IMC transmission photodiode has been aligned.
Which PD? The 'regular' DC one, or the newer one? Why did it need realigning? What mirrors did you touch to do the alignment?
Did you do anything else in the last 3 days? I want to see ALL the gory details, because it can help people doing future measurements, or help us debug if something is wrong with the interferometer later.
MORE WORDS! Thanks.
We have a plan for how we're going to measure the beam after PR3. Mike is going to write up a nifty program that will spit out the waist of the beam if you give it a bunch of razor blade measurement data.
Since the beam bounced off of the pitched ITMX is coming out of the chamber so high, it's kind of a pain to setup optics to steer the beam down the walkway next to the Yarm. So, I have a new vision.
I think that we can get the beam right after PR3 onto the PRM/BS oplev table using 3 clean mirrors (of which we have many spares, already clean). Once on the oplev table, we can put a 2" Y1 mirror to steer the beam down the walkway, after taking off the short east side of the table. Then we can use the little breadboard on the mobile blue pedestal for the razor blade / power meter setup.
The razor blade on a micrometer translation stage will be the first thing on that table that the beam sees. Then, a 2" lens to get the beam small enough to fit on the power meter. Then, obviously, the power meter. We can measure the distance between the oplev table and the razor blade using the laser range finder, which has pretty good accuracy (it's sub-centimeter, but I don't remember the exact number for the precision).
A lens is not okay if we're trying to get the beam directly onto the beam scanner, since it will distort the beam. However, as long as the razor blade is before the lens, and we're just using the lens to get the full intensity of the non-obscured part of the beam onto the power meter, I think using a lens should be fine. If we don't / can't use a lens, we're going to run into the same problem we have with the beam scanner, since the power meters all have a fairly small aperture. Even the big 30W power meter's aperture will be on the order of the size of the beam, so we won't be able to guarantee non-clippage.
The main problem I see with the technique as I have described it, is that the beam is going to hit 4 mirrors (3 in-vac, one outside) before going to the razor/lens/power meter. We have to make sure that we're not clipping on any of those mirrors. Also, this measurement version takes the beam after PRM, PR2 and PR3, but not after the BS and ITM. I don't think we're concerned with either of those 2 optics, (especially since this is refl off the front of the BS, so won't see any potential clipping on the BS cage), but just in case we are, this measurement isn't so useful, and we'd have to come up with a different way of placing the mirrors on the in-vac tables to get a beam bounced off of a yaw-ed ITMX.
Perhaps it would be easier to just go with the pitched ITMX version of the measurement, but I could use some ideas / advice on how to mount mirrors and lenses ~4 feet off the ground outside of the chambers, and not have them waving around on skinny sticks.
EDIT: Another idea is to instead use the beam transmitted through the BS, put a single clean steering mirror in the ITMY chamber, and get the beam out of the ITMY door. This could either be the beam before the ITM, or we could yaw the ITM a little and take the reflected beam.
I have given Den 4 G&H R>99.99% mirrors to be installed on the 4 active tip tilts. He's in there working on things (incl. installing and balancing the pitch of the mirrors) right now. He'll elog his work later.
We need to do the following things: Images of optics in DRMI chain, place black glass beam dumps, make sure pickoff beams get out, align IP POS/ANG.
Black glass: behind MMT1, behind IPPOSSM3, forward-going POP beam.
Images and pickoff stuff should happen at the end of each vent.
Images need to be taken of the following optics (with ruler edge at center of optic):
* BS (front and back?)
* Viewport as AS beam leaves chamber
* POYM1 (check no clipping on edge of mount)
* POXM1 (check no clipping on edge of mount)
Pickoff / aux beams:
* REFL path
We aligned the DRMI, and have concluded that it looks good enough that we should close up and pump down soon. We still need to use the camera to check things, and get all pickoff beams out of the chambers, so don't get too excited yet.
We looked at the mode matching telescope's calculated beam propagation, and since we're using spherical telescope mirrors at non-zero degree incidence angle, we expect an astigmatism about like what we are seeing on the AS camera. This matches up with the measurements that Mike posted from his and Q's measurements earlier today. We think that it has 'always' been this way, and someone just picked a camera position such that the beam used to look more round than it does now.
We aren't entirely sure what's up with the SRM - it almost looks like the pitch and yaw are coupled, but it was pretty easy to align the PRMI. We don't see any evidence of the crazy, crappy beam that we did before the vent. This means we have fixed most of the bad clipping problems we were seeing over the last ~year.
In the process of aligning the DRMI, we fixed up the input beam alignment - we were not hitting the exact centers of the MMT mirrors (in pitch, mostly), so we fixed that, and propagated the alignment fix through the chain. In all, we touched the knobs on PZT1, MMT1, MMT2, PZT2. The beam then went through the SRM, and we touched a few of the output steering mirrors to get the beam centered on all mirrors.
I remeasured the MC spot positions, and they're a little worse than they have been. Some of the spots seem to be off by 1.75mm (or less) on MC 1 and 3. The numbers, MC1,2,3 pitch, then MC1,2,3 yaw are: 1.749759 9.744013 1.025681 -0.791683 -1.338786 -1.779958
A question to consider before doing the final-final alignment checking is: do we need to get the MC spots centered better than this, especially in light of the potential PMC axis having moved?
I was helping Den get started in the cleanroom yesterday, and I noticed that the new active TTs, like the old passive ones, are set to be 4" from the table. So, like the old ones, we need 1.5" risers to get the center of the mirror up to our in-vac 5.5" beam height. I didn't see any risers in there when I was looking around.
