J. Kissel

I've finished generating the MEDM screens for the SUSPOINT to CAVITY BASIS projections, filled out the infrastructure with the appropriate 4k to 16k anti-imaging filters, and populated the EUL2IFO matrix as per T1500610.

I saw some suspicious behavior from an initial test of the signal flow (i.e. by taking point to point transfer functions across the network), so I don't want to declare victory just yet, but we've never been closer.

Attached are screen caps of the new MEDM screens. You can find the screens from the site map under the light-blue SEI button under the "MAIN" section with the rest of the stuff that's IFO location independent.

J. Oberling, P. King

LHO WP #5810.

Short Version

IT'S ALIVE!!!

Long Version

Today we began the HPO turn on procedure.  First things first, we put a water cooled 200W power meter head in the main beam path after the PMC (see attached picture 200W_power_meter_20160404.jpg).  This way no light is getting out of the PSL enclosure until we are ready for it, and once we have a recovered PMC we simply need to plug in a power meter so we can set the available power with IO_MB_HWP1. 

In an abundance of caution we began by repeating the HPO Laser Head turn on test we did back on March 22nd (see LHO alog 26193).  Everything came up without issues, just as in the previous test.  We then removed the HR mirror that sat in front of the HPO Output Coupler (OC); it is currently left in the HPO box, set to the side and out of the beam path (see attached picture OC_removed_20160404.jpg).  This taken care of, we set all the laser heads to 30 A of pump diode current and turned on the HPO.  As the currents were coming up we saw the HPO go through the first, low power stability range, but nothing at the high power stability range (which is what we expected, not enough pump power yet).  We repeated this at 35 A, 40 A and 45 A with the same results.  Getting a little discouraged we input the previous operating currents (from Peter's alog here) and turned on the HPO.  This time the laser came on!  It started at ~120 W of total power (~70 W in the forward direction and ~50 W in the backward direction).  We then increased the diode currents individually until they all read ~100% power and then let it sit for ~10 minutes so everything could come to thermal equilibrium; the output power settled at ~145 W.  As a final check we moved the pump currents up and then down slightly (~0.4A in both directions) to check that we were on the correct side of the stability range; we are.

Now with a running HPO we decided to try injection locking the 35 W FE.  Following the instructions in T1200259 we powered up the FE laser and pressed the "Lock" button on the PSL Beckhoff computer control screen.  It locked, without issue.  Total output power now read 208 W.  This seemed really high, and looking at the HPO diode currents it seemed the diodes for head 4 were suddenly delivering more power without changing current; power changed from 100% to 105% at the same diode current.  This is very odd and we currently cannot explain it.  We lowered the current back to 100% power and the total power out of the full system was reading 183 W.

It was at this point that we realized we had forgot to align mirror M5, which controls the beam out of the HPO.  This is important as this mirror needed to be tweaked when the HR mirror previously in front of the OC was installed back in 2014.  In the process of trying to realign this mirror we lost the alignment entirely and spent the afternoon trying to recover it.  We eventually turned the HPO off, reinstalled the HR mirror and used it and M5 to mostly recover the alignment.  We are currently at a state where spending more time recovering this alignment is a waste as we are going to have to do alignment work with the HPO on anyway.

We left the system with the HPO OFF and the lid on; as a safety measure we wrote down the last used HPO diode currents and set the current input fields to 0 A.  We the left the FE laser ON but shuttered, so there is no laser light available to the IFO.  We left the environmental controls (HEPA fans, AC, and Make-Up air) ON.

Tomorrow

Tomorrow we plan on once again removing the HR mirror and then beginning the recovery of the PSL subsystems downstream of the HPO; PMC, ISS, FSS, DBB (likely in that order).

