I decided to take a quick look at the data. Changes made to the ETMX coil driver board:
I also took the chance to check the integrity of the LM6321 ICs. In the past, a large DC offset on the output pin of these has been indicative of a faulty IC. But I checked all the ICs with a DMM, and saw no anomalies.
Measurement condition was that (i) the Fast input was terminated to ground via 50ohm, (ii) the Bias input was shorted to ground. SR785 was used with G=100 Busby preamp (in which Steve installed new batteries today, for someone had left it on for who knows how long) for making the measurement. The voltage measurement was made at the D-Sub connector on the front panel which would be connected to the Sat. Box, with the coil driver not connected to anything downstream.
Summary of results:
[Attachment #1] - Noise measurement out to 800 Hz. The noise only seems to agree with the LISO model above 300 Hz. Not sure if the low-frequency excess is real or a measurement artefact. Tomorrow, I plan to make an LPF pomona box to filter out the HF pickup and see if the low-frequency characteristics change at all. Need to think about what this corner freq. needs to be. In any case, such a device is probably required to do measurements inside the VEA.
[Attachment #2] - Noise measurement for full SR785 span. The 19.5 kHz harmonics are visible. I have a theory about the origin of these, need to do a couple of more tests to confirm and will make a separate log.
[Attachment #3] - zip of LISO file used for modeling coil driver. I don't have the ASCII art in this, so need to double check to make sure I haven't connected some wrong nodes, but I think it's correct.
Measurements seem to be consistent with LISO model predictions.
*Note: Curves labelled "LISO model ..." are really quad sum of liso pred + busby box noise.
My main finding tonight is: With the increased series resistance (400 ohm ---> 2.25 kohm), LISO modeling tells me that even though the series resistance (Johnson noise) used to dominate the voltage noise at the output to the OSEM, the voltage noise of the LT1125 in the bias path now dominates. Since we are planning to re-design the entire bias path anyways, I am not too worried about this for the moment.
I will upload more details + photos + data + schematic + LISO model breakdown tomorrow to a DCC page.
gautam noon 21 June 2018: I was looking at the wrong LISO breakdown curves. So the input stage Op27 voltage noise used to dominate. Now the Bias path LT1125 voltage noise dominates. None of the conclusions are affected... I've uploaded the corrected plots and LISO file here now.
I finished the re-soldering work today, and have measured the coil driver noise pre-Mods and post-Mods. Analysis tomorrow. I am holding off on re-installing the board tonight as it is likely we will have to tune all the loops to make them work with the reduced range. So ETMX will remain de-commissioned until tomorrow.
Initial tests look promising. Local damping works and I even locked the X arm using POX, although I did it in a fake way by simply inserting a x5.625 (=2.25 kohm / 400 ohm) gain in the coil driver filter banks. I will now tune the individual loop gains to account for the reduced actuation range.
Now I have changed the loop gains for local damping loops, Oplev loops, and POX locking loop to account for the reduced actuation range. The dither alignment servo (X arm ASS) has not been re-commissioned yet...
Per discussion today eve, barring objections, I will do the following tomorrow morning:
I checked the four rear coils on ETMX by exciting XXCOIL_EXC channel in DTT with amplitude 1000@ 500 Hz and observing the oplev PERROR and YERROR channels. Each coil showed a clear signal in PERROR, about 2e-6 cts. Anyway, the coils passed this test.
I also made xfer fctns of the 4 piston coils on ETMY and ETMX with OL_PIT. (I looked at all 4 even though the attached plot only shows three.) So it looks ike the coils are OK.
c1iscex machine is currently being setup and RT model c1scx is running.
But ETMX(south) didn't seem to be damped, so I checked it.
What I did:
1. Checked the wiring. It seemed to be OK.
Looked LEMO monitor output of SUS PD Whitening Board(D000210) with oscilloscope and they seemed to be getting some sensor signal except SDSEN.
SDSEN is funny. C1:SUS-ETMX_SPDMon decreases slowly when PD input cable is disconnected, and increases slowly when connected.
There might be some problem in the circuits.
Looked LEMO monitor output of SOS Coil Driver Module(D010001) with oscilloscope and they seemed to be receiving correct signal from DAC.
When ULCOIL offset is added, ch1 increased and so on.
