While meditating on other things, I have noticed / found the following today:
YARM ASS works okay. Yesterday I measured the sensing matrix for the ASS for both arms (although I forgot to copy one of the matrix elements to my text file for Xarm - needs remeasuring). I put the Yarm matrix in (after appropriate inversion, only non-zero pitch-to-pitch, yaw-to-yaw elements). I turned on the Yarm ASS, and the yaw converged pretty quickly (couple of minutes), with gains of -1 in the servos, overall gain of anywhere between 0.005 and 0.010. The pitch took much longer, and I had to 'pause' several times by turning off the overall gain for the yarm ass when the MC lost lock (which has happened several times tonight - unknown cause). Eventually, the pitch settled out, and quit changing, but the lockin outputs weren't zero, even though the error signal for the servos were almost zero (gains for the pitch servos were -0.5, overall gain ~0.005 was better than 0.01 - higher gain caused oscillations in the lockin outputs). I think this means that I need to remeasure the yarm pitch ass matrix. It's still much, much faster to just turn on the dithers, watch the striptool of the lockin outputs, and align the cavity by hand.
I think the ETMX Trans camera view is clipped a little bit. I went down there, and it doesn't seem to be on the last optic before the camera, and moving the spot on the camera doesn't change the shape of the image, so I don't think it's on the camera. We should look into this, since it's either clipping on the BS that separates some camera beam from the TRX beam, or TRX is getting a clipped beam too. If the clipping is any earlier in the Trans path, the Trans QPD could also have some clipping. This requires investigation. The xarm trigger needs to be reset/disabled so we don't lose lock every time we block the TRX beam (as was happening to me).
XARM really doesn't like to relock unless the POX whitening is turned off. Good flashes, doesn't really catch (10+ min waiting (while working on Yarm stuff) ). After turning off the whitening, it catches almost immediately. Even though it's on the to-do list to rethink the tuning of our whitening, we should probably implement the whitening triggering now anyway. It'll make things easier.
The double integrator that Rana implemented in the X and Y arm servo filters last week take 8 seconds to turn off (due to Foton settings), so even though they are triggered to turn off immediately upon lockloss, they sit around and integrate for 8 seconds, so have huge signals. If the cavity flashes and the locking trigger engages during that 8 seconds, we send a huge kick to the ETMs. I'm modeling the response of the filters to an impulse and noise, particularly in the case of ramping on the double integrators. The problem is that a flat filter has 0deg phase, but the double integrator has 180deg phase at low frequencies, so there's some weird sign flipping that can happen as we ramp - this is part of what I'm modeling.
MC is losing lock unusually often tonight. Everything on the servo board screen looks normal (which is good since that's all set by the autolocker). I just disabled the test exc in, but that's been left enabled for a while now, and it hasn't (I think?) been a problem since there shouldn't be anything connected to the board there. PMC transmission is a little low, 0.816, and FSS is starting to get near -1 on the slow actuator adjust, but we've seen locking of the PMC problems around -1.5 or -2 of the FSS, and the adjust value was at -0.8 earlier tonight and we still had MC locking problems. I have had the seismic channels open on Dataviewer for the last several hours, and I'm not seeing any spikes in any of the Guralp channels which correspond to the times that the MC loses lock. BLRMS don't seem particularly high, so MC lockloss cause is still a mystery for today.
The ETMX monitor selector on the VIDEO screen seems not to be switching the actual camera that's shown on the monitor. Using the script command itself works, so my screen is wrong.
Last week, Rana changed the integrators in the arm LSC servo filters to be double integrators with complex poles.
Yesterday, I found that using the "timeout" feature of Foton (at filter ON/OFF request, waits for zero crossing, or T seconds, whichever comes first) is useful for turning on the integrators, but bad for turning them off. When we're locked, the error signal is oscillating around zero, so there is often a zero crossing. When we lose lock, we want to turn off the filter immediately. But, as soon as lock is lost, the input signal gets large, and doesn't often cross zero, so the filter waits 8 seconds until actually turning off. If the arm flashes any time during that 8 sec, we send a big kick to the optics.
