We found that there was a small offset (~300 mV) at TP6 and TP8, in PD2 circuit (CH2 of the board). I replaced U3 AD822ARZ but did not see any affect. I disconnected the adaptor board in the back and saw that the offset went away. This might mean that the cable had some flaky short to a power supply pin. However, when I just reinserted the adaptor board back again, there was no offset. We could not find any issue with the board after that to fix, so we left it as it is. If this board gives offset issues in the future, most probably the ribbon cable would be the suspect.
Now all ADC channels are showing no offset or overflows in C1SU2 chassis.
I tested 2 more optics found by Paco and Yehonathan in QIL.
I would like someone to redo the second test. I'm not sure what was happening but I could not find the transmitted beam at all on my card even with all lights out. This is either too good a coating and not useful for us or I did something wrong while measuring it.
V6-704, V6-706 mirror seemed like a good candidate as the paper with it said it would be a 200 ppm mirror. But I measured a lot more transmission than that. Now that I see that paper more carefully, it is a 45 degree s-pol mirror, probably that's why it had so much transmission for p-pol at near-normal incidence.
LO1 is set to go through a free swinging test at 1 am tonight. We have used this script (scripts/SUS/InMatCalc/freeSwing.py) reliably in the past so we expect no issues, it has a error catching block to restore all changes at the end of the test or if something goes wrong.
To access the test, on rossa, type:
Then you can kill the script if required by Ctrl-C, it will restore all changes while exiting.
The frree swinging test was successful. I ran the input matrix diagonalization code (scripts/SUS/InMAtCalc/sus_diagonalization.py) on the LO1 free swinging data collected last night. The logfile and results are stroed in scripts/SUS/InMatCalc/LO1 directory. Attachment 1 shows the power spectral density of the DOF bassis data (POS, PIT, YAW, SIDE) before and after the diagonalization. Attachment 2 shows the fitted peaks.
The new matrix was loaded on LO1 input matrix and this resulted in no control loop oscillations at least. I'll compare the performance of the loops in future soon.
I did this simple calculation where I assumed 1W power from laser and 10% transmission past IMC. We would go ahead with V6-704/V6-705 ATFilms 3/8" optic. It would bring down the PRC gain to ~30 but will provide plenty of light for LO beam and alignment.
[Anchal, Paco, Yehonathan]
Connected in-cir cable to new flange on ITMY Chamber
Connected OSEM one-by-one. Starting from top right to left (PIn1)
1st connector: LL -> UR -> UL
2nd connector: LR -> SD
Loosening all OSEMs and taking them out and noting full bright readings:
:( We had to stop here as we were unable to actuate on the side coils. We checked the signal chain and found that the monitor output of AS1 LL/SD coil driver is responding to offset changes in the coil output filter module of AS1 side. However, when we connected the output of the coil driver through a breakout board to the AS1 Sat Amp, we saw no signal. We tried switching the coil driver bo with another one one the rack but we found the exact same issue. This led us to believe that something must be wrong with the AS1 Sat Amp. We checked the output of the AS1 LL/SD coil driver without connecting it to the sat amp and found that the output was responding to our CDS changes. Then we checked the second "Coil Input" port of the AS1 Sat Amp, and found that pins 2-7 and pins 3-8 are shorted. This means channel 5 and 8 on this box would be shorted. This is the reason why we were unable to actuate on the coils. I'll work on debugging this box, my first guess is that the ribbon cable is bad.
AS1 Sat Amp (S2100741) has a critical PCB issue on it's Ch5-8 board S2100548. This board is supposed to just feed through the coil driver signal from the front DB9 connector to the back DB25 connector but it has a short between pins 2 and 7 at the "Coil Input" end (connector J1). The short persists even after I disconnect the sat amp to the flange connector on the back of this board, which definitely means the short is present in the passive channeling through the PCB or at the soldering points of the two DB connectors. I just flipped the board and found that the soldering connections are clean and separate. I think we'll have to use one of the spare sat amp boxes for AS1 for now, while we either declare this one manufacture defected or fix the issue.