Steve says he still has the drawing that he gave to the shop for the old tip tilts, so he'll double check that the dimensions are the same, and then ask the shop to make 4 more.
After much fussing, we got a picture of MMT1 with the beam.
Using the iris doesn't seem feasible. Since it has to be significantly separated from the optic, it is hard to judge whether it is centered, especially in yaw.
It took ~30 min to get this picture. Comments on whether this kind of picture is good enough are welcomed, since there are many more to be taken.
I've been taking more photos. Obviously, it gets quicker as I go along and get the hang of it. Also, I've been taking overhead pictures with the Nikon so we can see what kind of parallax there is for each snapshot.
However, I just took MMT2, and the beam is nearly falling off the side of the optic! It seemed fine last night when Rana and I were working on it. The MC spots haven't moved significantly (I had measured yesterday, and again a few hours ago). WTF?
This means that I need to move the knobs of MMT1, and then redo the whole alignment chain all over again. Lame.
EDIT: MC spot positions, last night at 12:33am, and this afternoon at 2:12pm:
year month day hour minute MC1pit MC2pit MC3pit MC1yaw MC2yaw MC3yaw
./data_spotMeasurements/MCdecenter201209140033.dat 1.749759 9.744013 1.025681 -0.791683 -1.338786 -1.779958
./data_spotMeasurements/MCdecenter201209141412.dat 1.702974 7.916438 0.986519 -0.888736 -0.170237 -1.771267
All the photos so far:
More photos were taken. Will post Monday, because too hungry now.
Have eaten. Here's a PDF with all the pictures to-date, along with a few notes.
Also, the first thing we did on Saturday was to fix the yaw pointing of MMT1, so that the beam hit the center of MMT2. Then we had to touch PZT2 to compensate. We put the iris target on the BS, and adjusted PZT2 until the beam went nicely through there. The resulting beam looks good on the SRM, and teh beam is still hitting the AS camera.
We took the last of the in-vac photos of mirrors today. I'll post in the morning.
Tomorrow, I'll align the DRMI once more to check, and get IPPOS and IPANG out of the vacuum. I'll take a look at POX, POY and POP, but we may just have to cross our fingers and hope for the best on those ones. They were pretty hard to get out of the vac during their initial alignment, since they're so weak.
Also, tomorrow morning Steve is going to try out our new light access connector!!!! I'm so excited!
The goal is to put heavy doors on, on Wed, and start pumping Wed afternoon / Thurs evening.
The photos on the OMC table are particularly tricky, since the camera plus the 'bathroom' mirror add a lot of weight....even if the MC locked, the input beam would be completely different, so all of the beams would be wrong.
During some of the work on the BS table, ITMY was realigned to have its beam retro-reflect, since the weight of the camera plus mirror was shifting all of the suspended optics on the BS table. ITMY was restored after that, for subsequent photos.
I have touched PZT2 such that the beam goes through the 45 degree non-iris target on the beam splitter. This puts the beam at the center of ITMY, and without moving the BS, at the center of ITMX. I say "at the center", but what I really mean is I put the target approximately at the center, within what looks like, say, 2 mm, by looking from above. The target was many (5ish) centimeters away from the optic though, so that's why my side-to-side centering isn't so precise. Given that, the beam was always more than half going through the hole of the target for both ITMs, so I'm claiming that the spots on the ITMs are within a few mm of center.
With this alignment, the beam was also hitting the center of the SRM (with all the same caveats).
I was able to get the SRM to retroreflect, while I still had Michelson fringing, so I think that I had the SRMI at least close to aligned (I was looking at the SRM retroreflection at the beam splitter, not all the way out to the AS port). PRM is also pretty easy to align.
We're hitting the top of the AS camera, so I think things are pretty good. I don't see beam on the REFL camera, but no investigation of that has been done as yet.
There is some scattering going on in the BS / ITMX chambers that's making me kind of unhappy. I don't know how to get this to embed the youtube video, so here's the embed link, as well as the regular link:
youtube of AS and BS/PRM camera.
<iframe width="420" height="315" src="http://www.youtube.com/embed/QUbnMLXSS5U" frameborder="0" allowfullscreen></iframe>
Manasa watched the camera while I waved an IR card around in the BS chamber, and the only way I was able to get all the scatter spots to go away was to either block the beam incident on the BS (duh), or block the beam reflected off the BS, heading to ITMX. Manasa said that the scatter spots still looked like they were fringing though, so I'm confused. I may wave a card around in the ITMX chamber when I come back later tonight, to see what I can see. Also, I just misaligned the SRM, and the scatter spots moved. Now there's just some scatter off of what looks like the BS OSEM holders, as seen through the BS optic.
The DRMI was aligned once again tonight.
Here's a video: http://youtu.be/Cy8nHL9yMeM (Can someone please tell me / remind me how to make the elog embed videos?!?)
Description of video:
Video capture of AS camera.
NOTE: The beam is a few centimeters above ETMY with this alignment, so it will not be final.
Beginning is ITMY only.
ITMX is realigned to form MICH.
PRM is realigned to form PRMI.
SRM is realigned to form DRMI.
PRM is misaligned to form SRMI.
ITMX is misaligned to form SRY.
With this alignment, I opened up the ETMY door to find the beam there. The beam is ~half on, ~half off of the top of the glass baffle. Not the top of the hole, but the top of the piece of glass. This means that it's many centimeters too high at ETMY. This helps explain why, while swinging PZT2 around the other day, I could not see any beam on the cage. It did, however, look pretty close (within a centimeter....I didn't look closer than that since it was so off in pitch) to centered yaw-wise.