An alternative option could be ramping the filter on. However, since the double integrator has -180deg phase at low frequencies (until the poles at ~5Hz), the transition between no filter (0deg phase) and integrator on could be problematic. I simulated this, and find that for the very beginning of the ramping process, we would have a problem.
The filter is defined as: NoFilter * (1 - R) + Integrator * (R), so for R=0, the integrator is off, and for R=1, the integrator is fully on. R can be any value [0,1].
The first figure is the time series (1 second, 16kHz), ramp goes from 0->1 or 1->0 in 1 second:
The second figure is bode plots for selected values of R:
As R gets smaller and smaller, the notch goes to lower frequency, and becomes higher Q. So perhaps ramping is not a good answer here.
What if we go for single or triple integrator, to get rid of the (+1) + (-1) problem?
It seems as though there is something funny going on around ~1.5 Hz, starting a little over an hour ago.
We see it in the BLRMS channels, the raw seismometer time series, as well as in various suspensions and LSC control signals. It's also pretty easy to see on the camera views of all the spots (MC, arms, transmissions....AS is a little harder to tell since it's flashing, but it's there too).
The plots I'm attaching are only for ~10min after the jump happened, but there has been no change in the BLRMS since it started. Usually, we'd see an earthquake in all the channels, and even big ones ring down after a little while. This is concentrated at a pretty narrow frequency (some of Den's plots for later have this peak), and it's not ringing down, so it's not clear what is going on.
Here is a whole pile of plots. Recall that the T-240 is plugged into the "STS_3" channels, and we don't have BLRMS for it, so you can look at the time series, but not any frequency specific stuff.
We took a look at the Xend green, and we weren't able to make it lock. We improved the alignment a little bit, and when we looked at the error signal, it looked nice and PDH-y, but for whatever reason, the cavity won't catch lock.
While aligning the green to the arm, Jamie noticed that the reflection from the intracavity power (not the prompt reflection) was not overlapping with the input beam or prompt reflection. This means that the cavity axis and the input green beam were not co-linear. I adjusted the BS and ITMX to get the IR transmitted beam (which had been near clipping on the top edge of the first (2 inch) optic it sees out of the vacuum) back near the input green beam spot on the combining beam splitter. Then we continued tweaking the green alignment until we saw nice TEM00 flashes in the cavity. The SNR of the error signal increased significantly after this work, since the cavity buildup was much higher. But alas, still no lock.
I tweaked the alignment of ITMX and ETMX a teeny bit to get the TEM00 flashes back (the work in the previous elog was pre-dinner, so it had been a few hours), then took a screenshot of the error signal and refl dc power on the photodiode for the green xend setup.
The error signal is certainly noisy, although I think when Jamie and I were looking at it earlier this evening, the SNR was a little better.
I need to look at the modulation depth, to see if it's correct, ... maybe lock the Xarm on IR and scan the green laser PZT to check the sideband heights.
I should also check to make sure that the PD is powered, and the gain is high enough (currently the PD gain is set to 20dB). Earlier today, when I set the gain to 30dB, Jamie said that it was saturating, so I put it back down to the 20dB where we found it.
Still no lock of the green though :(
Edit: realized I was bad and didn't label the traces on the plot: green is refl dc power, blue is demodulated error signal.
Friday / pre-vent:
[done] Align the MC mirrors for the incident beam so that the mirrors can be the alignment reference [Koji]
[in progress] Center spots on MC mirrors [Jenne]
Put beam attenuator optics (PBS + waveplate) on PSL table, realign input beam to MC mirror centers
[In progress] See if we can design a set of nuts and bolts to use at bottom of tiptilt optic ring, to do small adjustments of pitch alignment [Steve]
After doors open:
Use CCD (Watek, with AGC on) to take images of everything we can think of, to see current status of clipping
Check that we get through the Faraday without clipping
Move PZT1 and MMT mirrors to get good spot positions on PR3, PR2. Make sure we're clearing the Faraday's housing
Install dichroic optics, perhaps completely readjust pitch alignment of those tiptilts (we will measure the spares later, and call that good enough for our phase mapping).
Use some kind of oplev setup to check pitch alignment of PR2, PR3.
