We found that one OP-amp used in ISS servo oscillated in 10 MHz, 100mV.

Moreover, we found another OP-amp had big noise.

We guess that these oscilation or noise cause saturation in high frequency, and they effect to lower frequency to cause 

 Attached files are open loop transfar function of ISS.

The blue points are open loop TF, and the green line is product of TF of ISS servo filter and TF of current shunt TF of servo filter.

This two must be same in principle, but They have difference f<2Hz and f>5kHz.

Back in November, Nic and Evan turned on an SR560 based ISS. It uses the PMC TRANS PD as the error signal and makes an AC coupled loop with 2 SR560's and then it drives the RF amplifier which drives the AOM upstream of the PMC.

This was the saturating SR560 under the PSL table that Steve found this week*. Tonight I found that the +24 V rack fuse for this was blown. I replaced the previous 2A fuse with a new 2A fuse (turned off the +/24 V Sorensens during this operation). I think all of the servo settings are basically the same as before, except that I'm using a gain of 10000 instead of 50000 on the first SR560. It was saturating otherwise. My guess is that the fuse blew many months ago and no one has noticed...

 I checked the out of loop performance in MC_TRANS and in the IFO REFL_DC and there's some high frequency improvement with the loops on.

The main improvement, however, was in lowering the HEPA fan speed. This should only be turned up to Hurricane when you are working on the table. Similarly, those of us trying to lock at night, can't really trust that the HEPA is set to its nominal low setting of 20%. The whole difference in the MC_TRANS from 5-50 Hz is from this however, so we can use this ISS reference .xml as a way to see if the HEPA is up too high.

If we want to do better for RIN from 100-1000 Hz for improving the REFL_DC/CARM noise, we would have to think of how to improve the PMC_TRANS PD RIN.

* Steve gets +1 point for finding this, but then -3 points for not elogging.

I re-centered the ITMX & ITMY Optical lever beams today since they were off. First I aligned the beam into the vacuum so that it went through the center of the on table optics and then tweaked the receiver optics alignment.

There are several bad practices on these which probably makes them drift:

• plastic bases on some lens mounts
• some lens mounts are fastened with a single dog instead of two
• there is no need to use dogs on mounts that have screw holes. Just put the mount so that 2 screws with washers can be used. The placement for these is not so critical.
• Use less steering mirrors! The ITMY OL path has 5 optics the beam enters the vacuum!!!

According to the datasheets, the laser has a beam diameter of 0.6 mm and a divergence angle of 1.3/2 mrad. So we can just calculate the right lens positions next time and not have to experiment with the whole visible laser lens kit.

For next Wednesday's cleanup, someone should volunteer to make the mounts more stable for the ITMs.

I went to see what was wrong with the ITMs and found that people have been working on them and have left them in a broken state with no elog entry.

This is sad and unacceptable.

Whoever is working on these should post into the elog what the Oplev layout plan is, have someone check it, and ONLY THEN get to work on it.

The layout as it looks tonight is too complicated. With too many optics we will not have a low noise optical lever setup. The new layout should use a bare minimum number of optics and only use very stable mounts.

I first set the bias sliders to 0 on the MEDM screen (after checking that the nominal values were stored), then shut down the watchdogs, and then pulled out the boards for inspection + photo-taking.

I've uploaded high-res photos + marked up schematics to the same DCC page linked in the previous page. I've noted the S/Ns of the ITM, BS and SRM boards on the page, I think it makes sense to collect everything on one page, and I guess eventually we will unify everything to a one or two versions.

To take the photos, I tried to reproduce the "LED light painting" technique reported here. I mounted the Canon EOS Rebel T3i on a tripod, and used some A3 sheets of paper to make a white background against which the board to be photographed was placed. I also used the new Macro lens we recently got. I then played around with the aperture and exposure time till I got what I judged to be good photos. The room lights were turned off, and I used the LED on my phone to do the "painting", from ~a metre away. I think the photos have turned out pretty well, the component values are readable.

Computar  75-12.5 zooms were installed for closer look at the resonant spots.  Their alignment and focus needs more loving adjustment.