Tomorrow I'd like a Clean assistant to help tweak PZT2 to hit the center of ETMY. We'll need to put the 45 degree target back on to make sure that we don't end up pointing funny down the arm. Then I'll realign the DRMI one more time.
Tonight, I can't check the full AS path, or any of the REFL path once it diverges from the main path. Steve's new contraption (which is awesome!) doesn't have doors/windows yet, so I can't open it to get an IR card anywhere near any optics in the IOO or OMC chambers. I waved PRM around a bit, but I can't find the beam on the REFL camera, so I definitely need to check that whole path again before we close up.
So, we're not closing up tomorrow, but progress has been made, and we're getting closer.
Note to self: These are the ITMX, ITMY, PRM, BS, SRM biases with this DRMI alignment. The DRMI is good, but the arms aren't, so these won't be final. The saved alignments are still those with (for the Yarm) the beam bouncing several times between ITMY and ETMY. BS was aligned at the time to hit the center of ETMX, and PRM and SRM should be retro reflecting in that alignment. So, it's possible, that aligning PZT2 to hit the center of ETMY and restoring all of the optics will get me close to being back to DRMI aligned, but in a condition that the arms are align-able too.
I'm making a separate entry to go along with this thread of photos...
Putting the camera and 'bathroom' mirror on any table pretty significantly changes the leveling of any table. The mirror especially is very heavy, although the camera is not feather light. We need to come up with a new plan for taking alignment-confirming photos without adding anything to the tables. That, or we have to level the table between each camera shot. Anyone who has ever leveled one of our in-vac tables should shudder in horror at idea #2, so we need to put some thought into idea #1 before our next vent. Vent Czar - can you put this on the list, in addition to the REFL rearrangement stuff?
As a result of this, PZT2 needed to be reverted to the place it was before work began on Saturday (so that the beam goes through the 45 degree target without any extra stuff on the table). This means, unfortunately, that all of the photos / still captures of optics after PZT2 are invalid.
The power buildup in the MC is ~400, so 100mW of incident power would give about 40W circulating in the mode cleaner.
Rana points out that the ATF had a 35W beam running around the table in air, with a much smaller spot size than our MC has, so 40W should be totally fine in terms of coating damage.
I have therefore increased the power into the vacuum envelope to ~75mW. The MC REFL PD should be totally fine up to ~100mW, so 75mW is plenty low. The MC transmission is now a little over 1000 counts. I have changed the low power mcup script to not bring the VCO gain all the way up to 31dB anymore. Now it seems happy with a VCO gain of 15dB (which is the same as normal power).
[Unni, Manasa, Jenne]
It turned out that the beam was a teeny bit high in the corner, so we touched PZT1 and PZT2 knobs to translate the beam down a bit.
Now the beam is centered on the BS (using the 45 degree non-iris target), centered on ETMY (using Steve's latest target, which worked perfectly), and then BS was aligned a tiny bit (really, it didn't need much) to get the beam centered on ETMX.
After dinner I'll align ITMX and ITMY such that their beams retroreflect and I get MICH fringes. I'll also align SRM and PRM to retroreflect. Check no clipping on AS path, get REFL path out, center IPPOS and IPANG, check POX, POY and POP. Then, I think we might be almost done.
Using the alignment of the PZTs and BS from pre-dinner, where the beam was hitting the center of both ETMs, we aligned the DRMI. The beam was off on the SRM in yaw by ~half a beam diameter, so I undid Koji's movement of SR2 from a week ago. I loosened the SR2 dog clamps, touched it gently on the base to do a little bit of angle, then re-clamped it. Once again, Steve's new brass centering target was awesome, since it was on the SRM while I was moving SR2.
We approximately recentered the beam on the AS camera, although it didn't need much once we got the beam out of the vacuum, by centering it on all of the output AS path mirrors.
We also got IPPOS out of the vacuum. Manasa was in the process of centering the QPD when the laptop died from too long being unplugged, so we leave that for tomorrow.
Left to do:
REFL path. REFL is not coming out of the vacuum, and with the light access connector I can't reach any of the REFL steering mirrors, since they're in the center of the IOO table.
IPANG. Should be easy.
POP, POX, POY. Need to the the camera-on-a-stick back down to the corner (from ETMY) and point it at the pickoff mirrors to ensure that beam is getting out of the vacuum.
My hope is that the DRMI flashes will be bright enough to see on the PO beams. IF we get 10 mW through the Faraday, you should get some buildup when the carrier resonates in the DRMI.
If the recycling gain is 10 and the pickoff fraction is 100 ppm you ought to get ~10 uW on PO. How much of the recycling cavity power gets out of POP?
We think this math is wrong.
If we have P mW through the Faraday, PRM's transmission is 5.5%, BS transmission is 50%, Recycling gain is ~10, pickoff fraction is ~100ppm, we have:
P mW * 5.5e-2 * 0.5 * 10 * 100e-6 = P * 2750e-8 mW = P * 2.7e-5 mW.
So, if P=10 (10mW through the Faraday), we should have 2.7e-4 mW = 2.7e-7 W = 0.27 microwatts = not so many watts.
If P = 100 (100mW through the Faraday), we should have 2.7 microwatts. Still, not so many watts.
We have the Watec pointed at POY right now, DRMI is flashing, I'm waving the IR card in front of the mirror, and Manasa isn't able to see anything on the monitor. The power into the vacuum is 100mW (we just measured and adjusted it), so even if we were getting a full 100mW through the Faraday, it would be hard to see. If we're assuming we get ~half the power through the Faraday, then we should only have 1 microwatt
[Jenne, Unni, Manasa]
I touched some in-vac steering mirrors, so we have REFL and IPANG coming out of the vacuum, not clipping. IPPOS was done yesterday. I re-checked a few optics in the AS path that were hard to see yesterday while the plastic light access connector was in place, and AS still looks good.
