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.
[EricQ, Jenne, brains of other people]
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 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.
Aim: to scan the cavitymodes of IMC
The circuit used:
We have installed the pick-off mirror at the ETMY table for the small-angle scattering measurement on ITMY. As we had already done for the X arm pick-off, the pick-off mirror at ETMY was aligned shooting a green laser normally through the viewport on the pick-off and steering it onto ITMY.
A baffle was also installed at a distance of about 30cm from ETMY near the edge of the table.
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.
For the current baffle (dia. 40mm) centered along the beamline place at 1.77" from the test mass, the baffle will allow ~8.6mm visibility on the camera from the center of the test mass (in case of ETMY).
*assuming the pick off mirror is placed at the edge of the tunnel
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.
With a curvature radius of about 57m for the ETMs, flat ITMs at the beam waist, and using 39m for the arm lengths, one finds that the beam radius at the ETMs is about 5.3mm. The clipping power loss of a 5.3mm beam through a 20mm radius baffle hole would be less than a ppm of a ppm if the beam was perfectly centered. If the baffle hole had 15mm radius, the clipping loss would be 0.01ppm. If the baffle hole had 10mm radius, the loss would be 810ppm. The loss values are calculated using the formula of the "Gaussian beam" Wikipedia article, "Power through an aperture" section. So I did not check if that one is ok.
* 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).
The alignment of the pick-off mirror near ETMX is done. Everything turned out to be easy once we realized that there is no sense getting the alignment laser (going through viewport to pick-off to ITMX) back to ETMX. It is only necessary to hit ITMX somehow, since this makes sure that there is one scattered beam that will make it from ITMX to pick-off through viewport.
After the auxiliary optic (that we never used in the end) was removed again, we levelled the optical table.
So in the current setup, we can have small-angle scattering measurements on ITMX and large-angle scattering measurements on ETMX.
This is how it was envisioned. The video camera was in nobodies mind to look through the 40 mm diameter hole than.
The required diameter for the baffle if it sits on the cage at 1.77" from the test masses: the current baffle (dia. 40mm) centered along the beamline, will allow ~8.6mm visibility from the center of the test mass (in case of ETMY).
Estimations of the visibility region (r1 on the test mass) with baffle (aperture size 40mm).
The baffle is installed on the cage at 1.125" from the test mass (distance changed from the previous elog after a double check).
The 40mm aperture is in no way going to help get clear view of the ITMs;
11MHz modulation source was turned off (disabled) at Marconi at 12:00.
Required baffle diameter to have a visibility region r1 = 3 times the beam diameter
Video Capture with the Sensoray works again. Pianosa just needed mplayer installed for it to play properly.
IMC transmission photodiode has been aligned.
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.
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.
No, not the "regular DC one", the "newer one" along with the controls of the corresponding mirror only i touched.
It needed to be realigned cause last week when we fitted a longer cable there, which may reach the network analyzer, it got misaligned since it got touched.
No other component in that box except that PD and the corresponding mirror controls I touched.
For my last 2 days work, I feel my last elog is reliable.
Today other than doing this, I checked for the higher order modes of the cavity, misaligning one of the MC mirror though the software only. I didn't mention it in my elog cause although I saw the presence of the higher order modes I didn't record it, so I can not upload any picture in support of such a statement.
I misaligned ITMX pitch on Friday and brought out the beam at 44" height. The beam was bouncing to much. I only realized it this morning why. The OSEM voltages are 1.8, 1.7, 0.2 and 0.9V Even with a stable 8-9 mm diameter beam you would be clipping
on the beam scanner 9 mm aperture. You can bring out the beam with one mirror right after PR3, just remove PRMOP2
We tweaked the mirror on the AP table to go through the center of the lens in order to get a more circular beam, but it seemed ineffective. So we put an IR card in front of the lens and behind the lens to see if the beam was circular or ovacular, but could not tell. We also moved the camera to see, but still couldn't see a distinct circle or oval. So Mike and Q will do a beam scan tomorrow in both the X and Y directions to see if the beam is circular or not.
On Friday, Koji and I adjusted the beam pointing into the DRMI using the PZT yaw and found that the beam inside the DRMI (as seen on the AS camera) looked OK (not distorted too much).
So it seems that the issue seen before, namely that the DRMI resonant mode is very strange, is no longer true.
The camera image at the AS port still looks elliptical. So Jenne and Mike have started to make this beam round by adjusting the lenses.
Our plan now is:
1) Fix AS camera optics to get a round beam (single bounce off of ITMY).
2) Flash DRMI to make sure the beam at AS is still round.
