40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log, Page 337 of 339  Not logged in ELOG logo
New entries since:Wed Dec 31 16:00:00 1969
ID Date Author Typeup Category Subject
  16897   Tue Jun 7 18:32:46 2022 DeekshaUpdateElectronicsNoise Budgeting ADC (of redpitaya)

Made plots on i/p noise of redpitaya . Need to reconsider sampling frequency (to improve plot at lower freq)

Attachment 1: ch1_0.5V.png
Attachment 2: ch2_0.0V.png
  16898   Tue Jun 7 19:13:12 2022 yutaUpdateSUSAgreement on suspension damping loop polarity conventions

Anchal, Paco and I agreed to follow the polarity conventions below for suspension damping loops.
Some of the polarity/gains were changed to homogenize all the suspensions to the convention.
All the suspensions are homogenized except for MC1 (which have all - in sensor inputs and all - in coil outputs) and AS1 (SDCOIL_GAIN have the same sign as LL).

*SEN_GAIN to be +1
INMATRIX to be the following, and calibrated so that SUSPOS/SIDE_IN will be um and SUSPIT/YAW_IN1 will be urad (calibration to be done later)
+ + + + *
+ + - - *
+ - - + *
* * * * +
SUS*_GAINS to be +

TO_COIL gains to be the following
+1 +1 +1  *
+1 +1 -1  *
+1 -1 +1  *
+1 -1 -1  *
 *  *  * +4
*COIL_GAIN to be the following or flipped one so that SUS*_GAINS will be +

To do this, the following changes were made

For BS, ITMX, ITMY, PRM, SRM, ETMX, ETMY, MC1, MC2 and MC3 ("old" suspensions), TO_COIL_5_4_GAIN (for side) is changed from +1 to +4 and SUSSIDE_GAINs are divided by 4 accordingly.
For ETMX, the sign of SUSSIDE_GAIN is flipped to +, and SDCOIL_GAIN to be -1 (it was +1).
For MC1, *SEN_GAINs are - (not following the convension; see 40m/16894). The sign of INMATRIX_4_5 (for side) is flipped to +, SUSPOS/PIT/YAW_GAIN are flipped to +, and *COIL_GAIN are flipped to - (not following the convension). IMC WFS output matrix components for MC1 were also flipped. 

Attachment 1: NoteBeforeChanges.JPG
  16899   Tue Jun 7 19:40:45 2022 AnchalUpdateSUSITMY changed output matrix to disable use of UL coil

Since UL coil actuation is lost, we modified the output matrix of ITMY to use only UR, LR and LL face coils for POS, PIT and YAW actuation. The output matrix was changed to following:

UL 0 0 0 0
UR 1 1 0 0
LL 1 0 1 0
LR 0 -1 -1 0
SIDE 0 0 0 1






After this change, the damping was still working as good as before. I took PIT to POS/PIT/YAW and YAW to POS/PIT/YAW coupling measurements by exciting C1:SUS-ITMY_ASCPIT[YAW]_EXC and seeing effect at C1:SUS-ITMY_SUS[POS/PIT/YAW]_IN1 when the damping loops were off. Attached are the results. We were able to reduce PIT to YAW and YAW to PIT coupling by 10 dB by this simple change in output matrix. More coil balancing or off-diagonal termsmight help more and should be attempted if required. The coupling to POS did not change much.

Note that attachment 1 shows transfer functions from excitation point to the DOF sensing inputs while attachment two looks at ratio of C1:SUS-ITMY_SUS[POS/PIT]_IN1 to C1:SUS-ITMY_SUSYAW_IN1 which is the actual quantity of interest. I didn't repeat the PIT measurement due to lack of time.

Also note that all such measurements are being recorded in our new measurements git repo. We'll populate this repo with diaggui template+data files as we do measurements.

Attachment 1: ITMY_PIT_to_POS-PIT-YAW_Coupling.pdf
Attachment 2: ITMY_YAW_to_POS-PIT-YAW_Coupling.pdf
  16900   Wed Jun 8 16:03:12 2022 KojiUpdateVACPower Outage 220608: Vacuum Recovery

=== Observation ===

  • TP1/2/3 failed. AUX RP did not survive the power outage (of course)

=== Initial Recovery of TP2/TP3 ===

  • Stopped TP1/2/3
  • Restored RP AUX at the wall breaker module
  • Restarted TP2/3

=== Rough pumping down ===

  • Found RP1/RP3 left connected (unusual)
  • Turned on RP1 and RP3
  • Opened V6 and V7 for roughing of the pump spool. Now 0.3 torr for P2/P3/PA* (annuli) - ready to open V4 and V5 to backup TP1 by TP2 and TP3. Waiting for TP2/3 to be accelerated

=== Towards main volume pumping ===

  • TP2 accelerated and opened V4 (This caused V6 to close). RP1 and RP3 stopped.
  • TP3 hasitated to spin up. Stopped for now.
  • TP1 needed to be reset to clear the displacement errors. Once the errors were cleared, TP1 was restarted (acclerating).
  • TP1 at normal speed. Opened V1 (main volume pumping started)
  • Disconnected RP1/RP3 line.
  • TP3 was restarted and is now stable at 55k RPM (indicated as soft spin / low speed). Pushed "Stand By On" and "then "Stand By OFF". This makes the TP3 back to "NORMAL". Switched to "Stand By On".
  • TP2 was also switched to "Stand By On".

Now the main volume and the annuli are pumped down TP1 and TP2/TP3 with RP AUX backing.

The attachment is the pressure glitch for the main volume.


Attachment 1: Screenshot_2022-06-08_16-43-13.png
  16901   Wed Jun 8 16:33:26 2022 KojiUpdateGeneralPower Outage 220608: HVAC restored

I found the HVACs for the ends were off. They were turned back on.

  16902   Wed Jun 8 16:57:46 2022 KojiUpdateIOOPower Outage 220608: IMC restored

The IMC alignment was restored and the IMC is nicely locking.

Once the vacuum level recovered P<1e-4 torr, the PSL shutter was able to be opened.

The IMC was still flashing, so the lock to TEM00 was possible.

Once it was locked, the MC2 alignment was tweaked and the autolocker and the WFS kicked in to help the locking/alignment.

The transmission is ~13k and seems reasonable considering the low PMC transmission of the PMC (0.672)

  16903   Wed Jun 8 18:16:20 2022 yutaUpdateSUSITMY ULCOIL mystery: Coil driver swap test

To see if the ULCOIL channel of the ITMY coil driver is working or not, I swapped ITMY coil driver and ITMX coil driver by swapping DB15 cable (see Attachment #2).

With this swap, I confirmed that ITMX can be kicked with C1:SUS-ITMY_ULCOIL_OFFSET, but ITMY cannot be kicked with C1:SUS-ITMX_ULCOIL_OFFSET (see Attachment #1).

This means that the issue is not the in-air electronics.
Mystery remains again...
We need to investigate ITMY ULCOIL in the next vent.

I revereted the swap and confirmed that damping loops work fine again.

