Jamie has arranged for phase map measurements this afternoon, so I will take the 6 dichroic LaserOptik optics over to Downs at 1:15 this afternoon.
Team Jamie+Nic will lead the effort to clamp down dog clamps as placement markers for all 4 in-vac passive TTs, and then pull all 4 TTs out of the chambers. They plus Den will move the TTs to the Cleanroom, and will start to install the new pitch alignment hardware.
When I return with the optics, we will install them in the TTs and re-balance them. Then we can put them back in the chambers and get back to work on alignment.
After we re-install the TTs, we will need to check the leveling of all 3 corner tables, just to be sure.
Raji took the optics over. They were all measured at 0 deg incidence angle, although we will use them at the angles required for the recycling folding mirrors. Here's the summary from GariLynn:
In general all six pieces have a radius of curvature of around -700 meters.
I measured the transmitted power @1064nm on one of the LaserOptik mirrors labled SN6
Here is the data
The mirror is not a good reflector at 0 deg.
After lunch we began where Raji and Jamie had left things. PR2 was unfortunately pitched down so far that it was almost hitting the table just in front of PR3. I loosened the 4 clamp screws that hold the wire clamp assembly to the mirror holder, and tapped it back and forth until I was within hysteresis range, re-tightened, then tapped the top and bottom until we were at the correct beam height just in front of PR3. I also had to unclamp it from the table and twist the base a tiny bit, since the beam was closer to hitting the beam tube than the optic. Finally, however, PR2 is adjusted such that the beam hits the center of PR3.
Moving on to PR3, the pitch looked good while we were looking at the aperture placed near the face of ITMY, so we left that alone. The beam is off in yaw though. Several times I unclamped the tip tilt from the table, and twisted it one way or another, but every time when I tighten the dog clamps, I'm too far off in yaw. The beam points a little too far south of the center of ITMY, so we were putting the beam a little north of the center before I clamped it, but even tightening the screws in the same order, by the same amount each time, causes a different amount of slipping/twisting/something of the TT mount, so we never end up directly in the center of the ITM. It seems a little like a stochastic process, and we just need to do it a few more times until we get it right.
We left it clamped to the table, but not in it's final place, and left for JClub. On Monday morning we need to go back to it. As long as we're pretty close to centered, we should probably also have someone at ETMY checking the centering, because we need to be centered in both ITMY and ETMY.
We have not touched the SR tip tilts, so those will obviously need some attention when we get to that point.
Maybe we have already discarded this idea, but why not do the alignment without the MC?
Just lock the green beam on the Yarm and then use the transmitted beam through the ITMY to line up the PRC and the PZTs? I think our estimate is that since the differential index of refraction from 532 to 1064 nm is less than 0.01, using the green should be OK. We can do the same with the Xarm and then do a final check using the MC beam.
In this way, all of the initial alignment can be done with green and require no laser Goggles (close the shutter on the PSL NPRO face).
[Jamie, Jenne, Raji, with consultation from Nic, Ayaka and Manasa]
We went back and re-looked at the input alignment, and now we're "satisfied for the moment" (quote from Jamie) with the PRC alignment. Also, by adjusting the PR folding mirrors, we are almost perfectly aligned to the Yarm.
What we did:
Set PRM DC biases to 0 for both pitch and yaw.
Aperture was attached to PRM cage, double aperture was attached to BS cage, free-standing aperture was placed in front of PR2.
Adjusted PZT1, PZT2 such that we were centered on PZT2, and through apertures at PRM and PR2. This was mainly for setting beam height in PRC.
Checked centering on PZT1, MMT1, MMT2, PZT2.
Adjusted PRM pitch bias and PZT2 yaw such that REFL beam was retro-reflected from PRM.
Checked that REFL beam came nicely out of Faraday.
Checked that beam was still going through center of PRM aperture, and pitch height at PR2 was good.
Moved PR2 sideways until beam hit center in yaw of PR2.
Twisted PR2 such that beam was hitting center of PR3.