I actually found the short on the PCB trace by just looking carefully at it. Attachment 1 shows the photo of it. Maybe we can fix this by simply cutting the tumor between the two traces (why are these traces so close together in such a large board anyways!!!), but I'm not sure if that is a reliable way of fixing this issue. I'll wait for Koji's comments on what to do with this. We'll recommence OSEM tuning for AS1 tomorrow with fixed electronics.
I fixed the issue in AS1 Sat Amp (S2100741) by using a razor blade. I cut the short between the two places, cleaned up the area and covered it with electrical tape. However, later feedback from Rana was to not use electrical tape as it dries up and becomes brittle and lfaky in long run. So after the AS1 OSEM tuning is over, I'll open this box again and use something else to insulate the exposed area. See attached pictures for current status.
[Anchal (vacuum work), Paco (outside)]
After the AS1 Sat Amp fix (40m/16579), we today were able to tune all OSEMs to the mid-bright level. But when we were about to call it, we were told that the new PEEK earthquake stop screw and bolts need to go on the thin suspended optics. Against better judgment, we decided to install the new back earthquake stop in-situ since we had tuned all OSEMs already. I installed the new stop but after that found that in the process I have broken off the side magnet and LR magnet from the optic adaptor and they are inside the OSEM coils now. This means we'll have to redo the AS1 suspension almost from scratch again . We have transported AS1 to the cleanroom where the work on re-suspension has begun.
After the debacle with AS1 (40m/16580), we decided the put the PEEK earthquake stop by first removing the lower OSEM plate and then doing it. So I unfastened AS4 from its position with the earthquake stops in place and moved the suspension to the center of the table. Then I carefully removed the bottom OSEM plate. But I found out that the LR magnet is broken and lying on the floor of the suspension . Given my past on the same day, it could be me breaking it again during the moving of the suspension of taking off the OSEM plate or there is a small chance that this break happened before. Regardless of fault, this meant we have to resuspend AS4 again as well. So we transported AS4 back to the clean room and the work on it's re-suspension has begun.
I corrected the calculation by adding losses by the arm cavity ends times the arm cavity finesse and also taking into account the folding of the cavity mirror. I used exact formula for finesse calculation and divided it by pi to get the PRC gain from there. Attachment 3 is the notebook for referring to the calculations I made.
Note that using V6-704 would provide 35 mW of LO power when PRFPMI is locked and 113 uW for alignment, but will bring down the PRC Gain to 17.5.
pre-2010 ITM (if it is still an option) would provide 12 mW of LO power when PRFPMI is locked and 28 uW for alignment, but will keep the PRC Gain to 24.6.
I still have to do a curvature check on the V6-704 optic.
Yeah, I counted the loss from arm cavities as the transmission from ETMs on each bounce. I assumed Michelson to be perfectly aligned to get no light at the dark port. Should I use some other number for the round-trip loss in the arm cavity?
I labeled all the newly installed flanges and connected the in-air cables (40m/16530) to appropriate ports. These cables are connected to the CDS system on 1Y1/1Y0 racks through the satellite amplifiers. So all new optics now can be damped as soon as they are placed. We need to make more DB9 plugs for setting "Acquire" mode on the HAM-A coil drivers since our Binary input system is not ready yet. Right now, we only have 2 such plugs which means only one optic and be damped at a time.
I updated the arm cavity roundtrip losses due to scattering. Yehonathan told me that arm cavity looses 50ppm every roundtrip other than the transmission losses. With the updated arm cavity loss:
AS4 was succesfully suspended and trasported to ITMY chamber (40m/16589). We placed it near the door to make it easy to tune the OSEMs. We connected the OSEMs and found that the LL OSEM is not responding. Even though the the OSEMs are completely out right now, there was no signal on this OSEM. This could be an issue in either at the LED driver circuit or the PD circuit in AS4 Sat Amp box, or it could be the OSEM that is bad. We'll investigate further next day. For now, we recorded the full brightness reading for the OSEMs:
Another thing to note is that UL value above is not changing at all. I checked the CDS screen and the the ADC input is overflowing in complete bright position of the OSEM.