Attachment 1: Screenshot_2022-06-08_18-10-44.png
Attachment 2: SWAP.JPG
  16904   Thu Jun 9 23:08:39 2022 ranaUpdateSUSITMY ULCOIL mystery: Coil driver swap test

what was the result of the inductance measurement? should be ~3.3 mH as measured from the flannge or cable that goes to the flange from sat amp.


  16905   Fri Jun 10 13:02:14 2022 yutaUpdateSUSITMY ULCOIL mystery: Coil driver swap test

ITMY ULCOIL was measured to have ~3.3 mH as measured from the flange. RTFE 40m/16896 .


what was the result of the inductance measurement? should be ~3.3 mH as measured from the flannge or cable that goes to the flange from sat amp.



  16906   Fri Jun 10 13:52:22 2022 JCUpdateOPLEV TablesITMX, ITMY, and Vertex Table Beam Paths

I have at taken photos and added arrows which signify the beam paths for ITMX, ITMY, and Vertex Oplev tables.

Attachment 1: DCE4F1D7-5AE0-491C-8AF6-F8B659C0787E_1_105_c.jpeg
Attachment 2: 4B24C891-654D-4C51-A8D9-D316364FCF68_1_105_c.jpeg
Attachment 3: F5B115E5-885F-463C-9645-BB2EB73B6144_1_201_a.jpeg
  16907   Fri Jun 10 15:02:04 2022 yutaUpdateSUSServo gain sign flipped for MC1 WFS relief

The servo gain for MC1 in /opt/rtcds/caltech/c1/Git/40m/scripts/MC/WFS/reliefWFS was flipped to account for COIL_GAIN flip done in 40m/16898.
The reliefWFS script now works fine.

ezcaservo -r 'C1:SUS-MC2_ASCPIT_OUT16' -g ${g} -t ${ts} C1:SUS-MC2_PIT_COMM & 
ezcaservo -r 'C1:SUS-MC2_ASCYAW_OUT16' -g ${g} -t ${ts} C1:SUS-MC2_YAW_COMM & 
ezcaservo -r 'C1:SUS-MC1_ASCPIT_OUT16' -g -${g} -t ${ts} C1:SUS-MC1_PIT_COMM &  
ezcaservo -r 'C1:SUS-MC1_ASCYAW_OUT16' -g -${g} -t ${ts} C1:SUS-MC1_YAW_COMM & 
ezcaservo -r 'C1:SUS-MC3_ASCPIT_OUT16' -g ${g} -t ${ts} C1:SUS-MC3_PIT_COMM & 
ezcaservo -r 'C1:SUS-MC3_ASCYAW_OUT16' -g ${g} -t ${ts} C1:SUS-MC3_YAW_COMM & 

Attachment 1: Screenshot_2022-06-10_15-04-46.png
  16908   Fri Jun 10 15:04:23 2022 ranaUpdateSUSITMY ULCOIL mystery: Coil driver swap test

Its good that the inductance test passed. This means that the coil is OK. How does the inspection photo look? This is the one you guys took of the ITM OSEM that shows the position of the magnet w.r.t. the coil. Also, how does the free swinging spectra look? Either one of these might indicate a broken magnet, or a sticky EQ stop.

  16909   Fri Jun 10 20:11:46 2022 yutaUpdateASCYarm ASS re-tuning in progress

[Anchal, Yuta]

We tried to re-tune Yarm ASS today. It cannot be fully closed as of now. I think we need to play with signs.

 - We want to make sure Yarm ASS work with current ITMY coil matrix (40m/16899).
 - ASS makes the beam positions on test masses to be the same every day.

What we did:
 - Adjusted A2L paths of C1:ASS-YARM_OUT_MTRX based on cavity geometry. For the paths to maximize the transmission using TT1 and TT2, we just assumed they are correctly calculated by someone in the past.
 - Adjusted OSC_CLKGAINs so that ITMY and ETMY will be shaken in the same amplitude in terms of radians. The ratio of the excitation was determined to take into account for the oscillator frequency difference between DOFs.
 - Checked the time constant of A2L paths by turning on A2L paths only, and checked that of max-transmission paths by turining on them only.
 - Adjusted DEMOD_SIG_GAINs so that their time constants will be roughly the same, with C1:ASS-YARM_SEN_MTRX fully identity matrix and all servo GAINs to be +1.
 - Re-tuned DEMOD_PHASEs to minimize Q signal. C1:ASS-YARM_ITM_PIT_L_DEMOD_PHASE and C1:ASS-YARM_ITM_YAW_T_DEMOD_PHASE were re-tuned within +/- 5 deg.
 - These changes are recorded in /opt/rtcds/caltech/c1/Git/40m/scripts/ASS/ASS_DITHER_ON.snap now.

 - A2L loops seems to be working, but max-transmission paths seems to diverge at some point. I think we need to play with the signs/gains of max-transmission paths for C1:ASS-YARM_OUT_MTRX.
 - Attached is the current configuration we achieved so far.

Attachment 1: Screenshot_2022-06-10_20-10-52.png
  16910   Fri Jun 10 21:10:01 2022 yutaUpdateSUSITMY ULCOIL mystery: Coil driver swap test

We checked the photos we have, but we didn't have the photos which show ULCOIL situation clearly.

Free swing of ITMY (and others) will be done this weekend to see the OSEM spectra and resonant frequencies.

  16911   Mon Jun 13 20:26:09 2022 yutaUpdateASCYarm ASS re-tuning in progress -part 2-

[Anchal, Yuta]

We are still in the progress of re-commissioning Yarm ASS.
Today, we tried to adjust output matrix by measuring the sensing matrix at DC.
Turning on yaw loops kind of works, but pitch does not. It seems like there is too much coupling in pitch to yaw.
We might need to adjust the coil output matrix of ITMY and ETMY to go further, and/or try measuring the sensing matrix including pitch - yaw coupling.

What we did:
 - Confirmed that turning on TT1 and TT2 loops (max-transmission loops) work fine. When we intentionally misalign TT1/2, the ASS loops correct it. So, we moved on to measure the sensing matrix of A2L paths, instead of using theoretical matrix caluclated from cavity geometry we used last week (40m/16909).
 - Instead of +/-1's, we put +/-2's in the ITMY coil output matrix to balance the actuation between ETMY and ITMY to take into account that ITMY is now using only two coils for actuating pitch and yaw (40m/16899).
 - Measured the change in C1:ASS-YARM_(E|I)TM_(PIT|YAW)_L_DEMOD_I_OUT16 error signals when offset was added to C1:SUS-(E|I)TMY_ASC(PIT|YAW)_OFFSET. We assumed pitch-yaw coupling is small enough here. Below was the result.

