Was the connection between the feedthrough (atmosphere side) and the connector on the optical table confirmed to be OK?
We had a similar situation for the TT1. We found that we were using the wrong feedthrough connector (see TT1 elog).
The major problem that Manasa and I found was that we weren't getting voltage along the cable between the rack and the chamber (all out-of-vac stuff). We used a function generator to put voltage across 2 pins, then a DMM to try to measure that voltage on the other end of the cable. No go. Jamie and I will look at it again today.
Everything was fine. Apparently these guys just forgot that the cable from the rack to the chamber flips it's pins. There was also a small problem with the patch cable from the coil driver that had flipped pins. This was fixed. The coil driver signals are now getting to the TTs.
Investigating why the pitch/yaw seems to be flipped...
[Jamie, Manasa, Jenne]
We started by verifying that the tip-tilts were getting the correct signals at the correct coils, and were hanging properly without touching.
We started with TT2. It was not hanging freely. One of the coils was in much further than the others, and the mirror frame was basically sitting on the back side yaw dampers. I backed out the coil to match the others, and backed off all of the dampers, both in back and the corner dampers on the front.
Once the mirror was freely suspended, we borrowed the BS oplev to verify that the mirror was hanging vertically. I adjusted the adjustment screw on the bottom of the frame to make it level. Once that was done, we verified our EPICS control. We finally figured out that some of the coils have polarity flipped relative to the others, which is why we were seeing pitch as yaw and vice-versa. At that point we were satisfied with how TT2 was hanging, and went back to TT1.
Given how hard it is to look at TT1, I just made sure all the dampers were backed out and touched the mirror frame to verify that it was freely swinging. I leveled TT1 with the lower frame adjustment screw by looking at the spot position on MMT1. Once it was level, we adjusted the EPICS biases in yaw to get it centered in yaw on MMT1.
I then adjusted the screws on MMT1 to get the beam centered at MMT2, and did the same at MMT2 to get the beam centered vertically at TT2.
I put the target at PRM and the double target at BS. I loosened TT2 from it's base so that I could push it around a bit. Once I had it in a reasonable position, with a beam coming out at PR3, I adjusted MMT1 to get the beam centered through the PRM target. I went back and checked that we were still centered at MMT1. We then adjusted the pitch and yaw of TT2 to get the transmitted beam through the BS targets as clear as possible.
At this point we stopped and closed up. Tomorrow first thing AM we'll get our beams at the ETMs, try to finalize the input alignment, and see if we can do some in-air locking.
The plan is still to close up at the end of the week.
Just for reference! The changes made to the TT matrix in order to fix the polarity problem:
The old matrix values are mentioned in elog!
PIT YAW New
Pit slider | -100 -100 | UL
0 | -100 100 | LL
Yaw slider | 100 -100 | UR
0 | 100 100 | LR
[Jamie, Jenne, Manasa]
Yesterday's goal was to get the input beam centered on the PRM, the BS and ETMY simultaneously.
Steve helped us remove the ETMY door first thing in the morning. We then iterated with TT1, MMT1 and TT2 to try to get the beam centered on all the optics. We were using MMT1 instead of TT1 for a while, so that we could keep TT1 in the center of its range, so that we had more range to use once we pump down. Also, at one point, the beam was high on PRM, centered on BS, and high on ETMY, so Jamie poked PR3 a little bit. This helped, although we closed up for lunch / group meeting soon after, so we didn't finalize any alignment stuff.
We decided to leave the rest of the full IFO alignment alone until after the PRM-flat test.
We had to work on redesigning the oplev layout in BSC when I found that the positions of the mirrors were clipping IPPOS and the green beam while updating the CAD layout.
To avoid any clipping, the prm oplev beam is steered into the vacuum by an oplev mirror and out of vacuum through 3 steering mirrors. The table weights had to be moved to allow room for the oplev mirrors. Hence table had to be re-leveled. I will update the CAD drawing with the current position of the mirrors and will reconfirm that the new mirrors are not in the way of any of the beams. In-vac photos are updated in picasa.
Jenne and I got the half PRC flashing. We could see flashes in the PRM and PR2 face cameras.
We took out the mirror in the REFL path on the AP that diverts the beam to the REFL RF pds so that we could get more light on the REFL camera. Added an ND filter to the REFL camera so as not to saturate.
We tweaked up the alignment of the half PRC a bit. Koji started by looking at the REFL and POP DC powers as a function of TT2 and PRM alignment.
He found that the reflected beam for good PRC transmission was not well overlapped at REFL. When the beam was well overlapped at REFL, there was clipping in the REFL path on the AS table.
We started by getting good overlap at REFL, and then went to the AS table to tweak up all the beams on the REFL pds and cameras.
This made the unlocked REFL DC about 40 count. This was about 10mV (=0.2mA) at the REFL55 PD.
This amazed Koji since we found the REFL DC (of the day) of 160 as the maximum of the day for a particular combination of the PRM Pitch and TT2 Pitch. So something wrong could be somewhere.
We then moved to the ITMX table where we cleaned up the POP path. We noticed that the lens in the POP path is a little slow, so the beam is too big on the POP PD and on the POP camera (and on the camera pick-off mirror as well).