Moved and twisted PR3 (many times) so that beam went through BS input and output apertures, and through center of ITMY aperture.
Found that beam was just getting through black glass aperture at ETMY, top left corner, if looking at the face of ETM from ITM.
Locked down dog clamps on PR2.
This required some re-adjustment of PR3. Re-did making sure going through BS apertures and ITMY aperture, locked down PR3 dog clamps.
Found that we are centered in yaw at ETMY, a little high in pitch on ETMY.
Replaced all of the light doors, to take a break. 4 hours in bunny suits seemed like enough that we earned a break.
This all sounds more straighforward than it was. There was a lot of iteration, but we finally got to a state that we were relatively happy with.
What we will do:
Tweak PZT2 a *tiny* bit in pitch, ~0.5 mrad, so that the beam goes through the ETMY aperture.
See if we can align EMTY and ITMY to get multiple bounces through the Yarm.
Remove ETMX heavy door, steer BS such that we're getting through the center of an aperture at ETMX.
Align ETMX and ITMX such that we get multiple bounces through the Xarm.
Check SRM, AS path alignment.
Check REFL out of vac alignment.
Check other pickoffs.
Check all oplevs.
We have a open-sided 2" mirror mount that we are considering using for the POY pick-off mirror. This might help us get a little more clearance in the Y-arm of the Michelson. Problem is the mount is not steerable, so we need to determine if that's doable or not.
We tweaked PZT2, PZT1 (yaw only), and PR3 (pitch only) to get the beam ~centered on the BS aperture, the ITMY aperture, and the ETMY aperture.
After lunch I'll tweak up the MC alignment, since, although the spots are in the right places, the transmitted beam could be higher power. This will make it easier to check our pointing, especially since the ETMY spot is larger than our aperture, but the beam is dim.
We're getting there!
We looked at beam spots on ITMY and ETMY. We switched to smaller apertures on the other side of the rulers. For ITMY beam spot was 1mm below and 1mm south (right if you look in the direction ITMY -> ETMY) from the aperture center, for ETMY - 4 mm up and 3mm north from the aperture center. We made a correction for this using PZT 1 and 2. Now beam spots are in the middle of the apertures on ITMY and ETMY.
We tried to look at reflected beam from ETMY but it was hard to see the dependence between ETMY DC offset and reflected beam. We'll continue tomorrow.
More data on the transmission. Measured the tranmission as a funtion of incidence angle at 1064nm
jamie, nic, jenne, den, raji, manasa
We were doing pretty well with alignment, until I apparently fucked things up.
We were approaching the arm alignment on two fronts, looking for retro-reflection from both the ITMs and the ETMs.
Nic and Raji were looking for the reflected beam off of ETMY, at the ETMY chamber. We put an AWG sine excitation into ETMY pitch and yaw. Nic eventually found the reflected beam, and they adjusted ETMY for retro-reflection.
Meanwhile, Jenne and I adjusted ITMY to get the MICH Y arm beam retro-reflecting to BS.
Jenne and I then moved to the X arm. We adjusted BS to center on ITMX, then we moved to ETMX to center the beam there. We didn't both looking for the ETMX reflected beam. We then went back to BS and adjusted ITMX to get the MICH X arm beam retro-reflected to the BS.
At this point we were fairly confident that we had the PRC, MICH, and X and Y arm alignment ok.
We then moved on the signal recycling cavity. Having removed and reinstalled the SRC tip-tilts, and realigning everything else, they were not in the correct spot. The beam was off-center in yaw on SR3, and the SR3 reflected beam was hitting low and to the right on SR2. I went to loosen SR3 so that I could adjust it's position and yaw, and that when things went wrong.
Apparently I hit something BS table and completely lost the input pointing. I was completely perplexed until I found that the PZT2 mount looked strange. The upper adjustment screw appeared to have no range. Looking closer I realized that we somehow lost the gimble ball between the screw and the mount. Apparently I somehow hit PZT2 hard enough to separate from the mirror mount from the frame which caused the gimble ball to drop out. The gimble ball probably got lost in a table hole, so we found a similar mount from which we stole a replacement ball.
