Timing Calibration

Jeff, Jim, Dave:

Jim synced up the atomic clock system to the NTP GPS receiver and then used it to sync the MCA unit which in turn drives the end station TCT units. The 1PPS originating from the MCA was connected to the first input of the MSR comparator. Jim also synchronized the original atomic clock to the same source, and we transported this unit (continually powered via UPS) to both end stations. At the end stations the time offset dip switches on the TCT units were changed to compensate for the TOF to the end stations. At the end stations the 1PPS coming from the TCT are being fed into the comparators, first channel.

We also connected the 1PPS from the NTP GPS to the second comparator input in the MSR.

A more detailed alog of these procedures is in the works.

PSL ISS model change:

Sudarshan and Jeff.

A new h1psliss model was created. This is a "stand alone" model, no common PSL parts are being used. Full details in Jeff and Sudarshan's alog.

HWS Beckhoff gain setting

Aidan, Elli, Nutsinee, Patrick

A HWS gain setting was incorrectly set as a read-only channel and therefore could not be changed from zero. Patrick has made this changeable and it is now 1.0

DMT channel list changed

John Z and Dave

John Zweizig requested a new DMT channel list be applied to the DAQ broadcaster, this was done at 15:00 local time.

LDAS Tape Robot Move

Greg, Dan, Jim, Dave

The LDAS tape robot was moved from the computer users room to the warehouse. Fiber optics cabling was added in the MSR between the warehouse patch panel and the Q-Logic switches in the DAQ racks.

LVEA: Laser Hazard
Observation Bit: Commissioning 
  
07:00 Karen & Cris – Cleaning in the LVEA
08:16 Karen – Out of the LVEA
08:17 Karen – Cleaning at End-Y
08:30 Filiberto – Cabling work at BSC1, BSC2, BSC3 & HAM4
08:30 Elli – Hartman work at End-Y
08:35 Jason & Perter – RefCav alignment work H1-PSL
08:40 Kyle – Bake out of RGA and pump work at End-Y
08:48 Hugh – Moving HAM2 seismometer to Beer Garden area
08:54 Jim – Sensor correction work on ETM-X
08:55 Bubba – 3IFO crane work in LVEA North Bay area
09:00 Add 125ml water to Crystal chiller
09:00 Jodi – 3IFO PM work at Mid-X and Mid-Y
09:01 Elli – Back from End-Y 
09:02 Elli – Going to LVEA to work on Hartman sensor
09:16 Nutsinee – Going into the LVEA
09:18 Paradise Water - delivery on site
09:25 Elli & Nutsinee – Out of the LVEA
09:30 Kyle – Going to Mid-X 
09:31 Robert – Staging in PSL for periscope tuning
09:42 Joe – Checking batteries in the LVEA
09:50 Karen – Finished at End-Y
09:53 Cris – Finished in LVEA – Going to End-X
09:56 Mitch – Going to Mid and End Y 
10:05 Nutsinee & Elli – Going to End-Y
10:13 Joe – Out of the LVEA
10:37 Elli & Nutsinee – Back from End-Y
10:40 Mitch – Back from Mid & End stations
10:43 Dave & Jim – Going to End-Y for atomic clock calibration 
10:58 Mike – Tour of LVEA ahead of VIP tour on 05/19
11:12 Elli & Nutsinee – Checking the TCS-X laser
11:23 Kyle – Back from Mid-X
11:30 Jason & Peter – Finished in the PSL
11:30 Robert – Going into the PSL for periscope work
11:32 Elli & Nutsinee – Out of LVEA
11:33 Jim & Dave – Finished at End-Y 
11:40 Jim – Going to End-X for atomic clock calibration
11:41 Elli & Nutsinee – Checking the TCS-Y laser
11:42 Jeff – DAQ restart
11:45 Filiberto & Andres – Finished in LVEA
11:48 Truck on site for tape robot move
12:04 Elli & Nutsinee – In LVEA working on Hartman sensor at TCS-HT4
12:15 Jim – Back from End-X
12:20 Kiwamu & Jason – Finished with OpLev-PR3 alignment
13:15 Jodi & Jim – In LVEA to recover a broken computer
13:29 Nutsinee & Elli – Out of the LVEA
13:31 Jodi & Jim – Out of the LVEA
14:12 6.8 Magnitude EQ in Japan 
14:15 Robert – Finished with PSL periscope alignment

See D1400363 for overall scheme and cable details.