Tweak (if necessary) PR2 & PR3 pitch to go through center of PRM, BS, hit center of ITMY
Check that we're not clipping on the BS cage anywhere
Use CCD to take images with Sensoray of everything we can think of, to confirm we don't have clipping anywhere. Want to see the edges of the beam on the targets, which would mean that the beam is hitting the center of the optic. If necessary, we'll stay open an extra day to get good camera images everywhere, so we have a good record of what's going on inside.
Note: While having good arm alignment would be good, we're willing to sacrifice some arm alignment to have good DRMI alignment, since we're re-venting and installing the new active tiptilts in another month or so.
Things I'm leaving for Jamie-the-Vent-Czar to plan:
Order of door opening
Beam dump assembly and placement
I am getting closer with the MC spot centering. I had everything but MC1 really great, but then I tweaked MC1's pointing, and things all went to hell.
I have to go home to let Butter out, but I'll be back tomorrow, and I'll try to get back to where I was in the 2nd to last measurement in the plot below.
I recenterd the WFS after moving the input beam, so that the beam was hitting the WFS at all.
We need to re-look at this new MC autolocker stuff, and the new MCL filters.
MC2 is getting kicked up (sometimes the watchdog trips, sometimes it just comes close) pretty regularly. I'm not sure yet what is causing this, but we need to deal with it since it's pretty obnoxious.
We are being riddled with earthquakes. Brawley, CA (~150 miles from here) has had 9 earthquakes in the last hour, and they're getting bigger (the last 4 have been 4-point-somethings). I may try to come back later, but right now the MC won't stay locked for the ~5 minutes it takes to measure spot positions. Koji and Jamie said they were coming in today, so they can call me if they want help.
Steve, do not vent tomorrow morning! We are still not prepared, and will not finish the preparation tonight. Hopefully we can finish the prep tomorrow, and then vent Tues.
Things we need to do before the vent:
MC spots centered [Jenne, tonight]
Use PZT2, BS to hit ~center of ETMs.
Realign arms, measure spot positions.
Make sure BS, ITMs are good - we want a good AS spot since we'll likely have to adjust some AS optics while we're inside
Insert attenuation optics, recover MC trans by rotating PBS cube to translate beam slightly
After shaking ITMX by the alignment bias in yaw, it came back.
As ETMX seems to be largely misaligned yaw (and did not come back with the alignment impact),
the condition of the magnets are not clear. Only the side OSEM is responding nicely.
It looks like we may lost 1 (or 3 ) magnets? Do not panic, it's not for sure
I tried to take some photos through the window of ETMX's chamber, to see if I could see any magnets. What we have learned is that Jenne is still not the world's best photographer. I was holding the camera at ~max zoom inside the beam tube between the table and the window, so that's my excuse for the photos being fuzzy. The only thing that I can really conclude is that the magnets look like they are still there, but Jamie thinks they may be stuck on the PDs/LEDs (now looking at the photos myself, I agree, especially with UL and LR).
It looks like the best thing to do at this point, since Koji already tried jerking ETMX around in yaw a little bit, is just wait and open the door, to see what's going on in there. I posted the photos on Picasa:
I propose that, if the magnets are broken, we pull the ETM out of the camber and fix it up in the cleanroom while we pump back down. This would restrict us from doing any Xarm work, but will force me to focus on DRMI, and we can put the ETM back when we vent to install the tip tilts.
The MC REFL path was checked. ==> Some clippings were fixed. MC WFS is working now.
- MC was aligned manually
- The steering mirror for the WFS and camera was clipping the beam. => FIxed
- The WFS spots were realigned.
- There was small clipping on the MC REFL RFPD. ==> Fixed
We have figured out that some of these measurements, those with the WFS off, were also not allowing the dither lines through, so no dither, so no actual measurement.
Jamie is fixing up the model so we can force the WFS to stay off, but allow the dither lines to go through. He'll elog things later.
Jamie and I have the MC spots centered. We did the normal move the input beam, realign jazz for a while, then when we got close, used the "move MC2 spot" scripts to get the MC2 spot back to ~center.