I tested the monitor ports on the SR2 Sat Amp Box but found that all LED Mon and PD Mon are giving expected values. I disconnected the cable to OSEM and checked the PD monitors and found no offsets in case of no PD current. I realised that PD transimpedance offset should be checked with PD inputs shorted instead. So I created a male DB 25 connector with pinds 2-3, 50-6, 8-9 and 11-12 shorted. This on connecting to the OSEM cable at the back of sat amp boxes should short the PD inputs. On using this plug, I found no offsets in any of the Sat Amp PD output channels.
It is possible that the issue is there because the magnet is missing the LED-PD path way because it is offset sideways. In fact, in my limited memory, I do not recall seeing the UL OSEM signal ever going to complete darkness either. Tomorrow, we should take a photo of the OSEMs from the back and see if any sideways adjustment of the top OSEM plate is required. If any adjustment is required, we must take the OSEMs out and then do the adjustment. Do not attempt to adjust OSEM plate with OSEMs inserted in-situ. That will most probably knock off the magnets.
It was indeed the issue of the top OSEM plate not being in the right place horizontally. But the issue was more non-trivial. I believe because of the wedge in thick optics, there is a YAW offset in the optic in the free hanging position. I had to readjust the OSEM plate 4 times to be able to get full dark to bright range in both upper OSEMs. After doing that, I tuned the four OSEMs somewhat near the halfway point and once I was sure I'm inside the sensitive region in all face OSEMs, I switched on POS, PIT, and YAW damping. Then I was able to finely tune the positions of both upper OSEMs.
However, on reaching to lower right OSEM, I found again the same issue. I had to stop to go to the 40m meeting, I'll continue this work in the afternoon. But OSEM plate adjustment in the horizontal direction, particularly for thick optics is required to be done before transporting them. I achieved the best position by turning the OSEM 90 degrees and using the OSEM LED/PD plates to determine the position. This was the final successful trial I did in adjusting the plate position horizontally.
I have further updated my calculation. Please find the results in the attached pdf.
Following is the description of calculations done:
Reflection fro arm cavity is calculated as simple FP cavity reflection formula while absorbing all round trip cavity scattering losses (between 50 ppm to 200 ppm) into the ETM transmission loss.
So effective reflection of ETM is calculated as
The magnitude and phase of this reflection is plotted in page 1 with respect to different round trip loss and deviation of cavity length from resonance. Note that the arm round trip loss does not affect the sign of the reflection from cavity, at least in the range of values taken here.
The Michelson in PRFPMI is assumed to be perfectly aligned so that one end of PRC cavity is taken as the arm cavity reflection calculated above at resonance. The other end of the cavity is calculated as a single mirror of effective transmission that of PRM, 2 times PR2 and 2 times PR3. Then effective reflectivity of PRM is calculated as:
Note, that field transmission of PRM is calculated with original PRM power transmission value, so that the PR2, PR3 transmission losses do not increase field transmission of PRM in our calculations. Then the field gain is calculated inside the PRC using the following:
From this, the power recycling cavity gain is calculated as:
The variation of PRC Gain is showed on page 2 wrt arm cavity round trip losses and PR2 transmission. Note that gain value of 40 is calculated for any PR2 transmission below 1000 ppm. The black verticle lines show the optics whose transmission was measured. If V6-704 is used, PRC Gain would vary between 15 and 10 depending on the arm cavity losses. With pre-2010 ITM, PRC Gain would vary between 30 and 15.
LO power when PRFPMI is locked is calculated by assuming 1 W of input power to IMC. IMC is assumed to let pass 10% of the power (). This power is then multiplied by PRC Gain and transmitted through the PR2 to calculate the LO power.
Page 3 shows the result of this calculation. Note for V6-704, LO power would be between 35mW and 15 mW, for pre-2010 ITM, it would be between 15 mW and 5 mW depending on the arm cavity losses.
The power available during alignment is simply given by:
If we remove PRM from the input path, we would have sufficient light to work with for both relevant optics.
I have attached the notebook used to do these calculations. Please let me know if you find any mistake in this calculation.
