kyle.ryan@LIGO.ORG - posted 10:15, Saturday 29 March 2014 (11085)
Kyle on site for rough pumping of Y-end -> Should be here several hours -> Will make aLOG entry when leaving
A. Staley, S. Dwyer, J. Kissel After speaking with Sheila and Alexa, trying to understand the spectrum in LHO aLOG 11026, I realized that -- because of so much unexpected excess noise -- the current ALS setup has diverged significantly from the baseline plan. As such, we've worked together to create a diagram that is to-the-best-of-(my)-knowledge accurate, and makes sure to show how every control signal gets around to its actuators, including passes through digital land. The only things I did not include were the demodulator boards between the REFL diodes (ARM REFL, MC REFL, and the two green XARM and YARM REFLs) and lame things like whitening, AA, and AI chassis that facilitate getting in-and-out of digital land. In particular, I draw your attention to the unorthodox and new features that were not part of the original design plan: (1) The PRM is misaligned. This way we can use IFO REFL red diode signal (after normalizing / linearizing it with the red arm cavity trans) to measure the arm and offload at low frequency to the CARM board in the second input. This is unorthodox because normally we would feed REFL straight to the CARM board in all analog and retain the large bandwidth, but because the noise is so large, it must be linearized in the front-end (the only place the Arm TRANS signal exists), and fed out one of the corner station LSC DACs. Note that this configuration is just a special technique for these particular series of measurements and is not designed to become a normal part of the lock acquisition scheme. (2) The Voltage Controlled Oscillator (VCO) actuated, Phase-Locking Loop (PLL) that's wrapped around the corner-station COMM and DIFF Phase-Frequency Discriminators (PFD) are used to reduce the noise enough to keep the PFD in the linear, phase detecting mode (check out pgs 6-8 of the AD9901 datasheet -- it's a really nice explanation of how it works). (3) Before the hand-off, there's another temporary step which is to use the Beckhoff system ("Slow ADC" in the diagram) to feed directly to the PSL VCO (again at low frequency) to reduce the noise enough for the COMM hand-off to work. This is most certainly an impressively complicated system! Note that this diagram has been committed into the noisebudget repo here: ${NBSVN}/trunk/HIFO/Common/ and I imagine will become an "as built" DCC document in the glorious future when everything is working beautifully.
Comments and my replies on the diagram from Bram, to be added/fixed later: You are missing the Fiber Distribution Box, which shifts the laser frequency by -160 MHz before it gets shipped to the end-stations to compensate for the PSL AOM. The lasers at the end-station are then locked at the + (X-end?) and - (Y-end?) 40 MHz around the ‘0’. Ah, yes. I had debated putting the distribution box in there, and decided against it for clarity because I forgot the important frequency shift feature. See D1200136 for details or Figure for in T1000555 for schematical diagram. Also, the F and S in the ‘servo’ block diagrams, is the S beckhoff? No -- the "F" and "S" are the "Fast" and "Slow" paths of what has been traditionally called a "common mode" board everywhere -- I was trying to start a clarifying revolution with this diagram... The lasers in the end-station get the slow temp control directly from the beckhoff from the demos error signal monitor. The beckhoff links are a little confusing, maybe make a little color legend?
started at ~18:50 will run for 8 hours.
Yesterday I went to end X to investigate the beam shape for the ALS WFS. (This is to follow up the measurements we made in alog 10774)
First I tried changing the alingment of the reaction chain, this didn't make a difference. Then I tried changing the TMS QPD offsets. This moves the lock point of the input alingment loops, changing the alingment of the green beam as it goes through TMS. This certaintly changes the beam quality on the WFS, screenshots of several different offsets are attached. In the end I left the offsets at ALS-X_IP_ANG_PIT at -50, ALS-X_IP_POS_PIT at 150.
I am not sure why changing these offsets makes such a difference in the beam quality.
