[Yuta, Suresh, Rana and Kiwamu]
The DC alignment problem of MC2 was fixed.
There were some loosely connected cables on the backside of a VME rack which contains the MC2 SOS driver.
We pushed those connectors to make them tightly connected. And then the problem disappeared.
(voltage unbalance on coils)
Before fixing it Yuta opened the satellite box and measured the voltage across the coils using a voltmeter.
At that time UL and LR showed 20 times smaller voltages than that of the other two when we moved the DC alignment slider from min. to max. on the medm screen.
This behavior is exactly consistent with the wired motion of a beam spot which we saw when we were aligning MC2.
(diagnostic using optical lever)
After pushing the connectors, we made an optical lever using a red laser pointer in order to check the actual motion of MC2.
We confirmed that MC2 respond correctly to the alignment slider.
It turned out that the DC alignment of MC2 from epics doesn't helathily work.
For example, the pitch slider does drive the yaw alignment as well.
We've put the old PRM and SRM (which were living in a foil house on the cleanroom optical table) into Steve's nifty storage containers. Also, we removed the SRM which was suspended, and stored it in a nifty container. All 3 of these optics are currently sitting on one of the cleanroom optical tables. This is fine for temporary storage, but we will need to find another place for them to live permanently. The etched names of the 3 optics are facing out, so that you can read them without picking them up. I forgot to note the serial numbers of the optics we've got stored, but the old optics are labeled XRM ###, whereas the new optics are labeled XRMU ###.
Koji chose for us PRMU 002, out of the set which we recently received from ATF, to be the new PRM. Suresh and I drag wiped both sides with Acetone and Iso, and it is currently sitting on one of the rings, in the foil house on the cleanroom optical table.
We are now ready to begin the guiderod gluing process (later tonight or tomorrow).
- Steve is working on the storage shelf for those optics.
- PRMU002 was chosen as it has the best RoC among the three.
We've aligned the guiderod and wire standoff to the PRM, each partly. They have both been aligned to the correct distance above the scribe lines, but they have not yet been centered forward/backward along the thickness of the optic. So, we're working on it...
We have positioned the guide rod and the wire-stand-off on the optic in the axial direction.
We have selected six magnets whose magnetic strength is +/-5% of their mean strength (180 Gauss). The measurement was made as follows:
1) each magnet was placed on its end, on the top of a beaker held upside down.
2) The Hall probe was placed directly under the magnet touching the glass from the other side (the inside of the beaker).
This ensures that the relative position of the magnet and the probe remains fixed during a measurement. And ensures that their separation is the same for each of the magnets tested.
With this procedure the variation in the measured B field is less than +/- 10% in the sample of magnets tested.
This afternoon I epoxied the guiderod and wire standoff to the new PRM. I also epoxied the magnets that Suresh picked out to the dumbbell standoffs. We'll let them all cure over the weekend, and then I'll glue the magnets to the optic on ~Monday.
Notes about the epoxy:
Previously, we had been using the "AN-1" epoxy, which is gray, with a clear hardener. Bob recommended we switch to "30-2", which is clear with clear, and has been chosen for use in aLIGO. Both were vacuum approved, but the 30-2 has gone through ~2 months of testing at the OTF (Optics Test Facility?) over in Downs under vacuum, to check the level of outgassing (or really, non-outgassing).
The 30-2 is less viscous than the AN-1, and it takes less glue to do the same job, so we should keep that in mind when applying the epoxy. When I put the glue next to the guiderod and standoff, it got wicked along the length of each rod, which is good. I can't reach the whole length of the rod with my glue applicator because the fixture holding them in place blocks access, so the wicking is pretty handy.
I've also added the updated version of my Status Table for the suspensions.
[Jenne, Suresh, Thanh (Bram's Grad Student)]
When we removed the grippers from the magnets on the PRM, one of the face magnets broke off. This time, the dumbbell remained glued to the optic, while the magnet came off. (Usually the magnet and dumbbell will stay attached, and both come off together). I had 3 spare magnet-dumbbells, but only one of them was the correct polarization. The strength of the spare magnet was ~128 Gauss, while the other magnets glued to the PRM are all ~180 Gauss. We considered this too large a discrepancy, and so elected to reuse the same magnet as before.
We removed the dumbbell from the optic using acetone. After the epoxy was gently removed, we drag wiped the AR face of the optic (Acetone followed by Iso, as usual), being careful to keep all the solvent away from all the other glue joints. We cleaned off the magnet with acetone (it didn't really have any glue stuck on it...most of the glue was stuck on the dumbbell), and epoxied it to a new dumbbell.