However, after putting PZT2 back together things didn't come back to the right place. We were somehow high going through PRM, so we couldn't retro-reflect from ITMY without completely clipping on the PRM/BS apertures. wtf.
Jenne looked at some trends and we saw a big jump in the BS/PRM osems. Clearly I must have hit the table/PZT2 pretty hard, enough to actually kick the table. I'm completely perplexed how I could have hit it so hard and not really realized it.
Anyway, we stopped at this point, to keep me from punching a hole in the wall. We will re-asses the situation in the morning. Hopefully the BS table will have relaxed back to it's original position by then.
Here is a two hour set of second trends of 2 sensors per mirror, for BS, PRM, ITMY and MC1. You can see about an hour ago there was a big change in the BS and PRM suspensions, but not in the ITMY and MC1 suspensions. This corresponds as best we can tell with the time that Jamie was figuring out and then fixing PZT2's mount. You can see that the table takes some time to relax back to it's original position. Also, interestingly, after we put the doors on ~10 or 20 minutes ago, things change a little bit on all tables. This is a little disconcerting, although it's not a huge change.
...Looks like the coating is out of spec at any angle for 1064nm. E11200219-v2
what's going on with those jumps on MC1? It's smaller, but noticeable, and looks like around the same time. Did the MC table jump as well?
more looking tomorrow.
But these jumps in the OSEMs are all at the level of 10-20 microns. Seems like that wouldn't be enough to account for anything; 20 microns / (pend length) ~ 50-60 microradians.
BS table and suspensions are fine.
The coating should have very low 1064nm p transmission at 45 degrees, which the plot seems to indicate that it does. That's really the only part of the spec that this measurement is saying anything about. What makes you say it's out of spec?
Ok, yes, sorry, the data itself does indicate that the transmission is way too high at 45 degrees for 1064 p.
Here's a plot of the BS, PRM, and MC1 suspension shadow sensor trends over the last 24 hours. I tried to put everything on the same Y scale:
There definitely was some shift in the BS table that is visible in the BS and PRM that seems to be settling back now. The MC1 is there for reference to show that it didn't really move.
Jamie, Jenne, Nic, Manasa, Raji, Ayaka, Den
We basically walked through the entire alignment again, starting from the Faraday. We weren't that far off, so we didn't have to do anything too major. Here's basically the procedure we used:
At this point things were looking good and we had Michelson fringes at AS. Time to align SRC. This is where things went awry yesterday. Proceeded more carefully this time:
At this point we felt good that we had the full IFO aligned. We were then able to fairly quickly get the AS beam back out on the AS table.
We took at stab at getting the REFL beam situation figured out. We confirmed that what we thought was REFL is indeed NOT REFL, although we're still not quite sure what we're seeing. Since it was getting late we decided to close up and take a stab at it tomorrow, possibly after removing the access connector.
The main tasks for tomorrow:
Then we'll be ready to close. I don't see us putting on heavy doors tomorrow, but we should be able to get everything mostly done so that we're ready on Monday.
** Comment: I continue to have no confidence that we're going to maintain good pointing with these crappy tip-tilt folding mirrors.
After everyone else did the hard work, I moved the AS first-on-the-table steering mirror sideways a bit so the AS beam is on the center of the mirror, then steered the beam through the center of the lens, onto the 2" 99% BS. I also moved the camera from it's normal place (the 1% transmitted through that BS) to the AS110 PD path, as we did last vent. We'll need to put it back before we go back to high power.
[Evan, Jenne, Jamie]
We used the green laser pointer technique to adjust the POP steering mirrors behind PR2 to get the POP backward beam out onto the table (rather, the mirrors were adjusted so that the green laser pointer, mounted on the POX table, was co-aligned with the beam between PR2 and PR3).