Except for POX, POY, POP, and putting the regular EQ stops back on PRM, I think we're done with the in-vac stuff.
We can't mathdo
[Rana, Jenne, Manasa]
POX is coming out of the vacuum. We'll do POY tomorrow. We were able to hold the Watec outside the chamber and focus it on the pickoff mirror, and make sure it was roughly centered. Then we took the lens off the camera, put the camera in the POX beam path, and I steered the pickoff mirror until we were hitting the camera. POY will be done the same way.
POP is more challenging, since the transmission of the G&H mirrors is so low. We're not able to see a beam on an IR card held in the POP beam path. I had thought of removing PR2, getting the beam out, then putting PR2 back (using the same dog clamping some alignment markers technique that we use for the test masses), but the G&H mirrors have a 2 degree wedge, so this won't work. It would be fine for pitch, since the arrow is on the side of the optic, but it wouldn't be correct for yaw.
Maybe we should do something similar to what Suresh et. al. did when they set POP up originally - I think they put a green laser pointer on the POX table, and aligned it such that they were hitting the correct spot on PR2 and PRM (correct = the same as the IR spot, which should be the center of the optics). If we can do that with the POP in-vac steering mirrors, then we're fine, and POP should come out when we're back to high power.
All video capture snapshots of tonights pictures are on the pianosa desktop.
We put a green laser pointer at ~4 inches on the POX table, and steered it using a mirror on the POX table to hit the center of the last in-vac mirror that POP sees. I then steered that mirror so we were hitting the center of the other POP in-vac steering mirror, and hitting the same spot as the main IR beam. It is easy to hold an IR card in front of PR2 and see the IR and green beams simultaneously. I aligned both of the POP in-vac steering mirrors such that the green beam is co-aligned with the IR beam at PR2, as well as as far as I could reach toward the face of PRM from the ITMX door.
Note: The drawings by Koji have the POP "forward" beam (transmission through PR2 of the beam from PRM to PR2) dumped, while the POP "backward" beam (transmission through PR2 of the beam from PR3 to PR2) leaving the vacuum. I aligned the steering mirrors such that the 'forward' beam would come out, although no dump is in place to dump the other beam. I can't think of a reason why we care one way or the other, but I feel like Koji has perhaps mentioned something in the past. I need to figure this out before we put doors on.
Like yesterday with POX, we used the Watec with the aperture fully open to look at the POY pickoff, while I held the IR card in front of the mirror, to confirm that the beam was ~on the center of the optic. Then we took the lens off the camera, and made sure that the POY beam hit the CCD on the POY table.
To do list for Monday: While we are putting the heavy doors on, someone needs to wave an IR card in front of the IPANG steering mirrors in the ETMY chamber, while someone else takes a photo / still snapshot with the Watec. Also, Manasa wanted to retake in-vac photos of at least the ITMY chamber, since SR2 was moved a very slight amount. Also, also, someone tall needs to put the regular EQ stops on the PRM face (we have the old spring ones in there now).
Before pumpdown, we also need to get the IPANG beam centered on the PD. The beam is cleanly coming out of the vacuum and hitting the first out of vac steering mirror, I just haven't centered it onto the QPD.
Barring any other thoughts that people have of things that *must* be done before we pump down, I think we're ready to start putting heavy doors on the chambers on Monday.
Other thoughts, for next vent: We need to re-look at the ITMY table. POY's pickoff is just too close to the main beam. Is it possible to move the AS steering mirrors and get POY from the BS table? VENT CZAR: please put looking at this on the next vent to-do list.
[The 40m Family]
The access connector and all heavy doors are back on.
Jamie put the regular viton EQ stops back on PRM, since he had to adjust the distance between the EQ stops and the PRM anyway. Jamie also waved an IR card near the IPANG steering mirrors in ETMY, but it was not possible to take a good photo. Jamie certifies that the beam is centered on both of those 2 optics.
I have centered IPPOS and IPANG QPDs.
All oplevs need a little realignment, especially ETMY, which had it's lens removed (Rana has a Wall of Shame photo of this, which is why it was removed by him). Steve will look into this tomorrow, after he starts pumping.
I have turned off all PZT high voltage supplies for in-vac PZTs: The input PZTs, the output PZTs, and the OMC PZTs (which weren't on, but I confirmed they were off).
I have also prepared the 3 low-power items for high power: MC refl's path was changed back to regular BS, AS camera was moved to its nominal position, and IPPOS has its ND filters back. MC refl and the AS camera will need to be realigned once we're actually at high power tomorrow afternoon.
Long vent, but good work everyone.
I've installed Guralp readout box back and it turned out that it does not work with voltage provided from the rack (+13.76 0 -14.94). +/-12 voltage regulators inside the box convert it to -0.9 0 -12. I've connected the box to +/-15 DC voltage supply to measure seismic motion at the ETMY table. Readout box works fine with +/- 15.
I'm not sure what the problem is here. Den and I looked at it for a few minutes, before I went back to helping with putting doors on. The Sorensons are not supplying the rack power for 1X1. There are some flat cables which go from the fuses on the side of the rack up to the cable tray, and go elsewhere. Den is going to continue looking into this, but I think it's a moderately high priority, since lots of things should be getting served by that same power.
What was the reasoning / resolution of the POP forward/backward beam? Are we going to have the right beam for DRMI locking?
From Koji's email to me:
"With the backward beam you can see the returning beam even when the PRM is misaligned. That's the only difference. Once the PRM is aligned both beams have the same information."