The PRM, as well as the magnet-dumbbell gluing fixture are in the little foil house, waiting for tomorrow's activities. Tomorrow we will re-glue this magnet to the optic, and Thursday we will balance the optic.
This still leaves us right on schedule for giving the PRM to Bob on Friday at lunchtime, so it can bake over the weekend.
Thanh and I re-glued the magnet to the PRM following the procedure outlined by Jenne
The PRM in the gluing fixture has been placed in the little foil house and left to cure for a day.
If all goes well the balancing the PRM will be done tomorrow.
The standoff glued. The incandescent lamp set for curing the epoxy.
Jenne and Suresh did the balancing job. The next job was to glue it.
They ran out of the clear epoxy, and tried to use the grey epoxy which we used on the other suspensions for the upgrade.
They found that the solution A with grey color one was dried out and grainy.
We made a test piece of the grey epoxy (mixed with the solution B) in order to see the glue is still usable or not.
After the PMA party, we found that the glue was not stiffening but brittle. We judged that the grey epoxy is no longer useful.
Steve found a pack of Vac Seal in the chemical fridge. We decided to use this one for the gluing of the standoff.
After the gluing, we set an incandescent lamp to make the glue warm.
Finally, we wrapped the suspension tower with Al foils and turned the HEPA fans again.
We took a look-see at the PRM after the gluing from last night. The balance is still okay. The reflected beam is a teeny bit below the laser aperture (center of the beam maybe ~2mm below, so ~1mRad low). This is within our okay range, since the DC offset that the OSEMs will give will be even more, and the coils can definitely handle this kind of offset.
We took the optic out of the tower, and gave it to Bob and Daphen to bake over the weekend.
Over the weekend, Bob and Daphen gave the PRM a 48hr. vacuum bake. This afternoon Suresh and I placed it back in the wire in the tower. We used the microscope-on-translation-stage technique to make sure the scribe lines on each side of the optic are at the same height, and then secured the PRM using all of the EQ stops. It is wrapped in foil, and ready for its journey into the IFO room. When we next have the BS chamber open, we should put the PRM in, and move the current PRM to its final place on the ITMY table as the SRM.
Physical Electronics: Vac-Seal #288-6000 arriving Monday. Our last bag used last week had a p/n 1002003 with expiration date .....2009 ? and it was stored in the
refrigerator all times. We are getting 68 small bags.
We should have precision gluing notes of epoxies/procedures used on our sus upgrade.
We have put together the new-old ETM towers. These are the ones which were hanging out on the flow bench down the arm for years and years, and have recently been re-baked. Interestingly, these are predominantly steel, whereas the newer ones are mostly aluminum. This caused momentary drama while we scrounged for the correct screws (we needed more silver-plated screws than anticipated, since we were screwing into steel and not aluminum), however the miscellaneous clean hardware collection came to the rescue. We did however use up all of the 1/4-20 3/4" silver plated screws, so hopefully no one else needs more later...
We only found 5 (enough for one of the two towers) spring plungers which are used to hold the OSEMs in place. Suresh is sending an email to Steve to ask him to buy some more, so we can get them cleaned in time for use. This is important, but not super urgent, since we have ~ 2 weeks before the ETMs will be ready for installation.
Koji has not yet had a chance to inspect the ETM data sheets and choose for us which pair of ETMs to use (ATF sent the 4 ETMs in matched pairs). So we will not begin the "arts and crafts" until tomorrow-ish.
Selection of ETMs
Of the four ETMs (5,6,7 and 8) that are with us Koji gave us two (nos. 5 and 7) for use in the current assembly. This decision is based on the Radius of Curvature (RoC) measurements from the manufacturer (Advanced Thin Films). As per their measurements the four ETMs are divided into two pairs such that each pair has nearly equal RoC. In the current case, RoCs are listed below:
The discrepancy between the measurements from these two companies leaves us in some doubt as to the actual radius of curvature. However we based our current decision on the measurement of Advanced Thin Films.
Assembly of ETMs
We drag wiped both the ETMs (5 and 7) and placed them in the Small Optic Gluing Fixture. The optics are positioned with the High Reflectace side facing downwards and with the arrow-mark on the Wire Standoff side (big clamp). We then used the microscope to position the Guide Rod and the Wire Standoff in the tangential direction on the ETMs (step 4 of the procedure specified in E010171-00-D)
We will continue with the rest of the assembly tomorrow.
I have selected a set of 16 magnets which have a B field between 900 to 950 Gauss (5% variation) when measured in the following fashion.
I took a Petri-dish, of the type which we usually use for mixing the glue, and I placed a magnet on its end. I then brought the tip of the Hall-probe into contact with the Petri-dish from the opposite side and adjusted the location (and orientation) of the probe to maximise the reading on the Gauss meter.