This was way easier when the measurements were real, and not just noise. Funny that.
The dark blue spot is the farthest from 0 in pitch, and it is 1.04mm. The cyan and yellow we've done a pretty good job of getting them equally far from zero. Since we aren't translating the beam, we can't get better than the point at which the cyan and yellow curves cross.
PMC transmission started going down this afternoon, around 3pm-ish. Right now it's 0.775, which is very, very low. The new MC locking stuff is engaged, so it's not the FSS slow servo's fault.
EDIT: I just realized that the limit of 0 counts output of the MC2 MCL filter bank was still engaged, from a time earlier this afternoon when I had switched back to the old servo, so there was no feedback going back to keep the slow drift of the laser in check. PMC trans isn't coming back instantly, so I'll check it again when I come in tomorrow.
We have now reduced the power being input to the MC from 1.25W to 10mW, and changed out the MC refl BS for a mirror.
The power was reduced via the PBS we introduced in Entry 7295.
While we were in there, we took a look at the AS beam, which was looking clipped on the monitor. Jenne felt that it appears that the clipping seems to be occurring inside the vacuum, possibly on the faraday. This will be investigated during the vent.
I stopped the regular MC autolocker and told the crontab to startup the low power Mc autolocker on op340m. Also, since we now have the new MC2 transmission setup, the power that gets to the 'regular' MC trans PD is lower, so I've lowered the lock threshold to 50 counts, from 100 counts.
We installed a Half Wave Plate -> Polarized Beam Splitter -> Half Wave Plate in the PSL beam line, immediately after the EOM, to be used for attenuating the beam when we vent, as in Entry 6892.
It was illuminating to discover that the optics labeled QWP0-1064-10-2 are indeed half wave plates, instead of quarter wave plates as QWP suggests.
The PBS transmits "P"/Horizontal polarization, but the beam coming from the EOM is "S"/Vertically polarized, and we want to keep that, since we do not want the beam attenuated quite yet.
So, we use the HWP to rotate the P from the EOM to S, so that the majority of the power passes through the PBS. The second HWP then rotates the transmitted S back into P, which continues to the mode cleaner. When we want to attenuate, we will simply rotate the first HWP to change the proportion of S polarized light that will pass straight through the PBS and towards the mode cleaner.
After setting the proper HWP angles, we aligned the PBS via minimizing the MC reflection.
Since we have not yet attenuated the power, we have not yet changed the BS for the MC reflection, since this would damage the PD. The beam splitter will be changed out for a 100% reflectivity mirror to increase the power to the PD when we do.
Before we did this, I centered PSL POS and ANG, which gives us a reference of where the PSL beam was good when the MC spots were ~centered. There had been a beam dump blocking them, possibly from the last time we put in the power attenuator optics. This beam dump was moved a little to be out of the way of the PSL QPDs, and the PBS placed closer to the lens after the EOM, so that the PBS reflected beam is dumped. However, we should not remove that razor dump when we remove the attenuation optics, since it is also dumping a stray IR beam from the PSL QPD pickoff windowd.
I have turned of the high voltage supplies for PZT1 and PZT2. The OMC PZT high voltage supplies were already off, since we aren't really using them currently.
I have closed the PSL shutter, but have not put in a manual extra beam dump yet.
All systems go for vent!
Steve - EricQ will be here around 8am to help with the vent.
[Jenne, Suresh, with support from Jamie and Koji]
MC spots measured, MC1, MC3 no change.
No clipping going through Faraday.
Beam hitting to the right of center of PZT1. It was translated sideways so we are now hitting it on the center. Knobs adjusted so we hit center of MMT1.
Beam totally obscured by Faraday on the way to MMT2. MMT2 moved north, so that we clear the Faraday by more than a beam diameter. MMT1 knobs adjusted to hit center of MMT2.
MMT2 knobs adjusted to hit center of PZT2.
PZT2 didn't have enough range with knobs, so we loosened it, pointed then adjusted with knobs so we're hitting center of PRM.
We need to check spot centering on PRM with camera tomorrow.
Suresh checked that we're not clipped by IP ANG/POS pickoff mirrors, but we haven't done any alignment of IP ANG/POS.