F. Clara, N. Kijbunchoo, R. McCarthy, V. Sandberg, P. Thomas

As per Work Permit #5809, we performed maintenance inspection and repairs as necessary on the EtherCAT DC Motor Controllers and Rotation Stages located on the PSL and the TCS X and Y arms.  The EtherCAT chassis "X1-PSL-C1" described in D1101114 and located in the LVEA CER was removed to the Electronics Lab.  There the chassis was inspected, the wiring was verified, and all connections were re-dressed and re-seated in their Beckhoff or spring-key connector blocks.  A number of build quality issues were found (e.g., too short a stripped wire, wires not properly seated, and ground screws not tight enough) and corrected.  The chassis was reinstalled and powered up.  The PSL rotation stage was checked by hand entry of commanded angles and found to operate satisfactory.  We left it at the minimal power angle, ~ -24 deg.  The TSC rotation stages were tested with a script that generated 100 random angles to be requested and recorded the final angle position.  Results are shown in the attached plots.  In all cases the measured angle was within 0.1 deg of the requested angle.  The angles spanned the range of -90 deg to +90 deg.  There was no observed problem dealing with angles in the neighborhood of zero degrees.

TITLE: 04/04 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in PT
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:'
LOG:

5:15 Jeff B. out to HAM6 area prepping clean room

5:27 Hugh out to lock HAM6 HEPI

6:30 Hugh out

7:00 Keita to ISCT6

9:15 Hugh locking up HAM5 HEPI

         Keita going back to ISCT6

9:34 Fill to CER to take down roation stage Ethercat chassis. This won't affect PSL power-up work.

9:50 Vern and Fill out of CER (with the chassis).

10:16 Travis head to EY to check PCal.

10:17 Bryn's taking a company  around the LVEA. They're informed to not go near HAM6.

10:28 Bryn and a company out of LVEA.

10:37 Bryn an company walking down the arm to EY VEA.

10:48 Jeff B out of the LVEA.

11:00 Travis back

11:35 Peter and Jason to PSL.

12:09 Vacuum team out

12:11 Jeff K restarting H1 OAF model

12:20 Bryn's back

12:35 Betsy to HAM5/6 area

13:13 Jeff B going back to HAM5/6 area

14:26 Jeff B out.

15:09 Fil to Y mid filling out the CP3

15:42 Kyle out working by BSC4

16:39 PSL Team out for the day. HPO fired up without problems.

1/2 open LLCV bypass valve, and the exhaust bypass valve fully open.

Flow was noted after 5 minute and 45 seconds, closed LLCV valve, and 3 minutes later the exhaust bypass valve was closed.

Next over-fill on Monday, April 6th before 23:00 utc.

J. Kissel, H. Radkins, R. McCarthy, A. Pele [remotely]

A brand new T240 has arrived from Nanometrics; the first of several over the next few year to replace our aging GND STS population. Yay, thanks Ken! 

The (order?) number on the outside of the 3 boxes we've received is 53341-2, and the serial number of the instrument itself is 953.

Our plan (eventually) will be to replace the ill-performing ETMX GND STS with this new instrument.
and then take the ill-performing STS and bury it outside to support wind-fend testing a la LHO aLOG 25842, and G1600548.

Arnaud has graciously offered to update the DCC's inventory E1200068. 

For now, I've put the T240 back in its box, and left it with the other two boxes in the shipping-and-receiving area. We still need to figure out the appropriate readout electronics situation, since we'd borrowed from 3IFO the *last* time we used a T240 at EX, and we'll now need both an STS readout (for outside) and T420 readout system (for inside).

Michael, Krishna

Right on cue, winds picked up today and we got a good chance to test out both BRS-2 at EY and BRS-1 at EX. The wind speeds were in the 20-30 mph range during the following measurements.

EY: The first pdf shows the ASD of Ground seismometer (STS-2) and BRS-2 data and the online tilt-subtracted Y super-sensor data. The magnitude of Y ground motion at ~ 50 mHz is 10 microns/rt(Hz) while the tilt-subtracted Y channel is at ~1 micron/rt(Hz). The second page shows three lines - the first is the coherence between the ground seismometer and BRS-2 showing ~99% coherence in 10-100 mHz region. The second is the coherence between BRS-2 and Stage 1 Y and the third is between Stage 1 rX and BRS-2, showing significant coherences between them.

With BRS-2, we modified the damping scheme to have the damping set at Q of ~50 in the quiet state and Q of ~5 if driven up to a very large amplitude state (>5000 counts). We expect that we won't reach this large amplitude state under wind-speeds of < ~60 mph. The Q=50 state seems to not add any additional noise so far. We will do a more detailed analysis on this soon.