The distribution of magnets observed is listed below
The set of sixteen has been have been placed inside two test tubes and left on the optical bench (right-side) in the clean room.
The ETM assembly has moved forward a couple of steps. We have completed the following:
1) Positioning the guide rod and wire stand-off on both the ETMs (5 and 7)
2) The magnets had to be cleaned with an acetone wash as they had touched the plastic Petri-dish (not cleaned for vacuum).
3) The magnets and the Al dumb-bells have been glued together and left to cure in the gluing fixture.
4) The guide-rod and wire stand-offs have also been glued to the optic and left to cure for 24 hrs.
JD: As you can see in my nifty status table, we are nearing the end of the suspension story.
JD: As you can see in my nifty status table, we are nearing the end of the suspension story.
We are going to try (but can't guarantee) to get ETMX to Bob for baking by Friday at lunchtime, that way we can re-suspend it on ~Monday, and place it in the chamber. Then we could potentially begin Green arm locking next week. Steve has (hopefully!!) ordered the spring plungers for ETMY. The receiving and baking of the spring plungers is the only current delay that I can foresee, and that only is relevant for one of the optics.
We (who is going to be in charge of this?) still need to move the SRM OSEMs & cables & connectors to the ITMY chamber from the BS chamber.
Today has been a downright miserable day in the world of suspension work. Thumbs down to that:
Yesterday, we had glued 2 full sets of magnets to dumbbells. Today, half of those broke. I think I put too thin of a layer of glue on the magnets when gluing them to the dumbbells. All magnet/dumbbell assemblies should pass the test of being picked up by the dumbbell while the magnet is stuck to the optical table or a razor blade. 6 of the 12 magnets failed this test. Suresh soaked the dumbbells that had been used in acetone, and scrubbed them, so we can reuse them when we reglue things tomorrow. By some miracle, we have exactly one full set intact (for each set of 6, we need 4 of one direction and 2 of the other). This was frustrating, but not yet a deal-breaker. That part comes next....
I got ETMU05 nicely aligned in the magnet gluing fixture, and then was on my last check of whether the side magnets would be glued in the correct place when I realized that the fixture is all wrong for the ETMs. This final check was added to the procedure after the drama with the ITMs of having the side magnets glued incorrectly as a result of the fixture being specific to the wedge angle of the optic. Kiwamu and I had set the fixture to be just right for the ~1deg wedge corner station optics, but the ETMs have a 2.35deg wedge (according to the Coastline spec sheet, which is consistent with our measurements when placing the guiderod and standoffs). Suresh and I need to reset the height of the optic in the fixture using more teflon sheets, but we don't have a whole lot of options ready in the cleanroom. We're going to cut some more pieces and ask Bob to clean them tomorrow. Since the way the fixture holds the teflon is a little hoaky, Suresh suggested just resting the optic on teflon pads, rather than screwing the teflon to the fixture, and then putting the optic on the pads. We'll try Suresh's method tomorrow, and hopefully it will be pretty easy.
At least the guiderods and standoffs were successfully glued to the optics....
Here's the updated Status Table. I don't think we're going to be able to have an ETM ready for the chambers early next week, but we should still be able to have both ready for the Monday after Thanksgiving. The spring plungers arrived today, and were given immediately to Bob and Daphen for cleaning.
To clean the glue off the magnets and dumbbells I soaked them in Acetone for about an hour and then scrubbed the ends clean with a lint free tissue soaked in Acetone.
I then examined the ends under a microscope and found that while the flat faces were clean some of the grooves were still filled with glue.
While examining the magnets I found some small magnetic fibers stuck to the magnets. Rana had mentioned these before as potential trouble makers which could degrade the high frequency performance of the OSEMs.
To try and get the glue out of the grooves I put the dumbells through an ultrasonic bath for ten mins. Most of the glue has been removed from the grooves. Pics below
I proceeded try and recover the lost time by sticking the magnets back to the dumbbells. Increased the quantity of the glue to a slightly larger amount than usual. It should definitely squish out a bit now. We will know tomorrow when we open the gluing fixture.
Suresh and I glued the intact-from-the-first-round magnets to ETMU05. I accidentally got too much glue on one of the dumbbells (the glue was connecting the dumbbell to the gripper - bad news if we let that dry), and while I was cleaning it, the magnet broke off. So I used one of the ones that Suresh had re-glued last night, and he is putting that one back together after some cleaning.
To set the fixture, Suresh had the great idea of using small pieces of foil underneath the teflon pads to set the height of the optic in the fixture. The optic still rests on the teflon pads, but with the foil we have finer control over how the optic sits. Neat. Since both ETMs are the same, we shouldn't have to do any more adjustment for the other ETM.