Tomorrow: Open ITMX door. Check with Watek that we're hitting center of PRM. Then look to see if we're hitting center of PR2. Then, continue through the chain of optics.
I tightened as many of the dog clamps on the bottom of the BS, ITMX and ITMY chambers as I could find. I used a torque wrench at 45 ft-lbs. Some of the bolts of the dogs were too long, and I couldn't find an extender thing to accommodate the bolt so I could reach the nut. None of the bolts moved that I was able to reach.
Steve, we're not doing final final alignment today (we will do it tomorrow), so please go around and double-check my work by checking all of the dogs first thing in the morning. Thanks.
We placed the Watek camera on the SE viewport of the ITMX chamber, and focused it on the face of PRM. We are not able to see any scattered light transmitted through the PRM, so this camera was an ineffective way to try to check spot centering on the PRM. Jamie placed one of the new targets on the PRM cage - see his elog for details.
To get more use of the camera, we need to mount it on something, at the 5.5 inch beam height, and then cover that something with clean foil so we can place the camera on the table, in the beamline in various places. We also need to carefully wrap the cables in foil so the don't dirty anything inside.
Jamie and Koji pointed out that we need to be doing the in-vac alignment with the PZTs at the center of their ranges. Also, we confirmed that they were set to "closed loop off", so the strain gauges were not supplying any feedback.
PZT1 was set to 0 for both pitch and yaw, since it has a very limited range of motion right now, so 0 is close enough.
For PZT2, Koji and I moved the slider in pitch and yaw, and watched the LCD output monitor on the PZT driver at the bottom of 1Y3. We saw the value on the LCD change between slider values +4 to -6 for PZT2 yaw, so it is set to -1 as the center. We saw the value on the LCD change between slider values -4 to +5 for PZT2 pitch, so it is set to +0.5 as the center. Beyond these slider values (the sliders all go -10 to +10), the LCD value didn't change, either at 0, or at the maximum.
Since PZT1 doesn't really move, this shouldn't affect any of the alignment work that Suresh and I did last night, although we should quickly confirm tomorrow. On the agenda for tomorrow is adjusting PZT2 such that we hit the center of PR2 (and hopefully that will also put us through the center of the PRM target, if the alignment was done well enough last time), so it's okay that we have only now set it to the center of its range.
Elog re: Friday's work
Adjusted PZT2 so we're hitting the center of PR2.
Noticed that the beam centering target is too low by a few mm, since the OSEM set screw holes that it mounts to are lower than the center line of the optic. This meant that while we were hitting the center of PR2, the beam was half clipped by PRM's centering target. We removed the target to confirm that the beam is really centered on PR2.
Checked the beam on PR3 - it looked fine. There had been concern last week that PR2 was severely pitched forward, but this turns out to be an effect of the PRM centering target being too low - shoot the beam downward to go through the hole, beam continues downward to hit the bottom of PR2, so beam is falling of the bottom of PR3. But when we actually centered the beam on PR2, things looked fine on PR3.
Checked that the beam approximately goes through the beam splitter. Again, the targets are too low, and these 45 deg targets' holes are smaller than the 0 deg targets, so we don't see any beam going through the target, since the beam is hitting the target higher than the hole. The beam looked left/right like it was pretty close to the hole, but it was hard to tell since the angle is bad, and I'm not infinitely tall. We should check again to make sure that the beam is going through properly, and we're not clipping anywhere. I'll need help from a height-advantaged person for this.
Checked that the beam is hitting the center of the ITMY, as best we can see by using an IR card at the back of the optic. We didn't try reaching around to put a target on the front side.
We were debating whether it would be worth it to open ETMY this week, to check that the beam transmitted through the BS hits the center of ETMY.
We also took a quick look around the AS optics, but since that depends on BS/ITMX alignment, we weren't sure how to proceed. We need a plan for this part. All suspended optics were restored to their last good alignment, but we haven't tried locking MICH or anything to confirm that the alignment.
To do list: Check no clipping on ITMY table of beam between BS and ITMY, clipping on POY optics. Also, oplev is clipping on cable holder thing on the table - this needs to be moved. .....other?
