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.
The oplev and the LSC are off.
I was trying to take a few more IR transmission scans with ALS when the ETMX got kicked again. I'm not sure how to fix this, so for the time being, I'm leaving the Oplev servo and the LSC turned off. The oplev spot looks really far off center especially in yaw, the yaw error is ~ -80.
I have put an offset of 1000 counts to C1:SUS-ETMX_ALS_OFFSET. This actually misalign the mirror a lot.
While the offset is applied. I adjusted the balance of the coil matrix.
UL 1.580 UR 0.620
LL 0.420 LR 1.380
> ezcaread C1:SUS-ETMX_TO_COIL_0_0_GAIN
C1:SUS-ETMX_TO_COIL_0_0_GAIN = 1.58
> ezcaread C1:SUS-ETMX_TO_COIL_0_1_GAIN
C1:SUS-ETMX_TO_COIL_0_1_GAIN = 0.62
> ezcaread C1:SUS-ETMX_TO_COIL_0_2_GAIN
C1:SUS-ETMX_TO_COIL_0_2_GAIN = 0.42
> ezcaread C1:SUS-ETMX_TO_COIL_0_3_GAIN
C1:SUS-ETMX_TO_COIL_0_3_GAIN = 1.38
Now, we can keep TEM00 for green with +/-1000counts of push although the fast step of the offset make the lock lost.
It turned out that the step longitudinal input temporary misalign the mirror in pitch because the length and pitch are coupled.
I guess that we don't excite pitch if we push the mirror slowly. Eventually, we need f2p transfer function adjusted in the output matrix.
The epoxy arrived. Eric managed to remove the excess glue below the guiderod with a razor blade (see attachment 1). The magnet and dumbell that came apart were reglued successfully and passed the stregth test of picking up the magnet from the table by the dumbell, so the magnet was glued back on the optic and is setting in the gluing apparatus (see attachment 2).
We double checked the polarity against the side magnets on ETMY. Because of the gluing position strategy (a fixed distance toward the HR side from the groove location), the other side magnet appears slightly below the center of the gluing barrel, which after some discussion with Koji was determined to be ok.
One step forward, two steps back...
While attempting to suspend ETMX, I broke off a side magnet
It is now gluing
(This is *not* the one that was previously glued. I.e., now both ETMX side magnets have been reglued)
Brief summary, some pictures and such follow in the daytime.
The epoxy needs at least 12 hours of room temperature air curing, so no touchy until 3:30PM on Jul 28!
Attachment #1 - After multiple trials shimming the magnet gluing rig with teflon spacers, we think that we managed to find a configuration in which the side magnet edge is between 0.25 mm and 0.5 mm from the groove in the ruby wire standoff in which the wire will sit.
Attachment #2 - Zoomed in view of the side magnet.
Of course we won't know until we suspend the optic, but we believe that we have mitigated the misalignment between the side OSEM axis and side magnet.
The short term plan is to try and suspend ETMY in the end chamber and have a look at the alignment between all magnets and OSEM coils for it. Once the epoxy on ETMX is cured, we will try and suspend the optic again, this time taking extra care while tightening the wire clamps.
Unrelated to this work: Bob just informed me that we had left the air bake oven on overnight - this unfortunately melted the plastic thermocouple inside.
This has been edited several times over the last several hours, as I try to change different parameters, to see if they affect the movement of ETMX. So far, I don't know what is causing the motion. If it is there, it is only present when the LSC is engaged, so I don't think it's wobbling constantly on a twisted wire.
FINAL EDIT, 9:10pm: The arm ASC was turning itself on when the arms were locked. Whelp, that was only 3 hours of confusion. Blargh.
For his penance for leaving the arm ASC engaged, Q has made a set of warning lights on the LSC screen, right next to the ASS warning lights.
ETMX might be having one of those days today, which is lame.
So far tonight, I have run the LSC offset script, set the FSS slow value to +0.2, and run the arm ASS scripts. Nothing too crazy I think.
Sometimes when I lock the single arms, the ETMs move around like crazy. Other times, not. What is going on here??? The ETMs don't move at all when they are not being actuated on with the LSC.