We moved the currently unused POP55 and POP22/110 RFPDs out of the way so we could move the POP RF PD and camera back closer to the focus. Things are better, but we still need to get a better focus, particularly on the POP PD.
We found two irides on the oplev path. They are too big and one of these is too close to the POP beam. Since it does not make sense too to have two irides in vicinity, we pulled out that one from the post.
Other things we noticed:
After the alignment work on the tables, we started locking the cavity. We already saw the improvement of the POPDC power from 1000 cnt to 2500 cnt without any realignment.
Once PRM is tweaked a little (0.01ish for pitch and yaw), the maximum POPDC of 6000 was achieved. But still the POP camera shows non-gaussian shape of the beam and the Faraday camera shows bright
scattering of the beam. It seems that the scattering at the Faraday is not from the main beam but the halo leaking from the cavity (i.e. unlocking of the cavity made the scattering disappeared)
Tomorrow Jenne and I will go into BS to tweak the alignment of the TEMP PRC flat mirror, and into ITMX to see if we can clean up the POP path.
Yuta, Manasa, Jamie, Jenne, Steve, Rana
Starting this morning, we removed the temporary half PRC mirror in front of BS and started to align the IFO in prep for an in-air lock of the PRMI.
This morning, using the new awesome steerable active input TTs, Jenne and I centred the beam on PRM, PR2/3, BS, ITMY and ETMY.
After lunch, Yuta and Manasa aligned the Y ARM, by looking at the multi-pass beam. The X-end door was still on, so they roughly aligned to the X ARM by centring on ITMX with BS. They then got fringes at the BS, and tweaked the ITMs and PRM to get full fringes at BS.
We're currently stuck because the REFL beam appears to be clipped coming out of the faraday, even though the retro-reflected beam from PRM is cleanly going through the faraday output aperture. The best guess at the moment is that the beam is leaving MC at an angle, so the retro-reflected beam is coming out of the faraday at an angle. We did not center spots on MC mirrors before we started the alignment procedure today. That was dumb.
We may be ok to do our PRMI characterization with the clipped REFL, though, then we can fix everything right before we close up. We're going to need to go back to touch up alignment before we close up anyway (we need to get PR2 centered).
Yuta and Manasa are finishing up now by making sure the AS and REFL beams are cleanly existing onto the AS table.
Tomorrow we will set up the PRM oplev, and start to look at the in-air PRMI. Hopefully we can be ready to close up by the end of the week.
We should check MC spot positions to see what they are.
Also, I'm not thrilled about the idea of a clipped REFL beam. Haven't we played that game before, and decided it's a crappy game? Can we recenter the MC, and recover quickly with TT1?
Lot's of alignment work, still no AS beam. REFL is clipped by Faraday output aperture......
Our guess is that this is because we skipped MC centering.
Alignment procedure we took:
1. AM work: Aligned input beam using TT1/TT2
such that the beam hits ETMY and ITMY at the center.
2. Coarsely aligned ITMY
such that the ITMY retro-reflected beam hits BS at the center.
3. Aligned ETMY (we didn't actually move ITMY)
such that Y arm flashes.
This tells you that ITMY is aligned well to the incident beam.
4. Aligned BS
such that the beam hits ITMX at the center.
5. Aligned ITMX
such that the ITMX retro-reflected beam hits BS at the center.
At this point, we saw MI fringes at AS port.
6. Fine alignment of ITMX:
MI reflected beam was not overlapping in front of BS after it was reflected by PRM.
We used this longer REFL path to tune alignment of ITMX to ITMY reflected beam.
We saw MI fringe at REFL port coming out of the chamber, but it was clipped.
7. Aligned PRM
by looking at REFL beam from PRM on the back face of Faraday (video FI_BACK).
We fine tuned the alignment such that PRM retro-relfected beam hits BS at the center and REFL beam from PRM overlaps with the MI fringes at the back face of Faraday.
8. Clipping of REFL at the Faraday output aperture:
We confirmed that the shape of the REFL beam from PRM was OK at the back face of Faraday. But some how, it was clipped at the output aperture. So, REFL beam coming out of the chamber is clipped now.
9. Tried to get AS beam out of the chamber:
We tweaked steering mirrors after SRM to get AS beam out of the chamber. But, we lost the AS beam between the very last folding mirrors (OMPO and OM6) in the OMC chamber......
1. Why clipping at the Faraday output aperture?
In principle, if PRM reflects the incident beam at normal incidence, it should pass the Faraday unclipped. But it's not!
Our guess is that the incident beam does not go well centered through the apertures of the Faraday. I think we have to do MC centering to get good pointing to the Faraday.
We also see that MI fringe at the back face of the Faraday is at the edge of its aperture, after all of these alignment work (we even used Y arm!). This tells you that some thing is wrong.
2. Why did you guys lose the AS beam?
AS beam is too weak after reflecting off of OMPO. The beam was neither visible on IR cards nor IR viewers. The beam is weaker than usual because PMC transmission is ~0.7 and MC REFL is getting high (~ 0.7). We didn't want to realign MC after all of this work today.