The main issue with SR2 OSEMs, now that I think of it, was that the BS table was very inclined due to the multiple things we removed (including counterweights). Today the first I did was level the BS table by placing some counterweights in the correct positions. I placed the level in two directions right next to SR2 (clamped in its planned place), and made the bubble center.
While doing do, at one point, I was trying to reach the far South-West end of the table with the 3x heavy 6" cylindrical counterweight in my hand. The counterweight slipped off my hand and fell from the table. See the photo in attachment 1. It went to the bottommost place and is resting on its curved surface.
This counterweight needs to be removed but one can not reach it from over the table. So to remove it, we'll have to open one of the blank flanges on the South-west end of BS chamber and remove the counterweight from there. We'll ask Chub to help us on this. I'm sorry for the mistake, I'll be more careful with counterweights in the future.
Moving on, I tuned all the SR2 OSEMs. It was fairly simple today since the table was leveled. I closed the chamber with the optic free to move and damped in all degrees of freedom.
SUSPENSION STATUS UPDATED HERE
AS4 is set to go through a free swinging test at 10 pm tonight. We have used this script (Git/40m/scripts/SUS/InMatCalc/freeSwing.py) reliably in the past so we expect no issues, it has a error catching block to restore all changes at the end of the test or if something goes wrong.
To access the test, on allegra, type:
SR2 is set to go through a free swinging test at 3 am tonight. We have used this script (Git/40m/scripts/SUS/InMatCalc/freeSwing.py) reliably in the past so we expect no issues, it has a error catching block to restore all changes at the end of the test or if something goes wrong.
The free swinging test was successful. I ran the input matrix diagonalization code (/opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMAtCalc/sus_diagonalization.py) on theSR2 free-swinging data collected last night. The logfile and results are stored in /opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMAtCalc/SR2 directory. Attachment 1 shows the power spectral density of the DOF basis data (POS, PIT, YAW, SIDE) before and after the diagonalization. Attachment 2 shows the fitted peaks.
The new matrix was loaded on SR2 input matrix and this resulted in no control loop oscillations at least. I'll compare the performance of the loops in future soon.
The free swinging test was successful. I ran the input matrix diagonalization code (/opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMAtCalc/sus_diagonalization.py) on the AS4 free-swinging data collected last night. The logfile and results are stored in /opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMAtCalc/AS4 directory. Attachment 1 shows the power spectral density of the DOF basis data (POS, PIT, YAW, SIDE) before and after the diagonalization. Attachment 2 shows the fitted peaks.
The new matrix was loaded on AS4 input matrix and this resulted in no control loop oscillations at least. I'll compare the performance of the loops in future soon.
tl;dr: Done no harm, no lasting change.
- Use /cvs/cds/caltech/target/c1psl/autoBurt.req as input to test snapshot "/users/anchal/BURTsnaps/controls_1210301_101310_0.snap" on rossa after not succeeding in donatella
- Browse /opt/rtcds/caltech/c1/burt/autoburt/snapshots/TODAY just to know where the snapshots are living. Will store our morning work specific snapshots in local user directories (e.g. /users/anchal/BURTsnaps)
- Switched channels around on video controls; changed C1:VID-MON7 to 16, back to 30, then C1:VID-QUAD2_4 to 16, to 18, then 20, back to 16, to 14 (which identified as PMCT), to 1 (IMC). Anyways, looks like IMC is locked.
[Yehonathan, Paco, Anchal]
- From IOO/LockMC, MC_Servo, FSS --> closed PSL shutter, reopen it and see the lock recovers almost instantly. Try MCRFL shutter, no effect. Toggled PSL shutter one more time, lock recovered.
- From IOO/LockMC, MC_Servo, toggle OPTION (after IP2A), lose and recover lock in similar fashion. MCRFL gets most of the light.
- Looked at IFO_OVERVIEW just to get familiar with the various signals.