In this screenshot you can see the end of a POX/POY lock stretch where everything was nice and good. Then, the arms were unlocked, and they have a bit of a DC offset. After settling from that step, they continue sitting nice and still. Then, I relock the cavities on POX and POY a little before -4 minutes. ETMY takes a moment to pull itself together, but then it's steady. ETMX just wobbles around for several minutes, until I turn off the LSC enable switch (happened after the end of this plot).
I'm not going to be able to lock like this. Eeek!
This is somehow related to light being in the Xarm. This next plot was taken while the arms were held with ALS in CARM/DARM mode.
I closed and re-opened all 3 green shutters. Now (at least the last 8 arm locks in the last 6 mintues) ETMX has never gone wobbly, except for a little bit right after acquisition, to deal with whatever the DC offset it. Why is this changing?
The arms were fine for one long ~30 minute lock while I stepped out for dinner. At some point after returned, the MC lost lock. When the arms came back, ETMX was being fussy again. Then, it decided that it was done.
In this plot, at -1 minute I started the ASS. Other than that, I did not touch any buttons at all, just observed. I have no idea why at about -3 minutes the bad stuff seems to go away.
I was curious if it had to do with the DC pointing of the optics, so I unlocked the arms, put ETMX about where it was during the long good lock stretch, then reaquired lock. I had to undo a little of that so that it would lock on TEM00, but at the beginning of the lock stretch (starting at about -3) the pitch is about the same spot. But, the oscillations persist. This time it was clear that the oscillations were around 80 mHz, and they started getting bigger until they settled to an amplitude they seemed to like.
Seems pretty independent from FSS temp. There are 3 lock stretches in the next plot (easier to see by looking at the Yarm transmission, green trace). The first one, the FSS slow was at 0.35. the middle one, it was around 0.05. The last one, it was around -0.4. Other than the different DC pointings (which I don't know if they are related), I don't see anything qualitatively different in the movement of ETMX.
I'm still not super happy with the low power level of the ETMX oplev, so I went to investigate.
This is a 3-year plot. The first ~year in the plot, the oplev sum is ~15000 cts, and in the most recent year, it's ~1000 cts. A new HeNe was installed in May 2011 (elog 4686), with an output of 2.6mW, after the old one had died. When the new one was installed, Steve said that it was giving ~1400 counts, so maybe 1000 isn't too, too embarrassing. There is, however, a lens on the injection side, which is AR coated for 1064. The power before this lens (measured with the Ophir, set to 632nm) was ~2.6mW. The power after this lens was ~1.5mW. Now THAT is embarrassing. I'm adding replacing that lens to the to-do list (elog 6595), although I don't want to do it until such a time (maybe in an hour, maybe in a few days?) when I've got the Xarm locked / aligned, so I can nicely re-center the oplev. UPDATE: The lens is a KBC 037 (-100) lens, and the sticker on the lens mount says coated for 1064. We don't have any KBC037's in the visible lens kits, so we need to get one before I can do this replacement (PURCHASED 10pm).
There is an elog (elog 5004) from July 2011, which mentions that these channels have not been saved for a long time, so that's why there's the year-long gap.
Anodized aluminum dumps replaced by 6 razor beam dumps.
Two more razor beam dumps added this afternoon. The picture will updated tomorrow.
There are 9 razor beam dumps at ETMY-ISCT
I added two green glass absorbers. The oplev centering may need a touch up when it is well aligned.
ETMX oplev had 6 mm diameter beam on the qpd. I relayed the beam path with 2 lenses to get back 3 mm beam on the qpd
BRC 037 -100 Bi _concave lens and PCX 25 200 VIS do the job. Unfortunately the concave lens has the AR 1064.
Coherence at 1 and 2-3 Hz only. He/Ne laser intensity noise is not an issue.
ETMX oplev qpd gain has to be increased.
Atm3, Oplev sum read 12,000 counts when the qpd was disconnected ?
Dark qpd was zero and normal He/Ne incident on qpd was 1,730 counts.
This QPD circuit (D980325-C1 ) uses the nice OP497 Quad FET opamp as the transimpedance amplifier. It has a low enough current noise, such that we can increase the resistors (R1-4) up to 100k and still be Johnson noise limited. We should also make sure that the compensation caps (C3-6) are ~2.2 nF so as to not destabilize the opamp. f_low = 1/2/pi/R/C = 730 Hz.