The updated Status Table:
I examined the magnet-dumbbell joints under the microscope to see whether the glue that I applied yesterday was sufficient or in excess.
I think the pictures below speak for themselves !
During the gluing process the Al dumbbell stays below and the magnet with a drop of glue on the lower face is placed on it and held in the teflon fixture. As seen in the pics the glue seems to have run up the surface of the magnet and has not collected in the narrow part of the dumbell. So it has climbed up along the narrow gaps between the magnet and the teflon fixture by capillary action. The glue stops where the teflon fixture ends, a little before reaching the free end of the magnet, which further indicates the capillary action.
A story about minor disasters, and crises averted:
Once upon a time, in a cleanroom not so far away..... there lived an optic. To preserve anonymity, we shall call him "ETMU05". This optic had a rough day. When removing the grippers from the magnet-to-optic fixture, 4 out of 6 magnets broke off the dumbbells (the dumbbells were still securely glued to the optic...these had come out of the same batch that had problems last week, same problem). The remaining 2, LL and LR, were sadly of the same polarity. This is bad, because it means that the "humans" taking care of "ETMU05" didn't check the polarity of the face magnets properly, and ensure that they were laid out in an every-other pattern (LL and UR having the same polarity, and LR and UL having the opposite). So, the humans removed all magnets and dumbbells from ETMU05. All remaining glue was carefully scrubbed off the surfaces of ETMU05 using lens paper and acetone, and the magnets and dumbbells were sonicated in acetone, scrubbed with a lint-free wipe, sonicated again, and then scrubbed again to remove the glue. ETMU05 had a nice cleansing, and was drag wiped on both the AR and HR surfaces with acetone and iso. ETMU05 is now on vacation in a nice little foil hut.
His friend, (let's call him ETMU07) had a set of magnets (with polarities carefully confirmed) glued to him. The cleaned magnets and dumbbells removed from ETMU05 were reglued to their dumbbells, and should be dry by tomorrow.
.....And then they lived happily ever after. The End.
The revised schedule / status table:
ETMU07 had its wire winched to the correct height, was balanced, standoff glued. Can be ready for going into the oven tomorrow, if an oven is available. (One of Bob's ovens has a leak, so he's down an oven, which puts everything behind schedule. We may not be able to get anything into the oven until Monday).
ETMU05 had magnets glued to the optic. Hopefully tomorrow we will winch the wire and balance the optic, and glue the standoff, and be ready to go into the oven on Monday.
The spring plungers were sonicated, but have not yet been baked. I told Daphen that we'd like the optics baked first, so that we can get ETMX in the chamber ASAP, and then the spring plungers as soon as possible so that we can install ETMY and put the OSEMs in.
The updated status table:
We removed ETMU07 from the suspension tower, after confirming that the balance was still good. Bob put it in the oven to bake over the weekend. The spring plungers and our spare magnets are all in there as well.
I tried to remove the grippers from ETMU05, and when I did, both side dumbbells came off of the optic. Unfortunately, I was working on getting channels into the DAQ, so I did not clean and reglue ETMU05 today. However Joe told me that we don't have any ETMY controls as yet, and we're not going to do Yarm locking (probably) in the next week or so, so this doesn't really set any schedules back.
The cleaning of ETMU05 will be tricky. Getting the residual glue off of the optic will be fine, but for the dumbbells, we'd like to clean the glue off of the end of the dumbbells using a lint free wipe soaked in acetone, but we don't want to get any acetone in the magnet-to-dumbbell joint, and we don't want to break the magnet-to-dumbbell joint. So we'll have to be very careful when doing this cleaning.
The Status Table:
ETMU05 : Gluing Side magnets back on to the optic.
The following steps taken in this process:
1) The two magnet+dumbell units which had come loose from the optic needed to be cleaned. A lint free wipe was placed on the table top and a few cc of acetone was poured on to it. The free end of the dumbbell was then scrubbed on this wipe till the surface regained its shine. The dumbell was held at its narrow part with a forceps to avoid any strain on the magnet-dumbbell joint.
2) The optic was then removed from its gluing fixture (by loosening only one of the three retaining screws) and placed in an Al ring. The glue left behind by the side magnets was scrubbed off with a optical tissue wetted with Acetone.
3) The optic was returned to the gluing fixture. The position of the optic was checked by inserting the brass portion of the gripper and making sure that the face magnets are centered in it [Jenne doubled checked to be sure we got everything right].
4) The side magnets were glued on and the optic in the fixture has been placed in the foil-house.
If all goes well we will be able to balance the ETMU05 and give it to Bob for baking.
