Committed to svn.

Here is the comparison between the readbacks of the REFL common mode board before and after the gain reallocation in the AO path.

The error signal shows a flat noise of unknown origin above 10Hz. The slow and ctrl signals should be identical above the 5Hz high pass in the ctrl path, but clearly are not. The gain reallocation actually made the coherence worse!

Turns out that the measurement in alog 45100 was done when RF level was particularly small but it got worse over time, just not as bad as before.

Microseism could explain the difference between somewhat smaller RF level after it got worse (right blue arrow) VS old high RF level (left blue arrow) but not the difference between particularly good (pink arrow) and  old high RF level (left blue arrow).

Just by looking at the time scale, it looks as if the heating was passing through the optimal point at the pink arrow and kept going in the other direction.

Keita asked us to check the ITM HWS sensors to see if the LSC-REFL_A levels correlated with the IFO heating during the increase in power.  It looks like ITMX doesn't change very much while going through the nominal point but ITMY is still trending.  Recall that the ITMY CO2 level during lock acquisition is 0.55 Watts while ITMX CO2 is 0.19 Watts, not to mention that there are point absorbers on ITMY which definitely affect the overall heating spherical power fitting.

Overall, it looks as if ITMY CO2  requires about +5-10 udiopters central heating to go from the steady state to the optimal point, which corresponds to about 50-100mW of extra CO2 heating.

The numbers I used are on the TCS simulation MEDM with the central mask actuation gain for a single pass being 2.5e-5 diopters/watt.

We increased the ITMY CO2 Guardian request hot state power to 0.02W from 0W. We lost lock before we could see if this made any improvement though.

Peter F and I went to IOT2L after a lockloss to look at the beams on the MC refl path.

We did not find the origin of the ghost beams on the camera; they're co-propagating with the main beam from at least as far back as MCR-BS1 (see diagram linked in Cheryl's alog). We put an iris just before L2, to block the beams visible on the camera and another, more spatially-separated, ghost beam, that was previously propagating through L2 and being blocked by the mount of L3.

We didn't see evidence of clipping, or stray beams getting through the aperture between BD5 and M14. The p-polarised beam going into BD6 was possibly hitting the dump a bit low, but it was hard to get a clear view of the front-face of the beam dump.

There was a ghost beam hitting the edge of M3, and generating a spray of light, however someone must have already known about this, as there is a beam razor blade beam dump on the air-side of the table for this "beam".

It's possible that the beam is clipping in vacuum, or that a REFL Periscope mirror shifted (though this was considered in the meeting today, and doesn't seem to fit), or that the IMC REFL beam is very misaligned through the IOT2L REFL beam path.  More than one beam on the GigE camera has in the past been associated with a IOT2L table beam misalignment.  Finding a beam that's scattering onto the table from IO_MCR_M3 is a clue that the table is misaligned, starting from the top periscope mirror, because the design of the optical layout and beam path does not place any beams near or over the edge of that optic.  That condition increases my concern about the alignment into the High Power Beam Dumps, since IO_MCR_M3 is the optic that launches almost the full power IMC REFL beam to the two 50W Trap-It beam dumps.  Unless the location of the beam on IO_MCR_M3 was intentional, the 50W beam dumps absolutely need to be checked.   On the REFL camera, there is significant extra light, and they extra light appears to be extra beams, and there should only be one beam coming through IO_MCR_BS1, so finding multiple beams coming through IO_MCR_BS1 is an indication that there are beams (whatever the source) getting past the beam dumps and pick-off mirror in front of that optic.

From the aolg I see that I realigned the REFL path in January (alog 40313), and it was checked by Sheila and Gabriele in June (alog 42362), though searching for these events is not a guarentee of finding all of them.

I looked at the alignment changes for the IMC from June until today, and found changes in the tens of urad in pitch for MC1, MC2, and MC3, and in yaw for MC3.

Changes: June 6th to November 9th:

Jim also zero'd the vertical DC drive that amounted to 600 counts on the outputs and about 15um in computed position.  This relief changed nothing either, as expected.

I'm attaching some plots of measurements done this morning. First attached asd compares the RY motion for different blend and loop configurations. At this point, the best fix I have seems to be turning off the RX loop, it makes the RY peak a little smaller.  The nominal config is with ~250mhz blends on X/Y/Z/RZ and something a little higher on RX/RY, the more aggressive RX/RY blends actually have a little higher cross-over, but have more ~.5hz gain peaking and more high frequency roll off. Going from the nominal config, pushes the peak down to .6hz and increases it's amplitude. Pushing the RX/RY blend up to 750mhz keeps the peak at ~1.1hz but makes it taller. Turning off the RX loop makes the peak in RY smaller, but changing the blend to either more or less aggressive either pushes it back down to .6hz and makes it taller, or just makes the peak taller. I don't think this is a good way to run the table, as leaving the RX loop off means there is no DC control of that degree of freedom. 

We also took measurements on HAM2 & 3, driving at the error point of the isolation loops while the tables were isolated, with nominal blends, sensor correction and  HEPI feedforward. So far, both chambers don't show glaring differences. Attached plots are HAM2 (first) HAM3 (second). On each plot, top right plot is the coherence from the Z drive to the local CPS & GS13 INF OUTs, and so after all the calibrations have been applied to the individual sensors, but before they are summed and composed into cartesian coordinates.

Top left is the phase for the z drive to inf out, bottom left is the magnitude. Bottom right is the tf from GS13Z Blend in to each of the local sensor outs. The similarity between the all of these tfs seems to indicate that this is not a problem with the calibration of any of the sensors.