Atm 1, ITMX  (  it was 10-40 mm Tamron before )

Atm 2, ITMY  ( it was 12mm wide angle showing the towers  before )

I focused these lenses so that we could get a clean image of the mirrors and the OSEMs.

Our goal is to have an image where the optic diameter almost fills the entire monitor. We want the focus to be adjusted for the YAG beam (which is almost the same as focusing for the OSEMs). This will NOT produce a nice image of the cage using visible light, but that is just fine.

When Justin Garofoli was here he found a nice lens combo that did the job, so if anyone can find his old email or elog, lets just go back to that.

For now, we do not need a camera/lens system to focus very tightly on the center of the optic.

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?

Needs inspection.

Two ITM spares (ITMU01/ITMU02) and five new PR3 mirrors (E1800089 Rev 7-1~Rev7-5) were transported to Downs for phasemap measurement

GariLynn worked on the measurement of E1800089 mirrros.

The result of the data analysis, as well as the data and the codes, have been summarized here:
https://nodus.ligo.caltech.edu:30889/40m_phasemap/#E1800089
 

ITMU01 / ITMU02 as well as the five E1800089 mirrors came back to the 40m. Instead, the two ETM spares (ETMU06 / ETMU08) were delivered to GariLynn.
Jordan worked on transportation.

Note that the E1800089 mirrors are together with the ITM container in the precious optics cabinet.

In preparation for locking tonight, I re-centered the spots on the Oplev QPDs for the ITMs, BS and PRM after locking and running the dither alignment for the arms and also the PRMI carrier. In the past, DC coupling the ITM Oplevs helped the angular stability a bit, let's see if it still does.

 The cabling on the seismic stack was rerouted so it could reach the south edge of the table: the cables  were removed from the viton padded clamps and repositioned this morning.

ITM-south tower's earthquake screw viton tips could be a little bit larger. They do not stay in their screw hole after a hard clamping action.

4-40 earthquake screws under the test mass:viton tips can fall out without action, the treads are cross threaded so the screws are wobbling

The two ITM spares and two ETM spares are together stored in the optic storage (B110) at Downs. c/o Liyuan and GariLynn

While trying to set up the SIS-FFT to use our new ITM phase maps, I noticed that the surface of our ITMs looks pretty good actually (even compared to the aLIGO pathfinder optic map on the AIC wiki). I'm attaching it here for your viewing pleasure.

The code to plot it has been added to the SVN in the PhaseMaps/mat directory.

[Anchal, Koji]

=== Summary ===
- ITMX SD OSEM migration done
- LO1 OSEM insertion and precise adjustment (part 1) done
- LO1 POS/PIT/YAW/SD motions were damped

=== General Remarks ===
- 15:00 Entered into ITMX.
- We were equipped with N95 and took physical distance as much as possible.
- 17:00 Temporarily came out from the lab.
- 18:30? Came into the chamber again
- 20:00 Sus damped. OSEM work continues
- 21:00 OSEM installation work done. Exit.

=== ITMX SD OSEM position swap ===
- Moved the LO1 suspension to the center of the chamber
- Removed the ITMX SD OSEM from the right side (west side) and tried to move it to the other side.
- Noted that the open light output of the ITMX SD was 908 at the output of the SDSEN filter module. So the half-light target is 454. These numbers include the "cnt2um" calibration of 0.36. That means the open light raw ADC count was supposed to be 2522.

- The OSEM set screw (silver plated, with a plunger) was removed from the old position. We first tried to recycle it to the other side, but it didn't go into the thread with fingers. After making ourselves convinced that the threaded hole was identical for both sides, we decided to put the new identical plunger set screw with an Allen-key was used to put it in and it went in!
- Now the ITMX SD OSEM was inserted from the east side. Once we saw some shadow on the OSEM signal, the SD damping was turned on with the previous setting. And this successfully damped the side motion. ⭕️
- A bit finer adjustment has been done. After a few trials, we reached the stable output of ~400. Considering the temporary leveling of the table, we decided this is enough for now ⭕️. The set screw was tightened.
- To make the further work safer w.r.t the ITMX magnets, Anchal fastened the EQ stops of the ITMX sus except for the bottom four.
- Photo: [Attachment 1]