We need a plan for the rest of the week. I want to be closing the heavy doors on Friday at the latest. Please add to / comment on this list!
* Lock MICH to get BS, ITMs aligned well
* Check if beam is hitting center of ITMs.
* Check for clipping around BS
- Use Watek in-vac to look at beam at all 4 BS ports - make sure no clipping going into BS, after BS in the michelson, or the AS port
* Try to get arms to flash??
* Prepare glass beam dumps??
* IPPOS / IPANG - make sure beam gets out of chambers (this may require opening ETMY)
* Jan take photos of ETMX scattering setup
* Manasa take in-vac photos of all tables, for table layouts
* Jan / Manasa viewport transmission
* Install glass beam dumps?
* If ETMY open, install glass baffle
* Check table levelling one last time on all tables.
* Close all heavy doors. (Access connector, ITMX, ITMY, BS, ETMX, ETMY? )
* Drag wipe test masses
* Start at ~10am?
Mon (if not Fri)
* Start pumping
Opened ETMY, beam was high and to the right (if you look at the face of ETMY). Tried walking beam up, since just doing PZT2 caused clipping at the BS before we got to the correct spot on ETMY. Moved PZT1, then PZT2, to translate beam, but we couldn't get far enough without starting to fall off of PZT2. Put PZT1 approx. back where it was. Jamie tapped on the top of PR3 (tip tilt just before BS), and then did some compensation with PZT2 to get the beam through the BS target to the center of ETMY.
The beam is very dim at ETMY. We ended up holding the big IR card with holes such that one of the holes was near the center of the optic, in front of the cage. Then one person turned off all the room lights so we could see the beam, another person moved PZT2 and PR3, then lights person turned on and off the lights so we could compare beam position with hole position. A total pain, but it ended up working better than just trying to follow the beam with a card.
We clearly need a better plan for adjusting the tip tilts in pitch, because utilizing their hysteresis is ridiculous. Koji and Steve are thinking up a set of options, but so far it seems as though all of those options should wait for our next "big" vent. So for now, we have just done alignment by poking the tip tilt.
Tomorrow, we want to open up the MC doors, open up ETMY, and look to see where the beam is on the optic. I am concerned that the hysteresis will relax over a long ( >1hour ) time scale, and we'll loose our pointing. After that, we should touch the table enough to trip the BS, PRM optics, since Koji is concerned that perhaps the tip tilt will move in an earthquake. Jamie mentioned that he had to poke the tip tilt a pretty reasonable amount to get it to change a noticeable amount at ETMY, so we suspect that an earthquake won't be a problem, but we will check anyway.
After doing all of that, we adjusted IPANG so that the beam gets out of the vacuum envelope. The beam must squeeze between the wall of the black beam tube and a lens for the oplev, so there is a very, very limited amount of space. The eventual new tables will be very helpful for alleviating this, but for now we must live with it. Even though it is pretty squishy right at the edge of the table, with the new layout we should think about giving IPANG a little more space. Basically, if there is any Yaw motion, the beam going to the QPD will be clipped, and we may get confusing info. We moved some of the IPANG optics that are on the end transmission table so the beam is centered on the optics while it just makes it through the space between the wall and the lens. The spot was centered on the IPANG QPD.
We still need to check on IPPOS, but it is always easier than IPANG.
We discovered that the 45deg SOS beam targets are awesome, especially the ones with the irises. The plain hole ones have very small holes relative to our beam size, so they are much more useful for the MC optics (which they were designed for). The 45deg targets were made such that the target holes do not line up with the mounting holes. This is good, since the mounting holes are lower than the center of the optic. I don't think ericQ and I realized that on Friday, so it's probable that we had installed the target upside-down. We still need to remake the 0deg targets for the next vent.
Jamie dogged down the new 'bathroom mirror' that lets us see BS and PRM on the same camera view. He also adjusted some of the masses on the BS table to relevel the table. We need to (at some point) rename the AS_SPARE camera to something like BS_PRM, since we plugged the new camera into the AS_SPARE port on the videoswitch.
tl;dr: Input beam adjusted so we're hitting center of ETMY. IPANG coming out of vacuum, QPD centered. Need better tip tilt in-situ adjustment capability.