So, we should be fine.
[Jenne, Evan Hall]
Both IPPOS and IPANG beams are (after turning on the input and output PZTs) hitting their QPDs. However IPANG was saturating. We went down to take a look, and we had ~2.8mW incident on the QPD. There was an ND filter sitting unmounted, next to the diode, and an empty fork directly in front of the diode. Since IPPOS also has an ND filter in front, we stuck this ND filter back in. Now we are no longer saturating.
We're not hitting (yet) the center of these 2 PDs, but we're at least hitting the diodes, so it shouldn't be too hard to steer the input PZTs.
Whomever took away this ND filter without elogging it was BAD!!! (Jamie, when we first found IPANG coming out of the vacuum during this vent, we moved some of the mirrors on the out-of-vac table in the IPANG path. Was the ND filter removed at that time? Or has it been out for much longer, and we never noticed because IPANG wasn't coming nicely out of the vacuum / was clipping on the oplev lens?)
[Jenne, Evan, Den]
MC REFL beam is back on the PD, and the mode cleaner locks. It looks like we're a little high on the MC Refl camera, but the MC spots were measured, and don't look like they changed from Friday (or maybe Monday?), the last time they were measured. We took this to be acceptable MC alignment, and did not touch the PSL table's pointing.
The laser power reduction optics were removed, and placed out of the way on the PSL table (where do they belong?). PSL-POS and PSL-ANG aren't quite perfectly centered, but a beam dump had been in the way of that path, so I don't know if they drifted bad, or if it was a sudden thing. The beam is still hitting the QPDs though. After removing the beam power reducing optics, we recentered the MC REFL beam on the REFL PD, still not touching any PSL alignment. MC mirrors were aligned (Den did this work while I showed Evan around, so I don't know by how much), and MC Trans was maximized (really MC Refl was minimized, making sure that the unlocked MC Refl was the usual 4.something units on the EPICS readback.
We turned on the PZT high voltage supplies for the output steering PZTs and for the input steering PZTs. We left the OMC locking PZT supplies off, since we're still not using the OMC. Sadly, the beam coming out of the AS port looks clipped somewhere. [SELF: attach the videocapture shot when you get to work tomorrow] We tried moving PZT2's sliders, but nothing happened!!! I can move BS and the ITMs to get the beam mostly unclipped, but I really need to be able to move the PZTs, or at least one of them. IPPOS and IPANG beams are hitting the QPDs (although they're not centered perfectly), so the PZTs came back mostly to the same positions, but not exactly. Evan and I sat next to the input steering PZT controllers in 1Y3, and moved the sliders around. For most of the range, nothing changes on the LCD screen for either PZT2 pitch or yaw. Yaw can make 2 small steps near the far negative side of the slider, but nothing happens for most of the slider. Pitch really doesn't do anything for any part of the slider. We ensured that the LED labeled "CL ON" was not illuminated, next to the button labeled "closed loop", for all 4 controllers (PZT1 and 2, pitch and yaw). Sad!! I don't know if the LCD screen on the front panel of the PZT controllers is a readback of signal supplied to the PZTs, or of the strain gauges. I really hope it's the controller that's not working, rather than the PZTs themselves. The PZTs were fine before we vented, and Koji and I did our centering of the PZT range check during the vent, so they were fine then. What happened??? All PZT high voltage supplies were off during the pump-down. I turned them off yesterday, and Evan and I turned them back on tonight around 9:30pm or 10pm. What else could make them bad?
Without being able to move PZT2, just using BS and / or ITMs, I was unable to completely make the beam look nice on the AS camera. I came close, but it still seems a little bit funny, and I had to move the suspended optics quite a bit to find that place. This is not good.
Since the MC spots are good, I put the beam back on WFS 1 and WFS 2.
Also, I changed the indicators on the LockMC screen to reflect the change in elog 7289, where we added another on/off switch for the WFS so that the ASS could be on, but the WFS off. For the last month, the WFS could be disabled, but the MC screen's indicators would suggest that we were pushing very significantly on all 3 MC mirrors. Now the MC screen reflects reality a little better.
I also uncommented the WFS lines in the mcup script. Den had commented them out, but didn't elog about it! C'mon Den, please elog stuff!!!! (He confessed out loud the other day, but it still wasn't in the elog).
I'm leaving the WFS loops disabled (even though the MC autolocker tries to turn them on, I have them manually disabled using the extra on/off switch) since they're unstable. I'm in the process of figuring out what's wrong. So far, the WFS improve the MC alignment for a minute or two, and then they totally misalign the MC. This is a work in progress.
Found a bug in the IOO screen: All of the 6 WFS signal indicators is liked to the same info (C1:IOO-MC1_PIT_OUTPUT).
Fix this, Jenne! Baaaaagghhhhh!
My bad. As it turns out, you can't copy and paste between MEDM instances. It is now fixed.
I'll come back to the PZTs later, but I want to write down all the elogs I have found so far that look relevant.
Jamie and I pulled the whole PZT driver for both PZT1 and PZT2.
Koji and I found that each HV power supply (the left-most module) has 2 fuses. Both HV supplies (PZT1 and PZT2) have one blown fuse. The "T2L250A" measures low resistance for both HV supplies, but the "T250mAL250V" measures Open for both HV supplies.
I have ordered 10 pieces of each kind of fuse, Next Day shipping, from DigiKey.
We naively hoped that just replacing the fuses would fix the problem with the PZT HV drivers. Alas, this was not the case.
All of our investigations (other than visual inspections) today have been of the PZT2 module. We have not applied any electricity to any PZT1 components/modules today.