                            ETM PIT error  ITM PIT error
ETM PIT OFFSET of +100cnts: -3.0cnts       -2.99cnts
ITM PIT OFFSET of +100cnts
: -11.94cnts      -5.38cnts

                            ETM PIT error  ITM PIT error
ETM YAW OFFSET of +100cnts:
-3.42cnts      -16.93cnts
ITM YAW OFFSET of +10 cnts: +1.41cnts      +0.543cnts

 - Inverted the matrix to get A2L part of C1:ASS-YARM_OUT_MTRX. Attachment #1 is the current configuration so far.
 - With this, we could close all yaw loops when pitch loops were not on. But vise versa didn't work.
 - Anyway, we aligned the IFO by centering the beams on test masses by our eyes and centered all the oplevs (Attachment #2).

 - Do coil balancing to reduce pitch-yaw coupling
 - Measure sensing matrix also for pitch-yaw coupling
 - Xarm ASS is also not working now. We need to do similar steps also for Xarm

Attachment 1: Screenshot_2022-06-13_20-47-12.png
Attachment 2: Screenshot_2022-06-13_20-44-43.png
  16912   Tue Jun 14 08:41:36 2022 JCUpdateOPLEV TablesBS Oplev Table Sketch


Lately, I have been working on a 3d sketch of the BS OPLEV Table on SolidWorks. This is my progress so far, a few of the components I will have to sketch myself, such as the HeNe laser and photodiodes. This will just be a general layout of the HeNe laser, optics, and photodiodes.

Attachment 1: BS_OPLEV_Table.PNG
  16913   Tue Jun 14 18:45:43 2022 AnchalUpdateSUSLO2 lower magnets are stuck in coil, won't come off

[Anchal, Yuta]

In the weekend, I ran a free swing test on all optics. During this test, LO2 magnets got stuck to the coil because LO2 PIT alignment was very high, making its lower OSEMs almost fully dark and upper OSEMs almost fully bright. Today we realized that LO2 is actually stuck and is not coming off even when we dither PIT alignment. We tried several ways but could not get this off. sad

Do we have any other method to get magnets off in vaccum?

It will be pretty bad if we try anything related to BHD with LO beam reflecting off a stuck mirror. Does anyone have any suggestions other than venting and fixing the issue?

  16914   Tue Jun 14 19:34:06 2022 yutaUpdateSUSResonant frequency identification from the free swing test

[JC, Anchal, Yuta]

We are working on resonant frequency idendification from the free swing test done last weekend.
Table below is the resonant frequencies identified, and attached are the plots of peak identification for some of our new suspensions.
To identify the resonant frequencies, the kicks were done in each degrees of freedom so that we can assume, for example, SUSPOS will be mostly excited when kicked in POS and the heighest peak is at the POS resonant frequency.
For PR3, AS1 and ETMY, the resonant frequency idendification needs to be done in the order of POS, PIT, YAW, SIDE and identified frequencies need to be removed when finding a peak.
Other than that, the identification was done without any prior assumptions on the suspensions.
For ITMY, ETMY, PR2, PR3, AS1, AS4, yaw has lower resonant frequencies than pitch, as opposed to other suspensions.
For LO1, POS and PIT frequencies might be swapped because LLCOIL is not working (40m/16898) and POS/PIT kicks both might be excited SUSPOS/PIT.
LO1 coil output matrix was temporarily modified so that we use only two coils for POS/PIT/YAW excitation (Attachment #7), as we did for ITMY (40m/16899).

The scripts for the free swinging test and analysis live in /Git/40m/scripts/SUS/InMatCalc

     POS    PIT    YAW    SIDE
BS   0.990  0.748  0.794  0.959 
ITMY 0.987  0.739  0.634  0.948 fPIT > fYAW
ETMY 0.979  0.816  0.649  0.954 fPIT > fYAW
ITMX 0.978  0.586  0.758  0.959 
ETMX 0.962  0.725  0.847  1.000 
PRM  0.939  0.541  0.742  0.990 
PR3  1.019  0.885  0.751  0.989 fPIT > fYAW
PR2  0.996  0.816  0.724  0.999 fPIT > fYAW
SRM  0.969  0.533  0.815  0.985 
SR2  0.978  0.720  0.776  0.997 
LO1  0.926  1.011  0.669  0.993 POS AND PIT MIGHT BE SWAPPED
LO2  0.964  0.998  0.995  0.990 WRONG DUE TO STUCK (40m/16913)
AS1  1.028  0.832  0.668  0.988 fPIT > fYAW
AS4  1.015  0.800  0.659  0.991 fPIT > fYAW
MC1  0.967  0.678  0.797  0.995 
MC2  0.968  0.748  0.815  0.990 
MC3  0.978  0.770  0.841  0.969 
Attachment 1: LO1.png
Attachment 2: AS1.png
Attachment 3: AS4.png
Attachment 4: PR2.png
Attachment 5: PR3.png
Attachment 6: SR2.png
Attachment 7: Screenshot_2022-06-14_21-07-09.png
  16915   Tue Jun 14 20:57:15 2022 AnchalUpdateASCYarm ASS working now

I finally got YARM AS to work today. It is hard to describe what worked, I did a lot of monkey business and some dirty offset measurements to create the ASS output matrix that gave results. Note that I still had to leave out ITMY PIT L error signal, but transmission was maximizing without it. The beam does not center fully on ITMY in Pit direction right now, but we'll mvoe on from this problem for now. Future people are welcome to try to make it work for this last remaining error signal as well.



  16916   Wed Jun 15 07:26:35 2022 JCUpdateVACBeginning Pumpdown

[Jordan, JC]

Jordan and I went in to retore the Vacuum System back to it's original state before the power loss on June 8, 2022. The process went smoothly as we first closed V7 and opened VM3 (in that order).

The RP1/3 line did not have the KF blank installed. That was added and the RP flex line was capped off.


[JC, Jordan, Paco, Chub]

We began with the pumpdown this morning. We started with the annulus volume and proceeded by using the following:

1. Isolate the RGA Volume by closing of valves VM3 and V7.

2. Opened valves VASE, VASV, VABSSCT, VABS, VABSSCO, VAEV, and VAEE, in that order.

3. Open VA6 to allow P3, FRG3, and PAN to equalize.

4. Turn on RP1 and RP3, rough out annulus volume, once <1 torr turn on TP3. Close V6. Open V5 to pump the annulus volume with TP3.

5. Re route pumping from RP1 and RP3 to the main volume by opening V3 and slowly opening RV1.

6. After ~3.5 hours the pressure in the arms was <500mtorr on both FRG1 and P1a. Turn on TP1 and wait to reach full speed 560 Hz

7. Open V1 with RV2 barely open. The pressure diff between P1a and P2/FRG2 needs to be below 1 torr. This took a couple attempts with the manual valve in different positions. The interlocks were tripped for this reason. Repeat step 7 until the manual gate valve was in a position that throttled pumping enough to maintain the <1 torr differential.

8. Slowly open the manual gate valve over the course of ~ 1 hour. Once the manual gate valve fully opened, pressure in the arms was <1mtorr.

9. V7 was closed, leaving only TP2 to back TP1, while TP3 was used to continue pumping the annuli. Left in that configuration overnight (see attached)


We did have to replace gauge PAN becuase it was reading a signal error. In addition, we found the cable is a bit sketchy and has a sharp bend. The signal comes in and out when the cable is fiddled with.


