The ITMX Oplev (installed in March 2019) was near end of life judging by the SUM channel (see Attachment #1). I replaced it yesterday evening with a new HeNe head. Output power was ~3.25 mW. The head was labelled appropriately and the Oplev spot was recentered on its QPD. The lifetime of ~20 months is short but recall that this HeNe had already been employed as a fiber illuminator at EX and so maybe this is okay.
Loop UGFs and stability margins seem acceptable to me, see Attachment #2-#3.
I've received a report that a pin of an ITMX NW feedthru connector was bent. (Attachment 1)
The connector is #1 (upper left) and planned to be used for LO1-1.
This is Pin25 and used for the PD K of OSEM #1. This means that Coil Driver #1 (3 OSEMs) uses this pin, but Coil Driver #2 (2 OSEMs) does not.
Anyways, I tried to fix it by bending it back. WIth some tools, it was straightened enough for plugging the cable connector. (Attachment 2)
It seemed that the pins were exceptionally soft compared to the ones used for usual DSUBs, probably because of the vacuum compatibility.
So it's better to approach the pins in parallel to the surface and not apply mating pressure until you are sure that all the 25pins are inserted in the counterpart holes.
I'm driving C1:SUS-ITMX_OLYAW and PIT_EXC with amplitude 0,1-0.3 while taking transfer funtions of oplev.
The transfer functions are normal. However I noticed that the LL osem is not responding to this excitations
Healthy sensor respons should be like Atm3
Because of the in-vac work on Oct. 4th (see this entry) , ITMX's OSEM offsets were changed.
The two upper OSEMs are still fine, but LL and LR seem to be out of the OSEM's range.
The plot below shows the trends of LL's and LR's readouts for about two weeks. (The channel name are in the old convention, i.e. ITMY)
Some data were missing due to the upgrade of the frame builder.
It is apparent that the offsets are changed after the in-vac work on Oct. 4th, and now they just show almost zero numbers.
The damping of ITMX can still work, if LL and LR are disabled.
At some point before pumping down, we have to check the leveling of the ITMX table again.
ITMX OSEM CONFIGURATION
I did a quick measurement of the ITMX oplev loops, both pitch and yaw have about the same upper UGF as previous measurements with the previous laser; about 4 Hz.
This morning, while attempting to align the IFO to continue with noise-budgeting, we noted the XARM lock was not stable and showed glitches in the C1:LSC-TRX_OUT (arm cavity transmission). Inspecting the SUS screens, we found the ULSEN rms ~ 6 times higher than the other coils so we opened an ndscope with the four face OSEM signals and overlay the XARM transmission. We immediately noticed the ULSEN input is noisy, jumping around randomly and where bigger glitches correlated with the arm cavity transmission glitches. This is appreciated in Attachment #1.
We'll do a full signal investigation on ITMX SUS electronics to try and narrow down the issue, but it seems the glitches come and go... Is this from the gold satamp box? ...
After running dither alignment for all mirrors, all oplevs were recentered. (Except ETMY, since we did that earlier today.)
Looking at Koji's template for OSEM signals, the ITMX UL sensor noise floor seems more in line with the LL sensor, though there continues to be more noise than in other mirrors.
Trending the sensor signals over the past 7 days, Koji's measurement looks to have been taken during a time when the UL sensor voltage had jumped down. Did someone squish the satellite box cable? I have not done so.
I think that the step right at the end is due to a new POS offset of -2k counts, which I think Koji put into place earlier today.
According to the wiki, the Vmax/2 values and the current values are:
Although this noise is bad, we have always had these kind of humps around the bounce mode. Our interpretation in the past was that this was due to poor alignment of the OSEM in the frame, leading to a large vertical to horizontal coupling. Once you implement the BLRMS for the SUS channels, we'll be able to trend the noise over long periods of time.
The issue on the ITMX UL sensor has been fixed. It was because of a loose connection in the sensor signal path.
After the fix, the sensor responses completely changed and the suspension became unable to be damped with the new matrix.
At the moment the ITMX suspension is damped by the default input matrix.
we should do the free swinging test once again.
The loose connection was found on the rear side of the 1X5 rack.