2. Checked the direction of SUSDOF motion when kicked with one coil.
The result was;
This table tells you, when ULCOIL_OFFSET increases, SUSPOS increases and so on.
If URCOIL and LLCOIL are swapped, they look correct.
Also, they have opposite sign to the usual optics(e.g. MCs, BS, PRM).
3. Changed TO_COIL matrix according to the table above(see Attachment #1). Changed signs of XXCOIL_GAINs.
4. ETMX damped!
- Check the wiring after SOS Coil Driver Module and circuit around SDSEN
- Check whitening and dewhitening filters. We connected a binary output cable, but didn't checked them yet.
- Make a script for step 2
- Activate new DAQ channels for ETMX (what is the current new fresh up-to-date latest fb restart procedure?)
Finally I see what kicks the sus damping off
Huh? So should we ask them to put the container back? Or do you have some other theory about ETMX tripping that is not garbage related?
ETMX sus damping recovered.
Note: The giant metal garbage container was moved from the south west corner of CES months ago.
ETMX sus damping recovered. PSL enclousure is dusty at 20V rotation speed. Rainy days as outside condition.
ETMX sus damping restored
No we can't do that because the c1scx model is not working properly.
If you look into the real time controller screen you will find what I mean.
Quote from #6180
ETMX sus damping restored. It is still noisy
I should have elogged, but I turned off the watchdog to remind myself that iscex computer is still crashed. "Turning on" the damping doesn't do anything since there aren't any signals going to the coils from the computer.
ETMX sus damping restored and PMC locked manually.
ETMX sus damping restored.
PMC locked and ETMX suspension damping restored.
ETMX suspension damping restored.
[Steve, Yuta, Koji]
The ETMX heavy door was removed.
[Koji, Jenne, Alberto, Steve, Bob]
ETMX has been drag wiped.
Around 2:45pm, after the main IFO volume had come up to atmospheric pressure, we removed both doors to the ETMX chamber. Regular procedures (wiping of O-rings with a dry, lint-free cloth, covering them with the light O-ring covers, etc.) were followed. Koji took several photos of the optic, and the rest of the ETMX chamber before anything was touched. These will be posted to the 40m Picasa page. Steve and Koji then deionized the optic.
Koji removed the bottom front earthquake stop, and clamped the optic with the remaining earthquake stops.
The clean syringes were prepared: These are all glass and metal (nothing else) medical syringes. The size used was 100microliters. Earlier today, we had prepared our solvents in small little beakers which had been baked over the weekend. Brand new glass bottles of Acetone and Isopropyl Alcohol were opened, and poured into the small beakers. To make sure we have enough, we have 3 ~10ml beakers of each Acetone and Isopropyl.
We started with Acetone. The syringe was filled completely with acetone, then squirted onto a kimwipe. This was repeated ~twice, to ensure the syringe was well rinsed. Then the syringe was filled a little past the 100 microliter mark. Koji held a piece of lens cleaning paper to ETMX and used an allen wrench underneath the optic to help guide the paper, and keep it near the optic (of course, the only thing in actual contact with the optic was the lens paper). In one smooth shot, the plunger of the syringe was pressed all the way down. (This is a bit tricky, especially when the syringe is totally full. You have to squeeze it so the plunger moves fairly quickly down the barrel of the syringe to get a good arc of liquid. The goal is to shoot all of the solvent to the same place on the lens paper, so that it makes a little circle of wetness on the paper which covers the coated part of the optic. The amount of solvent used should be balanced between having too little, so that the paper is dry by the time it has been wiped all the way down, and too much such that there is still a residue of liquid on the optic after the paper has been removed.) The target was to hit the optic just above the center mark (the oplev was on, so I went for just above the red oplev dot). Immediately after applying the liquid onto the paper, Koji slowly and smoothly pulled down on the lens paper until it came off of the bottom of the optic. The acetone was repeated, for a total of 2 acetone wipes. Because acetone evaporates very quickly, more acetone is used than isopropyl. The optimal amount turned out to be ~115 microliters of acetone. It is hard to say exactly how much I had on the second wipe, because the syringe is not marked past 100 microliters. On the first wipe, with about 105 microliters, the lens paper was too dry at the bottom of the optic.