=== LO1 OSEM installation ~ wiring ===
- Now LO1 was moved back to the planned position.
- For the wiring, we (temporarily) clamped the in-vac DSUB cables to the stack table with metal clamps.
- Started plugging the OSEMs into the DSUB cables.
- Looking at the LO1-1 cable from the mating side with the longer side top: The top-right pin of the female connector is Pin1 as usual. From right to left LL / UR / UL coils were inserted one by one while looking at the OSEM PD signals.
- LO1-2 cable has the LR / SD coils (from the right to the left) were connected.
- Photo: [Attachment 2]

- LO1 Open light levels (raw ADC counts) the 2nd number is the target half-light level

• UL 27679 (-> 13840)
• UR 29395 (-> 14697)
• LR 30514 (-> 15257)
• LL 27996 (-> 13998)
• SD 26034 (-> 13017)

=== RTS Filter implementation ===

- Anchal copied the filter module settings from other suspensions.
- We also implemented the simple input and output matrices.

=== LO1 OSEM insertion ===

- We struggled to make the suspension freely swinging with the OSEMs inserted.

- It seemed that the magnets were sucked to the OSEMs due to magnetic components.
- It turned out that the OSEMs were not fastened well and not seated in the holder plates.
- Once this was fixeded, we found that the mirror height is too high for the given OSEM heights.
  The suspension height (or the OSEM height should be decided with the OSEMs not inserted but fully fastened to prevent misalignment of them.
- Decided to lift up the OSEM plates in situ.
- Soon we found that the OSEM holder plates are not fastened at all [Attachment 3 arrows]
- The plates were successfully lifted up and the suspension became much more freely swinging even with the OSEMs inserted. ⭕️

=== LO1 damping and more precise OSEM insertion ===

- Once the OSEMs were inserted to the light level of 30~70%, we started to try to dampen the motion. The side damping was somewhat successful, but the face ones were not.
- We checked the filters and found the coil output filters didn't have the alternating signs.
- Once the coil signs were corrected, the damping became more straight forward.
- And the robust damping allowed us the fine-tuning of the OSEM insertion.

- In the end, what we had for the light levels were

• UL 14379 (52%)
• UR 14214 (48%)
• LR 14212 (47%)
• LL 12869 (46%)
• SD 14358 (55%)

The damping is working well. [Attachment 4]

Post continues at 40m/16552.

The ITMX Oplev (installed in March 2019) was near end of life judging by the SUM channel (see Attachment #1). I replaced it yesterday evening with a new HeNe head. Output power was ~3.25 mW. The head was labelled appropriately and the Oplev spot was recentered on its QPD. The lifetime of ~20 months is short but recall that this HeNe had already been employed as a fiber illuminator at EX and so maybe this is okay.

Loop UGFs and stability margins seem acceptable to me, see Attachment #2-#3.

I've received a report that a pin of an ITMX NW feedthru connector was bent. (Attachment 1)
The connector is #1 (upper left) and planned to be used for LO1-1.

This is Pin25 and used for the PD K of OSEM #1. This means that Coil Driver #1 (3 OSEMs) uses this pin, but Coil Driver #2 (2 OSEMs) does not.

Anyways, I tried to fix it by bending it back. WIth some tools, it was straightened enough for plugging the cable connector. (Attachment 2)

It seemed that the pins were exceptionally soft compared to the ones used for usual DSUBs, probably because of the vacuum compatibility.
So it's better to approach the pins in parallel to the surface and not apply mating pressure until you are sure that all the 25pins are inserted in the counterpart holes.

I'm driving C1:SUS-ITMX_OLYAW and PIT_EXC with amplitude 0,1-0.3 while taking transfer funtions of oplev.

The transfer functions are normal. However I noticed that the LL osem is not responding to this excitations

Healthy sensor respons should be like Atm3

Because of the in-vac work on Oct. 4th (see this entry) , ITMX's OSEM offsets were changed.

The two upper OSEMs are still fine, but LL and LR seem to be out of the OSEM's range. 

The plot below shows the trends of LL's and LR's readouts for about two weeks. (The channel name are in the old convention, i.e. ITMY)

 Some data were missing due to the upgrade of the frame builder.