There is an adapter card on the rear side, where the driver and sensor signals are combined into a single cable.
I pushed the sensor cable (bottom right in the picture) and the noise disappeared.
Note that I changed the labels on the adapter cards from the old X/Y convention to the new one.
After fixing the loose cable the ITMX suspension became unable to be damped.
So I put the input matrix back to the default and it immediately started damping happily. It means our new matrix is not valid any more.
Here is the latest noise spectra of the ITMX sensors damped with the default input matrix.
As usual all of them are limited by the ADC noise above 20 Hz. (ADC noise is plotted in purple curve)
During the work I also pushed not only ITMX ones but also the cable for the rest of the optics in the adapter cards.
Then PRM became unable to be damped, so it implies the PRM suspension also used to be the same situation.
The input matrix of PRM has been also back to the default.
Currently the damping of the ITMX suspension is intentionally disabled for the noise investigation.
As a suspension test I am leaving all of the suspensions restored and damped with OSEMS but without oplevs
According to the spectra, all of the suspensions had been damped with the OSEMs. The peaks around 1Hz are reasonably suppressed.
However the spectra from ITMX showed a noise floor at very high level. This is because of strange jumps in the signal of the UL shadow sensor.
I will check some analog circuits for the UL sensor.
(ITMX shadow sensors)
Here is the spectra of the ITMX shadow sensors taken during the damping test (#5534)- -
The UL sensor shows a unacceptable amount of noise.
Additionally I checked the time series of the ITMX shadow sensors and found ONLY the UL sensor frequently showed strange jumps in data.
Here is an example of the time series showing a jump ONLY in the UL sensor.
It is possible that the jumps are coming from some circuits, since the rest of the sensors (including the oplevs) don't detect the same jump.
(What we did)
* Moved SUS to edge of table for OSEM adjustment.
* Leveled the table in this temporary tower position.
* Rotated all OSEMs to give some seperation between magnets and LED/PD packages.
* Moved the upper OSEM bracket a little bit upward.
* All the OSEM holding set screws were short with flat heads; this is annoying since we would like to use them more like thumbscrews. Steve took the long set-screws out of the old ITMX cage and we swapped them. Need to order ~100 silver-plated socket head spare/replacements.
* Took pictures of OSEMs.
* Moved tower back to old position.
* Releveled the table (added one rectangular weight in the NW corner of the table).
* Find that ITMX OSEMs were a couple 100 micron out of position; we adjusted them in-situ in the final position of the tower, trying not to rotate them. All mean voltages now are within 100 mV of ideal half-light.
* Back/front EQ positions adjusted by the screw method. bottom/top stops adjusted earlier.
* OSEM cables tied down with copper wire.
* Increased the incident power up to 91 mW going into MC to temporarily make the POX beam more visible.
* The POX beam was checked. It was exiting from the chamber and going through about the center of the viewport.
So, was there real shifting in the ITMX alignment as seen in the DV trend or just mis-diagnosis from the ETMX violin mode? Or how would the ETMX violin mode drive the ITMX with the LSC feedback disabled?
I balanced the ITMX and ETMX tables into level position today, for which I had to move quite a few of the on-table weights. I'm recording their original positions for future use here.
This table was only off in 'pitch', I moved the middle weight to a new location as shown in the pictures. I added secondf disk weight on top of the one I moved, this one has to come out again when we install ETMX.
I moved some weights around as shown in the image, but didn't have to add any. We simply have to move them back to their original location when the time comes.
While in the chambers, I also took some pictures of the ETMX window and PR2, motivated by the dirty state of SR2. We might want to consider cleaning both, specifically PR2 is relatively easily accessible and can be cleaned when we open the ITMX chamber to remove its FC and move it back into position.
The ITMX table had relaxed overnight into a slightly misaligned state overnight - since the ITMX table holds PR2 and hence can affect the input pointing, we decided to fix this before commencing alignment work today. The misalignment was not as bad as what Johannes observed prior to his first re-leveling attempt, but was ~1 division on the spirit level. So I decided to move one set of weights to level the table again. It is entirely possible that over the next couple of days, the table will shift slightly again, but the hope is that we are closer to the 'ideal' orientation of the table now... Pictures to follow...