We then switched to Isopropyl. A new syringe was used, and again we rinsed it by filling it completely with isopropyl, and emptying it onto a kimwipe. This was repeated at least twice. We followed the same procedure for applying liquid to the optic and wiping the optic with the lens paper. On the first try with isopropyl, we used 100 microliters, since that was the preferred amount for acetone. Since isopropyl evaporates much slower than acetone, this was determined to be too much liquid. On the second isopropyl wipe, I filled the syringe to 50 microliters, which was just about perfect. The isopropyl wiping was done a total of 2 times.
After wiping, we replaced the front bottom earthquake stop, and released the optic from the other earthquake stops' clamping. The OSEM values were checked against the values from the screenshots taken yesterday afternoon, and were found to be consistent. Koji took more photos, all of which will be placed on the 40m Picasa page.
We visually inspected the optic, and we couldn't see anything on the optical surface of the mirror. Koji said that he saw a few particulates on some horizontal surfaces in the chamber. Since the optic seemed (at least to the level of human vision without a strong, focused light) to be free of particulates on the optical surface to start with, the suspense will have to remain until we button down, pump down, and try to lock the IFO to determine our new finesse, to see if the wiping helped any substantial amount.
We replaced the regular, heavy door on the inner side of the ETMX chamber (the side closer to the CES building), and put only a light door on the outer side of the chamber (the side closer to the regular walkway down the arm). We will look at the spectra of the OSEMS tomorrow, to confirm that none of the magnets are stuck.
We commence at ~9am tomorrow with ETMY.
* The LED lights are awesome. It's easy to use several lights to get lots of brightness (more than we've had in the past), and the chamber doesn't get hot.
* We should get larger syringes for the acetone for the large optics. It's challenging to smoothly operate the plunger of the syringe while it's so far out. We should get 200 microliter syringes, so that for the acetone we only fill them about half way. It was noticeably easier to apply the isopropyl when the syringe only had 50 microliters.
* It may be helpful to have a strong, focused optical light to inspect the surface of the mirror. Rana says that Garilynn might have such an optical fiber light that we could borrow.
ETMX enclosure feedtrouh cabeling corrected.
The enclosure top piece in the middle is still in the machine shop.
The carpenter who helps in the built just left for one week vacation.
The unit will be ready on April 1
I'd prefer doing the installation with the enclosure on the new table.
It's the only way to minimize the resonances of the enclosure with shimming.
Objective: measure the noise floor on the optical table and the floor so we can decide if the table needs better anchoring before swapping in
the larger optical table
The accelerometrs labeled as MC1 ( just north east of IOO chamber floor ) and MC2 ( north east leg of MC2 table floor ) were moved:
MC1 to the floor at the north west leg of optical table.
MC2 is in the north east corner of the optical table
Atm2 was taken after table leg bolts were tighed at 40 ft/lb
The spectrum looks similar to ETMY except the Z direction
Conclusion: up to 20 Hz this set up is good.
I didn't really appreciate this measurement until just now. IF you can save the DTT .xml file with all the traces in it (i.e. NOT just the plots), we should save this data for comparison plotting later. Perhaps Gautam can post the gzipped xml file for you into the log.
The accelerometers don't read any real noise below ~3 Hz, so we can't judge the difference down low, but this seems like a good measurement in the 5 - 100 Hz band.
Unfortunately I had closed all the DTT windows that Steve had used for the earlier plots. So I took the spectra again - there may be minor differences given that this measurement was taken at ~11pm at night. Anyways, plots and the xml data file are attached.
I switched off damping to the ETMX and used a reduced version of freeswing-all.csh script (called freeswing-ETMX.csh) to set it swinging. After about an hour I used the saved template ETMX/2008.08.06.xml to obtain the following plot.
There is something defintely wrong with the side sensor. It might be the electronics as it also has this problem with it slow channel readings (my previous elog today).
A few times this evening, I had been having trouble locking CARM and DARM with ALS, and holding it for very long. When it started happening again, I switched over to locking the individual arms with ALS. Yarm seems to be totally fine, but Xarm has something funny going on.
Rana and I have narrowed it down to being a problem with ETMX. We were watching ETMX's oplev and local damping error signals, and would see occasional glitch events. This happened when oplev + local damping were both on, both off, and when only local damping was on. We believe that this points to something weird with the coil driver and actuator chain.