We were unable (why? I feel like it wasn't so hard last time) to see the POX beam, with a camera pointed at an IR card. We ended up just waving a lens-free CCD camera around on the POX table where we expected POX to be, found the beam, and decided that if the beam was getting to the table, that was good enough.
We then waved the camera around on the POY table, and found the POY beam on the table. We also moved ITMY up and down in pitch, and saw that the POY beam was moving, so we were satisfied that we had the correct beam. We should go back and do this same check with POX, although I'm pretty sure that we already have the correct beam. But checking is good.
We confirmed that IPPOS was coming out of the chambers. I didn't end up touching any in-vac mirrors for IPPOS, since they all looked centered, and the beam on the table was already centered on the steering mirror on the out-of-vac table.
We got IPANG out of the chamber to the ETMY table. IPANG has, after the pickoff window, an adjustable mirror, and then a fixed mirror on the BS table. The beam was very close to the edge, in yaw, on that fixed mirror. Jamie unclamped it and moved it so the beam was centered, then twisted it until I got beam back down at the end, centered on the first steering mirror down there. Then Evan and I got the beam centered on the other steering mirror on the in-vac ETMY table, and got the mirror to ~the center of the first out-of-vac steering mirror. Then Evan adjusted the other steering optics so the beam was hitting the QPD.
We then got the real REFL beam out of the chambers. I still don't know what that ghost/fake beam is. Anyhow, we moved PRM around, and saw that the real REFL beam moves, while the fake one doesn't. We adjusted the adjustable REFL steering mirror in-vac such that the real REFL beam came out to the table. Once on the AP table, we moved the PRM around again, just to be doubly/triply sure that we had the correct beam. We put a beam splitter (found on the SP table) after the lens in the REFL path on the AP table, and put the camera on the reflected side of that BS. This is because, like the AS port, the beam is too dim at the normal camera spot (which for REFL is the transmission through a Y1 mirror).
Jamie has centered IPPOS and IPPANG QPDs, so we should look at the weekend trend come Monday, to see what things look like, and how they drift, if at all.
On Monday, we should:
* Check the alignment, and the centering of beams on all mirrors one last time
* Remove all apertures from suspended optics (I think BS and PRM may be the only two that have them at this time)
* Check oplev paths for all mirrors
* Check all pickoffs / beams that need to come out of the vacuum
* Start putting on doors
These don't show anything too interesting, but we're including them to show where the beams are right now on the cameras, so we can compare on Monday.
To get the camera shot of AS, Y1 mirror on the path was replaced by a 99% BS and transmitted beam was directed to the camera via a 50-50 BS (ND filters were distorting the image on the camera introducing fringes).
That's good, but I request two things:
1) Check that the REFL beam is coming from the HR surface and not the AR surface. The real REFL beam should have as much power as the Faraday output. And where does the AR surface reflection go?
2) Use frame grabber to get as many images of the spot positions on the mirrors as is reasonable. Don't endanger bumping the tables again, but take what images can be gotten by remote camera views.
IPANG / IPPOS trends:
c.f. screen caps from Friday:
Earlier this morning we thought things were looking pretty good. IPPOS, IPANG, and the AS and REFL spots looked like they hadn't moved too much over the weekend. Our plan was to do a quick check of things, check clearances, etc., tweak up the oplevs, and then close up. This is when I made the ill-fated decisions to check the table levelling.
The BS table was slightly off so I moved one of the thick disk weights off of the other disk weight that it was sitting on, and on to the table next to it. This seemed to improve things enough so I left it there. ITMY didn't need any adjustment, and I move a couple smaller weights around on ITMX. Meanwhile Jenne was adjusting the output PSL power back into it's nominal range (<100mW), and re-tweaking up the mode cleaner.
When we then looked at the vertex situation again it was far off in yaw. This was clearly evident on PZT2, where the beam was no longer centered on the PZT2 mirror and was near the edge. This was causing us to clip at the BS aperture.
We took some deep breaths and tried to figure out what we did that could have messed things up.