EX: The second pdf is for BRS-1, the ground STS-2 and a similar tilt-subtracted X super-sensor. The magnitude of Y ground motion at ~ 50 mHz is ~4 microns/rt(Hz) while the tilt-subtracted X channel is at ~0.7 micron/rt(Hz). On the second page,  the coherence between the ground seismometer and BRS-2 is ~96% in 10-100 mHz region. The coherences between BRS-2 and Stage 1 X and Stage 1 rY is smaller, especially that between rY and BRS-1 near the microseism. This last part is worrisome and I suspect that the rY sensor may have some problems - (I've noted this in the past - see 14426). Jim has promised to help look into this more by designing some high-frequency CPS-only blends for Stage 1. The idea is that by locking the platform as rigidly as possible to the ground, we can calibrate  the on-board rY sensor by comparing it to the ground (match T240 scale-factors). This may also prove useful for all other chambers which can be roughly calibrated by ensuring that the rY signal is small under quiet conditions.

The second minor issue with the EX data is that the coherence of BRS-1 with the ground seismometer data, and hence the subtraction is not as good as it was with the T240. Jeff tells me that this was the least reliable seismometer they had and will be replaced with a T240 very soon. A third issue is that the ~35 mph wind-gusts occasionally triggered the damper at EX. We will increase the large amplitude threshold for this damper, soon.

Summary: The tilt-subtraction at EX and EY is working reasonably well.

   First cleaning and vent prep staging are complete. Dust counts in the HAM6 cleanroom are excellent. They have been below 100 all day, even with the high level of activity around and in the cleanroom. There was one very high spike (18k both 0.3 and 0.5u particles), while there was cleaning going on inside the cleanroom. These cleared quickly after the crew left the cleanroom. Posted below are trends of the HAM6 dust monitor for the past 12 and 24 hours.   

   I did a compassion check of the new dust monitors and my HHPC-6 hand-held. No more than 10 count difference between the two monitors over several samplings.       

Gerardo, Kyle, Chandra

Vented HAM6 this morning, after soft closing GV5 & GV7. Removed all but four bolts from each of three doors. Vent lasted ~ 1 hour.

Averaging Mass Centering channels for 10 [sec] ...


There are 3 STS proof masses out of range ( > 2.0 [V] )!
STS EY DOF X/U = 3.345 [V]
STS EY DOF Y/V = 2.25 [V]
STS EY DOF Z/W = -4.708 [V]


All other proof masses are within range ( < 2.0 [V] ):
STS A DOF X/U = -0.337 [V]
STS A DOF Y/V = 0.17 [V]
STS A DOF Z/W = 0.584 [V]
STS B DOF X/U = 0.888 [V]
STS B DOF Y/V = 0.928 [V]
STS B DOF Z/W = 0.072 [V]
STS C DOF X/U = -1.081 [V]
STS C DOF Y/V = -0.328 [V]
STS C DOF Z/W = -0.434 [V]
STS EX DOF X/U = 0.55 [V]
STS EX DOF Y/V = -1.05 [V]
STS EX DOF Z/W = 0.414 [V]
 

This closes FAMIS task 4605.

Today I went to EY to investigate the issues with the PCALY OFS described in aLog 26229. The first thing I noticed upon approaching the PCAL TX module were a pair of cables (red and yellow) coiled underneath the TX module enclosure.  Upon first inspection, I didn't notice anything else egregious.  Everything was powered on and appeared to be functioning.  I then opened the TX module and verified that the PCAL beam was making it to the OFS PD.  As I was closing the TX enclosure, I noticed that a cable was exiting the TX module at a non-perpendicular angle.  I then noted that this particular cable was the OFS PD cable.  It practically fell into my hand as I went to check it.  I then plugged the cable back in and secured the fixing screws on the connector to the module.  For peace of mind, I then checked ALL cables on the TX module and chassis for security.  Satisfied I had fixed the problem, and unable to log into the workstation adjacent to the PCAL module, I returned to the control room.