The ITMX OSEMs report elevated noise in the 10-100 Hz band when we have high circulating power in the arm cavities, see Attachment #1. Since there is no LSC actuation on the ITMs in this state, this could be a radiation presssure effect, or could be scattered 1064nm light entering the OSEMs. The Oplevs don't report any elevated noise however. ITMY has the OSEM whitening broken for two channels, but the other two channels don't report as significant an increase as ITMX, see Attachment #2. I can't find the status of which OSEMs have the 1064nm blocking filters installed. The local damping loops are rolled off by ~100dB at 30 Hz, so the sensing noise re-injection should be attenuated by this factor, so maybe the OSEM sensor noise isn't the likely culprit. But radiation pressure didn't worsen the length noise in the past, even after our mirror cleaning and the increased PRG.
...maybe the opto-mechanical CARM plant is changing as a function of the CARM offset...
if the RP don't fit
u must acquit
sweep the laser amplitude
to divine the couplin w certitude
[Yuta, Anchal, Paco]
As described briefly by JC, there were multiple failure modes going during this work segment.
Indeed, the 64 pin crimp cable from the gold sat amp box broke when work around ITMX chamber was ongoing. We found the right 64 pin head replacement around and moved on to fix the connector in-situ. After a first attempt, we suddenly lost all damping on vertex SUS (driven by these old sat amp electronics) because our c1susaux acromag chassis stopped working. After looking around the 1x5 rack electronics we noted that one of the +- 20 VDC Sorensens were at 11.6 VDC, drawing 6.7 A of current (nominally this supply draws over 5 Amps!) so we realized we had not connected the ITMX sat amp correctly, and the DC rail voltage drop busted the acromag power as well, tripping all the other watchdogs ...
We fixed this by first, unplugging the shorted cable from the rack (at which point the supply went back to 20 VDC, 4.7 A) and then carefully redoing the crimp connector. The second attempt was successful and we restored the c1susaux modbusIOC service (i.e. slow controls).
As we restored the slow controls, and damped most vertex suspensions, we noticed ITMY UL and SD osems were reading 0 counts both on the slow and fast ADCs. We suspected we had pulled some wires around when busy with the ITMX sat amp saga. We found that Side OSEM cLEMO cable was very loose on the whitening board. In fact, we have had no side osem signal on ITMY for some time. We fixed this. Nevertheless the UL channel remained silent... We then did the following tests:
DO NOT TRUST THE SATELLITE BOX TESTER 2.
ITMX watchdog tripped around 5 Torr and the PRM around 450 Torr of this vent. They were restored than.
We are at 580 Torr now.
I fixed up the ITMX camera like we did for ITMY recently (removed T's and added strain relief - the lens was already OK).
I also updated the .SCAN field for the RMTEMP and RCTEMP channels to 0.1 second. This had been done via probe but was wiped out after reboot previously, because I forgot to update the psl.db file.
We removed the ITMX heavy door to fix the oplev situation.
My Plan for closing:
Today: I will work on the ITMX oplev situation today and go through the vent close-up checklist as far as I can get.
Tomorrow: We will do the final alignment check tomorrow with the light doors. The access connector and heavy doors should go in place late afternoon.
Thursday: We will start pumping down early in the morning on Thursday.
Today: I will work on the ITMX oplev situation today and go through the vent close-up checklist as far as I can get.
[Alex, Sujan, Manasa]
The ITMX oplev steering mirrors were laid out such that they were out of the way of the BS oplev leakage. But the halo associated with the He-Ne laser does exist even now. I conclude that this is something that can be dealt with after we pump down as well. So I did not change the ITMX oplev optics on the POX table.
BS, PRM, ITMY and SRM oplevs were aligned and centered.
We want to do IPANG and IPPOS alignment when the IFO is aligned satisfactorily and right before we put the heavy doors.
The arms were aligned and ASS'd before I went in to fix the oplevs. I haven't done anything but deal with the oplevs tonight. So I am being lazy by assuming the alignment is still good and calling it a night.
Tomorrow: We will do the final alignment check for the arms, PRC and SRC with the light doors on. Check IPANG and IPPOS. The access connector and heavy doors should go in place late afternoon.