  16917   Wed Jun 15 15:03:41 2022 KojiUpdatePSLPMC input beam aligned

The commissioners complained about the PMC alignment. The PMC input beam was aligned. It made the transmission improved from 0.72 to 0.74.

FYI: Which steering mirrors do we use for the PMC beam alignment?
The mounts are indicated with the red arrows in Attachment 2.
You have to move these two in common and differential for each pitch and yaw.
The first steering (the right one in the picture) has the beam going through the immediate back of the mount.
So touching the yaw knob of this mount needs some care so that you don't block the PMC refl beam.

Attachment 1: Screenshot_2022-06-15_15-03-16.png
Attachment 2: PXL_20220615_212304650.jpg
  16918   Wed Jun 15 15:07:07 2022 KojiUpdateSUSLO2 SUS stuck fixed

I checked the state of the LO2 suspension. I found that the coil driver Enable Mon was all red. Meaning, the actuation signals were not delivered to the coil driver. I wasn't sure if this was intentional or not.

Enabled the coils with "WD Master" Shutdown -> Normal.

Immediately I saw the OSEMS flipped the sign because there was an (non-intentional) alignment offset in pitch. I've adjusted the pitch offset so that all the OSEM PDs have the voltages 4~5V.

That's it.

Attachment 1: Screenshot_2022-06-15_15-00-22.png
Attachment 2: Screenshot_2022-06-15_15-00-40.png
  16919   Wed Jun 15 15:45:37 2022 yutaUpdateSUSLO1 LLCOIL now working, it was loose connection

We tracked the issue of LO1 LLCOIL not actuating LO1, and found that the DB9 cable from the coil driver to the sat amp was loose.
I tightened the screws and now it is working.
Never ever connect cables without screwing the connectors tightly! angryno

What I did:
 - Measured the resistance and the inductance of each coil with BK PRECISION LCR meter, as I did for ITMY (Attachment #1, 40m/16896). The result is the following and it shows that LLCOIL is there.

Feedthru connector: LO1 1
Pin 3-15 / R = 16.0Ω / L = 3.27 mH (UL)
Pin 7-19 / R = 15.8Ω / L = 3.27 mH (UR)
Pin11-23 / R = 15.7Ω / L = 3.27 mH (LL)

Feedthru connector: LO1 2
Pin 3-15 / N/A
Pin 7-19 / R = 15.6Ω / L = 3.22 mH (SD)
Pin11-23 / R = 15.9Ω / L = 3.30 mH (LR)

 - Swapped the DB25 cable which goes to the feedthru LO1 1 and feedthru LO1 2. LLCOIL could be drived from LR coil driver and LRCOIL could not be drived from LL coil driver. SD and UR worked fine with the swap. This means that there is something wrong with the LL driving.
 - Went to see the rack which have coil drivers and sat amp for LO1, and immediately found that the DB9 cable was loose (Attachment #2). Tightened them and the issue was fixed.
 - C1:SUS-LO1_TO_COIL matrix gains were reverted to default values (Attachment #3).

Attachment 1: Measurement.JPG
Attachment 2: BAD.JPG
Attachment 3: Screenshot_2022-06-15_15-59-05.png
  16920   Wed Jun 15 17:03:17 2022 yutaUpdateSUSITMY ULCOIL issue solved, loose connection in sat amp box

[Anchal, Yuta]

We fixed the issue of ITMY ULCOIL not driving ITMY by replacing one of the 64pin ribbon cable in the satellite amplifier box.
We thought the coil driver and the sat amp box are OK by checking the voltage change at the output of the sat amp box by giving an offset to UL coil driver, but it was not giving a current change, probably due to too much contact resistance in the cables.
It was sneaky because it was not completely disconnected.

All the coils for our suspensions are now working!

What we did:
 - Using breakout boards, the output current of sat amp box was measured using FLUKE multimeter. It turned out that UL is not giving measurable current. We also confirmed that UR coil driver can drive UL by re-directing the current from UR coil driver to UL. This means that the UL magnet was not de-magnetized!
 - Measured the coil resistance from at the coil driver output and found that UL coil seen from there has too high resistance which cannot be measured with the multimeter, whereas UR coil was measured to be ~30 Ohms.
 - Went back to the feedthru and measured the resistance of UL coil. Upto the output of the Satellite Amp Terimator, the resistance was measured to be ~16 Ohms, but not at the input of the Satellite Amp Terimator (Attachment #1,2).
 - It turned out that #16 pin of 64pin ribbon cable in between the Satellite Amp Terimator (LIGO-D990021) and the Satellite Amp board (LIGO-D961289) at the Satellite Amp Terimator side was not good (Attachment #3).
 - Replaced the cable and confirmed that ULCOIL can kick ITMY (Attachment #4).
 - C1:SUS-ITMY_TO_COIL matrix was reverted to default values.

 - We might have to re-commission Yarm ASS again since pitch-yaw coupling have changed. -> EDIT: Checked that it works (except for ITM PIT L), including offloading offsets (writeASS_offsets.py), 18:30 local.
 - Now that LO1 LLCOIL issue is solved and LO2 stuck is solved, we should do the free swing test again to identify the resonant frequencies.
 - OSEM sensor diagonalization (input matrix), coil balancing (and F2A)

Attachment 1: Measured16Ohms.JPG
Attachment 2: SatAmpTerminator.JPG
Attachment 3: BAD.JPG
Attachment 4: SUCCESSFUL_KICK.png
  16922   Thu Jun 16 15:29:03 2022 yutaUpdatePSLPMC input beam aligned again, IMC

[Paco, Tomislav, Yuta]

Somehow, when we were trying to measure WFS open loop transfer functions, PMC unlocked many times for the past two hours and PMC transmission got low.
PMC iput beam was aligned again, and IMC WFS DC offsets and RF offsets were adjusted.
PMC transmission is now C1:PSL-PMC_PMCTRANSPD~0.75, and IMC transmission is C1:IOO-MC_TRANS_SUM~1.4e4.
Actually, IMC transmission once reached 1.5e4 at 06-16-2022 20:01 UTC with PMC transmission of 0.75 (see Attached). There might be a better alignment.

Attachment 1: Screenshot_2022-06-16_15-27-30.png
  16923   Thu Jun 16 17:40:15 2022 YehonathanUpdateBHDComparison of MICH OLTF model with measurement

I made some progress in modeling MICH loop.

Putting all the LSC and SUS filters together with the MICH Finesse model I constructed an OLTF model and plot it with the measurement done by Paco and Yuta in this elog (attachment 1).

There are 2 unknown numbers that I had to adjust in order to fit the model with the measurement:

1. The SUS damping loop gain (found to be ~ 2.22), which seems to vary wildly from SUS to SUS.

2. The coil driver gain (found to be 45), which I should measure.

I find coil_driver_gain*SUS_damping_filter_gain by increasing it until the SUS damping loop becomes unstable.

The coil driver gain I find by making the measurement and model overlap.

