a remaining rotation stage bug

Craig, Sheila, Jenne, Travis

There is still at least one problem with the rotation stage, that sometimes it goes the wrong way when it first starts moving. 

The attached screenshot shows our first attempt at increasing the power since the vent, the rotation stage velocity and request are correctly set to 22 Watts and a velocity of 10, before the rotation stage starts moving.  When the rotation stage starts moving, you can see a drop in the input power (which happens faster than the normal rotation stage motion), the normalization (PSL-POWER_SCALE_OFFSET) is lowered by the guardian to adjust for this, but we loose lock anyway.  After the lock is lost the rotation stage proceeds at a reasonable pace to 20Watts, and the normalization follows correctly. 

This is not a new bug, we've had random locklosses like this for some time, but it is a bug that remains after last week's rotation stage fix. 

Manually over-filled CP3 at 23:01 utc

1/2 open LLCV bypass valve, and the exhaust bypass valve fully open. Flow was noted after 53 seconds, closed LLCV valve, and 3 minutes later the exhaust bypass valve was closed

changes in IMC alignment from April 4th to April 22:

Changes as measured by OSEM values: last IMC lock before laser work to stable IMC lock today

	April 4th	April 22	diff (urad)
MC1 p	-27	-13.5	+13.5
MC1 y	-1044	-1036	+8
MC2 p	500	504	+4
MC2 y	-688	-686	+2
MC3 p	-895	-895	0
MC3 y	-1027	-1018	+9
IM4 Trans p	-0.425	-0.490	-0.065
IM4 Trans y	0.103	0.081	-0.022

I worked on the IMs (IM1-4) this morning, and have verified that they are aligned to the April 4th values, so cannot account for the change in IM4 Trans.

The alignments of MC1-3 follow the alignment of the IMC input beam, so while the alignment changes for these optics are bigger than what we typically see, after the laser work they are not unexpected.

Power stabilisation work

This morning I measured the AOM drive voltage as a function of "offset slider %", and also the amount
of diffracted light both with and without the digital support loop.  All measurements were taken with
the HEPA fans running.

    With no diffracted light, the maximum output voltage on PDA was (-9.6,-9.3) V and on PDB was
(-9.65,-9.4) V.  No saturations were observed with the incident power at this level.

    Attached are the spectra and transfer function measured.  The relative power noise is about a
factor of 10 higher than it should be.  In the spectrum is a peak at ~1 kHz, the source of which
is unknown, but is probably related to the problems mentioned by Keita.  Pushing the gain higher
seems to increase the noise beyond 10 kHz.  The noise at frequencies below 100 Hz is significantly
higher than with the low power mode.

    At low frequencies the transfer function is not as clean as the measured result in the low power
mode.  I am not sure but this might be related to the linearisation of the AOM drive.

Attached are the plots for the AOM drive voltage and diffracted power as a function of
the offset slider.

    With the current settings with the offset slider at 6%, we are diffracting ~4.5 W.
The plotted and reported diffraction percentage on the MEDM screen needs to be recalibrated.

PSL ISS 3rd loop filter (for high power alignment stability)

Following up on Kiwamu's LSC model change, and in preparation for closing the ISS 3rd loop, I made a loop filter.

The idea is to make an ISS loop which sends the arm power signals (TRX and TRY) to the ISS 1st loop error point to prevent radiation pressure driven instabilities.  This loop only need to have gain around 0.5Hz (near the suspention pitch mode), so the open loop TF can be a peak around 0.5Hz with upper and lower UGFs a factor of 5 or so away (see figure 1).  The assumed plant transfer function is the interferometer coupled cavity pole aroud 0.7Hz, and the (yet to be realized) anti-aliasing filter (SR560 AC-coupled and with a pole at 10Hz, see figure 2).  The control CDS filter is shown in figure 3.

ISS issue (Sheila, Kiwamu, Jenne, Jim, Keita)

During relocking effort, for no apparent reason ISS went crazy several times (attached left), oscillating at about 1.6kHz (attached right). This is not unlike 2.5kHz oscillation reported in   alog 26666, but the frequency is different.

This is not FSS though FSS is affected by this, as the refcav was once knocked out of lock during the oscillation but the oscillation in ISS continued. It seems that FSS is affected because there's simply too much intensity noise (attached right top cyan and right bottom shows the refcav transmission DC).

HPO output itself seems to be fine (right top, brown trace), so this really sounds like something that happens in ISS.

Anyway, when this happens, do the following.