Tomorrow (my suggestion):
1. Align PMC (for higher power).
2. MC centering.
3. Input beam steering using TTs and redo the same alignment procedure (it shouldn't take longer than today).
==> Center beam on PR2 (Added by Manasa)
4. Maybe we should better check PRM reflection at REFL port after the Faraday, before doing the full alignment work.
5. Align AS, REFL, POP PDs/cameras.
6. Setup PRM/BS/ITMX/ITMY oplevs.
7. Balance the coils on these mirrors.
8. Lock PRMI.
What needs to be done before pumping down:
1. PRMI characterization: PR gain and g-factor
How can we do the g-factor measurement? Use additional laser? Kakeru method (elog #1434; we need to calibrate mirror tilt to do this)?
2. Glitch study in PRMI locking. If still glitchy, we have to do something. How is beam spot motion? (elog #6953)
3. Fine alignment of the flipped PR2.
4. Fine alignment of IFO using both arms.
We need to calculate whether this level of astigmatism is expected from the new active TT mirrors, but I claim that the beam is not clipped.
As proof, I provide a video (PS, why did it take me so long to be converted to using video capture??). I'm just showing the REFL camera, so the REFL beam as seen out on the AS table. I am moving PRM only. I can move lots in pitch before I start clipping anywhere. I have less range in yaw, but I still have space to move around. This is not how a clipped beam behaves. The clipping that I see after moving a ways is coincident with clipping seen by the camera looking at the back of the Faraday. i.e. the first clipping that happens is at the aperture of the Faraday, as the REFL beam enters the FI.
Also, I'm no longer convinced entirely that the beam entering the Faraday is a nice circle. I didn't check that very carefully earlier, so I'd like to re-look at the return beam coming from TT1, when the PRM is misaligned such that the return beam is not overlapped with the input beam. If the beam was circular going into the Faraday, I should have as much range in yaw as I do in pitch. You can see in the movie that this isn't true. I'm voting with the "astigmatism caused by non-flat active TT mirrors" camp.
Let's wait for astigmatism calculation.
In either case(clipping or astigmatism), it takes time to fix it. And we don't need to fix it because we can still get LSC signal from REFL.
So why don't we start aligning input TTs and PRMI tomorrow morning.
Take the same alignment procedure we did yesterday, but we should better check REFL more carefully during the alingment. Also, use X arm (ETMX camera) to align BS. We also have to fix AS steering mirrors in vacuum. I don't think it is a good idea to touch PR2 this time, because we don't want to destroy sensitive PR2 posture.
Calculations need to be done in in-air PRMI work:
1. Explanation for REFL astigmatism by input TTs (Do we have TT RoCs?).
2. Expected g-factor of PRC (DONE - elog #8068)
3. What's the g-factor requirement(upper limit)?
Can we make intra-cavity power fluctuation requirement and then use PRM/2/3 angular motion to break down it into g-factor requirement?
But I think if we can lock PRMI for 2 hours, it's ok, maybe.
4. How to measure the g-factor?
To use tilt-and-measure-power-reduction method, we need to know RoC of the mirror you tilted. If we can prove that measured g-factor is smaller than the requirement, it's nice. We can calculate required error for the g-factor measurement.
After using alamode to calculate the round-trip mode of the beam at the Faraday exit after retro-reflection form the PRM, I'm not able to blame the MMT and TT curvature for the beam ellipticity.
I assume an input waist at the mode cleaner of [0.00159, 0.00151] (in [T, S]). Propagating this through the MMT to PRM, then retro-reflecting back with flat TTs I get
w_t/w_s = 0.9955, e = 0.0045
If I give the TTs a -600 m curvature, I get:
w_t/w_s = 1.0419, e = 0.0402
That's just a 4% ellipticity, which is certainly less than we see. I would have to crank up the TT curvature to -100m or so to see an ellipticity of 20%. We're seeing something that looks bigger than 50% to me.
Below are beam size through MMT + PRM retro-reflection, TT RoC = -600m:
[Yuta, Manasa, Jenne, Jamie, Steve]
0. Measured MC centering (off by 5mrad) before getting the doors off.
1. Got the TTs to 0.0 in pitch and yaw.
2. Using the MMTs, the beam was centered on the TTs.
3. TT1 was adjusted such that the incident beam was centered at PRM (with target).
4. TT2 was adjusted such that the beam passed through the center of BS (with target).
5. Centered the beam on PR2 by sliding it on the table.
6. Moved PR2 and tweaked TT2 to center the beam on ITMY and BS respectively.
7. Using TTs, we got the beam centered on ETMY while still checking the centering on ITMY.
8. ITMY was adjusted such that it retro-reflected at the BS.
9. ETMY was aligned to get a few bounces in the arm cavity.
10. Centered on ITMX by adjusting BS and then tweaked ITMX such that we retro-reflected at BS.
11. At this point we were able to see the MI fringes at the AS port.
12. Tweaked ITMX to obtain reflected MI fringes in front of MMT2.
13. By fine adjustments of the ITMs, we were able to get the reflected MI to go through the faraday while still checking that we were retro-reflecting at the BS.