 It is apparent that the offsets are changed after the in-vac work on Oct. 4th, and now they just show almost zero numbers.

The damping of ITMX can still work, if LL and LR are disabled.

At some point before pumping down, we have to check the leveling of the ITMX table again.

Koji, Steve

ITMX OSEM CONFIGURATION

I did a quick measurement of the ITMX oplev loops, both pitch and yaw have about the same upper UGF as previous measurements with the previous laser; about 4 Hz. 

After running dither alignment for all mirrors, all oplevs were recentered. (Except ETMY, since we did that earlier today.)

Looking at Koji's template for OSEM signals, the ITMX UL sensor noise floor seems more in line with the LL sensor, though there continues to be more noise than in other mirrors. 

Trending the sensor signals over the past 7 days, Koji's measurement looks to have been taken during a time when the UL sensor voltage had jumped down. Did someone squish the satellite box cable? I have not done so. 

I think that the step right at the end is due to a new POS offset of -2k counts, which I think Koji put into place earlier today. 

According to the wiki, the Vmax/2 values and the current values are: 

Although this noise is bad, we have always had these kind of humps around the bounce mode. Our interpretation in the past was that this was due to poor alignment of the OSEM in the frame, leading to a large vertical to horizontal coupling. Once you implement the BLRMS for the SUS channels, we'll be able to trend the noise over long periods of time.

The issue on the ITMX UL sensor has been fixed. It was because of a loose connection in the sensor signal path.

After the fix, the sensor responses completely changed and the suspension became unable to be damped with the new matrix.

At the moment the ITMX suspension is damped by the default input matrix.

we should do the free swinging test once again.

(details)

 The loose connection was found on the rear side of the 1X5 rack.

There is an adapter card on the rear side, where the driver and sensor signals are combined into a single cable.

I pushed the sensor cable (bottom right in the picture) and the noise disappeared.

Note that I changed the labels on the adapter cards from the old X/Y convention to the new one.

After fixing the loose cable the ITMX suspension became unable to be damped.

So I put the input matrix back to the default and it immediately started damping happily. It means our new matrix is not valid any more.

 Here is the latest noise spectra of the ITMX sensors damped with the default input matrix.

As usual all of them are limited by the ADC noise above 20 Hz. (ADC noise is plotted in purple curve)

During the work I also pushed not only ITMX ones but also the cable for the rest of the optics in the adapter cards.

Then PRM became unable to be damped, so it implies the PRM suspension also used to be the same situation.

The input matrix of PRM has been also back to the default.

According to the spectra, all of the suspensions had been damped with the OSEMs. The peaks around 1Hz are reasonably suppressed.

However the spectra from ITMX showed a noise floor at very high level. This is because of strange jumps in the signal of the UL shadow sensor.

I will check some analog circuits for the UL sensor.

(ITMX shadow sensors)

Here is the spectra of the ITMX shadow sensors taken during the damping test (#5534)- -

The UL sensor shows a unacceptable amount of noise.

Additionally I checked the time series of the ITMX shadow sensors and found ONLY the UL sensor frequently showed strange jumps in data.

Here is an example of the time series showing a jump ONLY in the UL sensor.

It is possible that the jumps are coming from some circuits, since the rest of the sensors (including the oplevs) don't detect the same jump.

Currently the damping of the ITMX suspension is intentionally disabled for the noise investigation.

(What we did)

* Moved SUS to edge of table for OSEM adjustment.

* Leveled the table in this temporary tower position.

* Rotated all OSEMs to give some seperation between magnets and LED/PD packages.

* Moved the upper OSEM bracket a little bit upward.

* All the OSEM holding set screws were short with flat heads; this is annoying since we would like to use them more like thumbscrews. Steve took the long set-screws out of the old ITMX cage and we swapped them. Need to order ~100 silver-plated socket head spare/replacements.

* Took pictures of OSEMs.

* Moved tower back to old position.

* Releveled the table (added one rectangular weight in the NW corner of the table).

* Find that ITMX OSEMs were a couple 100 micron out of position; we adjusted them in-situ in the final position of the tower, trying not to rotate them. All mean voltages now are within 100 mV of ideal half-light.