After blowing a few more fuses (not good, we know, but we really didn't know what was going on at the time and were convinced that our changes between fuse installations should prevent fuse-blowing, including removing all modules except the HV driver), we found that the YAW driver for both PZT1 and PZT2 has severe discoloration on the PCB, and several resistors and other solder joints are damaged near some high voltage regulators. Pitch on PZT1 looks a tiny bit discolored, but doesn't look totally cooked like the 2 YAW modules do. So, at least PZT1's Yaw was cooked before we started replacing fuses, since we haven't plugged it in yet today.
We then began some more methodical checks:
We bypassed the fuses by applying 10 Vpp = ~7.2 Vrms to the input side of the big transformer on the PZT2 HV driver board. (This usually sees the 120 Vrms from the wall AC, so we were looking at things with a factor ~16 attenuation from what they normally see.) We then measured things on the other side of the transformer, and made sure that they made some sense (one path for 5V stuff, one path for 15V stuff, one path for 180V stuff). One of the rectifying diode bridges (the one for HV) didn't seem to be working, and didn't seem to have all of its pins connected, as if perhaps one or more diodes inside was destroyed.
When I went home for dinner, Koji continued looking at the low voltage supply capability of the PZT2 driver. He removed the diode bridge from the HV path, and also removed the FET that lives on the output side of the HV driver board. He was then able to energize the HV driver and the non-burnt pitch module. So the +\-5 V and +\-15 V paths have been confirmed okay for PZT2's driver stuff.
What I will do tomorrow (when there is someone here to rescue me if I crispy-fry myself) is solder a wire to the now open pin of the backplane connector on the HV driver board, so that we can supply an external 180V to the pitch / yaw modules (although, obviously we won't be using the burnt yaw modules as-is). Tomorrow I'll start by applying a nice small voltage, check that things still look okay, no shorts, and then I'll slowly increase the voltage until I get to the nominal 180V.
Since the low voltage stuff on the driver board is working, once we supply an external 180V (if successful), we should be able to re-install the PZT driver and drive PZT2.
Since both Yaw modules that we have are burnt, I am proposing that we use the PZT2 HV board (which has been checked and modified this evening) with the 2 pitch modules. Since we are not actively utilizing the strain gauge sensors, the fact that the calibrations on these modules are not exactly the same (rather, that PZT1's pitch is not the same as PZT2's yaw) should not matter at all. This means that we will not be able to energize PZT1 at all, but that shouldn't be a problem. Even when PZT 2 was working, PZT1 had very, very, very limited motion through the full range of applied voltage, so having no driver connected shouldn't have an impact.
Den noticed that the -15V LED on the TTFSS board was not illuminated. A further symptom of the FSS being funny was that the PC RMS Drive was constantly high (3.6 ish) and the FAST Monitor was very high, often saturated.
We took the TTFSS board out, and put an extender card in, and it looked like all of the correct power is being supplied to the board (the +\- 24V LEDs on the extender card were illuminated). Just to check, we put the board back in, and this time both +\- 15V LEDs came on. So it looks like the board is fine, it just wasn't seated in there all the way.
Now the readbacks on the FSS screen look good (PC RMS Drive is less than 1, FAST Mon is 5ish), the MC is locked, and I think we're back in business.
I think the ETMX slow machine might be dead. All of the regular FE readbacks are fine, and the c1iscex FE computer looks fine, but the slow readbacks are all whited out.
I turned off the damping loops for ETMX, since I don't have access to the watchdog disable/enable switch. I guess checking this out will be task #1 for Monday morning.
Something bizarre-o was going on with the PMC and FSS over the weekend. On the striptool, PMC's PZT looks like it was doing a sawtooth pattern for several hours. I opened up the FSS screen, and the FSS SLOWDC had walked itself up to +10. It's not supposed to get that far from 0.
Here are some trends, so you can see what was going on.
10 day trend: This weird behavior began ~Friday evening (FSS_SLOWDC ramps quickly).
1 day trend: You can see the sawtooth pattern in PMC_PZT more clearly here. It's at the same time as the FSS_SLOWDC is ramping rapidly, and the FSS_FAST is saturated.
For lack of a better idea, I keyed the crate. The computer came back up just fine, ETMX is happily damped again.
I connected a thick wire to pin 22 of the backplane connector of the transformer / power supply module of the PZT box. This is the pin that +180V is supposed to go on, to be distributed to the other boards in the crate. Last week I had drilled a hole in the front panel so the wire can come out (since no one on campus seems to have HV panel mount connectors in stock).
While the transformer module was isolated, not touching anything else, I applied (slowly ramping up) 180V DC, and it all looked good.
When I plugged the module back into the crate (first turning off and disconnecting the HV), I blew the 250mA fuse again. No HV yet, just the low voltage stuff that Koji had fixed last week. :(
We're now out of 250mA fuses, we're supposed to get a box of them tomorrow.
After the fuse-blowing fiasco earlier this afternoon, Koji and I took another look at the PZT controllers.
We put an ammeter in place of the fuse, and watched the current as we turned on the transformer module. The steady-state current with no other modules plugged in is ~15mA. However, there is a surge current right when you turn on the box which sometimes goes as high as 330mA. Since the fuse is 250mA, this explains the fuse blowing, even though Koji had already checked out the low voltage path.
The high voltage line was connected, with +180V to the HV out pin of the backplane connector, and the (-) terminal of the power supply connected to signal ground on the board.
We inserted the PITCH module for PZT2, and we started with ~10V as our "high" voltage, and slowly increased the value (current at this time was ~60mA). We also had a function generator plugged into the "MOD" input, which is where the epics slider goes, so that we should see a changing output voltage. We never saw a changing output voltage. Increasing the HV power supply didn't help.