14. Tweaked the PRM, such that the PRM reflected beam which was already visible on the 'front face back face of faraday' camera went through the faraday and made fine adjustments to see it fringing with the reflected MI that was already aligned.
15. At this point we saw the REFL (flashing PRMI) coming out of vacuum unclipped and on the camera.
16. Started with alignment to get the AS beam out of vacuum. We tweaked OM1 and OM2 (steering mirrors in the ITMY chamber) to center the beams on OM4 and OM3 (steering mirrors in the BSC) respectively.
17. We then adjusted steering mirrors OM5 and OM6 (in the OMC chamber) such that the beam went unclipped out of vacuum.
18. Note that we took out the last steering mirror (on the AS table) in front of the AS camera, so that we can find the AS beam easily. This can be fixed after we pump down.
0. REFL still looks like an egg, but leave it .
1. Align PRMI (no more in-vac!) .
2. Align POP/REFL/AS cameras and PDs.
3. Setup PRM/BS/ITMX/ITMY oplevs.
4. Balance the coils on these mirrors.
5. Lock PRMI.
Yuta and Manasa, you guys are awesome!
Small, inconsequential point: The camera image in the upper right of your video is the *back* of the Faraday in our usual nomenclature. The camera is listed in the videoswitch script as "FI_BACK". The camera looking at the "front" of the Faraday is just called "FI".
We set up POP camera and POPDC PD, and centered REFL PDs.
We also tried to center AS55 PD, but AS55 seems to be broken.
What we did:
1. POP path alignment:
Shot green laser pointer from ITMX table at where POPDC PD was sitting and centered green beam at optics in the POP path. Steered POPM1/M2 mirrors in the ITMX chamber to make green laser overlap with the PRM-PR2 beam as far as I can reach from ITMX chamber. We removed some ND filters and a BS for attenuating POP beam because POP power was somehow so low. Currently, POP is pick-off of the beam which goes from PRM to PR2.
2. POP camera and PD:
We first used camera to find the beam at where POPDC PD was sitting because it is much easier to find focused beam. Put an iris in front of the camera, and put POP DC behind it. Steered a mirror in front of PD to maximize DC output.
3. REFL PDs:
Steered mirrors in the REFL path to center the beam and maximized DC outputs, as usual.
AS55 was not responding very much to the flashlight nor AS beam. C1:LSC-ASDC_OUT looked funny. By swapping the ribbon cables of AS55, REFL55, and REFL165, I confirmed that AS55 PD itself is broken. Not the ribbon cable nor PD circuit at LSC rack. I don't know what happened. AS55 was working on Feb 8 (elog #8030).
We aligned PRMI coarsely. POP(right above) looks much better than before. REFL (left below) still looks elliptic, but ellipticity differs with the position on the camera. Some astigmatism is happening somewhere. AS (right below) looks pretty nice with MI aligned.
1. Fix AS55? Or replace it with POP55 PD, which is currently unused.
2. Confirm we are getting the right error signals or not, and lock PRMI.
We will start preparing for pumping down. Main goal for this is to demonstrate PRFPMI using ALS.
Here are to-dos before we pump down.
Feb 18 eveing
- check input beam and Y arm alignment again
- IPPOS/IPANG alignment
- check all oplevs
Feb 19 morning
- open ETMX chamber heavy door
- align BS to X end
- adjust OSEM values (added by YM)
- center beam on all AS optics
- make sure AS/REFL is clear
- take picture of flipped PR2 (added by YM)
- make sure green is not clipped by new PRM oplev mirrors (added by YM)
- center all oplevs
Feb 19 afternoon - Feb 20 morning
- close PSL shutter
- close all heavy doors and put the access connector back
- start pumping down
Feb 20 evening
- start aligning IFO
I undertook the investigation of the AS55 PD. I found the PD is not broken.
I tested the PD on the PD test bench and it works just fine.
I attatched the characterization result as there has been no detailed investigation of this PD as far as I remember.
The transimpedance gain at 55MHz is 420Ohm, and the shotnoise intercept current is 4.3mA.
We aligned IPPOS, IPANG and all OPLEVs (except for ETMX and SRM).
1. First aligned the IPPOS by tweeking the steering mirrors inside the BS chamber.
2. Aligned the IPANG by tweeking the steering mirrors inside the BS chamber and ETMY chamber.
3. Aligned the OPLEVS for the BS and PRM was done by tweeking the steering mirrors inside the BS chamber and checked that OPLEV beams were not clipped.
4. Centred the OPLEV beams for the ITMY and ETMY.
5. For the OPLEV of ITMX the alignment was done by tweeking the steering mirrors inside the ITMX chamber.
[Yuta, Sendhil, Jamie, Jenne, Rana]
1. After the MC centering, we tried to align the IFO using IPPOS and IPANG as reference. This did not recover the alignment perfectly. We were clipping at the BS aperture. Using TTs, we centered the beam at BS and PRM.
