hang.yu@LIGO.ORG - posted 02:07, Tuesday 21 July 2015 - last comment - 20:07, Tuesday 21 July 2015(19773)
HAM5 vs DARM
Rana, Matt, Hang We did some further investigation of HAM5's coherence with DARM, as suggested by Gabriele (aLog # 19756). A list of what we did: 05:35:10 (UTC): Tapped the lower middle flange south of HAM5. 05:35:32 (UTC); Tapped the same flange harder. 05:35:54 (UTC): Tapped gull wing. The interferometer lost lock. Before the unlock, the IFO was operating at 24 W with LSC FF on. A plot of the corresponded time series was attached (TSaccHam5vsDarm.png). We could see ringing corresponding to tapping the flange in HAM5 channel, yet they did not seem to have a significant effect on DARM. The frequency of the ringing was 207Hz with a decay time of 1.6s. No 90 Hz feature seen. The gull wing tapping did not appear in the ACC_HAM5_SR1 that Gabriele noted. Summary: no clear connection between this ACC and DARM.
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evan, rana
we did further slapping and shouting around HAM5/6 (from 10:25 - 10:39 UTC) and saw a few interesting things:
- rapping on the chamber doors (HAM5 / 6) made no noticeable change in the DARM spectrum
- brushing the pink clean room curtains produces no issues, except...
- many of the curtains are touching the HEPIs; touching these ones produce broadband glitches in DARM, presumably through some L4-C saturations
- the piece of beamtube between HAM5 and where the tube gets fat is in two pieces; the one with bellows on both ends has low frequency modes from 90-100 Hz. These are easily visible in DARM with gentle tapping. Not sure if this is related to the 90 Hz coherence seen in BruCo.
afterwards, we ran Hang's A2L script. It ran well, but takes awhile. We ought to run these in parallel.
Some times and events for analysis:
10:25:45 knocking on HAM5-south 10:26:01 knock on south door, upper west side 10:26:40 wiggle HAM5's curtains 10:27:40 wiggle HAM6's curtains 10:27:53 acoustic injection near HAM6 east side 10:28:12 ISCT6 acoustic noise 10:28:46 HAM5 north door 10:30:22 HAM5-HAM4 manifold 10:32:32 septum plate (north end) 10:34:39 HAM4-5 manifold whack 10:35:45 tube between bellows near HAM5 10:37:34 more of same 10:38:14 more of same