Jenne noticed that we had moved slightly on the PSL QPDs, so she adjusted the PSL output pointing to re-aquire the previous pointing, and realigned the MC. This had a very small positive affect, but not nearly enough to compensate for whatever happened.
We spent some more time trying to track down what might have changed, but were unable to come up with anything conclusive. We then decided to see if we could recover things by just adjusting the PZT input steering mirrors. We couldn't; recentering at PRM, BS, ITMY, and ETMY was moving us off of PR3.
Jenne suggested we look at the spot positions on the MMT mirrors. I had checked MMT1 and it looked ok, but we hadn't looked at MMT2. When we checked MMT2 we noticed that we were also off in yaw. This made us consider the possibility that the BS table had twisted, most likely when I was securing the moved mass. Sure enough, when I manually twisted BS table, by grabbing it with my hand, very little force would cause the input beam to walk much of the way across PZT2, more than accounting for the offset. The effect was also very clearly hysteretic as well; I could twist the table a little and it would stay in the new position.
At this point we had fucked things up enough that we realized that we're basically going to have to walk through the whole alignment procedure again, for the third time this vent. We were able to recover the PRM retro-reflection a bit, but the tip-tilts have drifted in pitch (likely again because of the table levelling). So we're going to have to walk through the whole procedure systematically again.
Lessons learned: Many things are MUCH more sensitive than I had been assuming. The tip-tilts are of course ridiculous, in that lightly touching the top or bottom of the mirror mount will move it by quite a lot in pitch. The tables are also much more sensitive than I had realized. In particular, tightening screws can twist the table hystereticly by milliradians, which can of course completely loose the pointing. We need to be a lot more careful.
Assuming the table hasn't moved too much we should be able to recover the alignment by just adjusting the PZTs and tweaking the pitch of the tip-tilts. At least that's the hope. No more touching the table. No more leveling. Hopefully we can get this mostly done tomorrow morning.
We had a big alignment party early this morning, and things are back to looking good. We have been very careful not to bump or touch tables any more than necessary. Also, we have removed the apertures from the BS and PRM, so there are no more apertures currently left in the chambers (this is good, since we won't forget).
We started over again from the PZTs, using the PRM aperture and the freestanding aperture in front of PR2, to get the height of the beam correct. We then moved PZTs to get the beam centered on BS, ITMY, ETMY. We had to do a little poking of PR2 (and PR3?) to get pitch correct everywhere.
We then went to ETMX to check beam pointing, and used BS to steer the beam to the center of ETMX. We checked that the beam was centered on ITMX.
We went through and ensured that ITMX, ITMY, PRM, SRM are all retroreflecting. We see nice MICH fringes, and we see some fringes (although still not so nice...) when we bring PRM and SRM into alignment.
We checked the AS path (with only MICH aligned), and made sure we are centered on all of the mirrors. This included steering a little bit on the mirrors on the OMC table, in yaw. Initially, AS was coming out of the vacuum, but hitting the side of the black beam tube. Now it gets nicely to the table.
For both AS and REFL, we made sure there is no clipping in the OMC chamber.
I recentered the beams for AS and REFL on their respective cameras.
IPPOS was centered on the QPD. This involved moving the first out-of-vac steering mirror sideways a small amount, since the beam was hitting the edge of the mirror. IPANG was aligned in-vac, and has been centered on the QPD.
Right now, Manasa, Jamie and Ayaka are doing some finishing touches work, checking that POY isn't clipping on OM2, the second steering mirror after the SRM, and they'll confirm that POX comes out of the chamber nicely, and that POP is also still coming out (by putting the green laser pointer back on that table, and making sure the green beam is co-aligned with the beam from PR2-PR3. Also on the list is checking the vertex oplevs. Steve and Manasa did some stuff with the ETM oplevs yesterday, but haven't had a chance to write about it yet.
We were trying to check POY alignment using the green laser in the reverse direction (outside vacuum to in-vac) . The green laser was installed along with a steering mirror to steer it into the ITMY chamber pointing at POY.