ETMU07 : It is still in the oven and we need to ask Bob to take out. It will be available for installation in the 40m tomorrow.
Last night I found that the response of ITMX against the angle offsets were strage.
Eventually I found a loose connection at the feedthrough connectors of ITMX chamber.
So I pushed the connector hard, and then ITMX successfully became normal.
It looked like someone had accidentally kicked the cable during some works.
This bad connection had made unacceptable offsets in the OSEM readout, but now they seem fine.
We put ETMX back in its tower, and confirmed its balance. It might be pointing a teensy bit upward, but it is way less than the DC pointing offset we see when we put the OSEMs in the towers (since the PDs and LEDs have some magnetic bits to them).
Discussions are ongoing as to where the ETM should sit on its table, but we'll probably toss it into the chamber later this evening.
I took ETMY out of the magnet gluing fixture, and put it in a ring, in the foil house. It is ready to have the wire winched and get balanced at our convenience.
[Kiwamu, Jenne, Koji, Suresh]
The following steps in this process were completed.
1) Secured the current ETMX (Old ETMY) with the earth quake stops.
2) Removed the OSEMs and noted the Sl no. of each and its position
3) Placed four clamps to mark the location of the current ETMX tower (Old ETMY's position on the table)
4) Moved the ETMX (Old ETMY) tower to the clean table flow bench. In the process the tower had to be tilted during removal because it was too tall to pass upright through the vacuum chamber port. It was scary but nothing went wrong.
5) Koji calculated the location of the new ETMX and told us that it should be placed on the north end of the table.
6) Moved the OSEM cables, counter balancing weights and the 'chopper' out of the way. Had to move some of the clamps securing the cables.
7) Moved the ETMU07 tower from the clean room to the ETMX table
8) Positioned the OSEMs as they were placed in the earlier tower and adjusted their position to the middle of the range of their shadow sensors. The four OSEMs on the face did not give us any trouble and were positioned as required. But the side OSEM could not be put in place. The magnet on the left side, which we are constrained to use since the tower is not designed to hold an OSEM on the right side, seems a little too low (by about a mm) and does not interrupt the light beam in the shadow sensor. The possible causes are
a) the optic is rotated. To check this we need to take the tower back to the clean room and check the location of the optic with the traveling microscope. If indeed it is rotated, this is easy to correct.
b) the magnet is not located at the correct place on the optic. This can also be checked on the clean room optical bench but the solution available immediately is to hold the OSEM askew to accommodate the magnet location. If time permits the magnet position can be corrected.
We have postponed the testing of the ETMU07 tower to 1st of Nov Dec.
We finished the installation of ETMX into the chamber.
In order to clear the issue of the side OSEM, we put a spacer such that the OSEM can tilt itself and accommodate the magnet.
Though we still don't fully understand why the side magnet is off from the center.
Anyway we are going to proceed with this ETMX and perform the REAL green locking.
(what we did)
- took the ETM tower out from the chamber, and brought it to the clean room again.
- checked the rotation of the ETM by using a microscope. It was pretty good.
The scribe lines at the both sides are at the same height within the diameter of the scribe line.
- checked the height of the ETM by measuring the vertical distance from the table top to the scribe line. This was also quite good.
The height is correctly 5.5 inch within the diameter of the scribe line.
- checked the magnet positions compared with the OSEM holder holes.
All the face magnets are a little bit off upward (approximately by 1mm or less).
The side magnet is off toward the AR surface by ~ 1-2mm.
(yesterday we thought it was off downward, but actually the height is good.)
- raised the position of the OSEM holder bar in order to correct the miscentering of the face magnets.
Now all the face magnets are well centered.
- brought the tower back to the chamber again
- installed the OSEMs
We put a folded piece of aluminum foil in between the hole and the side OSEM as a spacer.
- leveled the table and set the OSEMs to their mid positions.
- slided the tower to place
ETMU05 (ETMY) had its wire winched to the correct height, was balanced, and had the standoff glued. Since it's kind of like final exam week at Caltech, Suresh had his suspension exam today, and did most of this work himself, with me hanging around and watching.
As you can see in my almost entirely green table, all that is left to do with the whole suspensions project is bake the optic (hopefully Bob has time / space this week), and then stick it in the chamber! Hooray!!! (Can you tell I'm excited to not spend too much more time in the cleanroom?)
The ETMU05 has been removed from the suspension and put into the little foil house.
Before removing it I checked the position and pitch of the optic with reference to the table top.
Using the traveling microscope I checked the height of the scribe lines from the table top. They are at equal heights, centered on 5.5 inches, correct to about a quarter of the width of the scribe line.