We tried to watch for a while to see if it was a step event (something switching on and off periodically), or an impulse event (some transient oscillation in an opamp perhaps), but the problem went away again. We have come to no conclusions other than we have a problem that needs watching.
During our investigations, to more softly turn off the damping, Rana set the local damping gains, as well as the oplev gains to zero using a ramp time. We don't recall the precise numbers, and conlog doesn't have the gains recorded, so we made an educated guess. The local damping seems fine, but the oplev damping should be re-confirmed. Steve, can you please show Harry how, and have him help you measure the ETMX pitch and yaw oplev loops, and set the gains so that they match up to the references, and then post the measured bode plots when you're done?
There was 0.2 mW green at the X end.
The doubling oven temp was changed from 37.5 to 36 degrees C
Power at green shutter 3 mW The alignment was not touched.
I found that the X end SLOW control was left on for ~15days. The output of the filter had grown to ~2e7.
This yielded the laser temperature pulled with the maximum output of the DAC.
This was the cause of the power reduction of the X end SHG; phase matching condition was changes as the wavelength of the IR was changed.
Once the SLOW output was reset, the green REFL was reduced from 4000cnt to 1800cnt.
Handing over message to the next step
ETMX: guide rod gluing (done) -> fixture unmounting side -> fixture setting -> magnet gluing -> suspend -> pitch balance -> ruby gluing -> air bake
ETMY: magnet (done) -> fixture unmounting -> air bake
- A transport setup was made with a donut holder for a 3" optic, glass jar, stain less tray, and a CS Stat zipbag. (Attachment 1)
- The magnets have been glued witht the gluing fixture. (Attachment 2)
- We checked the dimensions of the glued magnet and found that the thicker side has to be raised by 1mm. (We used the fact that the relative distance between the wire groove and the magnet is always the same.)
- The ETMs have 2.5deg wedge and this corresponds to 3.2mm height difference between the left and right edges. This meant that the thinner side had to be raised by 4.2mm.
- We used a 0.9mm Teflon sheet for the thicker side (Attachment 3) and two 2.2mm Teflon pieces for the thinner side (Attachment 4). For stabilization of the fixture, two Teflon tubes with a diameter of ~3mm are inserted to the top and bottom side of the mirror (Attachment 5).
- Mirror orientation in the fixture (Attachment 6).
- It was confirmed that existing UR, LR, and Right SD magnets have the polarity of N facing out, S facing out, and N facing out. And we confirmed that this is consistent with ETMX and the procedure document (E970037)
- Along with the procedure document, we arranged the magnet-dumbbells UL, LL, and Left SD magnets to have S-out, N-out, and N-out. (Attachments 7, 8, and 9)
- In prior to gluing, all three dumbbells surfaces were cleaned by acetone and razor blade scrubbing.
- After the epoxy curing test (see below), the three magnet-dumbbell pairs have been glued on the mirror. A single dub of EP30-2 was applied to each dumbbell surface.
- Attachments 10, 11, and 12 shows how glue is spread at each joint.
Guide rod positioning:
- The longitudinal position of the guide rod was adjusted using the micrometer microscope such that it located at the center of the mirror thickness.
- The guide rod is not long enough to have the edges sticking out from the form of the fixture arm. Therefore only arm finger of the arm held the guide rod.
- The height was adjusted to be 1.73mm (68mil) lower than the mirror scribe line. The mirror is fixed on the fixture upside down. So this bonds the guide rod above the scribe line.
- Then the epoxy was applied to the guide rod. The glue was applied to two edges of the rod, but capillary action spread the glue around the rod. It seemed that the fixture and the rod were connected with the glue. Care should be taken when the fixture is going to be removed. (Attachment 13)
- The top side (in the picture) where the stand-off will come is still relatively kept clean. So it must be OK for the stand off. If there is an issue, we can shave the epoxy with a razor blade.
- EP30-2 tends to fail to get cured. In order to check the mixture is properly made or not, we put a test piece into air bake oven.
- The procedure says, 200F 15min bake show if the glue is in a good shape or not.
- We have the temperature sensor setup on a air bake oven, but it seemed that the indicated temperature there is overestimate.