We found that the green laser did follow the path back into the chamber perfectly; it was clipping at the edge of POY. To align it to the center of POY (get a narrower angle of incidence at the ITMY), the green laser had to be steered in at a wider angle of incidence from the table. This is now being limited by the oplev steering optics on the table. We were not able to figure out the oplev path on the table perfectly; but we think we can find a way to move the oplev steering mirrors that are now restricting the POY alignment.
The oplev optics will be moved once we confirm with Jenne or Steve.
We aligned the ETM oplevs yesterday. We confirmed that the oplev beam hit the ETMs. We checked for centering of the beam coming back at the oplev PDs and the QPDsums matched the values they followed before the vent.
Sadly, they have to be checked once again tomorrow because the alignment was messed up all over again yesterday.
Can we have a drawing of what you did, how you confirmed your green alignment as the same as the IR (I think you had a good idea
about the beam going to the BS...can you please write it down in detail?), and where you think the beam is clipping? Cartoon-level, 20
to 30 minutes of work, no more. Enough to be informative, but we have other work that needs doing if we're going to put on doors
Thursday morning (or tomorrow afternoon?).
The ETMs weren't moved today, just the beam going to the ETMs, so the oplevs there shouldn't need adjusting. Anyhow, the oplevs I'm
more worried about are the ones which include in-vac optics at the corner, which are still on the to-do list.
So, tomorrow Steve + someone can check the vertex oplevs, while I + someone finish looking briefly at POX and POP, and at POY in
If at all possible, no clamping / unclamping of anything on the in-vac tables. Let's try to use things as they are if the beams are getting to
where they need to go. Particularly for the oplevs, I'd rather have a little bit of movement of optics on the out-of-vac tables than any
changes happening inside.
I made a script that averages together many photos taken with the capture script that Rana found, which takes 50 pictures, one after
another. If I average the pictures, I don't see a spot. If I add the photos together even after subtracting away a no-beam shot, the
picture us saturated and is completely white. I'm trying to let ideas percolate in my head for how to get a useful spot.
The way to usually do image subtraction is to:
1) Turn off the room lights.
2) Take 500 images with no beam.
3) Use Mean averaging to get a reference image.
4) Same with the beam on.
5) Subtract the two averaged images. If that doesn't work, I guess its best to just take an image of the green beam on the mirrors using the new DSLR.
PRM and SRM OSEM LL 1.5V are they misaligned?
We have two ready for vacuum 1.5" mirror mounts with pico motors in our hands.
Steve's elog 7682 is in response to the conversation we had at group meeting re: Jamie's proposed idea of re-purposing the active tip tilts.
What if we use the active TTs for the PR and SR folding mirrors, and use something else (like the picomotors that Steve found from the old days) for our input steering?
Steve's elog 7682 is in response to the conversation we had at group meeting re: Jamie's proposed idea of re-purposing the active tip tilts.
I think we will still need two active steering mirrors for input pointing into the OMC, after the SRC, so I think we'll still need two of the active TTs there.
My thought was about using the two active TTs that we were going to use as the input PZT replacements to instead replace the PR2/3 suspensions. Hysteresis in PR2/3 wouldn't be an issue if we could control them.
With static input pointing, ie. leaving PZT2/3 as they are, I think we could use PRM and PR2/3 to compensate for most input pointing drift. We might have to deal with the beam in PRC not being centered on PRM, though.
Koji's suggestion was that we could replace the PZTs with pico-motors. This would give us all the DC input pointing control we need.
So I guess the suggestion on the table is to replace PZT1/2 with pico-motor mounts, and then replace PR2/3 with two of the active tip-tilts. No hysteresis in the PRC, while maintaining full input pointing control.
With Picos, we lose the ability to dither the input beam as well as align the beam with the IFO locked. And the active TT will still have hysteresis, but also actuators. Once in vacuum, I'm not sure how we adjust them - what's the error signal for PR2/PR3 ?
If the interferometer is aligned, why not just pump down now? I'm not sure that we have evidence of TT hysteresis issues once people stop touching them.