1. Open PSL_ISS MEDM.
2. Press AUTOLOCK OFF.
3. Press Manual Mode. Manual mode MEDM screen will open.
4. Press red OFF button in Manual mode MEDM.
5. If Refcav is unlocked, open the PSL_FSS MEDM, press AUTOLOCK OFF, then AUTOLOCK ON, and wait for the FSS to acquire lock.
6. Go back to Manual mode MEDM screen and press green ON button.
7. At first the red average trace in "DIFFRACTED POWER in %" on the ISS screen will be off the screen. Wait until the red trace becomes visible.
8. Press green ON+INT button.

Optical Lever 7 Day Trends

With the main laser down, it looks like some work effecting the oplevs must have happend over the last week, because some signals sit at 0 and then recover to typical levels.

I zoomed in on the Y axis to the sections of data that have reasonable signals.

Attached:

• oplev SUM
• oplev PIT
• oplev YAW

HAM11/HAM12 leak hunting

Kyle, Gerardo 

0900 - 1100 hrs. local -> In and out of LVEA, used Main Crane to "fly" leak detector over YBM.  

Dissatisfied with the slow recovery of the HAM11/HAM12 annulus system, we decided to do some unscheduled (no work permit) helium leak testing -> We found a minor leak on a conflat which was mitigated by torquing the flange fasteners but were surprised to discover several very loose chamber flange bolts, i.e. we could visually see the bolt shanks between the flanges!  In total we found (4) adjacent bolts on the flange connecting HAM11 to the OMC adapter spool to be very loose and (9) adjacent flange bolts that we could spin easily with our fingers on the flange connecting HAM12/septum/HAM11 -> these were torqued using twentieth century "old school" wrenches after we were unable to find a cell phone app.  

There are (3) pump carts running in the LVEA over the weekend, (2) at HAM11/HAM12 and (1) on the SW corner of BSC4.

Good catch! We visually inspected the CFFs on diagonal before pumping it down but did not physically touch each bolt. 

Vacuum web medm screen shots revised

The web page displaying detailed vacuum medm screens has been modified to show old and new medm screens for the site overview and LVEA.  

During the installation of new vacuum controls, some information is available on the old screens, some on the new.  For the site overview and LVEA, the new system screens are shown to the right of the original screens.  This is a temporary display change, once the new controls are installed the medm screens will be updated and the web page will be rearranged again.

Very nice!  Thanks Jim, this is quite useful.  

Ops Eve Shift Summary

TITLE: 04/22 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: Got through initial alignment, then was immediately halted by ISC_LOCK trying to get the ETMX ESD to function.  After finding the last remaining person on site (Kiwamu!), he agreed to drive to EX to try and reset the ESD driver.  He discovered that it was not a problem with the ESD driver, but an issue with ISC_LOCK not checking all the channels it needed to to get the ESD up and running.  Kiwamu edited the ISC_LOCK guardian to check that the requested DC bias was not zero.  Then, just as I was starting to continue with locking, there was another 6.0 EQ in Ecuador (haven't they been through enough already?).  Kiwamu suggested that with no one else here and the EQ ringing us up over 1 um/s, we should call it a night.
LOG:

23:51 Dave and Jim restarting SUS ETMX PI model

2:45 Kiwamu to EX looking at ESD driver (He noted that he was unable to open sitemap on one of the workstations at EX)

3:10 Kiwamu back

3:45 Calling it a night with the seismic plot going through the roof
 

COMM beatnote power reduced, realigned.

Sheila, Matt, Jenne, Travis, Kiwamu

We went to ISCT1 because we were not finding the beatnote even when we moved PR3 back to its old alignment and we had aligned the X arm using WFS and the camera.  It turned out that the COMM beatnote diode was saturated, so we reduced the power using the half waveplate and PBS in the SHG path.  We realinged the beams, and ended up with a beatnote power of about 4dBm.  

We might need to readjust this once we have a good alignment of the full IFO to get a good reference.

Also, it seems like we have less DC light on AS AIR, so we might need to adjust its alignment again.  To get through the SRY alignment, I lowered the threshold for SRY triggering from 30 to 20.  

Free running RIN measured by first loop diodes: Now and O1

Just FYI.

Even without ISS, during O1 the 1st loop diodes didn't rail, but they do now. The power on these diodes seems to be the same as before (I assume Peter and Jason adjusted them).

Attached left is the trend of the past 26 hours. ISS first loop was on at first, but is off right now. You can see that the first loop diodes seem to be railing without ISS.

Attached right show the same channels, but from O1 when ISS first loop was off (seems to be related to ISS investigation in alog 24171).

If you compare the DC level of PDA and PDB from O1 against the recent trend when ISS was on, it seems like the DC power on the diodes are the same as before. This is not a digital filter issue, there's no digital filter on these channels except a calibration factor, and the calibration factor didn't change in the filter file. Dewhite is applied after PDA and PDB output in PDA_REL and PDB_REL channels.