A cross-coupling test has been set to trigger at 05:00 am on April 1st, 2021. The script is waiting on tmux session 'cB' on pianosa. /scripts/SUS/OutMatCalc/MC2crossCoupleTest.py is being used here. The script will switch on oscillator in LOCKIN1 of MC2 at 13 Hz and 200 counts and would send it along the POS, PIT and YAW vectors on output matrix one by one, each for 2 minutes. It will take data from C1:IOO-MC_F_DQ, C1:IOO-MC_TRANS_PIT_ERR and C1:IOO-MC_TRANS_YAW_ERR and use it to measure 'sensing matrix' S. Sensing matrix S is defined as the cross-coupling between excited and sensed DOF and we ideally want it to be an identity matrix. The code will use the measured S to create a guess matrix A which on being multiplied by ideal coil output matrix would give us a rotated coil output matrix O. This guess O will be applied and the measurement will be repeated. On each iteration, next, A matrix is defined by:
This recursive algorithm converges A to the inverse of initial S. The above relation is derived by noticing that in steady state . I've taken this idea from a mathematics paper I found on some more complex stuff (c.f. https://doi.org/10.31219/osf.io/yrvck).
At each iteration, all three matrices A, O and S will be stored in a text file for analysis later.
The code has the error-catching capability and would restore the optic to the status quo if an error occurs or watchdogs trip due to earthquakes.
The coil balancing attempt failed. The off-diagonal values in the measured sensing matrices either remained the same or increased.
The attempt in the morning was too slow. By the time we reached, it had reached to iteration 7 only and still nowhere near optimum sensing matrix had reached. We still needed to see if the optimum would eventually reach if more iterations happened.
<Radhika came for shadowing us and learning about 40m>
So we worked a bit on speeding up the data loading process and then ran the code again which now was running much faster. Still within 1 hr or so, we saw it had reached to iteration 7 with no sign of sensing matrix getting any better.
<Paco left for vaccination>
To determine if the method would work in principle, I decided to stop the current run and start with a 0.5 Hz bandwidth run (so about 7 averages with 8s duration data and welch method). This completed 20 iterations before Gautum came. But it was clear now that the method is not converging to a better solution. Need to find a bug in the implementation of the algorithm mentioned in last post or find a better algoritm.
Attachment 1 is the plot of how the sensing matrix's distance from the identity matrix increased over iterations in the last run.
Attachment 2 is the plot for different off-diagonal terms in the sensing matrix. It is clear that POS->PIT,YAW coupling is not being measured properly as it remains constant.
Attachment 3 Gautum told us that there is some naming error in nds and MC_TRANS_PIT/YAW can be read through C1:IOO-MC_TRANS_PIT_ERR and C1:IOO-MC_TRANS_YAW_ERR channels instead. To test if they indeed point to same values, we did a test of exciting YAW degree through LOCKIN1 and seeing if the peaks are visible in the channels. This was also done to give Radhika an opportunity to do something I could confidently mentor about. and to experience using diaggui.
After fixing a few things we felt were wrong in our implementation of the algorithm, we ran the coil balancing for 12 iterations with just 11s per excitation and still taking CSD with 0.1 Hz bandwidth. This time we saw the distance of sensing matrix from identity going down.
Came in a little bit after 8 and found the MC unlocked and struggling to lock for the past 3 hours. Looking at the SUS overview, both MC1 and ITMX Watchdogs had tripped so we damped the suspensions and brought them back to a good state. The autolocker was still not able to catch lock, so we cleared the WFS filter history to remove large angular offsets in MC1 and after this the MC caught its lock again.
Looks like two EQs came in at around 4:45 AM (Pacific) suggested by a couple of spikes in the seismic rainbow, and this.
As mentioned in last post, we earlier made an error in making sure that all time series arrays go in with same sampling rate in CSD calculation. When we fixed that, our recursive method just blew out in all the efforts since then.
We suspect a major issue is how our measured sensing matrix (the cross-coupling matrix between different degrees of freedom on excitation) has significant imaginary parts in it. We discard the imaginary vaues and only use real parts for iterative method, but we think this is not the solution.