However, there is one outstanding discrepancy between the measurement and the model: Paco and Yuta measure the MICH calibration to be 1.3e9 cts/m while my model shows it to be 1.3e10 cts/m, an order of magnitude larger.


The model can be summarized with these lines of code (I assume that the product of the ADCs(DACs) and and whitening(dewhitening) filters is unity):

BS2AS55 = TFs["AS_f2"]["BS"]

PD_responsivity = 1e3*0.8 #V/W
ADC_TF = 3276.8 #cts/V
demod_gain = 6.77 #According to https://wiki-40m.ligo.caltech.edu/Electronics/LSC_demoddulators
whitening_gain = 10**(24/20) #24 dB
BS2MICH = BS2AS55*PD_responsivity*demod_gain*whitening_gain*ADC_TF

DAC_TF = 6.285e-4 #V/cts, elog 16161

coil_TF = 0.016 #Newton/Ampere per coil, elog 15846 

coil_R = 20e3 #Ohm

actuation_TF = DAC_TF*coil_TF/coil_R

OLTF = (BS2MICH*MICH_ctrl_cmplx*-6*0.5 + OSEM_filters_cmplx*OSEM_TF*2.22)*coil_filters_cmplx*actuation_TF*SUS_cmplx*45

  • BS2AS55 is the optical plant, calculated with Finesse
  • MICH_ctrl_cmplx is the MICH control filter with gain of -6
  • 0.5 factor comes from the LSC output matrix
  • OSEM_TF is the product of the OSEMs input filters and damping loop filters.
  • coil_filters_cmplx are the coil filters
  • SUS_cmplx is the suspension transfer function (w0 = 1Hz, Q=200)
Attachment 1: MICH_Model_Measurement_Comparison.pdf
  16925   Thu Jun 16 18:30:07 2022 AnchalUpdateSUSNew diagonalized input matrices applied

I used the same fre swing data to diagnolize input matrices of following optics:
MC1, MC2, MC3



For all these optics, the new input matrices worked well. Next step should be to take the local damping open loop transfer functions and standardize the loops to same UGF.

What didn't work:

  • The calculated input matrix for ITMX differed from existing matrix too much, including overall sign of rows POS and PIT. Even after correcting those signs, I was not able to get a good damping loop configuration. So I have committed the new matrix to the repo but have not implement it. More close analysis or another test might be required for this optic.
  • LO1, LO2, and ITMY were not analysed because their free swing test was not valid. LO1 and ITMY had non-working coils and LO2 was stuck during the test. We'll take another free swing test for these three optics (and possible ITMX) in near time.

All diagonalization results are present in https://git.ligo.org/40m/scripts/-/tree/main/SUS/InMatCalc

For looking at the results at this point, go to this commit: https://git.ligo.org/40m/scripts/-/tree/7ef6a47d1b2051a0732f46477624a9e625737fe8

Attachment 1: SUSInpMatDiag_MC1_MC2_MC3_BS_IMTX_ETMX_ETMY_AS1_AS4_SR2_PR2_PR3.pdf
  16926   Thu Jun 16 19:49:48 2022 CiciUpdateGeneralUsing the SR785

[Deeksha, Cici]

We used a python script to collect data from the SR785 remotely. The SR785 is now connected to the wifi network via Ethernet port 7.

  16927   Fri Jun 17 12:05:32 2022 YehonathanUpdateBHDComparison of MICH OLTF model with measurement

I should write down what I didn't include for completeness:

1. AA filters

2. AS55 input 60Hz comb filter

3. Violin filters

After discussing with Paco, we agreed that the discrepancy in the MICH calibration might come from the IQ mixing angle which for the IFO is not optimized, while in Finesse is set such that all the amplitude is in one quadrature.


I made some progress in modeling MICH loop.

Putting all the LSC and SUS filters together with the MICH Finesse model I constructed an OLTF model and plot it with the measurement done by Paco and Yuta in this elog (attachment 1).

There are 2 unknown numbers that I had to adjust in order to fit the model with the measurement:

1. The SUS damping loop gain (found to be ~ 2.22), which seems to vary wildly from SUS to SUS.

2. The coil driver gain (found to be 45), which I should measure.

I find coil_driver_gain*SUS_damping_filter_gain by increasing it until the SUS damping loop becomes unstable.

The coil driver gain I find by making the measurement and model overlap.

However, there is one outstanding discrepancy between the measurement and the model: Paco and Yuta measure the MICH calibration to be 1.3e9 cts/m while my model shows it to be 1.3e10 cts/m, an order of magnitude larger.

  16928   Fri Jun 17 13:07:08 2022 KojiUpdateBHDComparison of MICH OLTF model with measurement

I'm curious why the actual OLTF included the 60Hz comb...? It is undesirable to have such structure in the OLTF around the UGF as it can cause servo instability.
And if you remove them, you don't need to model them :-)

  16929   Fri Jun 17 16:22:21 2022 yutaUpdateLSCActuator calibration of BS. ITMX, ITMY, updated MICH displacement spectra from c1cal

Following what we have done in 2013 (40m/8242), actuator calibration was done using MICH.

AS55_Q in MICH : 9.74e8 counts/m
BS   : 26.08e-9 /f^2 m/counts
ITMX : 5.29e-9 /f^2 m/counts
ITMY : 4.74e-9 /f^2 m/counts

Optical gain is 25% lower than the measurement in June 6 (40m/16892), probably because our estimate was too rough then and also we now have ~15% lower IMC transmission.
Actuator gains are 2-30% higher than the measurement in 2013.

MICH error signal calibration:
 C1:LSC-AS55_Q_ERR was calibrated by taking data with C1:LSC-ASDC_OUT, when Michelson was aligned and free swinging (Attachment #1).
 AS55_Q and ASDC were X-Y plotted and fitted with ellipse to get an amplitude of AS55_Q to be 82.51 counts (Attachment #2).
 4*pi*A/lambda gives you 9.74e8 counts/m, where meters are in terms of difference between BS to ITMX length and BS to ITMY length.
 Jupyter notebook: https://git.ligo.org/40m/scripts/-/blob/main/CAL/MICH/MICHOpticalGainCalibration.ipynb

Openloop transfer function for actuator calibration:
 C1:LSC-MICH_GAIN was lowered to -1 (instead of -6), and some of filters are turned off to make the MICH UGF to be ~10.
 Also, ellip("LowPass",4,1,40,50) was added to C1:LSC-MICH_A filter bank to cut the feedback above 50 Hz, so that the loop does not suppress the measurement.
 The configuration is in Attachment #3.