[Jenne, Jamie, Manasa, Ayaka]
Flipped mount of OM2, moved OM2 behind POY pickoff so we're out of the way of POY. Adjusted and recovered rest of AS path.
We found that IPANG was not on its photodiode, but determined that it was centered on all of the in-vac mirrors, and that it was just a little bit of steering on the ETMY end out-of-vac table that needed to be done.
Got green flashes in Yarm, moved down periscope to the north by ~1 inch in order to get y green out to PSL table. This also involved moving the steering mirror on the IOO table immediately after the down periscope to match. We measured the MC spot positions before and after touching the periscope, and there was no significant change.
Aligned X green to X arm (centered on ITMX, ETMX, although no flashes since we didn't move ETMX's biases around), then made sure it was centered on all of its steering mirrors, and came out of the vacuum.
Manasa took photos of all test mass chambers and the BS chamber, so we can keep up-to-date CAD drawings.
Oplevs and IPPOS/IPANG are being centered as I type. Manasa and Ayaka are moving the lens in front of IPANG such that we have a slightly larger beam on the QPD.
In the morning, Jamie is going to put apertures back on 2 of the suspended mirrors for one last check that moving things on the IOO table didn't do anything bad, but since the AS and REFL beams on those cameras didn't move significantly, we think things are fine.
Heavy doors go on in the morning, and access connector at ~1pm, if not before lunch. Then Steve will start pumping early Monday morning! Hooray!
PS, for reference,
" We found that IPANG was not on its photodiode, but determined that it was centered on all of the in-vac mirrors, and that it was just a little bit of steering on the ETMY end out-of-vac table that needed to be done."
The lens in front of IPANG on the out-of-vac table was moved to get a larger beam giving reasonable signals at the QPD.
IPPOS did not need much adjustment and was happy at the center of the QPD.
All oplevs but the ETMY were close to the center. I had to move the first steering mirror about half an inch on the out-of-vac table to catch the returning oplev beam from ETMY and direct it to the oplev PD.
* We have taken reasonable amount of in-vac pictures of ETM, ITM and BS chambers to update the CAD drawing.
Oplevs and IP ANG are still centered. Why do the SRM and PRM move 5X more ? I could not check the sensing voltages because the computer failed.
AS and REFL are looking the same as last night.
ALL LOOKING GOOD!
I didn't make any concrete progress today. AS and REFL cameras are in place, and Manasa has put ND 0.5 filters on both. I used a
camera to look at the back of the Faraday, and aligned PRM such that it was retroreflecting, and then tried to align ITMY to have once
fringes with the PRM at that place. I failed in this, since the AS beam on the AS table was starting to dall off the first mirror on the table.
I then restored all the suspensions to where they were before I started touching them today.
I moved ETMY face camera so that it is looking at the front of the black glass, but it's hard to tell where the beam is. I was thinking
about setting up a temporary camera to look at the back of ITMY to help guide PZT steering, but I haven't done this yet.
Koji and I then talked about the several different options I have for references, and how many different knobs I can turn. I'm sleeping
on it for now, and hopefully I'll have more insight on what to do tomorrow.
We aligned accurately 00 green in yarm, changed voltage on PZT2 to see red flashing at TRY at the normalized level 0.2-0.3. The plan was to lock yarm using POY11 and green from other side, maximize red TRY by adjusting PZT2. But POY11 does not go out of the vacuum, so we adjusted TRY by flashing. 2 DOFs of PZT2 is not enough to match 4 DOFs of red beam so we adjusted both PZT2 and cavity mirrors. TRY flashing is 0.5-0.6 and green is still locking to 00 though its transmission is not maximized. We'll fix it later by adjusting input green beam.
Next we wanted to get red beam on TRX PD. Beam steering was done by BS only. We misaligned BS in pitch and excited BS angle motion by 1000 counts. We could see red beam moving on the wall of ETMX chamber. We moved it to ETMX mirror frame, estimated position of the mirror center and moved BS to this position. The beam should be approximately in the middle. For now we can not see red beam on the camera at ETMX table, more work is needed.