The 71 MHz sine is ported to D1400155 in TCS-X1-R2-27 SE of BSC1.  From there sync signals go to the three BSCs corners 1 & 3 satellite racks.  At each BSC, the corner 1 signal is passed on to corner 2 with a local cable.

Attached are three plots with the three BSCs showing reference traces from early this morning before the big EQ.  Current traces are from later today.  There are no combs popping up suggesting there are no cross talking sync signals.  There is variablilty between the reference and current noise floors.  Some are lower a few are slightly higher but nothing standing out affecting an entire corner (see ITMX ST2 H2.)  I suspect when the middle of the night comparison is done with similar conditions, they will look even better and that cables are okay.

Low temp baking RGA on BSC6 during maintenance periods -> Also, temporarily shut off instrument air to X-mid VEA while re-routing copper line

J. Oberling, P. King

Summary

We tweaked the beam alignment into the PMC in the horizontal direction using both mirrors M06 and M07.  Final PMC transmitted power was 22.3 W with a visibility of 91.5%.  This did not recover the FSS RevCav TPD voltage, so we transitioned to realigning the FSS RefCav.  We found the beam clipped between mirror M26 and the 21.5MHz EOM.  We corrected this using mirror M25 and the used mirror M26 and the top input periscope mirror to tweak the alignment into the FSS RefCav.  Final RefCav TPD was 1.37V.  Still unclear where the drift in the RefCav TPD is coming from.

Details

We measured the power before the FSS AOM, after the AOM (single pass), and at the base of the RefCav input periscope.  Peter also measured the power between M34 and L05 (after the 35W pickoff for the DBB)

• Before AOM: 63 mW
• After AOM (single pass): 45 mW
• Base of RefCav input periscope: 30 mW
• Between M34 and L05: 297 mW

According to Peter this is all reasonable, so we moved on to the PMC.  Motive here is to make the reflected beam shape more concentric, thereby improving the beam alignment into the PMC, and increasing the transmitted power (and hopefully the FSS RefCav TPD in the process).  We tweaked the horizontal alignment using mirrors M06 and M07, and ended with a final transmitted power of 22.3 W, an improvement of about 0.3 W.  We then had to adjust the alignment into the PMC Refl PD, PD03, by adjusting mirror M20 and thin film polarizer TFP03 (to keep the unlocked voltage reading of the PD at ~-1.5V).

• PMC Refl PD before
  • locked: -0.305 V
  • unlocked: -2.85 V
• PMC Refl PD after
  • locked: -0.132 V
  • unlocked: -1.55 V

This gives a PMC visibility of 91.5%.  Unfortunately this did not significantly increase the FSS RefCav TPD, so it seems we really do have an alignment issue.

This first thing we did was to check the beam position on various irises in the beam path.  We found the beam clipping on the iris high and to the west between M26 and the 21.5 MHz EOM.  We corrected this with M25, and then used M26 and the top periscope mirror to tweak the RefCav TPD.  While a small bit of lateral adjustment was needed, the majority of the adjustment was to pitch.  The final TPD voltage was 1.37 V, and the RefCav Refl PD read 0.060 V while the RefCav was locked.  Unfortunately we are still unclear where the RefCav drift is coming from...

Jason, Kiwamu (WP 5199)

PR3 oplev is now back to functional.

As reported in the last week (alog 18246), PR3 was found to be not functional. This morning we took a look at the PR3 oplev and found that the beam had been clipped. We fixed it by steering the launcher telescope and recalibrtated both pit and yaw signals.