Here we present cross-spectral density of different channels representing the three sensed DOFs (normalized by ASD of no excitation data for each involved component) and the sensing matrix (TF estimate) calculated by normalizing the first cross spectral density plots column wise by the diagonal values. These are measured with existing ideal output matrix but with the new input matrix. This is to get an idea of how these elements look when we use them.
Note, that we used only 10 seconds of data in this run and used binwidth of 0.25Hz. When we used binwidth of 0.1 Hz, we found that the peaks were broad and highest at 13.1 Hz instead of 13 Hz which is the excitation frequency used in these measurements.
Today, we finally crossed the last hurdle and got a successful converging coil balancing run.
We ran again this method but with the 'b' parameter as a matrix instead. This provides more gain on some off-diagonal terms than others. This gave us a better convergence with the code reaching to the tolerance level provided (0.01 distance of S matrix from identity) within 16 iterations (~17 mins).
Attachment 1 again shows how the off-diagonal terms go down and how the overall distance of sensing matrix from identity goes down. This is 'Cross coupling budget' of the coils as iterations move forward.
PMC lost lock between 21:00 and 22:00 UTC on April 11th as seen in the summary pages:
That's between 2pm and 3pm on Sunday for us. We're not sure what caused it. We will attempt to lock it back.
Mon Apr 12 08:45:53 2021: we used milind's python script in scripts/PSL/PMC/pmc_autolocker.py. It locked the PMC in about a minute and then IMC catched lock succefully.
However, the PMC transmission PD shows voltage level of about 0.7V. On medm, it is set to turn red below 0.7 and yellow above. In Summary pages in the past, it seems like this value has typically been around 0.74V. Simil;arly, the reflection RFPD DC voltage is around 0.063 V right now while it is supposed to be around 0.04 nominally So the lock is not so healthy.
We tried running this script and the bashscript version too (scripts/PSL/PMC/PMCAutolocker) a couple of times but it was unable to acquire lock.
Then we manually tried to acquire lock by varying the C1:PSL-PMC_RAMP (with gain set to -10 dB) and resetting PZT position by toggling Blank. After a few attempts, we were able to find the lock with transmission PD value around 0.73V and reflection RFPD value around 0.043. PZT control voltage was 30V and shown in red in medm to begin with. So we adjusted the output ramp again to let it come to above 50V (or maybe it just drifted to that value by itself as we could se some slow drift too). At Mon Apr 12 09:50:12 2021 , the PZT voltage was around 58V and shown in green.
We assume this is a good enough point for PMC lock and move on.
We tried two sets of filters on the output matrix POS column in MC2. Both versions failed. Following are some details.
The filters were somewhat successful, how much we can see in attachment 1. The tip about difference between eigenmode basis and cartesian basis was the main thing that helped us take data properly. We still used OSEM data but rotated the output from POS, PIT, YAW to x, theta, phi (cartesian basis where x is also measured as angle projected by suspension length).
** The notation here is [UL, UR, LR, LL]
We did a step response test with MC2 Suspensoin Damping Gains and optimized them to get <5 oscillations in ringdown.
In the afternoon, we'll complete doing the above steps for MC1 and MC3. Their coil balancing has not been done on DC so, it is bit non-ideal right now. We'll look into scripting this process as well.
Note: The AC gains were measured by keeping output matrix to ideal values of 1s. When optimizing DC gains, the AC gains were uploaded in coil ouput gains.
Today we had some trouble launching an excitation on C1:IOO-MC_LSC_EXC from awggui. The error read:
awgSetChannel: failed getIndexAWG C1:SUS-MC2_LSC_EXC ret=-3
What solved this was the following :
awg free 37008
Today we tested the F2A filters created from the DC gain values listed in 16066.
We extended the f2a filter implementation and diagnostics as summarized in 16086 to MC1 and MC3.
Attachment 1 shows the filters with Q=3, 7, 10. We diagnosed using Q=3.
Attachment 2 shows the test summary, exciting with broadband noise on the LSC_EXC and measuring the CSD to estimate the transfer functions.
Attachment 3 shows the filters with Q=3, 7, 10. We diagnosed using Q=3.