2. Using TTs, the beam was centered at ITMY and ETMY.
3. IPPOS and IPANG mirrors in-vacuum were aligned and were centered at the out-of-vacuum optics.
4. We checked the centering of the beam on optics in the BS and ITMY chamber. (Yuta will make an elog with the layout)
5. We retro-reflected ITMY at the BS and aligned ETMY such that we saw a couple of bounces in the arm cavity.
6. Using BS, the beam was steered to go through the center of ITMX and ETMX.
7. At this point we were able to see the MI fringes at the AS port.
8. We made fine alignments to the ITMX such that we saw MI reflected at the Farday.
9. We retro-reflected ITMX and aligned ETMX to see the beam bounce at the ITMX.
10. We aligned PRM such that PRC flashes. But we were not happy with the flashes (they were in higher order modes). We suspect that minor tuning of the input pointing might be necessary.
11. We closed for the day
I attached clipping/centering checklist for the alignment.
Blue ones are the ones we checked today. Red ones should be checked tomorrow. Circles indicate centering on the optics, rectangles indicate clipping check, and arrows indicate retro-reflecting or bounces.
We found mis-centering on MMT1, PR2 and SR3 tonight (by ~0.5 beam diameter). They are also indicated.
I think we don't want to touch MMT1 and PR2 anymore, because they change input beam pointing.
I'm a little bit concerned about high beam on SR3, because we had PRC flashing in vertical higher order modes. We also see ETMX slider values high in pitch (~ 5.4).
Also, the diameter of ETMX reflected beam on ITMX looked larger and dimmer than ITMX transmitted beam, which doesn't seem reasonable.
Wednesday, Feb 20:
- tweak TT1/TT2 and PRM so PRC flashes
- re-check Yarm/Xarm bounces
- center beam on all AS optics, starting from SR2
- make sure REFL and AS is clear
- check if TRY/TRX are coming out from the ends
- check beam centering on mirrors in IMC/OMC chamber as far as you can reach
- inject green from both ends
- make sure green beams are not clipped by mirrors on BS chamber, IMC/OMC chamber
- re-center all oplevs, with no clipping
- check all OSEM values
- take pictures of flipped PR2 and input TTs (and everything)
- close all heavy doors and put the access connector back
Thursday, Feb 21:
- make sure we can lock PRMI
- start pumping down when Steve arrives
After in-vac alignment work last night, PRC is flashing brighter than PRMI alignment last week.
My hypothesis is that "we aligned PRM to junk MI fringe last week". Possibly, we used MI fringe caused by AR reflection of ITMs, or MI fringe reflected from SRM.
PRC flashing last week (youtube, elog #8085, elog #8091)
PRC flashing this time (Lens in-front of AS camera was taken out)
My hypothesis can explain:
- why we had dimmer POP last week (flash in half-PRC was way brighter even when we had more attenuators (youtube))
- why I thought AS55 is broken (AS was too dim)
Be careful of junk beams.
I have updated the vacuum checklist for in vacuum alignment. Please take a look (https://wiki-40m.ligo.caltech.edu/vent/checklist) and see if I missed anything. My goal was to make it incredibly step-by-step so there can be no mistakes.
[Yuta, Manasa, Sendhil, Jenne, Steve, Jamie, Koji, Evan]
The interferometer is well-aligned, and ready for pump-down. The access connector is in place, as are the ETM heavy doors. We will do ITM and BS doors tomorrow, then begin pumping.
Before we redid the ITM pointing, I confirmed that I could see both POX and POY on their respective tables, on a camera, unclipped. I should check again quickly now that the ITM pointing has been finalized.
We went back to the arms, to perfect the ITM pointing. Input beam was already centered at ETMY. ETMY was pointing so that beam reflected to ITMY. ITMY was adjusted a few (less than 4?) steps of 1e-3 size, to make reflected beam hit center of ETMY.
BS was already pointing so beam hit center of ETMX. ETMX was pointing to hit center of ITMX. ITMX was adjusted a few (less than 4 again?) steps of 1e-3 size to make reflected beam hit center of ETMX.
Checked centering on AS path. AS beam comes out of the vacuum a little low, but this wasn't discovered until after the access connector was in place. We could adjust PZT3 (last AS mirror on BS table that sends beam over to OMC table), but we don't want to do this since we won't be able to re-confirm centering on the 3 mirrors on the OMC table.
Green beams (first Y, then X) were aligned using out-of-vac steering mirrors until beams were flashing in their respective arm cavities. Green Y is a little close to the edge of the bottom periscope mirror, on the "up" periscope. Since there is no steering between the arm and this periscope, fixing it would require moving the periscope. We leave this to the next vent, when we finally install the BS table extension. We were flashing a higher order yaw mode (5ish nodes) for the Y arm, and the very edge of the higher order mode on one side was a little bit clipped after reflecting off the steering mirror on the OMC table. This is happening because that mirror is in the mount backwards (so we have access to the knobs). We are confident that the straight-through beam is well centered on that mirror, so once we get it aligned to TEM00, there will be no clipping. We then did the X arm green, which was flashing a pitch higher order mode (again 5ish nodes). The very edge of the higher order mode is clipping a little bit on the top mirror of the "down" periscope on the IMC table, but again the straight through beam is okay, and we're confident that the TEM00 mode will make it unclipped. We could have touched some steering mirrors on the BS table, but since this was once upon a time well aligned, we don't want to futz with it.