This moved the QPD A by 0.07 counts and QPD B by 0.04 counts. Pablo and I redid the pointing of TMS to the baffle PDs, but it hadn't changed more than the normal change between ISI trips. However, switching these offsets does move the beamspot on ISCT1, I moved PR3 by 0.9urad in pitch to bring the spot back.
After realinging the arm, we re checked the phasing of the WFS. We did this by putting an exictation on LSC-X_EXTRA_AO_1_EXC at 50Hz and looking at the signals of the individual segments, which seems fine. This is saved in /home/sheila.dwyer/ALS?HIFOX/WFS/WFS_PhaseDTT_March282014.xml
Then we started the sensing matrix measurement in Alexa's alog 11073
This week, I tested the ETMX UIM P2P and Y2Y filters (described in alog 10912). The results are showing that filters are working as expected giving a single pendulum transfer function falling at 1/f^2 after the resonnance (f=0.45Hz for pitch, f=0.6Hz for yaw). Also the coupling between pitch and yaw is small (~5%) so unless this is too much, there's no need for diagonalization for UIM.
Attached pdf are showing P2P P2Y (first pdf) Y2Y Y2P (second pdf) transfer functions with/without the filter.
Left to do for next week :
ETMX : Long decoupling on UIM/PUM
ETMY
ITMX/ITMY
sorry for the 90degrees rotated pdfs ! couldn't find a way to rotate and save them.
I got the medms populated so the cartesian location values are now valid. These initial values today are the 'Aligned' numbers. They will probably be a little different after these range of motion/linearity tests complete and the stress of the system are further released/shaken out.
Removed iLIGO RGA hardware from BSC10 and installed 10" blank in its place*installed ESD interlock gauge and 4.5"-2.75" zero-length reducer on BSC10*Installed 2.5" aLIGO RGA isolation valve and 10"-4.5" zero-length reducer on BSC6 (remaining aLIGO RGA components to be installed later) "Bumped" dial indicator cluster on BSC10's NE support tube -> readings from these dial indicators can be considered "bogus" as a result Running QDP80 overnight but couldn't start Turbo pump as its foreline pirani gauge isn't working now(?) -> I'll fix this gauge tomorrow while rough pumping the Y-end with the QDP80.
(Alexa, Daniel, Sheila)
We measured the WFS sensing matrix for both PIT and YAW. The matrices were computed by exciting ITMX/ETMX PIT/YAW at 1.5Hz with 0.3 amplitude, and looking at the WFS transfer function. The results can be found in the following DTTs saved in /ligo/home/sheila.dwyer/ALS/HIFOX/WFS/:
Inverting the results gives...
YAW input sensing matrix:
-2.294 -3.155
0.529 -2.604
PIT input sensing matrix:
-0.494 -0.239
0.302 -0.489
These values are in microradians; however the factor of 1e-3 is taken care of in the gain of the filter module. We also adjusted the signs as follows:
Under this configuration, with all four DOFs engaged (DOF 1,2 P,Y) the WFS_A/B_I_YAW/PIT_OUTMON all converge to zero. The lock appears to be stable with a transmission betweeen 950 to 1050 counts. Futher investigation needs to be done...
Aidan. Dave H. Greg G. Thomas V.
We have, basically, finished installing all the electronics and cabling on the TCSX table. There are a few outstanding issues (summarized in the attached PDF). The ones that are preventing us from turning on the laser are listed below.
We hope to address all these early on Monday to get the laser running to check the output power.
Chiller settings:
We adjusted the bypass valve on the back of the TCSX chiller to achieve the following settings (to mimic what's at LLO)
Flow rate: 3.4GPM
Pressure: 60.5PSI
Laser housing leak.
The replacement laser installed on the TCSX table also has a slow leak from the laser housing (in the same place as the first one) - about 1 drip every 5 minutes. We will check the output power of this laser before we pull it. See photos 3 & 4
This trip happened around the time of a beckhoff restart. A beckhoff restart causes a crash of the IMC guardian, which causes it to stop. Its not clear to me why this should cause MC2 to get a large signal, but it seems to. This causes a cascade of trips. Even though I don't know why this happends, creating a safe state in the IMC guardian so that it handels missing channels better could help with the problem.
