Let's use this entry to list of the test results of new donatella.
I tested the mixer by feeding it a 300 kHz signal sourced from a Moku:Go. I kept the LO input the same - 231.25 kHz from the signal generator. The mixer output was a ~70 kHz waveform as expected, so demodulation is not the issue in green locking.
Next I'll align the arm cavities with IR and check to see if the green REFL signal looks as expected. If not, we'll have to invesitage the REFL PD. If the signal looks fine, and we now know it's being properly demodulated, the issue must lie further downstream.
While changing out one of the N2 tanks today, one of the fitting stripped. This caused a major loss of pressure. I replaced one fitting then realized there was a second leak around the area of the gauge. Paco and I changed this and everything should be back up and running. Thhe interlocks may have been tripped within the last 2 hours.
Fields at the BHD BS. More on this later.
[Anchal, Paco, Yuta]
Attachment #1 is the same plot as 40m/17303 but with MICH sensitivity for ASDC and AS55 also included (in this measurement, BH55 demodulation phase was set to 140.07 deg to minimize I fringe).
Y-axis is now calibrated in to counts/m using BS actuation efficiency 26.54e-9 /f^2 m/counts (40m/17285) at 311.1 Hz.
2nd X-axis is calibrated into MICH offset using the measured AS55_Q value and it's MICH sensitivity, 8.81e8 counts/m (this is somehow ~10% less than our usual value 40m/17294).
ASDC have similar dependence with BHDC_SUM on MICH offset, as expected.
AS55_Q have little dependence with MICH offset on MICH offset, as expected.
This plot tells you that even a small MICH offset at nm level can create MICH sensitivity for BHDC_DIFF, even if we control LO phase to have BH55_Q to be zero, as MICH offset shifts zero crossing of BH55_Q for LO phase.
Attachment #2 is the same plot, but BH55 demodulation phase was tuned to 227.569 deg to have no MICH signal in BH55_Q (a.k.a measurement (c)).
In this case, LO phase will be always controlled at 0 deg (90 deg away from optimal), even if we change the MICH offset, as BH55_Q will not be sensitive to MICH.
In this plot, BHD_DIFF have little sensitivity to MICH, irrelevant of MICH offset, as expected.
MICH sensitivity for BH55_I is also constant, which indicate that LO phase is constant over this measurement, as expected.
Attachment #3 is the same plot, but BH55 demodulation phase was tuned to 70 deg.
This demodulation phase was tuned within 5 deg to maximize MICH signal in BHD_DIFF with large MICH offset (20).
In this case, LO phase will be always controlled at 90 deg (optimal), even if we change the MICH offset, as BH55_Q will not be sensitve to LO carrier x AS sideband component of the LO phase signal.
In this plot, BHD_DIFF have high sensitivity to MICH, irrelevant of MICH offset (at around zero MICH offset it is hard to see because LO_PHASE lock cannot hold lock, as there will be little LO phase signal in BH55_Q, and measurement error is high for BHD_DIFF and BH55 signals).
MICH sensitivity for BH55_I and BH55_Q is roughly constant, which indicate that LO phase is constant over this measurement, as expected.
These plots indicate that BH55 demodulated at MICH dither frequency can be used to control LO phase robustly at 90 deg, under unknown or zero MICH offset.
LO phase delay:
From these measurements of demodulation phases, I guess we can say that phase delay for 55 MHz in LO path with respect to MICH path (length difference in PR2->LO->BHDBS and PR2->ITMs->AS->BHDBS) is
2*(227.569-70(5)-90)-90 = 45(10) deg
This means that the length difference is (omegam=5*2*pi*11.066195 MHz)
c * np.deg2rad(45(10)+360) / omegam = 6.1(2) m (360 deg is added to make it close to the design)
Is this consistent with our design? (According to Yehonathan, it is 12.02 m - 5.23 m = 6.79 m)
Attachment #4 illustrates signals in BH55.
- Lock LO PHASE with BH55 demodulated at MICH dither frequency (RF+audio double demodulation), and repeat the same measurement
- Finer measurement at small MICH offsets (~1nm) to see how much MICH offset we have
- Repeat the same measurement with BH55_Q demodulation phase tuned everytime we change the MICH offset to maximize LO phase sensitivity in BH55_Q (a.k.a measurement (b)).
- What is the best way to tune BH55 demodulation phase?
I've turned off HEPA fan and all lights at
PST: 2022-11-24 11:23:59.509949 PST
UTC: 2022-11-24 19:23:59.509949 UTC
c1ioo model has been updated to acquire C1:IOO-MC2_TRANS_PIT_OUT and C1:IOO-MC2_TRANS_YAW_OUT at 512 Hz rate.