Corner oplevs are all centered on their QPDs. (The ETM oplevs were centered a few days ago).
Access connector and ETM doors are on.
The last 3 vertex doors will go on tomorrow when Steve gets in, and then we'll start pumping.
There are no in-vac PZTs that need to be turned on (we've been using the output steering PZTs as non-energized fixed mirrors for some time), so we can lock at our leisure tomorrow afternoon.
Manasa and I are trying to get the AS beam onto the AS camera with a focusing lens. Currently, the mirror immediately preceding the camera has been removed and the camera and lens are sitting directly behind the BS.
After aligning IFO and putting the access connector on, we also centered IPANG/IPPOS and all oplevs (except SRM).
To avoid clipping of PRM/BS oplevs, we re-arranged oplev steering mirrors on BS table.
What we did:
1. Checked IPANG comes out unclipped after putting on the access connector.
2. Centered IPANG on its QPD.
3. Checked oplevs beams for ITMX/ITMY centered on in-vac mirrors, and centered them on their QPDs.
4. Checked IPPOS beam is centered on the mirrors inside BS chamber, and centered IPPOS on its QPD.
5. Tweaked oplev mirrors on BS chamber to make PRM/BS oplev beam unclipped and centered on mirrors, and centered them on their QPDs. To avoid clipping of oplev beams in BS table, we re-arranged oplev steering mirrors on BS table (outside the vaccum).
QPD values, IFO_ALIGN/MC_ALIGN screens, OSEM values attached.
- IR incident beam and IFO aligned
- X/Y end green coming out to PSL table (in higher order modes)
- IPANG/IPPOS available
- All oplevs available
- AS/REFL/POP cameras ready
- access connector, ETMX/ETMY heavy doors on
- ITMX/ITMX/BS heavy doors are not on
- AS/REFL/POP PDs not centered
- POX/POY/TRX/TRY not aligned
- AS beam coming out of the OMC chamber low by ~ 1 beam diameter (my bad)
- Align AS/REFL/POP PD and lock PRMI
- Take pictures of ITMX/ITMY/BS stacks
- Put heavy doors on ITMX/ITMY/BS chambers
- Start pumping down
Please confirm the SRM OL beam is not too bad and also find where the mis-aligned SRM puts its beam. WE want to be sure that there is not too much unwanted scattering from SRM into the PRFPMI.
Currently, SRM is misaligned in pitch so that SRM reflected beam hits on the top edge of SR3 (not on the mirror, but on the cage holding the mirror).
We also confirmed that SRM oplev beam is coming out from the chamber unclipped, and centered on QPD when SRM is "aligned".
Blue ones are the ones we checked yesterday.
Green ones are the ones we checked today.
Red ones are the ones we couldn't check.
We noticed mis-centering on green optics and partial clipping of higher order modes, but we did not touch any green optics in-vac. This is because green beam from Y end and X end has different spot positions on the green optics after periscopes. We confirmed that direct green beam from ends are not clipped.
I believe we have checked everything important. Any other concerns?
Is the beam going towards the OMC going to cause backscatter because of uncontrolled OMC or can we park that beam somewhere dark?
I'm not sure about the OMC situation at 40m. I think there are no direct beam reflected back into IFO from OMC path. There must be some backscatter, but we have to open OMC chamber again to put a beam dump.
I don't think we want to put one in OMC path for this pump-down, but we can put a beam dump to dump reflected beam from mis-aligned SRM tomorrow, if available.
We aligned Y arm to Y green and tweaked TT1/TT2 to get IR locked in Y arm.
1. Align ETMY/ITMY to maximize TEM00 green transmission to PSL table. We reached ~240 uW.
2. Aligned PRM and TT2 so that PRM reflected beam go through FI and get ITMY-PRM cavity flashing. This is to coarsely align input pointing to Y arm. After this alignment, we got tiny Y arm flash. Input pointing to IPANG QPD was lost.
3. Aligned TT1/TT2 to maximize TRY in TEM00. We reached ~0.92.
I was struggling with finding Y arm flash. I was using IPPOS/IPANG as input pointing reference, and slider values (C1:SUS-(ITMY|ETMY)_(PIT|YAW)_COMM) or OSEM values (C1:SUS-(ITMY|ETMY)_SUS(PIT|YAW)_IN1) before pumping for Y arm alignment reference. But it was a lot more easier if Y arm is aligned to green and having Yarm cavity axis assured.
- X arm flash in IR
- Steer X end green
- If X arm or AS looks bad, adjust IR input pointing and Y arm alignment. We have to steer Y end green afterwards.
That's good news. I was ready to give up and say we should vent and remove the baffles. It will be interesting if you can find out how much the sensors and OL and IPANG are off from their pre-pump values. We should think about how to have better references.
Also, what is the story with the large drift we are seeing in IPANG?
[Jenne, Evan, Yuta]
After Y alignment, X arm is aligned to IR and we got both arms locked in IR.
There's some dift (input pointing?) and this made aligning both arms tough. I will elog about it later.
