsinee set the monitor thresholds to.
Also, since writing the above alog I changed the Guardian code for turning off the damping. It is no longer executed inside an if statement; it's just executed directly in the main() function of COIL_DRIVERS.