POY11 does not go out of the vacuum
It does but slighty low and does not get on mirrors. We need to change optic mounts to adjust the height. Red is flashing in yarm at 00 and 10 modes. TRY is ~0.4-0.5.
I've adjusted BS angle, camera and TRX PD at ETMX table so I can see red flashing at 03 mode while green is locked to 00 and its transmission is maximized. I thought that by adjusting BS angle, I will be able to align red to 00 not disturbing green, but this was not the case. Maximum TRX I could get was 0.1. I've adjusted POX to get into PD and I can see PDH signal though I can't lock as cavity is still misaligned for red.
You have constraints for the IR beams (i.e. one PZT and one BS for 8 dofs), so now you need to align the arms for the input IR beams.
The PZT and BS should be aligned so that you have the beam spots as center as possible with the above restrictions.
Then realign end greens for the given arm alignment. You can replace the mounts if necessary to align the end green.
Even if you lose the coarse alignment of the green, realignment is not difficult as you know now
We put the POY beam onto the POY PD. The Yarm is currently locked on IR with ~0.65 transmission.
Today at 11:13 AM the stack of invacuum BS table was kicked and IFO misaligned. We adjusted PZT2 voltage by ~20 V in yaw such that IPPOS was restored. Then we could lock arms.
For those of you who like to do work on the interferometer without reporting it in the elog because you think that what you did doesn't affect anything, this is your example of how our time can be wasted by such laziness.
I'm taking full responsibility for this action and I told them after lunch Friday.
HOW NOT TO:
The BS isolation stack supported by two beam tubes and they can pivot around the pivot point.
BS chamber seemed to be kicked again around 10:00 am today.
I moved PZT mainly in YAW and locked both arms. I adjusted the beam to be almost on the center of both ETM by sights.
Today I've set c1ass model to improve alignment of X and Y arms. I've added all measured parameters to ASS scripts. I've also added a script to c1ass.adl that downloads calculated OFFSETs to corresponding ASC filter banks and blocks outputs. It should be called after alignment convergence.
XARM phase rotation and sensing matrix
Output gains were (-0.5, 0.5, -0.25, -0.25). XARM Gain was set to 0.5.
YARM phase rotation and sensing matrix
Output gains were (-0.25, 0.25, 0.7, -0.7). YARM Gain was set to 0.8.
This looks like a good performance tuning for these. It would be good if you can codify this procedure in the wiki so that even unexperienced people can tune up the system after reboots or vacuum work.
Is it possible to have some python scripts automatically measure and set the phases and matrices? If so, can we also run them iteratively so that after the second run we can confirm that they have converged? Then the script can output a short report of numbers telling us how well the system is now tuned.
I suppose that there is also a similar system possible to align the arms in a continuous way; i.e. low level drives and very low bandwidth. Also something fast / slow for the the DRMI.
c1ass was really useful today when we slowly aligned PZT and servo kept arms aligned to the input beam. I think it is possible to automate phase and matrix measurements. DRMI servo will be very useful.
Today I tried to investigate the mode in PRCL and MICH. I locked them but power build-up was only 27. The beam on the POP camera looked like interference of 00 mode and a long strip of fringes. (I wanted to make videocaptures but script is not working - the problem is that it is looking for /usr/lib/*.so.4 libraries but they were updated to *.so.5, I made a few links .so.4 -> .so.5 but this kept going for many libraries, so this should be fixed in a better way).
We looked at PRM and BS faces and they had the same shape - interference of a circle with a strip. There were also a lot of bright spots all over the frames. Loops were closed and circle was not moving. Strip was oscillating at ~1Hz and also its position significantly changed with alignment. Looking at PRM face camera we made a conclusion that the length of the strip is ~5 cm and width ~1cm. Interesting that strip has plenty of power - approximately 10 times of transmitted beam when cavity is not locked. As a result POYDC was oscillating at the same frequency as a strip.