Attached is ETMYF. ETMXF, ITMYF, ITMXF when both arms are locked by IR.
1. Algined BS/ITMX to get MI fringe in AS. We got X arm flashing at this point.
2. Use BS/ITMX/ETMX to get TRX maximized, without losing good MI fringe in AS. We reached 0.75.
3. There was clipping of TRX beam at Xend optics. Since whole IFO alignment is started from Y green, this clipping is because of poor Y green pointing. But we needed clear TRX for aligning Xarm, so we re-arranged Xend TRX path to avoid clipping.
X arm issues:
- Beam motion at TRX is larger than TRY. Turning off clean table air didn't help. Maybe we need BS oplev on or ETMX coil gain balancing.
- X green scatters into TRX PD and ETMXT camera. Fix them.
Both arms are aligned starting from Y green.
We have all beams unclipped except for IPANG. I think we should ignore IPANG and go on to PRMI locking and FPMI locking using ALS.
IPANG/IPPOS and oplev steering mirrors are kept un-touched after pumping until now.
Current alignment situation:
- Yarm aligned to green (Y green transmission ~240 uW)
- TT1/TT2 aligned to Yarm (TRY ~0.86)
- BS and Xarm alined to each other (TRX ~ with MI fringe in AS)
- X green is not aligned yet
- PRMI aligned
Current output beam situation:
IPPOS - Coming out clear but off in yaw. Not on QPD.
IPANG - Coming out but too high in pitch and clipped half of the beam. Not on QPD.
TRY - On PD/camera.
POY - On PD.
TRX - On PD/camera.
POX - On PD.
REFL - Coming out clear, on camera (centered without touching steering mirrors).
AS - Coming out clear, on camera (centered without touching steering mirrors).
POP - Coming out clear, on camera (upper left on camera).
Optic Pre-pump(pit/yaw) PRFPMI aligned(pit/yaw)
ITMX -0.26 / 0.60 0.25 / 0.95
ITMY -0.12 / 0.08 0.50 / 0.39
ETMX -0.03 / -0.02 -0.47 / 0.19
ETMY 0.37 / -0.62 -0.08 / 0.80
BS -0.01 / -0.18 -1 / 1 (almost off)
PRM -0.34 / 0.03 -1 / 1 (almost off)
All values +/- ~0.01. So, oplevs are not useful for alignment reference.
Optic Pre-pump(pit/yaw) PRFPMI aligned(pit/yaw)
ITMX -1660 / -1680 -1650 / -1680
ITMY -1110 / 490 -1070 / 440
ETMX -330 / -5380 -380 / -5420
ETMY -1890 / 490 -1850 / 430
BS 370 / 840 360 / 800
PRM -220 / -110 -310 / -110
All values +/- ~10.
We checked that if there's ~1200 difference, we still see flash in Watec TR camera. So, OSEM values are quite good reference for optic alignment.
On Saturday, when Rana, Manasa, and I are trying to get Y arm flash, we noticed IPANG was drifting quite a lot in pitch. No calibration is done yet, but it went off the IPANG QPD within ~1 hour (attached).
When I was aligning Yarm and Xarm at the same time, TRY drifted within ~1 hour. I had to tweak TT1/TT2 mainly in yaw to keep TRY. I also had to keep Yarm alignment to Y green. I'm not sure what is drifting so much. Suspects are TT2, PR2/PR3, Y arm and Y green.
I made a simple script(/opt/rtcds/caltech/c1/scripts/Alignment/ipkeeper) for keeping input pointing by centering the beam on IPPOS/IPANG using TT1/TT2. I used this for keeping input pointing while scanning Y arm alignment to search for Y arm flash this weekend (/opt/rtcds/caltech/c1/scripts/Alignment/scanArmAlignment.py). But now we have clipped IPANG.
So, what's useful for alignment after pumping?:
Optic alignment can be close by restoring OSEM values. For input pointing, IPPOS/IPANG are not so useful. Centering the beam on REFL/AS (POP) camera is a good start. But green works better.
We want to measure the g-factor of the PRC using the beat note of the main laser with an auxiliary NPRO laser.
We are going to phase lock the NPRO to the main laser (taking it from POY) and then we will inject the NPRO through the AS edge of the ITMY.
Today Sendhil and I installed the auxiliary laser on the ITMY table moving it from the AS table.
We also installed the beam steering optics, except the BS which will launch the beam through the AR edge of the ITMY.
To do: install the BS, take the POY beam and mix it with the auxiliary laser on a photodiode to phase lock the two lasers, do better calculations for the mode matching optics to be used for the auxiliary laser beam.
[Jenne, Manasa, Yuta]
We temporarily centered the beam on IPANG to see input pointing drift. From eyeball, drift was ~ 0.1 mrad/h in pitch.
What we did:
1. Aligned TT1/TT2 and aligned input pointing to Yarm.
2. Tweaked TT2 in pitch to center the beam on the first steering mirror of IPANG path. We still saw Yarm flash in higher order modes at this point. Before tweaking, the beam was hitting at the top edge.
3. Centered the beam on IPANG QPD.
4. Moved IPPOS first steering mirror because IPPOS beam was not on the mirror (off in yaw, on mirror edge). Also, IPPOS beam was coming out clipped in yaw.