Actuator calibration of BS, ITMX, ITMY:
 With this MICH OLG, transfer functions from C1:LSC-BS,ITMX,ITMY_EXC to C1:LSC-AS55_Q_ERR were measured.
 AS55_Q was calibrated to meters using the calibration factor above, and fitted the transfer function with 1/f^2 in 70-150 Hz range to get the actuator efficiency mentioned above (Attachement #4).
 Thus, meters in this calibration is in terms of ITM POS motion (not in BS POS motion).
 Jupyter notebook: https://git.ligo.org/40m/scripts/-/blob/main/CAL/MICH/MICHActuatorCalibration.ipynb

MICH displacement noise:
 Measured values were added to c1cal model as follows.
  C1:CAL-MICH_CINV FM2: 1/9.74e8 = 1.03e-9
  C1:CAL-MICH_A FM2: 2.608e-8 (it was 2.07e-8 from 2013!)
  C1:CAL-MICH_A_GAIN = 0.5 to take into account of C1:LSC-OUTPUT_MTRX_8_2=0.5 in the LSC output matrix for BS
 Spectrum of C1:CAL-MICH_W_OUT (now calibrated in nm) with configuration in Attachment #5 was taken.
 Attachement #6 is the result. I also took the spectrum with PSL shutter off to measure the sensing noise. The sensing noise limits our sensitivity above ~40 Hz at 5e-11 m/rtHz.

Attachment 1: MICHOpticalGainCalibrationFig1.png
Attachment 2: MICHOpticalGainCalibrationFig2.png
Attachment 3: Screenshot_2022-06-17_14-23-04_MICHOLTF_ActuatorCalibration.png
Attachment 4: MICHActuatorCalibration.png
Attachment 5: Screenshot_2022-06-17_15-54-41_MICHCalibrationFilters.png
Attachment 6: Screenshot_2022-06-17_15-53-41_MICHDisplacement.png
  16930   Mon Jun 20 19:46:04 2022 TomislavUpdateASCSimulation plots

In the attachment please find IMC ASC simulation plots. Let me know what you think, if you want some other plots, and if you need any clarification.

Attachment 1: pit_mot_cl_MCs.png
Attachment 2: loc_damp_cl_MCs.png
Attachment 3: contr_output_cl_MCs.png
Attachment 4: sens_output_cl_MCs.png
Attachment 5: BS_motion_cl_MCs.png
  16931   Tue Jun 21 08:36:50 2022 AnchalUpdateSUSDiagonalized input matrices for LO1, freeSwing on ITMY and ITMX

Over the weekend, I ran freeSwing test with sequential kicks in specific DOFs for LO1, ITMY, ITMX. LO1 results were successfully used to diagonalize LO1 input matrix. There are some issues for ITMY, ITMX still. I could not run LO2 test.


The free swing test ran successfully, resonant frequencies for different DOFs was extracted, and new input matrix was calculated. The new matrix was only slightly different from before and it worked fine with existing damping loops. The observed resonance frequencies were different from previous values by POS: -6 mHz, PIT : -3 mHz, YAW: -9 mHz, SIDE: -2 mHz. Attached are the diagonalization result.


The peculiarity of ITMX remained even after the second free swing test. The calculated input matrix is very different from existing one with sign flips across PIT and POS rows. I found that our LR osem is always bright in ITMX at the current alignment position. I see that LR osem comes in range when C1:SUS-ITMX_PIT_COMM is raised above 0.5. Maybe we should run this test when we know for sure ITMX is in correct position.


In ITMY on the other hand, I found that SIDE OSEM was completely bright. This happened during the YAW kick to ITMY. We'll need to reduce kick amplitudes for ITMY and redo this test.


For LO2, I could not initiate the test. On reducing the alignment offsets for LO2 (so that it doesn't get stuck in the fre swing test), the damping loops were not working. This is a clear evidence also that input matrix is different for different positions of the optic. We need to think about some other strategy to do this test, maybe see if ideal input amtrix works at no offsets and use that to damp during the test.

Attachment 1: SUSInpMatDiag_LO1.pdf
  16934   Tue Jun 21 18:41:46 2022 TomislavUpdateASCSimulation plot

In the attachment please find a comparison of error signals of simulation and reality. For C1:IOO-WFS1/2_PIT_IN1 excess signal ('belly') between a few Hz up to 70-80 Hz might be caused by air turbulence (which is not included in the simulation).

Attachment 1: sens_output_comparison.png
  16935   Tue Jun 21 21:17:16 2022 yutaUpdateBHDRTS models for BHD added but PCIE error remaining

[Anchal, Yuta]

RTS models for BHD homodyne phase control (c1hpc) and angular control (c1bac) are created and added to c1sus2.
c1su2 and c1lsc models were modified accordingly.
We still have issues with IPC PCIE connection sending DCPD A and B signals to c1lsc and DC error 0x2000 in c1su2 model.

c1hpc (host: c1sus2) Attachment #1
 This model is for homodyne phase control.
 It can dither LO1, LO2, AS1, AS4 in POS and demodulate mixture of DCPD A/B signals for the phase control to feedback to those optics.
 It also sends DCPD A/B signals to c1lsc via cdsIPCx_PCIE.
 Dither and controls signals are sent to the optics via cdsIPCx_SHMEM.

c1bac (host: c1sus2)
 This model is for BHD angular control.
 It is basically the same as c1hpc, but it is for PIT and YAW dithering of LO1, LO2, AS1, AS4.

c1su2 (host: c1su2) Attachment #2
 LSC and ASCPIT/YAW feedback signals from c1hpc and c1bac via shared memory were added to send them to corresponding optics.
 Somehow Mux/Demux didn't work to send SHMEM signals inside the subsystem in the Simulink model (this works for ADC, but probably not for IPC stuff?), and we had hard time make-install-ing this model.

c1lsc (host: c1lsc) Attachment #3
 DCPD A/B signals from c1hpc via PCIE were added for our new error signals for LSC.

Starting and restarting the models
 After having some troubles make-install-ing modified models (be careful of goto and from tags!), we stopped all the models in c1sus, c1ioo, c1lsc, c1sus2 and started all of them, including new c1hpc and c1bac models.
 This somehow created RFM errors in c1scx and c1scy.
 So, we proceeded to do the same step we did in 40m/16887 and 40m/15646, now including c1sus2 for the restart.
 Initial attempt made c1lsc, c1sus, c1ioo mostly red, so scripts/cds/rebootC1LSC.sh was run again on pianosa.
 RFM issues for c1scx and c1scy were solved.
 Shared memory within c1sus2 seems to be working, but sending DCPD A/B signals from c1hpc to c1lsc is not working (see Attachement #4).

 - Fix C1:HPC-LSC_DCPC_A/B issue
 - Make/modify MEDM screens

Attachment 1: Screenshot_2022-06-21_20-12-55_C1HPC.png
Attachment 2: Screenshot_2022-06-21_20-14-56_C1SU2.png
Attachment 3: Screenshot_2022-06-21_20-13-38_C1LSC.png
Attachment 4: Screenshot_2022-06-21_20-34-44_RED.png
  16937   Tue Jun 21 22:22:37 2022 TomislavUpdateASCPlots

In the attachment please find a comparison of error signals of simulation and reality after including air turbulence as input noise.