RobertS, RickS

We went out to investigate the inability to transition to 20% on the make-up air fan.  

Apparently, we had failed to read the laminated procedure carefully enough.  

When going from "Commissioning Mode" to "Science Mode," one needs to stop the make up air fan, then set the speed to 20%.

This is carefully detailed in the procedure.  One just has to be diligent about executing each step of the procedure until this control system is updated.

The system now appears to be in the nominal "Science Mode" state.

After talking with Bubba, we decided that a power cycle was a good first step (as it almost always is).  To this end, after checking the commissioning status with Jenne (they were performing an initial alignment), I went out and power cycled the PSL enclosure AC units and entered the enclosure to visually confirm the status of the AC displays in the Laser Room.  Both displays were active, and when I followed the standard procedure for turning on the ACs (press the ON button on the AC display twice), both displays indicated that the AC units were ON.  I then exited the enclosure and returned it to Science Mode so as not to interrupt commissioning.  I left the ACs ON at the breaker (but OFF on the display).  I watched the enclosure temps for a couple minutes and saw no sign that the ACs remained ON (as Cheryl saw and reported in her alog here), but will continue to check on this throughout the day.  If anyone notices that the PSL enclosure temps are not normal (I believe there's a verbal alarm if the temp sensors at the AC vents read too low), please let me know.

1. On Tuesday, the AC units resumed their behavior of staying on when the controller shows that they are turned off.
   • I verified this on the controller screen (screen showed that AC was OFF), so I had to flip the breakers to actually turn the AC off.   See Alog 45075. 
2. Team PSL has not had to use the breakers to stop the AC for quite some time, meaning a number of months. 
   • This would suggest that the controller has more than one operational state, and has again switched to the state where the controller screen shows the AC in one state (OFF) when it's really in another state (ON). 
   • This would also suggest that the symptom where we change numbers on the controller and they appear to change, but when we revisit the setting after a time (usually hours+) we find that the numbers did not actually change.
3. It would be interesting to look at the reboot history of the controller, to see if there's a recent reboot that may account for the change.

Changed the ETMX HWS camera (please see attached images for new camera information/settings). The serial number of the removed camera is 013.

I've attached scope prints of the current RF levels.  Remember the factor of 14 for the (Actual RF to demod/RF monitor pickoff) compensation.

Actual RF to demod
--------------------
REFL9pp  = 210 mVpp
POP9pp   =  98 mVpp
REFL45pp = 700 mVpp
POP45pp  =  28 mVpp


Overall, RF levels seem reduced from before.  Also attached are the RF slider settings at the time of the measurement.

Old Pre-O3 RF levels

EDIT: The RF slider now for 9 MHz is the same as it was during the old measurement, but the 45 MHz slider is 3 dB lower.

A comment on the limiter: There is a limiter in the fast path of the common mode board. It 'soft' limits the output voltage to ~3V. It is intended to limit the transients during lock acquisition. This at some time was important for the IMC to keep the FSS well behaved. It should never be engaged, once lock is acquired. For the common mode boards other than the IMC, it was never required and should be off at all times. The signal of the ifo CM board was extremely small at the fast output, so it couldn't have been limiting.

Update: alog 45132

In my post above, the 9 MHz are in the first plot, and 45 MHz in the second.
REFL is green, and POP is blue.
The names are in the png name itself.

Associated with FRS Ticket 11740.

On Anamaria's suggestion we tried steering the ITM compensation plates and looking at the spots on the PR2 camera.

The spots on the ballast mass originate from both CP's. See attached photos:

1.before the CP move

2. with only the IX CP pitched (-ve)

3. with both ITM CP's pitched (-ve)

4. with both ITM CP's pitched (+ve)

Please see attached pdf for the overlay and identification of IFO items seen in Georgia's alog picture. (Sent previously via e-mail and now posted here for record.)

Eddie and Calum

Again previously on e-mail and adding here for record ...

From Corey Austin:

Those are second order ghost beams from ITM-AR and/or CP (so ITM-AR->ITM-HR->ITM-AR->PR3->masses). The attached slide shows pictures taken at LLO in full lock before/after we added a baffle in front of those masses during our last vent.

LLO has a 'tie-fighter' shaped spot on our camera that we decided was coming from the beamsplitter which may be your 3 beams.

From Alena / Calum / Eddie:

For future use /  reference LHO has that baffle Corey refers to (before / after pics attached again) on the shelf at LHO. To see it in more detail (at LLO) see table baffle on pg. 3, Detail 'D' of  LIGO-D0900520-v14 (https://dcc.ligo.org/LIGO-D0900520) and yes you have to be careful with placement so as not to clip the main beam!

Hiro, GariLynn and I had been discussing the ghost beams around PR2 and Hiro looked into the BS ghosts due to the wedge, see below and attached.

From Hiro:

The ghost beam around PR2 due to the wedge of BS is 90mm from the center of PR2.

Attaching Zemax simulations for all four conditions:
1 - detector view in front of PR2 baffle before ITM CPs alignment change
2 - detector view in front of PR2 baffle ITMX CP -200 um pitch
3 - detector view in front of PR2 baffle ITMX CP -200 um pitch and ITMY CP -300 um pitch
4 - detector view in front of PR2 baffle ITMX CP +200 um pitch and ITMX CP +300 um pitch

The detector is looking in both direction, the model does not have the baffle spacer and ballast masses therefore in zemax we may see more beams than on camera photos. The group of ghost beams highlighted with a dashed line matches the ghost beams seen on the mass in front of the baffle.
Adding a simulation of the ghost beams in front of PR2 baffle from an older aLog https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=30010 [Denis Martynov]