Attachment 4 shows the test summary, exciting with broadband noise on the LSC_EXC and measuring the CSD to estimate the transfer functions.
Our main observation (and difference) with respect to MC2 is the filters have relative success for the PIT cross-coupling and not so much for YAW. We already observed this when we tuned the DC output gains to compute the filters.
We ran the f2a filter test for MC1, MC2, and MC3.
The new filters differ from previous versions by a adding non-unity Q factor for the pole pairs as well.
This in terms of zpk is: [ [zr + i zi, zr - i zi], [pr + i pi, pr - i pi], 1] where
We uploaded all these filters using foton, into the three last FM slots on the POS output gain coil.
We ran tests on all suspended optics using the following (nominal) procedure:
C1:IOO-WFS_GAIN to 0.05.
** Excitation = 0.05 - 3.5 Hz uniform noise, 100 amplitude, 100 gain
WFS1 noise injection
C1:LSC-XARM_IN1_DQ / C1:LSC-YARM_IN1_DQ
C1:SUS-ETMX_LSC_OUT_DQ / C1:SUS-ETMY_LSC_OUT_DQ
C1:SUS-MC1_**COIL_OUT / C1:SUS-MC2_**COIL_OUT / C1:SUS-MC3_**COIL_OUT
C1:IOO-WFS1_PIT_ERR / C1:IOO-WFS1_YAW_ERR
** denotes [UL, UR, LL, LR]; the output coils.
We redid the WFS noise injection test and have compiled some results on noise contribution in arm cavity noise and IMC frequency noise due to angular noise of IMC.
Attachment 1: Shows the calibrated noise contribution from MC1 ASCPIT OUT to ARM cavity length noise and IMC frequency noise.
We today measured the calibration factors for XARM_OUT and YARM_OUT in nm/cts and replotted our results from 16117 with the correct frequency dependence.
Calibration of XARM_OUT and YARM_OUT
Inferring noise contributions to arm cavities:
Edit Mon May 10 18:31:52 2021
See corrections in 16129.
A few corrections to last analysis:
Attached is the control loop diagram when main laser is locked to IMC and a single arm (XARM) is locked to the transmitted light from IMC.
We picked a few parameters from 40m summary page and plotted them to see the effect of new settings. On April 4th, old settings were present. On April 28th (16091), new input matrices and F2A filters were uploaded but suspension gains remained the same. On May 5th (16120), we uploaded new (higher) suspension gains. We chose Sundays on UTC so that it lies on weekends for us. Most probably nobody entered 40m and it was calmer in the institute as well.
We can download data and plot comparisons ourselves and maybe calculate the spectrums of MC_TRANS_PIT/YAW and MC_REFL_DC when IMC was locked. But we want to know if anyone has better ways of characterizing the settings that we should know of before we get into this large data handling which might be time-consuming. From this preliminary 40m summary page plots, maybe it is already clear that we should go back to old settings. Awaiting orders.
We came in the morning with the following scene on the zita monitor:
The MC1 watchdog was tripped and seemed like IMC struggled all night with misconfigured WFS offsets. After restoring the MC1 WD, clearing the WFS offsets, and seeing the suspension damp, the MC caught lock. It wasn't long before the MC unlocked, and the MC1 WD tripped again.
We tried few things, not sure what order we tried them in:
Nothing worked. We kept seeing that ULPD var on MC1 keeps showing kicks every few minutes which jolts the suspension loops. So we decided to record some data with PSL shutter closed and just suspension loops on. Then we switched off the loops and recorded some data with freely swinging optic. Even when optic was freely swinging, we could see impulses in the MC1 OSEM UL PD var which were completely uncorrelated with any seismic activity. Infact, last night was one fo teh calmer nights seismically speaking. See attachment 2 for the time series of OSEM PD variance. Red region is when the coil outputs were disabled.
Edit Thu May 13 14:47:25 2021 :
Added OSEM Sensor timeseries data on the plots as well. The UL OSEM sensor data is the only channel which is jumping hapazardly (even during free swinging time) and varying by +/- 30. Other sensors only show some noise around a stable position as should be the case for a freely suspended optic.