[Unclipping]

Looking at the returning beam, we found that the beam was largely clipped on the west side and its bottom side. Apparently this was causing the nonideal cross-coupled behavior as reported in alog 18246. We could not identify what object was occulting the returning beam, but according to Jason, it could be somewhere around the viewport for the return beam. We decided to steer the launcher telescope to unclip the beam. The unclipping went smooth and no major issue was found. Since we moved the beam toward the East, we had to recenter the QPD stage afterwards. The beam is now about 1 cm away from the clipping edge, meaning we can move PR3 by several 100 urads until clipped. This is good enough.

After the unclipping, Jason checked the beam shape and confirmed that there was no sign of clipping. We also briefly checked the responsivity of each segment by placing the beam on each segment by steering PR3. This convinced us that the responsivity is almost the same among the four segments. We physicallyt locked the launcher telescope as a part of the normal procedure so that it is not going to move.

[Recalibration]

After the unclipping, I recalibrated the oplev. Here is a summary of the new calibration:

I also updated the SDF accordingly. The data and fitting code are attached as a zip file.

One thing I found during the calibration is that there is still some cross-coupling between pitch and yaw at 10% level. I don't think this is a big issue, but those who use PR3 oplev should be aware of it. I am not sure what part of it is causing the cross-coupling.

SudarshanK, DaveB, JeffK,

We made changes to psl iss model to include the DC signal from the eight photodiodes on the array.  These  DC signals are acquired before the whitening in the transimpedance amplifier. This psliss model restart  didnot affect the psl itself, which we were afraid it might. Good to know for future restartts. The DAC restart was made around 11:30 local time. These 8 additional channels will be available to  trend via epics channel. These signals are also used to normalize the ISS PD signals to obtain the RPN.  The channel names are as follows:

H1:PSL-ISS_SECONDLOOP_PD1_DC

........

H1:PSL-ISS_SECONDLOOP_PD8_DC

Attached is the new front end model that includes the changes.

Had to add H1:TCS-ITMX_HWS_POSITIONDETECTOR2SUM and H1:TCS-ITMY_HWS_POSITIONDETECTOR2SUM to the exclude list. Looks like we may need to change the HartmannSensor library again at some point to make these read only. They change (rapidly) now that the gain is no longer 0.

Added 242 channels. Removed 45 channels.

Daniel, Elli, Patrick, Nutsinee

I changed the OPC_PROP_RIGHTS of PostionDetector2SUMGain from 1 (read only) to 3 (read/write) in the HartmannSensor library code. I checked the change into SVN. I updated from source, recompiled and restarted PLC3 on h1ecatc1.

Yesterday Nutsinee made a code change to PLC1 on h1ecatc1 and checked it into SVN. This was to fix the picomotor labels. I updated from source, recompiled and restarted PLC1 on h1ecatc1.

I restarted the EPICS IOC on h1ecatc1. I did caputs to H1:TCS-ITMX_HWS_POSITIONDETECTOR2SUMGAIN and H1:TCS-ITMY_HWS_POSITIONDETECTOR2SUMGAIN to change them from 0 to 1.

WP 5199, 5200

Did before its expected biweekly crash. Burtrestored to 10:10 am.

The ETMX ESD driver medm screen 'Active light' has been flickering when it is OFF. To fix this issue, I pushed this lower threshold to +/-325 from +/-200.

I also changed this in SYS_DIAG.

While talking about SYS_DIAG, I have made a wiki page for troubleshooting the usermessages that it will bring up. This is a page mainly to help operators find the source of the problem and how to resolve it.

It can be found here:  https://lhocds.ligo-wa.caltech.edu/wiki/SYS_DIAG%20Guardian

My usual image of ASD and coherence between the three corner station STS2s.

Great coherence pretty much on everyone from 1 hz down to .002hz except HAM2 Y.  HAM2 X is better but still not as good as Z or the other instruments.  With this signal size, there is no excuse for poor coherence.  I'm going to move the HAM2 sensor back to the BierGarten for one final check.

Sheila, Kiwamu, Evan, Stefan

Today we first recommissioned the QPD transmon to ITM loops.
- We set the transmon QPD offsets to zero at 10W input power and engaged all four loops. This brought the recycling gain up to about 40 consistently.
- The optimal QPD offset seems to slightly depend on input power, which is why we set them at 10W for now.
- We want to see whether this type of QPD loop is consistent from day to day before we physically center them.
- The loops are now engaged at low bandwidth in the script.
- We haven't designed propper plant inversion and roll-off filters for the loops..

