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Reports until 02:47, Wednesday 30 November 2016
H1 ISC (DetChar, ISC)
andrew.lundgren@LIGO.ORG - posted 02:47, Wednesday 30 November 2016 - last comment - 11:23, Friday 02 December 2016(32002)
Check 1080 Hz band coherence with jitter witnesses 
Could someone on site check the coherence of DARM around 1080 Hz with the usual jitter witneses? We're not able to do it offsite because the best witness channels are stored with a Nyquist of 1024 Hz. What we need is the coherence from 1000 to 1200 Hz with things like IMC WFS (especially the sum, I think). The DBB would be nice if available, but I think it's usually shuttered.

There's indirect evidence from hVeto that this is jitter, so if there is a good witness channel we'll want to increase the sampling rate in case we get an SN or BNS that has power in this band.
Comments related to this report
cheryl.vorvick@LIGO.ORG - 03:23, Wednesday 30 November 2016 (32003)
Link

  • IMC WFS channels are ALL collected at 2048Hz
  • I can't search for an IMC WFS coherence with DARM at 1080Hz
  • I put in an FRS, #6800
evan.goetz@LIGO.ORG - 07:52, Wednesday 30 November 2016 (32006)
Link 

@Andy I'll have a look at IOP channels.
evan.goetz@LIGO.ORG - 08:46, Wednesday 30 November 2016 (32010)DetChar, ISC
Link 

Evan G., Keita K.

Upon request, I'm attaching several coherence plots for the 1000-1200 Hz band between H1:CAL-DELTAL_EXTERNAL_DQ and many IMC WFS IOP channels (IOP-ASC0_MADC0_TP_CH[0-12]), ISS intensity noise witness channels (PSL-ISS_PD[A,B]_REL_OUT_DQ), PSL QPD channels (PSL-ISS_QPD_D[X,Y]_OUT_DQ), ILS and PMC HV mon channels, and ISS second loop QPD channels.

Unfortunately, there is low coherence between all of these channels and DELTAL_EXTERNAL, so we don't have any good leads here.
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keita.kawabe@LIGO.ORG - 11:23, Friday 02 December 2016 (32105)
Link

A2L: How to know if it's good or bad at the moment.

Here is a dtt template to passively measure a2l quality: /opt/rtcds/userapps/release/isc/common/scripts/decoup/DARM_a2l_passive.xml

It measures the coherence between DARM and ASC drive to all test masses using 404 seconds worth of data.

All references started 25 seconds or so after the last a2l was finished and 9 or 10 seconds before the intent bit was set (GPS 116467290).

"Now" is actually about 15:00 UTC, 7AM PT, and you can see that the coherence at around 20Hz (where the ASC feedback to TM starts to be dominated by the sensing noise) significantly worse, and DARM itself was also worse, so  you can say that the a2l was worse AT THIS PARTICULAR POINT IN TIME.

Thing is, this might slowly drift around and go better or worse. You can run this template for many points in time (for example each hour), and if the coherence seems to be consistently worse than right after a2l, you know that we need a2l. (A better approach is to write a script to plot the coherence as a time series, which is a good project for fellows.)

If it is repeatedly observed over multiple lock stretches (without running a2l) that the coherence starts small at the beginning of lock and becomes larger an hour or two into the lock, that's the sign that we need to run a2l an hour or two after the lock.

[EDIT] Sorry wrong alog.

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