georgia.mansell@LIGO.ORG - posted 01:17, Wednesday 12 September 2018 - last comment - 01:20, Wednesday 12 September 2018(43957)
Locking this evening - Hard loop improvement and power up to 17 W
Hang Sheila Georgia
- Tuesday maintenance recovery - with the EY power glitch at roughly 1800 UTC, the ALS EY camera references and QPD offsets got reset to outdated values. Sheila updated many many ALS and ISC SDF differences to help prevent this kind of thing happening again.
- X arm initial alignment - with the ETMX L1 lock gain fix, WFS DOF3 now takes a long time to converge and can do with some extra gain. We have not fixed this problem in guardian yet, this is just a note to tomorrow morning's initial alignment team.
- Violin mode guardian - last night Sheila and Hang left the IFO locked with the violin mode damping guardian running. 27 modes were successfully damped, and 5 undamped modes have been identified. Attachment 1 shows DARM spectra at the beginning and end of the lock. Another close doublet has been identified at 504.885/504.891 Hz (bottom plot attachment 1). We're working on putting gain adjustment in the guardian, so that the gain is increased when the monitor filter is low, and decreased when the monitor filter is high.
- Hard loops improvement - we took quick transfer functions of the DHARD pit and yaw loops, they seem to match O1 levels now. We increased the gain of the CHARD loops massively. CHARD yaw gain was increased from 0.3 to 2, giving a UGF of ~6-7 Hz; CHARD pit gain was increased from 0.3 to 60 (!!), giving a UGF of ~7Hz. These changes have been included in the guardian (REFL_POP_WFS state), with the +30 dB filter module now being engaged for CHARD_Y.
- Soft loops - we left the soft loops unchanged, including the low bandwidth CSOFT_P.
- Power up! - We first powered up to 9W. The increased hard loop gains increased the low frequency DARM noise, so we ran the A2L script to reduce angular coupling to length. We then gradually powered up to 17 W, we started to see reductions in recycling gain and on POPAIR18 at 10 W, as we're not using TCS yet. The OMC suspension saturated when we tried 20 W and we brought it back to 17 W but lost lock anyway.
- We lost lock at 08:12:50 UTC, and left the IFO in the down state so that the HWSs can record cool-down data.
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Attached are 3 ASC measurements:
1) CHARD Y with the gain set to 0.3, which is the same gain as in the reference. You can see that the phase delay at 1.8 Hz is gone.
2) CHARD Y with the gain set to 1, we increased the gain to 2 before powering up but didn't remeasure.
3) CHARD P with the 46dB of additional gain
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