* Back/front EQ positions adjusted by the screw method. bottom/top stops adjusted earlier.

* OSEM cables tied down with copper wire.

* Increased the incident power up to 91 mW going into MC to temporarily make the POX beam more visible.

* The POX beam was checked. It was exiting from the chamber and going through about the center of the viewport.

So, was there real shifting in the ITMX alignment as seen in the DV trend or just mis-diagnosis from the ETMX violin mode? Or how would the ETMX violin mode drive the ITMX with the LSC feedback disabled?

I balanced the ITMX and ETMX tables into level position today, for which I had to move quite a few of the on-table weights. I'm recording their original positions for future use here.

ETMX

This table was only off in 'pitch', I moved the middle weight to a new location as shown in the pictures. I added secondf disk weight on top of the one I moved, this one has to come out again when we install ETMX.

ITMX

I moved some weights around as shown in the image, but didn't have to add any. We simply have to move them back to their original location when the time comes.

While in the chambers, I also took some pictures of the ETMX window and PR2, motivated by the dirty state of SR2. We might want to consider cleaning both, specifically PR2 is relatively easily accessible and can be cleaned when we open the ITMX chamber to remove its FC and move it back into position.

The ITMX table had relaxed overnight into a slightly misaligned state overnight - since the ITMX table holds PR2 and hence can affect the input pointing, we decided to fix this before commencing alignment work today. The misalignment was not as bad as what Johannes observed prior to his first re-leveling attempt, but was ~1 division on the spirit level. So I decided to move one set of weights to level the table again. It is entirely possible that over the next couple of days, the table will shift slightly again, but the hope is that we are closer to the 'ideal' orientation of the table now... Pictures to follow...

Summary:

The ITMX OSEMs report elevated noise in the 10-100 Hz band when we have high circulating power in the arm cavities, see Attachment #1. Since there is no LSC actuation on the ITMs in this state, this could be a radiation presssure effect, or could be scattered 1064nm light entering the OSEMs. The Oplevs don't report any elevated noise however. ITMY has the OSEM whitening broken for two channels, but the other two channels don't report as significant an increase as ITMX, see Attachment #2. I can't find the status of which OSEMs have the 1064nm blocking filters installed. The local damping loops are rolled off by ~100dB at 30 Hz, so the sensing noise re-injection should be attenuated by this factor, so maybe the OSEM sensor noise isn't the likely culprit. But radiation pressure didn't worsen the length noise in the past, even after our mirror cleaning and the increased PRG.

if the RP don't fit

u must acquit

sweep the laser amplitude

to divine the couplin w certitude

[Yuta, Anchal, Paco]

As described briefly by JC, there were multiple failure modes going during this work segment.

ITMX SatAmp SAGA

Indeed, the 64 pin crimp cable from the gold sat amp box broke when work around ITMX chamber was ongoing. We found the right 64 pin head replacement around and moved on to fix the connector in-situ. After a first attempt, we suddenly lost all damping on vertex SUS (driven by these old sat amp electronics) because our c1susaux acromag chassis stopped working. After looking around the 1x5 rack electronics we noted that one of the +- 20 VDC Sorensens were at 11.6 VDC, drawing 6.7 A of current (nominally this supply draws over 5 Amps!) so we realized we had not connected the ITMX sat amp correctly, and the DC rail voltage drop busted the acromag power as well, tripping all the other watchdogs ...

We fixed this by first, unplugging the shorted cable from the rack (at which point the supply went back to 20 VDC, 4.7 A) and then carefully redoing the crimp connector. The second attempt was successful and we restored the c1susaux modbusIOC service (i.e. slow controls).