Thursday: We will start pumping down early in the morning on Thursday.
Looked at ITMX. Johannes and I both saw a fairly large speck of dust near the center of the HR side. We tried to take some photos but couldn't get any with good focus.
We ran out of illuminator juice, and short-term charging couldn't restore enough battery life to continue the work. We should be able to get some better pictures tomorrow.
Looked at ITMX. Johannes and I both saw a fairly large speck of dust near the center of the HR side. We tried to take some photos but couldn't get any with good focus
Multicolor flash light:
- It seems that the usb port charging doesn't work.
- There is a battery charger on Steve's desk. I set the batteries on it.
White LED flash light:
- I temporarily brought a compatible charger from WB. It's charging two batteries behind the LCD display on my desk.
The ITMX 10" flange with four DSUB-25 feedthroughs has been install with the cables connected at the in-vac side. See photo; as requested, LO1-1 and LO1-2 are connected to the top row of feedthroughs from left to right respectively and the opposite ends of the cables placed left to right on the laser table. PR2-1 and PR2-2 are connected to the lower row of feedthroughs from left to right respectively, with the opposite ends placed on the surface below the laser from left to right. This seemed the easiest way to keep the cable orientation clear.
Thanks for the installation.
With regard to the connector convention, let's use the attached arrangement so that it will be consistent with the existing flange DSUB configuration. Not a big deal.
Good job Q! Give us more details please or play Rachmaninoff Piano Concernto #2
Atm2, EQ 3.5 and 4.1
confirming ITMX is really free
Taking inspiration from J. Lewis et. al, ITMX has been freed.
Rana came by and freed ITMX again. I think it shouldn't be a problem for me to free it if it happens again.
In hopes of getting better SNR on the free swing spectra, we kicked all optics at around 7pm. The damping should come back on a little after midnight. ITMX did not get stuck after this kick.
We started an ITMX freeswing run at this time
Thu Aug 11 18:58:59 PDT 2011
But the optic did not repond to the kick. It is possible that the earthquake stops are close to the face and/or rear of the optic and prevent it from oscillating. We will check again and see what is up in a few hours.
Jenne and Koji
We successfully hung ITMX on the SOS. Side magnet is ~2mm off from the center of the OSEM. ITMX aligned using the QPD. The OSEMs changes the alignment. It looks that something magnetic is inside the OSEM PD or LED.
Reguled ITMY side magnet.
Cleaned up the lab for the safety inspection.
We successfully hung ITMX on the SOS. Side magnet is ~2mm off from the center of the OSEM.
Some details on the side magnet situation from today:
To glue the magnets+dumbbells to the optics, we use the magnet-dumbbell gluing fixture. This fixture is supposed to have teflon 'pads' for the optic to sit on while you align it in the fixture, however the fixture which we received from MIT (it's Betsy's....but it came via MIT) only had one of the 4 teflon pads.
Kiwamu and I decided (last week, when we first glued ITMX's magnets) that it would be bad news to let the AR face of the optic sit on bare metal, so we fashioned up some teflon pads using stock in a cabinet down the Yarm. We were focused on thinking about the face magnets, and didn't think about how the thickness of the teflon affected the placement of the side magnet. We chose some teflon that was too thin by ~1mm, so the optic sat too low in the fixture, resulting in the side magnet being glued too close to the HR side of the optic (this is all along the Z - axis, where Z is the direction of beam propagation).
Why it ended up being 2mm off instead of only 1mm I don't really have an explanation for, other than perhaps tightening the set screws to hold the optic (by the barrel) in the fixture pushes the optic up. I observed this happening when I didn't put any effort into keeping the optic flat on the teflon pads, but I thought that I made sure the optic was seated nicely in the fixture before starting to glue. When I glued the new ITMY side magnet tonight I tried to make sure that the optic was seated nicely in the fixture. We'll see what happens.
Before gluing the new ITMY side magnet (and now it's set for all future magnet gluings....), I found 4 teflon pads of all the correct thickness. It turns out that we have a magnet gluing fixture of our own, which I found in the cabinets in the clean room. This fixture had all 4 teflon pads, so I stole them and put them into the one that we're using for this round of upgrade / suspension hangings. The height of all future side magnets should be correct. The thickness of the pads in the 'spare' fixture matched the one which came with the fixture from MIT as closely as I could feel by putting them on the same flat surface next to each other and feeling if there was a step.