Another solution is to have the SUS WDs not trip HEPI. Can we get that fix soon?
HAM2 also tripped at the same time, Jeff and Hugh brought that back.
To be clear, IMC guardian did not "crash" in this particular situation. The guardian responded exactly as it's currently programmed to respond, which is to go into ERROR when it looses communication with any of the channels it's monitoring. I want to distinguish and ERROR condition, which is something that guardian handles, to a "crash", which means that the guardian process died unexpectedly.
Here's my guess for the sequence of events:
It's possible guardian could be made slightly more robust against loss of some of it's channels, but that only helps up to a point. Eventually guardian has to drop into some error condition if it can't talk to whatever it's trying to control. It could try to move everything to some sort of safe state, but that only works if it can talk to the front-ends to actually change their state.
A Beckhoff restart also causes the IMC servo board to be reset, as well as all whitening for photodiodes, wavefront sensors and QPDs. I assume that the resulting transient caused the MC to trip. It would be interesting to know, if this is due the length or alignment system. Is it the initial transient or a run-away integrator? In either case this should not result in a trip. A better action would be to simply turn off the ISC inputs.
After taking a look at the time of WD trips, it seems like HAM3 ISI trips before MC2, see green plot vs red plot (the X axis is the number of seconds after gps=1080083200)
Please mind the signs here at HAM4, there is an Optic suspended here. Commissioning to commence shortly.
Day Shift Summary LVEA Laser Safe Apollo - Bolting dome on BSC10, working on view ports at End-Y Mitch – Check ACB at End-Y Hugh – Working on HAM5 HEPI Richard – Y-Arm TCS cabling 08:35 Mitch – Going to End-Y 08:53 Dave – LVEA working on TCS cabling 09:00 Justin – Moving laser barriers around the HAM4 TCS table area 09:18 Andres – Working on dog clamp shelves next to HAM2 09:20 Hugh & Jim – Working on HAM5 HEPI 09:29 Betsy & Margo – Going to End-Y for BSC10 closeout 11:26 Filiberto – Going to Mid-Y to pick up TCS panels 13:00 Justin – Transition LVEA to laser hazard 13:20 Dave & Thomas – Turning on TCS chillers 14:00 Filiberto – Going to End-Y to check ACB feed through 14:05 Andres – Working on dog clamps shelves next to HAM2 15:30 Jax – Briefly transitioning End-Y to laser hazard to make a PZT check 15:36 Michael – Going to End-Y to check chamber close status
At Richard's request I disabled the End Y picomotors, so that they will not be used durring the pumpdown.
Tested the forward voltage for the ACB diodes. BSC10 Flange F1-3C1 (air side). Pin 1&2 PD forward voltage: 0.431V Pin 4&5 PD forward voltage: 0.423V Pin 7&8 PD forward voltage: 0.431V Pin 10&11 PD forward voltage: 0.423V All results within spec.
Margot and I performed all of BSC10 closeout tasks listed in my previous alog regarding this closeout. We pulled the FC from the ETMy optic a little after 11am, and the door was going on at ~1:30. It took "so long" (ha) because we ended up having to spend some extra time calling in the troops about one of the ISC viewports having what appeared to be a scratch on it's inside surface. More details to come as needed.
Here are some further pictures of the ACB swing back and the FirstContact spray cone attachment to the HR side of the ETMy QUAD structure from yesterday. Yes, the cone protrudes into the baffle. Yes, Margot still was able to fit her head and an arm with the spray bottle in the cone.
The last picture shows the placement of the horizontal wafer and verticle 1" witness optic in the center of the chamber, placed today just before the door went on the chamber.