Since the EOM's signal combiner (splitter backwards) is frequency-independent, Koji and Jamie (in the proper turn off, turn on order) put the 55MHz signal back to the EOM, and put the MC mode scan input to the 11MHz port. This way we can lock the Michelson tomorrow, and we don't have to keep switching cables around when Riju wants to take some scans.
* Hit center of ETMY, using input optics, PR3.
* Get IPANG out of vac, center QPD.
* AM: Riju do MC mode scans
* Starting right after 40m meeting, if not before: Lock MICH to get BS, ITMs aligned well
* Check if beam is hitting center of ITMX.
- Use Watek to look at beam at all 4 BS ports - make sure no clipping going into BS, after BS in the michelson, or the AS port
- Use some old in-vac mirrors to direct beam out the BS door. Cameras are waiting near BS chamber.
* IPPOS - make sure beam gets out of chamber
* Install glass baffle at ETMY. Jan maybe install baffle at one of ITMs.
[EricQ, Jenne, brains of other people]
Checked at ETMY that the pointing hadn't changed a whole lot. Jamie and Koji pointed out that we were half falling off of the IPANG QPD. Adjusted PZT2 sliders so that we were again centered on IPANG's QPD. Before we close up, we'll want to put the sliders back to their nominal positions, and use the knobs to hit IPANG, but this is equivalent and fine for now. The tip tilts don't seem to have moved much overnight, since the beam drift on both IPANG and ETMY was fixed simultaneously with PZT2 (recall, IPANG picked off before tip tilts exist in the beam path). This left us hitting the center of ETMY. We moved ETMY sliders to make the reflected beam hit the center of ITMY (same spot position as transmitted beam from BS). Then moved ITMY to get prompt reflection to hit same spot on ETMY as original primary beam from BS. Checked at ITMY that we didn't need to move ETMY anymore. (Actually, I forget how many iterations we did, but in the end, all of the reflections that we can find are co-located on the test masses.)
Align BS so we're hitting the center of ETMX
Tap / readjust ITMX OSEM which is at 0.3 to get it back to the center of its range
Align ITMX to lock MICH
Check no clipping on POX / POY optics, no clipping around BS
Check PRM, SRM alignment (what exactly do we want to do here? Try to lock PRMI / SRMI?)
Get IPPOS out of vac
Fix clipped ITMY / SRM oplev
Install 'black' glass beam dumps - forward-going POP beam, 2 places in BS chamber (check old elog from Jenne/Yuta for the places).
Get green spots co-located with IR spots on ETMs, ITMs, check path of leakage through the arms, make sure both greens get out to PSL table
I couldn't understand the Y-End green setup as the PD was turned off and the sign of the servo was flipped. Once they are fixed, I could lock the cavity with the green beams.
I had turned the green refl PD off on Tuesday while we were doing the IPANG alignment, since the beam was not so bright, and the LED on top of the PD was very annoyingly bright. I forgot to turn it back on. The sign flip on the servo, I can't explain.
I was having trouble centering IPANG using the PZTs, and I suspected something funny was going on at the end. I went down there, and the beam was focused right on the PD, and the spot was very very small. I think this means that when I was trying to center the beam, I was falling into the gap between the pieces of the diode. Also, as Koji pointed out to me the other day, if the PD is at the focal point of the beam, any parallel rays hitting the lens just before the PD will all go to the same place, no matter how the input beam has moved. This means we're not getting as much info out as we'd like.
So. I moved the lens a little bit farther from the PD such that we are just beyond the focal point of the beam. The beam size is now ~1mm on the QPD.
This means, however, that I moved the beam on the QPD such that IPANG is no longer a reference of the input pointing. Ooops. I think this adjustment needed to be done though. Right now, the PZTs are set to where we had them yesterday, when we moved them slightly to center the IPANG QPD, and I've recentered IPANG.