A side note about this magnet gluing fixture that I found: It has the word "TOP" etched into it, to prevent exactly my problem with the ITMY side magnets in the first place. Unfortunately the threads for the set screws which hold the optic are shot (or something is funny with them), so we can't just use this fixture.
Gluing notes regarding the standoffs and guiderods:
There's more glue than I'd like on the guiderods / standoff for ITMX. The glue was starting to get a little tacky when I glued the standoff in place after we balanced the optic, so it was hard to get it in the right place. I'm confident we have a good epoxy contact, and we don't have much glue that I think it'll be a big problem. Certainly I'll be a lot better at manuvering my glue-stick a.k.a skinny piece of wire around the suspension tower to get to the standoff for the rest of the optics that we're hanging, and I won't have glued something like ITMY side magnet immediately beforehand, which took enough time that the glue started to get tacky (not very tacky, just barely noticeably tacky).
I'd say that most gluing activities should be completed within ~10-15min of mixing the glue, after spending ~2min stirring to make sure it's nice and uniform. It doesn't dry fast enough to be a huge rush, but you should get right on the gluing once the epoxy has been mixed.
As well as the oplev construction for ITMs.
We anticipate the drift of the stack. So we need to revisit the alignment again.
Some tools and the level gauge were removed from the table.
Picture of the ETMX - reflection from the ITMX is hitting the mirror and Jamie's windmill.
0. The suspension tower had been placed on the table close to the door.
1. Brought the OSEMs from the clean room. Connected the satellite box to the ITMX suspension.
2. Went into the chamber. Leveled the table.
3. Released the mirror from the clamp. Put and adjust the OSEMs.
- Note that the side OSEM is located to the south side of the tower
so that we can still touch it after the placement of the TT suspension at the north side of the SOS tower.
4. Clamped the mirror. Moved the SOS tower according to the CAD layout.
5. Leveled the table again.
6. Released the mirror again and adjusted the OSEMs.
7. Turned on the end green laser pointer.
- The spot was slightly upside and left of the mirror. Adjusted it so that the spot is at the center.
8. Align ITMX in Pitch
- The spot was hitting the tube. Moved the pitch bias such that the beam get horizontal.
9. Align ITMX in Yaw
- Moved the SOS tower such that the approximate spot is on the ETMX. If I hit the right spot I could see the tube get grown green because of the huge scatter.
10. Adjusted the OSEMs again and check the alignment again. Repeated this process 2~3 times.
- Bias values at the end of the work: Pitch 0.7800 / Yaw 0.270
11. Close up the chamber
- Remove the level gauge. Some of the screws are still in the Al ship in the chamber.
- Close the light door.
In other, semi-unrelated news, the ITMXF camera has been not working for a while. The bottom right quad on the test mass tv has been dark for at least a week or two. Steve, when you have a chance (after the oplevs are all taken care of), can you see if there's something obvious that's wrong?
While helping Charles string the ethernet cable (elog 7698) for the power strip in the vertex (from 1Y1 to 1X1), I looked at the ITMX power cord. It was connected to the same power strip as the illuminator, which, since the illuminator was turned off by turning off the power strip, meant no power was going to the camera. Since Charles is very close to having the new power strips set up, I unplugged the ITMX illuminator and turned the power strip back on. ITMX camera is back to normal.
I was investigating several issues on the IFO. As many of you noticed and not elogged, ITMX had frequent kicking without its oplev servo.
Also I had C1:LSC-TRY_OUT flatted out to zero even though I could see some fringes C1:SUS-ETMY_TRY_OUT.
Restarted all of the realtime models (no machine reboot).
Now I don't find any beam on REFL/AS/POP cameras.
If I look at BS-PRM camera, I can see big scattering, the beam is in the BS chamber.
I jiggled TT1 but cannot find neither a Michelson fringe nor POP beam.
So far I can't figure out what has happened but I'm leaving the lab now.
IMC is locked fine.