Notes and dcc numbers for Contamination Control Samples (ones that came out and ones that went in) to WBSC10 before doors went on: 1. Vertical 1’’ optics on QUAD: T1400246 (SN1195) out and T1400247 (SN 262) in. 2. Vertical 1’’ optic under quad: T1400248 (SN261) placed at end of closeout. 3. Vertical wafer on quad: T1400249 attached to quad under HR of ETM. 4. Horizontal wafer on floor under quad:T1400250 placed at end of closeout. 5. Horizontal 1’’ optic: T1400251 was left on beam tube floor between BSC10 and BSC6. Looking up SN/history. Didn’t take it out, because we had no clean optic containers handy. 6. 24’’ PET swipe sample taken in tube near purge today close to end of closeout. Labeled, and taken to PET microscope area.
This morning, SEI, TMS, and SUS gave a cursory "approval" of their systems in order to proceed with chamber close-out tasks. So, after lunch, Margot and I applied First Contact to the ETMy-HR surface which will be pulled just before closing the door tomorrow. The order of events this afternoon (and late morning in order to catch the alog up):
Jim locked the ISI and put final touches on chamber feedthru cable routing.
Apollo+Joe+Gerardo had a viewport party at the BSC10/6 area.
Margot and I locked the lowest masses of the ETMy QUAD. Then we,
Secured the ACB locking bracket and used the wedge to swing it back and prop it into place. See notes on this in attached alog.
Attached the FC QUAD cone to the structure and sprayed FC (standard 3 coats) on the HR surface.
Removed the cone from the suspension. Finished FC layer reinforcement.
Removed the wedge from the ACB and restored it's nominal hanging position. Removed the ACB locking bracket screws.
Started stowing all left over bags of "junk" left outside of the chamber door on various table surfaces by SUS and every other team that visited this last month. If you're missing something (and you noticed), I took ownership of it.
Jim arrived and unlocked the ISI. The ETMy QUAD will remain locked during dome replacement.
Apollo started gearing up to remove walking plates from upstairs and crane the dome on the chamber.
Tomorrow's to-do list which Margot and I will do until the last step:
Inspect insides of viewports.
Adjust ACB to check magnet gap which may or may not have shifted slightly due to the swing back from today.
Clean the chamber, vacuum, etc.
Take final PCL swipes.
Blow various other optic surfaces. Or not.
Swap in final 1" witness optic on QUAD structure.
Check/Remove all tools.
Remove ETMy-HR with N2 blow.
Set and lock all 64 QUAD EQ stops and nuts, accounting for buoyancy.
Set QUAD BOSEMs to account for buoyancy.
Quick QUAD health check with DTT TFs.
Lay final witness plates.
Exit chamber.
Finish stowing everything around door and move it out of the way.
Put door on.
So, when we went to swing back the ACB and stuff the wedge into place, the wedge could not be inserted in the gap all of the way due to interference with the round balance weight attached on top of the baffle. We pushed the wedge in ~2/3 of the way which gave us ~2/3 more working area than we had with out swinging it back at all. Good enough. (Removing the round weight would have cause the balance of the ACB to be out of alignment so that wasn't an option.) Also, even though the locking bracket was engaded which provided some support to the down tube of the ACB, the ACB was still a bit "rickety" during this maneuver.
The first picture below is of the ACB wedge not quite installed as far in as it could. This meant that the screw holes to secure the wedge in place could not be engaged. ACB engineers must have anticipated this so they provided us with a "safety" chain which one could tie up "somewhere" such that the wedge doesn't come flying out at you if you bump the baffle while it's up. The chain was of limited length, so they best Margot and I could do was wind it around the post loosely a few times. Note, the wedge seemed wedged in well enough that it didn't budge when we did happen to bump the baffle a bit here and there with the cone work.
Also note, the ACB did not hang the same way after we restored it. Mitchell had to make some minor tweeks to the balance today in order to recover the correct gap setting for the magnets (specifically 0.09 inches! - Really? Not 0.08" or 0.1", but 0.09", huh!? Seems a bit tight given the grossness of both the swing back application and the shear size of the baffle... but what do I in SUS know.) In the end, as usual the ACB comes with in a few mm of the QUAD structure at the head of one of it's screws (see 2nd picture with red circle around it).