Attachment 1: sens_output_comparison_with_air_turbulence.png
  16938   Wed Jun 22 14:44:03 2022 AnchalUpdateBHDFixed DC error in c1su2, added new library model for suspensions

The 0x2000 error in c1su2 happens whenever we make it and install it as the default data acquisition rates are too much in the suspension model. Earlier we used activateSUS2DQ.py to fix this. I followed the suggestion in 40m/16537 to include COIL_OUT at 16k, damping channels at 256 Hz and OL channels at 1024 Hz. I created new suspension model at /cvs/cds/rtcds/userapps/trunk/sus/c1/models/lib/sus_single_control_new.mdl. The model also contains filter modules names C1SUS_OPT_BIASPOS, C1SUS_OPT_BIASPIT, C1SUS_OPT_BIASYAW which acts on the alignment offsets so that a low pass filter can be added there and alignment offsets always happen slowly. The new suspension model is now used inc1su2 for teh 7 new suspensions, and now the model starts without errors.

Still remaining to fix: IPC communication between c1hpc and c1lsc.

  16940   Wed Jun 22 18:55:31 2022 yutaUpdateLSCDaily alignment work; POY trouble solved

[Koji, Yuta]

I found that Yarm cannot be locked today. Both POY11 and POYDC were not there when Yarm was aligned, and ITMY needed to be highly misaligned to get POYDC.
POY beam also could not be found at ITMY table.
Koji suggested to use AS55 instead to lock Yarm. We did it (AS55_I_ERR, C1:LSC-YARM_GAIN=-0.002) and manually ASS-ed to get Yarm aligned (ASS with AS55 somehow didn't work).
After that, we checked ITMY table and found that POY beam was clipped at an iris which was closed!
I opened it and now Yarm locks with POY11 again. ASS works.
PMC was also aligned.


Attachment 1: Screenshot_2022-06-22_17-17-42_XYaligned.png
Attachment 2: Screenshot_2022-06-22_18-58-26_Transmission.png
  16941   Wed Jun 22 19:41:13 2022 KojiUpdateLSCDaily alignment work; POY trouble solved

Before the final measurement of the DC values for the transmissions, I aligned the PMC. This made the PMC trans increased from 0.67 to 0.74.

  16942   Thu Jun 23 15:05:01 2022 Water MonitorUpdateUpgradeWater Bottle Refill

22:05:02 UTC Jordan refilled his water bottle at the water dispenser in the control room.

  16943   Fri Jun 24 12:13:16 2022 JCUpdateIOOWFS issues

[Yuta, JC]

It seems that early this morning MC got very misaligned. Yuta was able to align the Mode Cleaner again by individually adjusting the MC1 MC2, and MC3. Once transmission reach ~12000, we went ahead and turned on WFS. Oddly enough, the transmission began plummeting and MC fell out of lock. After this, Yuta reset the WFS offsets and realigned the WFS QPDs. We then locked MC and turned on WFS once again, but the same issue happened. After fiddeling around with this, we found the if we set C1:IOO-MC2_TRANS_PIT_OUTPUT and C1:IOO-WFS1_YAW_OUTPUT equal to 0, WFS does not cause this issue. Is there a proper to reset WFS, aside from only zeroing the offsets?

Attachment 1: WFS.png
  16944   Fri Jun 24 13:29:37 2022 YehonathanUpdateGeneralOSEMs from KAGRA

The box was given to Juan Gamez (SURF)


I put the box containing the untested OSEMs from KAGRA near the south flow bench on the floor.


  16945   Fri Jun 24 17:16:59 2022 PacoUpdateALSXAUX cable in control room

[JC, Paco]

We took the long BNC cable that ran from ETMX to ETMY and ran it from ETMX into the control room instead. This way Cici and Deeksha can send small voltage signals to the AUX PZT and read back using the beatnote pickoff that is usually connected to the spectrum analyzer.

  16946   Sat Jun 25 14:29:48 2022 AnchalUpdateIOOWFS issues

This issue is very weird and still unresolved. Without WFS loops, we'll have to realign IMC often and we might loose IMC alignment completely during weekends or long weekends.

I tried following things today but nothign worked:

  • Blocked WFS PDs and reset DC offsets (sitemap>C1IOO>C1IOO_WFS_MASTER>! Actions>Correct WFS DC Offsets).
  • Switched off MC chamber lights.
    I felt that they might be on, but later I feel that wasn't the case. Anyways, this didn't help.
  • Algined IMC manually using cavAlign tool with MC2-MC3 and then tweaking MC1 and MC3 a little bit. Reach 13.6k in C1:IOO-MC_TRANS_SUM. Then I unlocked IMC with autolocker off, centered beam on WFSs (they were pretty off even though we have been centering them this week), and then reset RF offsets (sitemap>C1IOO>C1IOO_WFS_MASTER>! Actions>Correct WFS DC Offsets). This did not help either.
  • The fact that IMC started misbehaving since Thursday onwards was bugging me that maybe the FE models did not come online properly, that maybe some RTS link is broken in IOO model which is causing the feedback loop to not work. So I went ahead and restarted all models, that didn't help either.
    • Now we have a restartAllModels.sh script which restarts all cds system and restores state to just before restarting. It also makes sure that watchdogs are engaged safely particularly for new suspesnions where alignment offsets are ramped.

We need to investigate this as first priority. Maybe some cable is loose, some PD power supply not working etc. Until we fix this, people should align IMC to > 12000 transmission counts whenever they have a spare 5 min. We need to work in place of WFS for sometime.

  16947   Sat Jun 25 20:23:59 2022 KojiUpdateIOOWFS issues

I could run the WFS servo (6dofs) for more than 15min by flipping the sign for the MC2 Pit and WFS1 Yaw. (See attachments)

This may mean that the sign of the loops / the input matrix / the output matrix, as well as the sensors and actuators, have the problem.
Isn't it the time to measure the sensing/actuation matrices? Maybe Tomislav already has the data?

I have reverted the changes as you may need more careful investigation.

Attachment 1: Screen_Shot_2022-06-25_at_20.23.21.png
Attachment 2: Screen_Shot_2022-06-25_at_20.29.24.png
  16948   Sat Jun 25 22:18:41 2022 TomislavUpdateASCSimulation and reality comparisons

In the attachment please find plots comparing controller output, local damping output, and error signals.

Input noises of the simulation are seismic noise, osem noise, input power fluctuations, sensing noises of WFSs and QPD, and air turbulence noise for WFSs. There is also optical torque noise (radiation pressure effect). 

The procedure to get optical gains and sensing noises:
Having the actuator response A rad/cnts @ 3 Hz. I was shaking MC1/2/3 in pitch with B cnts @ 3 Hz and getting WFS1/2 QPD signals of C cnts @ 3 Hz, which means WFS1/2 QPD optical gain is D cnts/rad = C / (A * B) cnts/rad. So, if WFS1/2 QPD IN1 has a noise spectrum (at higher freqs) of E cnts/rtHz, that corresponds to E/D rad/rtHz of sensing noise for WFS1/2 QPD.

Actuator response [rad/cts] I was getting shaking mirrors at 3 Hz and measuring amplitudes of OSEM output (knowing the geometry of the mirror). I scaled it to DC. From here I was getting ct2tau_mc (knowing the mirror's moment of inertia, Q, and natural pitch frequencies). OSEM calibration factors [cts/rad] I was getting from the input matrix and geometry of the mirror.