Q and I aligned the BS such that we were hitting the center of ETMX. The ETMX cage does not have OSEM setscrew holes on the front, so it is not possible to put the targets that Steve made on this optic. So, I put the freestanding ruler in front of the optic, with the edge of the ruler at the center (as viewed from above) of the optic. Then Eric steered the BS until we were hitting the 5.5" mark, and roughly half of the beam was obscured by the ruler.
We then aligned ITMX such that the prompt reflection was colinear with the incoming beam.
I checked the 2 spots through the BS, heading to the AS port. (2 spots since MICH hasn't been locked / finely aligned yet). They were being clipped on the 2nd output PZT. I adjusted the knobs of the first output PZT to center the spots on the 2nd PZT. Note that the output PZTs' power is still off, and has been off for some unknown length of time. I had found them off when prepping for the vent a week or two ago. So the current alignment depends on them staying off. We don't really need them on until we're ready to employ our OMC.
The beams now look nicely unclipped on the AS camera, and we're aligning MICH.
I was going to lock MICH, but I don't see anything on dataviewer for either AS55Q or ASDC. I went out onto the table, and there is beam on the diode, but no mV out on a voltmeter connected to the DC monitor point. I shine a flashlight, and still I see 0.0mV. So, something is up with AS55, but since the michelson is aligned right now, I'm not going to mess with the PD. I won't lock MICH, I'll just move on. Koji is taking a look at the diode, but if he doesn't get it figured out tonight, we can take a closer look after we pump down.
Never mind. I was using an LED flashlight, which doesn't emit light that the PD is sensitive to. A regular flashlight gives plenty of signal on the DC out.
Using an SR560 with 30Hz low pass and gain of 100, it was pretty easy to align the light on the PD.
Koji calculates in his head that there is about 6 microwatts of light incident on the PD, which is not a lot of light. Our SNR may be kind of lame for locking right now.
* Found that IPANG was no longer centered, so we used PZT2's sliders to get the spot back on the center of the QPD. Koji points out that I should have moved the lens even farther away, to have a larger beam (many mm, not just ~1) on the QPD.
* Found that MICH alignment had drifted, so used ITMX to realign MICH.
* Aligned PRM, got REFL beam through viewport. Just made sure reflected beam was colinear with incident beam.
* PRC flashes were visible on AS camera.
* PRM was more precisely aligned to have good interference with ITM reflections, by looking at AS camera.
* Decided to align SRM. Spot was ~5mm too far to the north on the SRM....so we were off from center by ~5mm.
* Moved SR2 yaw a little bit to get spot centered on SRM.
* Couldn't align SRM within bias slider range, so moved SRM in yaw to get reflected beam colinear with incident beam.
* Centered the spot on the steering mirrors. The 2nd steering mirror after the SRM was moved by ~1 inch. All mirrors after that were aligned to match this new beam.
* Found spot on AS table, aligned AS table mirrors so that beam hits AS55 PD window. Haven't actually centered beam on PD.
* Transmission of 99% reflector was too weak to use with a card to get the beam back on the AS camera, so we moved the camera over to the AS110 path.
* Precisely aligned PRM and SRM by watching AS camera.
* Both the PRC and SRC look kind of funny. Koji agrees. Seriously. They're a little weird. We can't align either recycling cavity, one ITM at a time (so PRM with ITMX, PRM with ITMY, SRM with either single ITM) to get rid of all the fringes. Something is definitely funny. It's got to be in the recycling cavities, since the weirdness is common between both ITMs for a given recycling mirror. We need to take Sensoray views of these tomorrow.=
* There is some clipping on the right side of the AS camera view. We have determined that it is not clipping at the viewport exiting the vacuum, but we aren't sure where it is. It is at least before PZT4 (the 2nd PZT in the output AS path).
To capture video with the Sensoray, open the GUI (python ./demo.py), simply press "Save," enter a filename, and hit "Stop" when you wish to stop recording. If you want to change the video format, there is a dropdown menu labelled "Format." I recommend MP4 for standard video, and nv12 for RAW video.
I also installed mplayer on rossa, so we can play the videos there.
Even though Mike won't admit it, the video stuff is all in /users/sensoray/ . I opened the demo.py from there, and it also works.
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.