ITMY SatAmp SAGA

As we restored the slow controls, and damped most vertex suspensions, we noticed ITMY UL and SD osems were reading 0 counts both on the slow and fast ADCs. We suspected we had pulled some wires around when busy with the ITMX sat amp saga. We found that Side OSEM cLEMO cable was very loose on the whitening board. In fact, we have had no side osem signal on ITMY for some time. We fixed this. Nevertheless the UL channel remained silent... We then did the following tests:

• Test PD mon outputs on the whitening card. We realized the whitening cards were mislabeled, with ITMX and ITMY flipped . We have labeled them appropriately.
• Tested input DB15 cable with breakout board.
• Went to the ITMY sat amp box and used the satellite box TESTER 2 on J1. It seemed correct.
• We opened the chamber, tested the in-vacuum segments, they all were ok.
• We flipped UR-UL OSEMs and found that the UL OSEM is healthy and works fine on UR channel.
• We tested the in-air cable between satellite box and vacuum flange and it was ok too.
• We suspected that the satellite box tester  is lying, so we replaced the satellite box with the spare old MC1 satellite box, and indeed that solved the issue.

DO NOT TRUST THE SATELLITE BOX TESTER 2.

Current state:

• IMC locking normally.
• All suspensions are damping properly.
• Oplevs are not centered.
• No flashing on either of the arms. We had no luck in ~20 min of attempt with just input injection changed.
• On kicking PR3, we do see some flashing on XARM, which means XARM cavity atleast is somewhat aligned.
• All remaining tasks before pumpdown are still remaining. We just lost the whole day.

ITMX watchdog tripped around 5 Torr  and the PRM around 450 Torr of this vent. They were restored than.

We are at 580 Torr now.

I fixed up the ITMX camera like we did for ITMY recently (removed T's and added strain relief - the lens was already OK).

I also updated the .SCAN field for the RMTEMP and RCTEMP channels to 0.1 second. This had been done via probe but was wiped out after reboot previously, because I forgot to update the psl.db file.

[Koji,Manasa]

We removed the ITMX heavy door to fix the oplev situation. 

My Plan for closing:

Today: I will work on the ITMX oplev situation today and go through the vent close-up checklist as far as I can get.
Tomorrow: We will do the final alignment check tomorrow with the light doors. The access connector and heavy doors should go in place late afternoon.
Thursday: We will start pumping down early in the morning on Thursday.

My Plan for closing:

Today: I will work on the ITMX oplev situation today and go through the vent close-up checklist as far as I can get.

[Alex, Sujan, Manasa]

The ITMX oplev steering mirrors were laid out such that they were out of the way of the BS oplev leakage. But the halo associated with the He-Ne laser does exist even now. I conclude that this is something that can be dealt with after we pump down as well. So I did not change the ITMX oplev optics on the POX table.

BS, PRM, ITMY and SRM oplevs were aligned and centered.

We want to do IPANG and IPPOS alignment when the IFO is aligned satisfactorily and right before we put the heavy doors.

The arms were aligned and ASS'd before I went in to fix the oplevs. I haven't done anything but deal with the oplevs tonight. So I am being lazy by assuming the alignment is still good and calling it a night.

Tomorrow: We will do the final alignment check for the arms, PRC and SRC with the light doors on. Check IPANG and IPPOS. The access connector and heavy doors should go in place late afternoon.
Thursday: We will start pumping down early in the morning on Thursday.

Looked at ITMX. Johannes and I both saw a fairly large speck of dust near the center of the HR side. We tried to take some photos but couldn't get any with good focus. 

We ran out of illuminator juice, and short-term charging couldn't restore enough battery life to continue the work. We should be able to get some better pictures tomorrow.

Multicolor flash light:

- It seems that the usb port charging doesn't work.

- There is a battery charger on Steve's desk. I set the batteries on it.

White LED flash light:

- I temporarily brought a compatible charger from WB. It's charging two batteries behind the LCD display on my desk.

The ITMX 10" flange with four DSUB-25 feedthroughs has been install with the cables connected at the in-vac side.  See photo; as requested, LO1-1 and LO1-2 are connected to the top row of feedthroughs from left to right respectively and the opposite ends of the cables placed left to right on the laser table.  PR2-1 and PR2-2 are connected to the lower row of feedthroughs from left to right respectively, with the opposite ends placed on the surface below the laser from left to right.  This seemed the easiest way to keep the cable orientation clear.

Thanks for the installation.

With regard to the connector convention, let's use the attached arrangement so that it will be consistent with the existing flange DSUB configuration. Not a big deal.