3) Using the moveable Watec camera and Sensoray, get images of the spot on all DRMI mirrors with DRMI flashing. Use targets and rulers whenever possible to get quantitative measurements of the beam positions. (i.e. just saying "Oh, its pretty much in the center" is the Mickey Mouse approach to science)
4) Align all pickoff beams in this situation. Make sure there is no in vac clipping. Align IP POS and ANG using this input beam pointing.
5) Pump down.
We conducted a beam scan on the AP table of the AS beam. We used a lens to focus the beam onto a power meter, and slowly moved a razor blade across the beam using a micrometer, vertically and horizontally both in front of and behind the beam. We also had to block the beam next to the AS beam in order to do this, but is unblocked now. Mike will begin curve fitting the data to try and see if there is a different spot size given by the x-axis vs. the y-axis, and if the lens has any effect.
Eric Quintero and Mike Jenson received 40m specific basic safety training.
Rana is proposing 50 mm hole in the baffle plate that is attached to the tower. Atm1
Atm2 is showing the back side where the solid line is 40 mm
Summary: Recorded the presence of higher order modes in IMC
What I did: Misaligned the flat mirror MC1 by small amount in both pitch and yaw (it was needed to be done cause at the beginning of the experiment no higher order modes were present) and scanned the cavity for frequency-range 32MHz to 45MHz.
I found the presence of higher order modes around 36.7MHz (1st order) and 40.6MHz (2nd order) along with two other strong modes near 35MHz and 42.5MHz.
[ericq, mikej, some input from zach]
After realigning the MC, the measurement was repeated this afternoon. This time, however, we isolated the beam from ITMY by misaligning ITMX. The beam looked somewhat elliptical to me, and Mike should have fits up tonight. Afterwards, ITMX was returned to the position I found it in, and the PMC shutter and access connector were closed. (Sorry about last night!)
Please, restore condition after you finished and update elog right away! People wasted hours yesterday not knowing the condition of the MC
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.
14.112 hundredths of an inch in the vertical direction
10.883 hundredths of an inch in the horizontal direction
Plots and error bars to come soon.
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
The PMC reflection made it seem that the beam going into it was misaligned. I went to the table and aligned the input beam to maximize the PMC transmission. I got ~10% improvement.
Just to check if something was loose, I started tapping things upstream of the Faraday. When I tapped the actual PMC body it seemed to get unseated and the reflected (unlocked) power jumped up by more than a factor of two.
I don't understand how this could be. The attached trend of the PMC channels shows that ever since the PSL upgrade, the PMC refl has been at the low level of ~0.3 V, except for a brief phase soon after the upgrade late in 2010 and then also for a few hours early in May of 2012.
If the PMC body actually moved, it seems that the pointing into the MC would also change and I don't see that. So what else can it be? Is there some clipping or dust or a burn spot on the PMC REFL path?
The PMC refl image was lost after the body re-settled itself. Jenne and I re-aligned it and added a 0.5 ND filter to the existing ND in order to account for the higher power. We should hide all of the reflective ND filters and just use absorbtive ND for the cameras to prevent reflections.
This image of the past hour shows the event at just before midnight (0650 UTC) where the PMC reflection goes up from 0.28 to 0.85.
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 have given Den 4 G&H R>99.99% mirrors to be installed on the 4 active tip tilts.
I've installed the mirrors on 4 tip-tilts. I was able to align 3 of them in pitch, the last one has a screw with damaged thread, I'll continue with it tomorrow.
Alignment accuracy in pitch is ~0.1 mrad. Mirrors oscillate a lot probably due to air flow coming from the side wall.
After looking at the in-vacuum layout I think we should make two changes during the next vent:
1) Reduce the number of mirrors between the FI and its camera. We install a large silvered mirror in the vacuum flange which holds the Faraday cam (in the inside of the viewport). That points directly at the input to the Faraday. We get to remove all of the steering mirror junk on the IO stack.
2) Take the Faraday output (IFO REFL) out onto the little table holding the BS and PRM Oplevs. We then relocate all 4 of the REFL RFPDs as well as the REFL OSA and the REFL camera onto this table. This will reduce the path length from the FI REFL port to the diodes and reduce the beam clutter on the AS table.
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.
Looks good. Any way that you can tell in an unambiguous way, where the beam is, is very good. Ideally we want to have1-2 mm accuracy.
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:
I've measured seismic and acoustic noise on BS and AS tables. It seems that horizontal motion of BS table is ~1.5-2 times more then AS table in the frequency range 5-50 Hz.
More photos were taken. Will post Monday, because too hungry now.
I've suspended microphones around the lab
This seismic measurement is for BS and AS tables.
This was in response to my suggestion to move the REFL beam path to the table containing the BS/PRM Oplevs. From this seismic data it is clear that the BS table is no worse than the AS table, so we should plan to make the layout change during the next vent.
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.