The flat noise at higher frequencies from the local damping and controller output channels is presumably quantization/loss of digits/numerical precision noise which I don't include in simulations for now?!

Regarding air turbulence, in KAGRA it has been reported that air turbulence introduces phase fluctuations in laser fields that propagate in air. According to Kolmogorov’s theory, the PSD of phase fluctuations caused by air turbulence scales as ∝ L*V^(5/3)*f^(−8/3). Here, L is the optical path length and V is a constant wind speed. Since it is not obvious how can one estimate typical V in the beam paths I was taking this excess noise from the error signals data between 10 Hz and 50 Hz, extrapolated it taking into account ∝ f^(−8/3) (not for frequencies below 2 Hz, where I just put constant, since it would go too high). I expect that I won't be able to get a parameterized model that also predicts the absolute value. The slope is all I can hope to match, and this I already know. QPD chamber is much smaller (and better isolated?) and there is no this excess noise.

Regarding other things in simulations (very briefly): beam-spots are calculated from angular motions, length change is calculated from beam-spots and angular motion, cavity power depends on length change and input power, and torque on the mirrors depends on beam-spots and cavity power. From other things, local-sensor basis conversion (and vice versa) is worth noting.

Attachment 1: sens_output_comparison_23_6_new.png
Attachment 2: contr_out_comparison_23_6_new.png
Attachment 3: local_damp_out_comp_23_6_new.png
  16949   Mon Jun 27 12:32:45 2022 yutaUpdateIOOWFS issues fixed

[Anchal, Yuta]

We found that MC1 local damping loop signs were revereted to the state before our standardization on June 7th (40m/16898), but the WFS output matrix was not reverted.
This caused the sign flip in the feedback to MC1, which caused the IMC WFS issue.
This probably happened when we were restarting the models after RTS modeling (40m/16935). We might have used wrong snap files for burt-restoring.

We went back to the snapshot taken at 09:19 June 21, 2022 and now the IMC WFS is working,

  16950   Mon Jun 27 13:25:50 2022 CiciUpdateGeneralCharacterizing the Transfer Loop

[Deeksha, Cici]

We first took data of a simple low pass filter, and attempted to perform a fit to both the magnitude and phase in order to find the Z of the components. Once we felt confident in our ability to measure tranfer functions, we took data and plotted the transfer function of the existing control loop of the AUX laser. What we found generally followed the trend of, but was lower than, 10^4/f, which is what we hoped to match, and also had a strange unexplained notch ~1.3 kHz. The magnitude and phase data both got worse after around 40-50 kHz, which we believe is because the laser came out of lock near the end of the run. 


[Attachment 2 and 3] are the frequency response of the low pass filter, curves fitted using least squares in python.

[Attachment 1 and 4] is the same measurement of OLTF of the actual AUX circuit, and the control diagram pointing out the location of excitation and test point.

Attachment 1: TF_measurement_b.png
Attachment 2: transfer_function_mag_fit.png
Attachment 3: transfer_function_phase_fit.png
Attachment 4: control_flow.png
  16951   Mon Jun 27 13:39:40 2022 DeekshaUpdateElectronicsSetting up the MokuLab

[Cici, Deeksha]

On Friday Cici and I set up the Mokulab to take readings of our loop. The aim is to characterise the PZT, in a similar manner as before, by exciting the circuit using our input noise (a swept sine) and recording the corresponding changes in the output. We used the MokuLab to observe the beat note created by the signals of the AUX and PSL, as well as the ASD of the output signal. The MokuLab simplifies the entire process.

Pictured : The beat note as observed by Cici

Attachment 1: WhatsApp_Image_2022-06-24_at_5.21.28_PM.jpeg
  16952   Mon Jun 27 18:54:27 2022 yutaUpdateLSCModulation depths measurement using Yarm cavity scan

[Yehonathan, Yuta]
EDITED by YM on 22:11 June 27, 2022 to correct for a factor of two in the modulation index

Since we have measured optical gain in MICH to be an order of magnitude less compared with Yehonathan's FINESSE model (40m/16923), we measured the power at AS55 RF PD, and measured the modulation depths using Yarm cavity scan.
We found that 50/50 beam splitter which splits AS55 path into RF PD and RF QPD was not included in the FINESSE model. Measured modulation index were as follows:

TEM00 peak height: 0.6226 +/- 0.0237
RF11 peak height: 0.0067 +/- 0.0007
RF55 peak height: 0.0081 +/- 0.0014
RF11 modulation index: 0.208 +/- 0.012
RF55 modulation index: 0.229 +/- 0.020
RF11 modulation index: 0.104 +/- 0.006
RF55 modulation index: 0.114 +/- 0.010

Here, modulation depth m is defined in E=E_0*exp(i*(w*t+m*sin(w_m*t))), and m m/2 equals to square of the intensity ratio between sidebands and TEM00.

Power measurement at AS55 RF PD:
 - ITMY and ITMX single bounce reflection was measured to be 50-60 uW at the front of AS55 RFPD.
 - In the FINESSE model, it was expected to be ~110 uW with 0.8 W input to PRM (0.8 W * 5%(PRM) * 50%(BS) * 50%(BS) * 10%(SRM) * 10%(AS2) gives 100 uW)
 - In AP table, AS55 beam was split into two paths with 50/50 beam splitter, one for AS55 RF PD and one for AS WFS and AS110. This will be included in the FINESSE model.

Modulation depth measurement using Yarm cavity scan:
 - Aligned Yarm using ASS, and unlocked Yarm to get the 2sec scan data of C1:LSC-TRY_OUT_DQ, C1:LSC-POY11_I_ERR_DQ, C1:LSC-AS55_I_ERR_DQ.
 - TRY data was used to get TEM00 peak heights
 - POY11/AS55 data was used to find RF11/RF55 sideband peaks, and height was measured at TRY (see attached).
 - If we define m to be E=E_0*exp(i*(w*t+m*sin(w_m*t))), the amplitude of TEM00 I_00 is proportional to J_0(m) and the amplitude of upper/lower sideband I_f1 is proportional to J_1(m), where J_n(m) is the bessel function of the first kind.
 - m can be calculated using 2*sqrt(I_f1 / I_00).
 - Results were shown above. Error is calculated from the standard deviation of multiple measurements with multiple peaks,
 - The code for doing this lives in https://git.ligo.org/40m/measurements/-/blob/main/LSC/YARM/modulationIndex.ipynb

 - Power at AS55 account for the factor of 2, In the FINESSE model, modulation index of 0.3 was used (could be m=0.3/2 or m=0.3; needs check). These combined can explain a factor of 3 at least (or 6).
 - Gautam's measurement in Jan 2021 (40m/15769) gives almost double modulation index, but I'm not sure what is the definition Gautam used. It agrees with Gautam's measurement in Jan 2021.

Attachment 1: YarmModIndex.png
ELOG V3.1.3-