The retro-reflection of the He-Ne laser beam is correct to within one diameter of the beam at a distance of about 1.5m. This is the reflection from the rear, AR coated, surface. The reflection from the front, HR coated, surface was down by about two diameters.
Jenne has checked with Bob and agreed on a date for baking the optic.
I am leaving ITMX and ETMX freely swinging, so that later I can take the spectra and diagonalize the input matrices.
Please don't restore the watchdogs until tomorrow morning.
The input matrix of ITMX has been diagonalized.
The evaluation of this diagonalisation will be done tonight by freely swinging ITMX again.
(Somehow I couldn't get any data for ETMX from the DAQ channels. I will try it again tonight.)
For solving the matrix, I used Yuta's python code called inmartixoptimizer.py.
I took the transfer functions of UL->UR, UL->LL and UL->LR as described in this entry.
In the measurement, the frequency bin was set to 0.001 Hz and the data were 50 times averaged on dtt.
Here is the new input matrix.
[[ 0.87059649 1.14491977 1.07992057 0.90456317]
[ 0.64313916 0.55555661 -1.44997325 -1.35133098]
[ 1.13979571 -1.19186285 -0.89606597 0.77227546]]
This matrix should give a better performance than before.
The oplevs have been installed on ITMX and ETMX.
Now the oplev servos are running.
The lock of the green beam became more stable after the oplevs were activated.
(what I did)
- opened the ITMX and ETMX chamber.
- rearranged the oplev mirrors in the vacuum chambers so that we can have the reflected oplev beam coming out from the viewport.
At the ITMX table, I put the oplev mirrors approximately on the designed places.
- aligned the beam on the optical benches
- strung a ribbon cable at the 1X9 rack.
This cable connects the oplev interface board and the ADC blue golden board.
- modified c1scx simulink model.
Since the model didn't have proper connections to the ADC channels, I added four ADC channels and plugged them into oplev servo in the model.
- relaunched the c1scx code after building and installing it.
- activated the oplev servos. Amazingly the default gains did work (i.e. all the gain = 1)
- after aligning X arm to the green beam, I did final centering of oplev beams
- - - - - ADC connection for ETMX oplev signals :
ADC0_24 = segment_1
ADC0_25 = segment_2
ADC0_26 = segment_3
ADC0_27 = segment_4
Tonight, swing again.
Please do not restore the watchdogs until tomorrow (Dec.9) morning.
We measured Open loop TF for oplev pitch on ITMX.
All feed back filter of oplev was on as same as before. Original notch filters which notches above 10Hz resonance should be modified with some measurements of present resonant frequency. Up to 10Hz, a simple f^2 filter is used, so the notch should not affect this measurement.
Measured upper UGF is about 2Hz with gain slider 1, and lower UGF is 1.3Hz. Phase margin is 40 degree, so it is not a good idea to increase the gain drastically.
I have measured the coherence also but I could not find a way to put it on this picture. Anyway coherence below 0.6Hz was not so good like ~0.95. This can be improved if larger excitation is used next time.
During this measurement around 0.2-0.3Hz, small earthquake happened but seemed OK for the control.
We will measure the other TF, yaw, ETMX or somthing, maybe tomorrow, due to free swinging ITMX and ETMX tonight.
After Kiwamu had set the free swinging mode for ITMX and ETMX, I found a big jump of ITMX pitch and yaw. This jump is shown on oplev and OSEM plots.
I talked with Kiwamu on the phone that a shutdown of suspensions does not add a big offset, and so that it should not make a big jump.
We were not sure that this jump was due to the shutdown or drift or something else. Anyway I put ITMY oplev on center again at 0;57am.
In this morning, the same thing happened but to opposit direction when Kiwamu activated ITMX and ETMX. Then it turned out that 1000ct offset was existing on pit of ITMX. Erasing the offset fixed ITMX to normal position.
However a big drift exists in 11hours plot on ITMX 0.1->-0.25 at OLPIT, -580->-605 at SUSPIT and 0.08->0.15 at OLYAW, no significan drift at SUSYAW. On the other hand, ETMX has no big drift but has 10-30minites order fluctuations.
After 6am both the drift and the fluctuation became, roughly saying, 10 times larger, probably due to the human activity.
[Koji, Osamu and Kiwamu]
We found that the ETMX free swinging spectra showed a strange resonant frequencies.
We are going to inspect the suspension today.
In a ideal case the SOS (Small Optic Suspension) is supposed to have the following resonant frequecies.
(Although we didn't carefully identify which corresponds to which)
f_POS ~ 0.98 Hz
f_PITCH ~ 0.66 Hz
f_YAW ~ 0.8 Hz
f_SIDE ~ 0.99 Hz
However ETMX showed the following resonant frequencies.
f_POS ~ 0.91 Hz
f_PITCH ~ 0.7 Hz
f_YAW ~ 0.93 Hz
f_SIDE ~ 1.0 Hz
Especially f_YAW looks pretty high. Also the others are not at the right frequencies.