While the signals on the PCALY MEDM appeared to be reasonable, Kissel suggested that I turn the 3 PCALY exc. lines back on the verify.  When I did so, I saw that the oscillation monitor railed.  Turning them on one at a time, I could get the first two on, but the third (1kHz, 15000 amp.) line caused a rail.  I gradually stepped up the amplitude of the 1kHz (3rd) line, and saw that at ~4000, it railed.  I began playing with the OFS offset, which was set to 0.56V, and saw that by increasing by a factor of ~3, I could turn on the 1kHz, 15000 amp. line without issue.  Trending the offset, I saw that it changed from 4V to 0.56V on Mar. 23.  I could not find an aLog referencing this change, so I have restored it to 4V. 

After finding an OPS shift aLog referencing Fil and Peter doing table access system work on Mar. 17, I asked Fil if they were doing similar access system work at PCALY on the 18th.  He told me that they had replaced the key switches on the PCAL setup that day.  He also told me that the pair of cables I had noticed coiled under the TX module were for the access system, but had been done further in the past.  Mystery 1: What could have happened to the OFS? SOLVED.  Mystery 2: Why does LIGO always have a loose cable? Unlikely to ever be solved.

We have an oscillation in H1 that has been with us for a long time, is not understood, and can be mitigated by moving alignment offsets, and gets worse at high power.  All the information in this alog is elsewhere in the log, this is just a summary.

For about 6 months we didn't change our soft loop offsets because when we did we would get the oscillation, this is how we stayed stable through O1.  The main symptom is that the pitch optical levers move at frequencies around 0.45 Hz, all in phase with each other, and if you look at the relative sign of the optical levers it looks like CSOFT motion. the POP and arm transmitted powers also oscillate. Now that our soft loops are working again, we are probably in a position to again tune the soft loop offsets to be stable at 20 Watts, but it seems like this won't be a great solution as we try to increase the power even further. 

There have been many alogs about this, but I wanted to summarize some of the recent things we have looked at. 

It seems like the torque that moves the test masses isn't coming from any of the arm ASC loops, or the optical lever damping.  The first screenshot shows this, this is from Tuesday night when we powered up several times in slightly different configurations and repeatedly saw the same size of oscillation.    The solid lines here show what was our normal configuration before Tuesday, with ITM optical lever damping on and ETM optical lever damping off.  The dashed lines show the test configuration, where we added notches to the soft loops that reduce the actuation by about a factor of 100 at the oscillation frequency, and lowered the CHARD gains by a factor of 10. You can see that in the test configuration we also have about 5 and a half times less DHARD drive in the test configuration than in the normal one.  Since all of these ASC drives are smaller in the test configuration but the oscillation is about the same, it seems like the force that moves the test masses must not be from these control signals. 

It seems like the fluctuating radiation pressure due to changes in circulating power alone can't provide enough torque.

In the attached matlab script I estimated the miscentering we would need on each optic so that the approx 900 W changes in circulating power we see during the oscillation could provide the radiation pressure torque.  These are way too large, ranging from 8-33 cm on the different optics.  As a sanity check I also assumed that the alignment shift we see powering up before the soft loops get a changce to correct is due to radiation pressure (which it may not be).  From that I estimate miscenterings ranging from 0.5-3 cm. I used the moment of interias from Evan Hall's alog , which he tells me are slightly wrong but not enough to matter.

The oscillation frequency does seem to depend on circulating power

The evidence for this may be a little shaky since it is hard to get enough cycles of the oscillation to get a spectrum with nice resolution, but the second attached screen shot shows a spectrum of ETMX optical lever pit for 3 different circulating powers.  These circulating powers are based on Dan Hoak's calibration and the TR XB QPD.  The frequency of the lower two powers is the same within the resolution of my spectra. This may not hang together perfectly because I have included a little bit of time when we were powering up or down in the spectrum.

Other ideas?

We have also tried putting a resonant gain the DARM loop(no impact), changing A2L feedforward (no impact), and centering on the ETMs (improvement).  One possible test we could try to understand this better would be to drive the laser intensity and see if we can produce angular motion.