aLIGO LHO Logbook

H1 PSL

jenne.driggers@LIGO.ORG - posted 21:02, Saturday 15 October 2016 - last comment - 07:39, Sunday 16 October 2016(30564)

ISS 1st loop using PD_B

[Jenne, JeffB]

After our lockloss this afternoon, we couldn't get the ISS to quit oscillating. Eventually we were able to engage the loop using PD_B, and since the new PD_A location didn't seem to make a big difference in DARM, we left it on PD_B for this lock. Someone may want to revisit this on Monday.

Comments related to this report

jeffrey.bartlett@LIGO.ORG - 23:30, Saturday 15 October 2016 (30567)

Link

  Sheila & Jeff B.

  While the ISS was oscillating, Sheila dropped the gain from 30.0dB to 24.0dB and the ISS stopped oscillating. The ISS appears to be behaving better. Trending the gain showed on 10/11/16 the gain was changed from 18.0dB to 30.0dB. 

   Over the past several Ops shifts, after a lockloss the mode cleaner, ISS, and FSS would be oscillating continuously during the green locking; breaking the lock. After many such attempts ALS would finally lock. Since Sheila adjusted the gain, it has taken a just a couple of tried to get past LOCKING_ALS. The MC, ISS, and FSS are now relocking more quickly after a Lockloss.

kiwamu.izumi@LIGO.ORG - 07:39, Sunday 16 October 2016 (30570)OpsInfo

Link

The gain should be 18 dB for PD B (29942) as 24 dB sounds too close to an oscillation point. Also, the gain was set to 30 dB purposely for PD A to compensate for the smaller amount of light on the newly moved PDA (30426).