When Koji spun the "DC offset" knob really fast and then stopped, sometimes the output voltage as measured on the connector-converter board between the white and red wires would jump up, and then settle back down. It came back to the same value that it always was, but it was bizzarre that it would jump like that. We suspect that that knob is an offset for use with the closed loop setting, so it isn't relevant for us anyway. Watching the MON output, the value never changed, even when Koji did his fancy knob twirling.
We switched to the other PITCH module, and watched the output voltage on the MON output. This time, with the function generator unplugged, so no modulation input (so we were expecting a steady DC output voltage) the number on the LCD and the MON output fluctuated wildly. We plugged in the function generator, and the fluctuations did not change in approximate amplitude or DC offset. They kind of looked the same.
So, we have concluded that (a) the PZT drivers don't work, and (b) we don't understand why. Therefore, we don't know how to fix them.
With that in mind, we are thinking of totally circumventing the PZT drivers.
I plugged in the PZT1 connector converter board, which has Koji's circuit that he made last time when PZT1 died. I plugged the ribbon cable which goes to the PZT, and the +\- 30V power supply, and the PZT responded! Just plugging in the power supply puts the PZTs near the center of their nominal range. I then put a function generator on the epics inputs for pitch and yaw (one at a time), and saw the spot move around at the ~1Hz that I was applying. Yay!
What I think I'll do for tonight - modify the other connector converter board so that I can just use 2 HV power supplies (current limited) to steer the PZT. I set up a TV monitor next to the PZT electronics (1Y3? 1Y4? I forget), and it's connected to output 20 of the video switch, so I can watch the AS camera and move the PZTs by hand. Then maybe I can try to align some stuff. (Evan is coming to work tonight, so if I electrocute myself, someone will be here to call 5000) Koji suggested buying 2 single-channel thorlabs piezo drivers, like we have on the PSL table for the FSS loop. These take in 0-10V and output either 0-75V, 0-100V or 0-150V (depending on which setting you choose). These cost $712 each. This would be a more permanent solution than me just sitting out there, since we could once again control PZT2 via epics.
Note to self:
The ENV-40 amplifiers that we have supply -10V through +150V .... so don't exceed those limits.
We were sitting trying to lock MICH (hooooorraaaayy!!!), and the emergency lights above the control room door came on, and then ~1 minute later turned off. Steve, can you see what's up?
We applied some volts across both the pitch and yaw pin sets of the ribbon cable that goes to PZT2. We ended up with ~40V yaw and ~14.5V pitch. That was the nice happy center of the clipping that we can see on the AS camera. Once we found the center of the PZT clipping range with the ITMY beam, we recentered the AS camera (actually, this took a few iterations, but now it's good).
We then aligned MICH, but aren't able to get it to lock. Before falling asleep, we have decided to align the PRM and SRM, so right now we have a flashing DRMI. Both the SRMI and PRMI look a little funny the closer you get to 'good' alignment, so I'll investigate a little more tomorrow, and include pictures. (The video capture script has barfed again, and I'm not in the mood to deal with it today.)
Riju hasn't been in the lab in a long time to do any measurements, so I put the signals back to how they should be.
I turned off / confirmed off the things which were sending signal to the EOM: the network analyzer, the RF generator box, and the Marconi which supplies the 11MHz.
I removed the cavity scanning cable, and terminated it, and put the regular 11MHz cable back on the splitter.
I then turned on the RF gen box and the Marconi. The Marconi had been off, so we were not getting any 11MHz or 55MHz out of the RF gen. box. This is why I couldn't lock any cavities last night (duh).
On to locking!
----------------- In other news,
While swapping out the EOM cable, I noticed that the DC power supply sitting under the POX table was supplying a weird value, 17 point something volts. I checked on the table to remind myself why that power supply is there...it's powering an RF amplifier right after the commercial PD that is acting as POP22. The amplifier wants +15 and GND, so I reset the power supply to 15V. We should add this to the list of things to fix, because it's dumb. Either we need to put in the real POP22 (long term goal), or we need to get this guy some rack power, and do the same for any amplifiers for the Beat setup. It's a little hoakey to have power supplies littering the lab.
I moved some of the REFL optics on the AS table by a teeny bit to accomodate the new place that the REFL beam exits the chamber (none of this was done while we were at air....we were only dealing with the AS beam at the time, and were happy that REFL came out of the vacuum).
The REFL beam is now on the REFL camera (with PRMI aligned), and the beam is going toward the 4 REFL RF PDs, but it's not aligned to any of them.
I have some questions as to mystery optics on in the REFL path. There is a 90% BS, and I don't know where the 10% reflection goes....is it going to beat against the AUX Stochino laser?
I have to go, and I didn't fix the videocapture script today, so pix tomorrow, I promise.
Today I checked the optical lay-out in MC REFL board of the MC REFL path on the AS table (I will put the updated diagram in a few hours), and took a record of the reflected power of unlocked MC and power entering MC REFL PD. The power coming out of MC cavity when unlocked is 1.25W and power entering REFL PD 112mW (Jenne measured these powers for me).
I also got a description of the MC demodulation board from Jenne.
(Edits by Jenne)
Also, when I walked through the control room later, the WFS were driving the MC crazy. I turned off / disabled the WFS from the WFS screen. In my infinite spare time, I need to put in the real-time triggering, so that the WFS turn off as soon as the cavity unlocks.
Apparently all of the ION pump valves (VIPEE, VIPEV, VIPSV, VIPSE) opened, which vented the main volume up to 62 mTorr. All of the annulus valves (VAVSE, VAVSV, VAVBS, VAVEV, VAVEE) also appeared to be open. One of the roughing pumps was also turned on. Other stuff we didn't notice? Bad.