So we are suspicious that something wrong is happening on the ETMX suspension.
We checked the ETMX suspension and found the UR OSEM was close to the magnet.
So we rotated the UR OSEM so that it won't touch the magnet any more.
We will check the resonant frequencies again by taking the spectra.
In fact the ETMX stacked when we applied a big angular offset to Yaw direction.
This was because that the magnet was actually touching the UR OSEM.
The earthquake stops were fine, they weren't touching the test mass.
Also we looked at the wire and the standoffs, they seemed fine.
We aligned the beam axis pointing down to both X and Y arm.
Now the beams are hitting the centers of both ETMX and ETMY.
Amazingly Osamu made X arm flashing by aligning the cavity.
(what we did)
- opened almost all the chambers except for the MC2 chamber.
- locked and aligned the MC.
We set Marconi to the right frequency, which had been set to the default values, probably due to the power outage in the last weekend.
Also we found a DAC cable disconnected from the IO chassis of c1sus. So we connected it in order to damp the MC suspensions.
- aligned MMT2 and PZT2 in order to let the beam go through the center of PRM.
- checked the beam centering at the two TTs (PR2, PR3).
- rotated PR3 to make the beam go through the centers of both ITMY and BS at the same time.
- tried finding the beam spot at the ETMY chamber, and successfully found it.
To see such faint beam spot, we used an IR viewer.
In addition to that, we put a large piece of aluminum foil as a screen in the chamber.
- aligned the beam to the center of ETMY by tweaking the PZT mirror (SM2).
- aligned the BS so that the reflected beam at the BS goes through the center of ITMX.
- tried finding the beam spot at the X end, and successfully found it hitting the wall in the chamber.
- aligned the BS in order to let the beam hit the center of ETMX.
- tried aligning ETMX and ITMX to the beam.
Eventually we made the X arm flashing.
However the flash was a bit too weak to completely align the cavity.
(plan for tomorrow)
- reinstall some steering mirrors into the BS chamber
- check and neutralize PZT1
- alignment of IP_ANG
Good news. I feel multi-chromatic-locking success is just around the corner.
By the way, there's a new presentation on the DCC from the ANU group where they've locked a short single cavity with both colors - G1000735:
This plot shows ETM oplev and OSEM trend for 10 hours on day before yesterday as almost the same as plot shown this entry. I reported the 10-30minites fluctuations were seen, but I noticed it comes from not suspension but from oplev power fluctuation.
After Kiwamu fixed the ETM OSEM touch yesterday afternoon, still the same trend was seen, so we had thought what we fixed was not enough. This morning I looked at the yesterday's and day before yesterday's trend and noticed the simila trend both the pit and yaw in ETM oplev but not on the OSEM trend. Kiwamu suggested me to put the oplev sum on the same plot. It was!
So, ETMX is not bad, but in fact, still alignment fluctuation exist on the cavity. ITM?
This graph shows 5 hours data in minute trend for ITMX and ETMX from 5am to 10 am today. ITM pitch drift is 3 times lager than ETM pitch if the OSEM sensitivity is assumed to be the same.
This graph is last 1 hour data of above graph in second trend.
It is clealy seen that ITM yaw is jumping between two stages. I guess ITM is something wrong, touching magnets or earthquake stops?
I wish I could use a bigger font for this, but, the suspension work is totally done for the upgrade!!!
Now, nobody break any suspensions, or we're not going to be friends for a while.
Koji and I put ETMY back in its tower, and made sure that both scribe lines are at the correct height. We also confirmed that the balance is good (as Suresh mentioned in a previous elog, since we balanced using the AR surface, the HR surface is pointing downward a little bit, but it's well within the OSEMs ability to correct.
While we were in there, we also looked at Tip Tilt number 002. As mentioned in elog 3645, the pitch pointing was off by a little bit. Since the TTs don't have actuators, the pointing has to be pretty good. We tweaked the balancing, and now the reflected beam goes completely back into the laser aperture, so it's as balanced as it's going to get. This TT is now ready for installation onto the ITMY table as part of the SRC.
Kiwamu confirmed that he's going to install these optics tomorrow, since he's doing some other alignment work today.
Just for good measure, the Table:
I found that a few connections in the simulink model of c1scx was incorrect, so I fixed them correctly.
It had been a mystery why we had to put a funny matrix on ETMX (see this entry).
But now we don't have to do such a voodoo magic because the problem was solved.
Now the damping of ETMX is happily running with an ordinary output matrix.