I can see some higher order mode of the Yarm green, so the Y arm alignment is no so far from the correct one.
ITMX is kicked up periodically. ITMX_PD_MAX_VAR is lowered to 500 from 1350
It started at Friday morning 8-1
Tonight we've noticed that ITMX local damping was kicking the optics. This happened because LR shadow sensor was not working. In ~30 minutes it started to work again. Evan and I were working on installation, moving and focusing cameras and locking prcl and mich. We've installed a camera on BSC and plugged it in to PSL_SPARE input.
I'm not sure that this can be correlated to ITMX LR shadow sensor behaviour.
As I feared, since I couldn't see the magnet-to-dumbbell joint from all angles, they ended up being off by ~1/3 of a magnet diameter.
Because I don't want to deal with finding another failed glue joint tomorrow, I removed the magnet and dumbbell from the optic, and broke the manget off of the dumbbell. As with yesterday, I kept track of which end of the magnet had been glued to the dumbbell.
I got a new dumbbell, removed all the glue from the magnet, and reglued them together, in the fixture that ensures they are well aligned.
Tomorrow I will come in and glue the magnet dumbbell assembly to the ITM.
Tomorrow afternoon I'll remove the optic from the fixture, and put it in the oven.
I believe that the UR and LR magnets are stuck. There was no earth quake at 16:18 yesterday. Something had to kick it into this position. See 4days plot
Please advise freeing details.
Something strange happened to the ITMX osem reading around 4.pm. PDT as shown below.
Also the there was no response of the reading as we adjusted the PITCH and YAW. :(
Note that we restarted the slow machine: c1susaux,c1ausex this afternoon because of the unresponced interface.
When I restarted c1susaux yesterday, I didn't know that I needed to disable the coil outputs first. So when it came back online, it attempted to damp all the vertex area optics and ITMX got stuck
We should make a note in the Computer Restart Procedures wiki page indicating the importance of disabling the coils before rebooting c1susaux, c1auxex, and c1auxey. Today c1auxey was rebooted properly without incident. If the slider values etc go back to their previous values on their own, is it necessary to do a BURT restore? I tried doing one for c1susaux today and there were some errors for ASC channels, but the alignment sliders went right back to the proper place after reboot yesterday.
Please advise freeing details
I misaligned ITMX. The oplev servo for ITMX is now turned off. You can restore ITMX alignment by running "restore".
The new ITMX was aligned by changing the DC biases.
The resultant DC biases are reasonably small.
C1:SUS-ITMX_PIT_COMM = -0.2909
C1:SUS-ITMX_YAW_COMM = -0.0617
The alignment was done by trying to resonate the green light in the X arm cavity.
The spot position of the green light on the ITMX mirror looked good. This was confirmed by inserting a sensor card.
I did the OSEM mid-range adjustment and the rotation adjustment but at the end the OSEM DC voltage has changed due to the DC bias operation.
The OSEM rotation was approximately optimized so that all the face shadow sensors are sensitive to the POS motion but the SIDE shadow sensor is insensitive to the POS motion.
It needs a free swinging diagnosis.
ITMX OSEMs UL 1.8V, UR 1.7V, LR 0V, LL 0V, SD 1.3V at the same bias setting shown above. May be a lose earth quake tip?or magnet is touching?
[Koji, Manasa, Sujan]
[Steve, Gautam, Manasa]
While we checked the ITMX oplev situation yesterday, we found that the beam hitting the ITM and the in-vacuum steering mirrors had a halo around them. We used the set of irides in the path of the ingoing beam and cut the stray light around the beam. This reduced the intensity of the halo around the mirrors. We noticed that the halo accounted for 2000 counts of 6500 at the oplev QPD. We tried changing the laser and this did not make the situation any better.
Also there are a couple or more strong stray beams from the BS oplev.
I suspect that the BS oplev leakage is messing with the ITMX oplev. Why?? We have been seeing the breathing of transmitted beam from the X arm cavity and the shadow sensor readings have been bigger than usual since the last vent (when we changed the BS oplev path). Also, the ingoing oplev beam is close to clipping at the PR2 stack.
I think it would be best to open the ITMX chamber and modify the in-vac steering mirror layout of the oplev.