Several of the suspensions were kicked pretty hard (600+ mV on some sensors) as a result of this quick vent wind. All of the suspensions are damped now, so it doesn't look like we suffered any damage to suspensions.
Steve has promised to fix up all of the oplevs, but it hasn't happened yet, so I've turned all of the oplev gains to zero, so that when the optics are restored we don't have to quickly click them off.
Oplev values that were changed to zero:
PRM P=0.15, Y=-0.3
SRM P=-2.0, Y=2.0
BS P=0.2, Y=-0.2
ITMY P=2.1, Y=-2.0
ITMX P=1.0, Y=-0.5
ETMX P=-0.2, Y=-0.2
ETMY P=0.5, Y=0.6
Also, PRCL was changed in the LSC input matrix from REFL33I to AS55I, since there is no REFL beam out of the IFO :(
Evan and I are starting to lock, and there is lots of new, unfortunate white stuff on several different screens.
C1:TIM-PACIFIC_STRING is gone, C1:IFO-STATE (MC state) is gone, C1:LSC-PZT..._requests are gone (all 4 of them), C1:PSL-FSS_FASTSWEEPTEST from the FSS screen is gone (although I'm not sure that that one is newly gone), lots of the WF AA lights on the LSC screen are gone.
Those are the things I find in a few minutes of not really looking around.
EDIT: IPPOS is also gone, so I can't see how my current alignment relates to old alignments.
We aligned the PRMI. We definitely can lock MICH, but we're not really sure if PRCL is really being locked or not. I don't think it is.
Anyhow, we found 2 different places on the AS camera that we can align the PRMI. One (middle, right hand side of the camera), we see the same weird fringing that we've been seeing for a week or two. The other (lower left side of the camera), we see different fringing, almost reminds me more of back in the day a few months ago when the beam looked like it was expanding on each pass. As I type, Evan is uploading the movies to youtube. I *still* don't know how to embed youtube videos on the elog!
Also, we found both forward-going and backward-going POP beams coming out onto the POX table. We placed the 2" lens in the path of the backwards beam, so that we can find it again. We can't see it on an IR card, but if we put some foil where we think the beam should be, we can use a viewer to see the spot on the foil. Poking a hole in the foil made an impromptu iris.
Lower left on camera
Middle right on camera
How can you lock the PRMI without the REFL beams? c.f. this entry by Kiwamu
Which signals are you using for the locking?
I think the first priority is to find the fringes of the arms and lock them with POX/POY.
As for the POP, make sure the beam is not clipped because the in-vac steering mirrors
have been supposed to be too narrow to accommodate these two beams.
I was using AS55I for PRCL, and AS55Q for MICH. I snuck that into the last line of an unrelated elog, since I did both things at the same time: see elog 7551. Kiwamu's measurements (elog 6283) of the PRMI sensing matrix show that the PRCL and MICH signals are almost orthogonal in AS55 (although the optickle simulation doesn't agree with that...) He was able to lock PRMI with AS55 I&Q (elog 6293), so I thought we should be able to as well. Locking the PRMI was supposed to help tune the alignment of the PRM, not be the end goal of the night. Also, we only tried locking PRCL in the "middle right" configuration, not the "lower left" configuration, but we were seeing what looked like recycling flashes only in the "lower left" configuration.
I agree in principle that we should be working on the arms. However, since we can't use the old steer-the-beam-onto-the-cage trick to find the beam, I was hoping that we could steer the beam around and see some light leaking out of the ETM, onto the end table. However, with the 1% transmission of the ITMs and ~10ppm transmission of the ETMs, there's not a lot of light back there. I was hoping to align the PRMI so that I get flashes with a gain of 10 if I'm lucky, rather than just the 5% transmission of the PRM. With the PRMI aligned, I was expecting:
(1W through Faraday) * (10 PR gain) * (0.5 BS transmission) * (0.01 ITM transmission) * (10ppm ETM transmission) = 0.5uW on the ETM tables during PRCL flashes.
I was hoping that things would be well enough aligned that I could just go to the end table, and see the light with a viewer, although as I type this, I realize that if the beam was not on the end table (or even if it was...) any time I move the PZTs, I'd have to completely realign the PRMI in order to see the flashes. This seems untenable, unless there are no other options.
We then got sidetracked by trying to see the POP beam, and once we saw the POP beam we wanted to put something down so we could find it again. POP is also small, but not as small as expected at the end:
(1W through Faraday) * (10 PR gain) * (20ppm PR2 transmission) = 0.2mW on POP during PRCL flashes.
POP was very difficult to see, and we were only able to see it by putting the foil in the beam path, and using a viewer. I think that we once were able to see it by looking at a card with the viewer, but it's much easier with the foil. I'd like to find an iris that is shiny (the regular black iris wasn't helpful), to facilitate this alignment. Since we were just looking at the reflection off of the foil, I have no comment yet about clipping vs. not clipping. I do think however that the forward-going beam may have been easier to find....when the PRMI alignment drifted, we lost the beam, but I could still see the forward-going beam. Probably I should switch to that one, since that's the one that was lined up with the in-vac optics.
Ideas are welcome, for how to align the beam to the Yarm (and later to the Xarm), since our old techniques won't work. Aligning the PRMI was a distraction, although in hopes of getting flashes so we could see some light at the end tables. I'm going to go see if I can look through a viewport and see the edges of the black glass aperture, which will potentially be a replacement for the steering-on-the-cage technique, but if that doesn't work, I'm running out of ideas.