I looked at the wiring diagram of the ETMX suspension (it's on Ben's web page) and confirmed that the coils are arranged in order of UL, LL, UR, LR.
But then I realized that in our simulink model they had been arranged in order of UL, UR, LL, LR.
So UR and LL had been swapped incorrectly !
So I just disconnected and plugged them into the right outputs in the simulink model.
I rebooted c1iscex in order to reactivate c1scx front end code.
After rebooting it, I changed the output matrix to the usual one, then everything looked okay.
(actually it's been okay because of the combination of the wrong connections and the funny matrix).
The alignment of the ITMs and the PRM has been done.
As a result their reflections now come out at the REFL port successfully.
The vacuum work is going on well as we scheduled at the last meeting.
(plan for tomorrow)
- installation of ETMY
- installation of OSEMs on ETMY
- alignment of the beam to the center of ETMY
- alignment of the ETMY to the beam
- final alignment of IP_ANG
- setting up the oplev for ETMY
- replace one of the steering mirrors at the RFEL path by a 0 deg mirror (see here).
- setting up POX/POY (if there are time)
- aligned the PRM tower such that the reflected beam goes back to exactly the same path as that of the incoming beam.
- leveled the ITMY table because the OSEMs of ITMY had been completely out of range.
- aligned the ITMY and ITMX in order to let the reflections back to REFL.
- with a help from Osamu, we put a CCD camera, which actually had been used as OMC_T, just after the view port on the AP table.
- looking at the CCD monitor we were able to see the reflected lights from the ITMs. (In fact sensor cards didn't help looking for the lights.)
- playing with the alignment of the ITMs, we easily obtained Michelson fringes, which were also visible on the CCD monitor.
[Zach and Kiwamu]
We installed the new ETMY tower and successfully aligned the beam to the center of ETMY.
Also we finished the final alignment of IP_ANG.
(what we did)
- took the old ETM out from the chamber and put it on the flow bench at the X end.
- with a help from Joe and Osamu, we brought the new ETM and put it roughly on place.
- did a fine positioning of ETMY.
- covered the ETM tower with a large peace of aluminum foil in order to see the spot on a video monitor.
- stoled a compact video monitor that was sitting on the PSL table since we don't have any monitors at the Y end.
- made a ~1cm hole on the foil as a target for the beam.
- steered PZT1 in order to correct the beam position on ETMY. This is done by looking at the spot on the video monitor.
- steered IPANG_SM1 to let the beam hit a steering mirror in the ETMY chamber which Koji installed recently.
Now we have IP_ANG coming out from the viewport of the ETMY chamber.
[Koji, Oasmu and Kiwamu]
We made the following progresses :
(1) installation of the last TT called SR2.
(2) fixing an earthquake stop issue on the BS
(3) fixing a clipping of beams at the dark port
(earthquake stops on the BS)
- When we were aligning the BS, we found that the BS showed funny behaviors.
For example a kick on LR didn't shake LRSEN, and a big DC angular offset (~ 8 in the medm screen ) was needed to keep a horizontal beam axis in the reflection.
We checked all the earthquake stops and found two suspicious earthquake stops at right bottom side.
They looked like slightly touching the BS. So we moved them further away from the BS.
Then the problem had gone. We doublechecked the health by kicking, applying an angular offset and so on.
We found transmitted/reflected beams from the BS to the dark port was clipped at the BS tower.
We moved the BS tower by ~1cm and realigned the rotation of the BS tower.
We also found the beam spots on the two TTs, PR2 and PR3, were offcentered. Especially the beam spot on PR3 was almost on the edge of the mirror.
Probably this was because we touched PZT1 when aligning the beam to the Y end.
So it means, it is not a good idea to align the beam to the end only by steering PZT1. We should use PR2 and PR3 as well when we align the beam to the Y end.
We realigned them such that the beam hits the center of PR2, PR3 and ETMY.
We worked on some more vacuum businesses. Today we finished did the following works:
- alignment of the POX mirrors
- alignment of the POP1 and POP2 mirrors
- installation of OSEMs onto SRM
- alignment of the SRM tower
(alignment of POP mirrors)
Since a beam on the POP path was quite too weak to see even by IR viewers, we used a He-Ne laser to imitate the real beam instead.
We injected the He-Ne beam from an optical bench to the chamber, and made it go through the PRM and PR2 by using some steering mirrors.
The pin assignment was flipped in a way of mirror image due to the extension cables which cause a mirroring.
So we made mirroring connectors to flipp them back to the correct pin assignment, and plugged the mirroring connectors in between the feedthrough of the BS chamber and the SRM satellite box.
This is a picture showing how they are connected now.