I will do the swap later today unless someone else gets to it first. (note: check for oscillations w/ fast scope probe after installing)
I did these modification tonight. The slideshow of some images is attached. Instead of 100k, I used 97.6k thin film, since this seemed like an oddball size that doesn't get used otherwise. I forgot to measure the dark noise of the quadrants before doing the swap, but comparing the pit/yaw/sum before/after the swap shows that the signal is basically unchanged (since pit/yaw is normalized by SUM), but that the noise is lower by a factor of a few above 100 Hz due to being above ADC noise now. Previously, it was bottoming out at ~10 prad/rHz. Since the signal is unchanged, I guess that the calibration and therefore the loop gain should not have changed either...
And the sum went up by almost 10x as expected from the resistor change.
Kiwamu and Steve,
This is one of the better oplev set up we have. Single bounce from TM, no mirror on stack. One lens and one mirror on ISCT. Old Uniphase 1103P laser on heafty 3" od mounts.
Somewhat big ~5-6 mm spot on qpd in 1,300 counts.
The intensity noise effect can be seen at 1 Hz and 3-20 Hz
Oplev servo was OFF
The ETMX oplev returning beam is well centered on the qpd. We lost this signal 2 days ago. I will check on the qpd.
ETMX sus damping restored. c1iscex computer is down
The ETMX oplev returning beam is well centered on the qpd. We lost this signal 2 days ago. I will check on the qpd.
ETMX sus damping restored
As reported a couple days ago, the ETMX IO chassis has no timing signal. This is why we there is no QPD signal and why we turned off the ETMX watchdog. In fact, I believe that there is probably nothing coming out of the ETMX suspension controller at all.
I'm working on getting the timing board replaced. Hopefully today.
For some reason or another, I decided that we should see if the optical lever servos were injecting too much noise into the test masses. The ITMs are much worse than the ETMs and I am afeared that they might be making the main noise for our arms in the 20-40 Hz region. Jenne is checking up on these feedback loops to see what's up.
To estimate the actuator gains of the mirrors, I turned on 1 count drives from LSC/CAL oscillators into the LSC drives of each test mass at the frequencies shown in the plot with the resulting peaks showing up in in POX/Y with the single arm locks in red. I will leave these going permanently, but with 0.1 count ampltiudes; we need to make it so in the scripts.
I'm in the process of filling this table
I should replace ETMX He/Ne laser
I took loop measurements of ETMX pit and yaw, and set the upper UGF to be ~6Hz for both. This required a pitch gain of 25, and a yaw gain of 16.
The spectra look similar to what they were before Steve did the swap.
I've turned the ETMX oplev servos off for the time being. (At the input side, so that no scripts will accidently turn it on).
Thus, only the local damping is being applied, let's see if we see any kicks...
During this time period, it looks like there was maybe one excursion. Here are the individual OSEM signals, which I think to be calibrated to microns.
When I'm doing other things, I'm going to intentionally leave the watchdog tripped, and see if anything happens.
During a ETMX kick that just occured, with only local damping on, the slow VMon channels didn't show any noticable change.
How many volts does it take to pitch the ETM by 5 urad?
By looking at the oplev and Vmons before and after a step of 90 counts in SUS-ETMX_PIT_OFFSET, I observe:
UL: +1.53mV / urad
UR: -1.94mV / urad
LR: -1.54mV / urad
LL: +1.92mv / urad
The random error associated with these measurements is ~0.02mV
So, the ~7urad urad shift seen in my earlier post would mean a change of around 10mV in the Vmon signals, which isn't evident in the traces. So, this is possibly a piece of evidence in favor of a real mechanical shift, rather than an electronic glitch.
I believe that the Xend aux laser was turned off earlier today, for Steve's work swapping out the oplev. When I went down there, the red "off" LED was illuminated, and the LCD screen was showing something. I pushed the green "on" button, and I immediately got green.
Also, I saw that the 24Hz roll mode was very rung up on ETMX. I looked at the FM5 "bounce roll" filter, and it had some old values, 12Hz and 18Hz for the resonant gains. All other optics have the proper 16Hz and 24Hz frequencies. I copied the BS oplev bounce roll filter over to ETMX pit and yaw (both were wrong), and loaded them in. The mode is starting to ring down.
UR osem IR shield glass is pushed back. It came out of its clip holder. The magnet is free.
Atm2, UL & LL magnets centered poorly. Almost hinging on opposite sides.
UR & LR centered well. There have plenty of room to move in an earth quake.