Next we went to low noise and re-examined the SRCL coupling For some reason the SRCL coupling gave no subtraction at all - just some noise reshaping. (It could be due to our QPD-to-ITM loop.)
- We remeasured the coupling by i) first driving SRC_EXC, and measuring the TF from SRCL_OUT to DARM_IN1, and ii) SRCFF to DARM_IN1. iii) the ratio i/ii should be the desired FF path.
- We first hand-fitted the TF: 
    poles: 0,0, 800 (Q=2)     zeros: 32 (Q=7) , -180
    or
    zpk([2.28571+i*31.9183;2.28571-i*31.9183;-180],[0;0;200+i*774.597;200-i*774.597],1,"n")gain(5)

- Note the negative frequency zero - a clear indication that we have two coupling paths. We should just design two separate FF path - this would allow for easy individual tuning of low and high frequency feed-forward.

- Unfortunately an earthquake struck during the filter designing, so we couldn't test them.

Related alog: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=18269

Summary:

During long lock stretches where POPAIR_B_RF90 slowly drifts up, SR3 pitches up, and this seems to be a real PIT motion, not some bogus signal, even though SR3 is not touched by ASC nor LSC.

Turning SR3 back to the original angle when in lock doesn't restore POP90 (see the above alog by Evan), so this PIT is not the cause of POP90 drift, but rather the result of something else affecting both SR3 and POP90.

The time constant of SR3 drifting in-lock is much slower than the time constant of SR3 getting back after lock loss as was pointed out by Evan. The former looks as if it could be the mirror heating, and the latter could be the wire cooling.

The power buildup in the SRC itself is about 120mW or so according to Kiwamu and probably is not enough to cause wire heating by some scattered light.

Based on these, one possibility that Stefan came up with is that the heating of the ITMs changes the amount of higher order mode spilling over on the SR3 wires, causing PIT. Since wire heating is much quicker than the mirror, the time constant is equial to that of the mirror. Once the lock is lost, the power is lost immediately, and the cooling is determined by the wire alone.

We could play with TCS during a long lock to see how POP90 responds, and/or scan OMC to see the mode change during a long RF lock.

Details:

The two plots show the same set of signals. The first one is from last night and the second one is when Evan changed SR3 PIT manually while in lock.

If you look at POP90 (ch2), SR3 OPLEV PIT (Ch6) and SR3 M3 witness BOSEM PIT signal (ch9) in the first plot, they are almost perfectly correlated, and in this case SR3 moved by 0.7 urad. The fact that the motion is seen by oplev and bosem suggests that this is real.  Also, if the oplev signal is caused by e.g. some scattered light caught by oplev, the oplev sum (ch.8) should change at least 2% over the lock stretch, but in reality it changed by less than 0.2%.

SR2 PIT (Ch. 13) and SRM YAW (Ch.12) are also coherent with POP90.

SR2 PIT should be the result of ASC feeding back to SR2. In the second plot, when Evan turned SR3 back, SR2 also moved back.

SRM YAW might be the similar effect as SR3.

SudarshanK, DarkhanT

We introduced two Pcal lines at 240 Hz and 310 Hz on photon calibrator at Y end.  The Pcal lines are about a factor of 10 above the DARM sensitivity at those frequencies. We will look into any changes in the amplitude and phase of these lines to determine the the position of cavity pole frequency. The cavity-pole has been observed at frequencies listed in  alog LHO #18360.

Last week we put the EY HWS on it's own separate power supply to see if this would reduce the 57Hz coupling of the HWS into DARM.  This workes. When the EY HWS is on, we see no coupling into DARM at 57Hz. (See attached sprectum.)  EX is still on the shared power supply, and the 57Hz line is clearly present.  The current setup at EY is only as temporary setup.  It looks like we should permanantly move all the HWS onto their own power supplies.