5. Centered the beam on IPPOS QPD. We put lens in the path to focus the beam on the QPD.
6. Left input pointing untouched for 4 hours.
7. Restored TT2 again. We tried to align Y arm with IPANG available, but it was not possible without touching TRY path and AS was also clipped.
Below is the trend of IPANG sum, X, and Y. IPANG Y (IBQPD_Y) drifted by ~0.8 counts in 4 hours. IPANG is not calibrated yet, but Jenne used her eyeball to measure beam position shift on IPANG steering mirror. It shifted by ~2 mm. This means, input pointing drifts ~0.1 mrad/h in pitch.
Compared with yaw, pitch drift is quite large considering beam size at ETMY(~5 mm). We can monitor input pointing drift in weekends get longer trend.
- IPANG and IPPOS are both changed from the state before pumping.
I'm working on getting the input beam centered on the Yarm optics. To do this, I measured the spot positions, move the tip tilts, realign the cavity, then measure the new spot positions. While doing this, I am also moving the BS and Xarm optics to keep the Xarm aligned, so that I don't have to do hard beam-finding later.
Here is the plot of spot measurements today. The last measurement was taken with no moving, or realigning, just several hours later after speaking with our Indian visitors. I'm closer than I was, but there is more work to do.
Checking the drift in input pointing (TT2 is the main suspect)
I have centered IPPOS and the 2/3 part of IPANG that comes out of vacuum to the QPDs to see the drift in input pointing over the weekend or atleast overnight.
If anybody would be working with the IFO alignment over the weekend, do so only after recording the drift in IPANG and IPPOS or if you will be working later tonight, center them ion the QPDs before leaving.
I centered ipang and ippos on the QPDs (using only the steering mirrors) and wanted to see the drift over the weekend.
1. IPANG has drifted (QPD sum changed from -6 to -2.5); but it is still on the QPD.
2. IPPOS does not show any drift.
3. In the plot: The jump in IPANG on the left occured when I centered the beam to the QPD and that on the right is from the 4.7 earthquake and its aftershocks this morning.
1. Do we need to worry about this drift?
2. Which of the two TTs is resposible for the drift?
3. Do the TTs tend to drift in the same direction everytime?
P.S. The TTs were not touched to center on IPANG and IPPOS. The last time they were touched was nearly 6 hours before the centering. So the question of any immediate hysteresis is ruled out.
Spot centering on Y arm - DONE!
1. I went back to the IFO alignment slider positions from Friday. The Y arm was flashing in HOM because the earthquake this morning tripped all suspensions and the slider values were not real. X arm did not have any flashes.
2. Y arm aligned using TT1 and TT2. Spot centering measured using Jenne's A2L_Yarm script.
Pitch 6.48 4.39
Yaw -7.42 -3.135
3. I started centering in pitch. I used the same in-vac alignment method (down on TT1 and up on TT2 in pitch) and measured spot positions.
4. When the spot positions were centered in pitch, I started with yaw alignment.
5. I had to use TT1 to center on ITMY and move TT2 and ITMY to center on ETMY.
6. Spot positions after centering:
Pitch -1.22 -1.277
Yaw 0.42 -0.731
7. I wanted to go back and tweak the pitch cenetering; but framebuilder failed and dataviewer kept loosing connection to fb
AS seems clipped. Although it could be because of the misaligned BS.
IPANG was centered on the QPD, but it is so clipped, that I'm not sure we can trust it. Max sum right now is -4, rather than the usual -8 or -9.
Once fb is fixed, we should align the X-arm which will be followed by green alignment.
Over the last few weeks, it has been observed that there is some strong seismic activity that starts at around 9PM everyday and goes on for a couple of hours. It seems unlikely that it is our geologist neighbour (Jenne met with the grad student who works on the noisy experiment).
Steve just told those of us in the control room that the custodian who goes into the IFO room regularly steps on the blue support beams to reach the top of the chambers to clean them. Since we have seen in the past that stepping on the blue tubes can give the tables a bit of a kick, this could help explain some of the drift, particularly if it was mostly coming from TT2. The custodian has promised Steve that he won't step on the blue beams anymore.
This doesn't explain any of the ~1 hour timescale drift that we see in the afternoons/evenings, so that's still mysterious.
Tega and I went in to adjust the POP being in the ITMX Table. The beam entered the table high, so we adjusted the this by adding mirrors (The highlighted in Turqoise are mirrors which adjust the pitch of the beam). All the mirrors are set and we are now in the process of adjusting the PD.
Got POP beam centered on camera and nominally on the two PDs. Attachment #1 shows "carrier" camera.
Yehonathan and I attempted to align the LO2 beam today through the BS chamber and ITMX Chamber. We found the LO2 beam was blocked by the POKM1 Mirror. During this attempt, I tapped TT2 with the Laser Card. This caused the mirror to shake and dampen into a new postion. Afterwards, when putting the door back on ITMX, one of the older cables were pulled and the insulation was torn. This caused some major issues and we have been able to regain either of the arms to their original standings.
[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.