The heating setting of 2 was enough to show the temp of 100degC although EP30-2 didn't get cured with this setting.
- Our experience says that heater setting of "5" makes the temperature ~90degC. On July 12nd, this setting showed the temp of 90degC. Today (July 13rd) it didn't. In the both cases, the epoxy got cured nicely. So we should use this setting.
The pickle puckers came off ETMY cleanly ETMY now rests in the ring holder, under a glass jar, with all of its magnets.
We removed the guiderod gluing fixture from ETMX without any apparent damage to the fixture arm, optic, or guiderod epoxy joint.
I started measuring some distances on the optic for the side magnet gluing, but am not sure of it yet. So, I didn't manage to start the gluing today.
I had hoped to do some ALS work, but I realized too late that we loaned our HP analyzer to Andrew. I decided instead to do some ETMX testing.
I have a script running that'll misalign both ETMs and back by about 0.5mrad with half hour rests in between. It'll be done around 6AM.
Seems like the angular position was fairly stable, though there is some change in the ETMX pitch that could be hysterisis or normal drift. I didn't mention it explicity in the previous log, but the misalignment was purely in pitch. I'll give it another shot with a bigger misalginment, and maybe a mix of pitch and yaw.
I was hoping to glue a standoff and guide rod today, but some problems have reared their heads. Story follows:
Upon first placng the optic into the standoff gluing fixture, I was presented with a geometric problem. In the assembly procedure, one glues the rods before the magnets, which prevents a situation like this:
When what you want to do is this:
So, I spun the optic around such that the magnet is on the far side of the scribe line from the side arm, and instead of extending the side arm past the scribe line, will bring it back towards the near side. I also swapped the arms of the fixture such that the guide rod will be glued on the opposite side of the optic than the side magnet, so the side magnet won't get in the way when doing the pitch adjustment of the second standoff.
Then, I found the scribed ruby rods, and took a look at one under a microscope. The groove looks nice and sharp. I placed the standoff in the side arm of the fixture.
However, the fact that the groove does not go all the way around the standoff leads to problem #1: when adjusting the position of the side arm, the standoff seems to roll around unpredictably, making it hard to deterministically position it while keeping the groove facing outwards.
Problem #2 is not too surprising give Steve's finding about the guide rod holding arm in ELOG 12264. Given that the tip is banged up, the guide rod does not sit straight in the arm, making it crooked. This would lead to the second standoff's groove not being well aligned to the suspension wire.
I will meditate on solutions to these problems... I have covered the optic and fixture with the same foil hut Koji made on Friday.
Also, I peeked at the aluminum standoffs under the microscope. Since the groove goes all the way around, we don't really know where the wire was seated before. Still, there are some places where the groove looks kind of worn:
With the new input matrix, it looks like YAW and SIDE are not quite decoupled on ETMX.
It needs one more kick and free swinging test.
- - - details
To see what exactly is going on, I changed the input matrix from the default to the new one, which Jenne computed (#5421) on ETMX.
I started putting the elements of the input matrix from POS through SIDE, one by one.
It seemed that POS and PIT worked fine. However the YAW signal looks containing a lot of the SIDE signal.
Similar to YAW, SIDE also interact with the YAW motion and somehow rings up both YAW and SIDE signals as Jenne reported ( #5438).
So right now the YAW and SIDE rows are partially reburted to the default elements in order to avoid ringing up.
but ETMX and BS were not good at all. ETMX was ringing up when I turned on the damping.
Excited all the optics. They will be automatically back after 5 hours.
Sat Sep 17 02:02:07 PDT 2011
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
We have talked about the drift of ETMX sus on the Wednesday meeting.
It has stopped moving on Jan 8, 2015 and it has been reasanable stable since than.
ETMX has some periodic oscillation. It's damping was found tripped this morning.
We tracked this down to the power normalization stuff that Yoichi added over the weekend.
With a non-zero normalization factor, and a small TRX transmission, the input the XARM controller gets really big. When XARM is then triggered, a huge impulse is sent into the SUS_ETMX_LSC input, which causes the Vio2 filter in FM0 to ring like crazy. This probably also explains why Yoichi was seeing trouble locking the arm when the normalization is on
The solution, as Yoichi also mentions, is probably to trigger the normalization like we trigger the rest of the boost filters.