I'll update when I turn the HEPA on again. I plan to turn it on for a few hours everyday to keep the PSL enclosure clean.
Turned on HEPA again at:
PST: 2022-11-25 12:14:34.848054 PST
UTC: 2022-11-25 20:14:34.848054 UTC
However this was probably not a low noise state due to vacuum disruption mentioned here.
I tried following the steps and the method I was using converged to same output matrix upto 2 decimal points but there is still left over cross coupling as you can see in Attachment 1. With the new output matrix, WFS loop can be turned on with full overall gain of 1.
-2. 4.8 -7.3
3.6 3.5 -2.
2. 1. -6.8
3.44 4.22 -7.29
0.75 0.92 -1.59
3.41 4.16 -7.21
Note: The standard deviation on the averages was very high even after averaging for 30s. This data should be averaged after low passing high frequencies but I couldn't find the filter module medm screens for these signals, so I just proceeded with simple averaging of full rate signal using cdsultis avg command.
Fri Nov 25 12:46:31 2022
The WFS loop are unstable again. This could be due to the matrix balancing done while vacuum was disrupted. The above matrix does not work anymore.
I came today to find that PSL shutter was closed. I orginially thought some shimmer obersvations are underway in the quiet state. But that was not the case. When I tried to open the shutter, it closed back again indicating a hard compliance condition making it close. This normally happens when vacuum level is not sufficient, so I opened the vacuum screena dn indeed all gate valves were closed. This most probably happend during this interlock trip. So the main volume was just slowly leaking and reached to milli torr level today.
Lesson for future: Always check vacuum status when interlock trips.
Paco came by to help. We went to asia (the Asus laptop at vacuum workstation) but could not open the medm or find the nfs mounted files. The chiara change did something and nfs mounted directories are not available on asia of c1vac. We rebooted asia and the nfs mount was working again. We can't simply restart c1vac because it runs acromag channels for vacuum system and needs to be done more carefully, a task for Monday.
After restarting asia, we opened the the vacuum control medm screen and followed the vaccum pump down instructions (mainly opening of the gate vales as the pumps were already on). Point to keep in mind, rule of thumb, do not open valve between a turbo pump and a volume if the pressure differential is more than 3 orders of magnitude. Saving turbo pumps is the priority.. Now the main volume is pumping down.
Turned off HEPA at:
PST: 2022-11-25 15:34:55.683645 PST
UTC: 2022-11-25 23:34:55.683645 UTC
Turned on HEPA back at:
PST: 2022-11-28 11:14:31.310453 PST
UTC: 2022-11-28 19:14:31.310453 UTC
Five more mode cleaner alignment controllers were tested this morning (remotely). These were designed to run in tandem with the standard controller, instead of supplanting it. Before the test, c1ioo was burt restored back to the settings of the previous test on Oct 28, and in MC TRANS PIT/YAW filter banks the 80 dB gain filters were disengaged and outputs were enabled. Subsequently, all settings were returned to the original values. Each test consisted of five minutes with pitch alignment uncontrolled, five minutes with the standard controller only, and twenty minutes with both controllers enabled. GPS times for each phase of testing are the following:
[Anchal, Paco, Yehonathan, JC]
Last night at 9:15 pm PST (Nov 27th, 2022) some kind of disruption happened to FEs. See attachment 1 to see the changes in FE state words of the IOP models. on c1lsc, c1sus and c1scex, change of 140 happend, that's 2nd, 3rd and 7th bit of the FE word was flipped, which I think is the TIM, ADC and DAC KILL (DK). When we came in morning, IMC suspensions were undamped and not responsive to coil kicks, vertex suspensions the same case, ETMX also same. The c1sus2 modelw as all in red.
To fix this, we restarted all rtcds models on all FEs by sshing into the computers and doing:
Then we burt restored all models to 27th Nov, 3:19 am point doing following on rossa:
Note: this issue was previously seen when fb1 was restarted without shutting down the FEs, and once when the martian switch was disrupted while FE models were running.
I'm not sure why this happened this time, what caused it at 9:15 pm yesterday, and why only c1lsc, c1sus and c1iscex models went to DAC KILL state. This disruption should be investigated by cds upgrade team.
C1:PSL-PMC_PMCTRANSPD was increased from 0.72 to 0.731
I changed the script in /opt/rtcds/caltech/c1/Git/40m/scripts/SUS/outMatFilters/createF2Afilters.py to read the measured POS resonant frequencies stored in /opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMatCalc/resFreqs.yml instead of using the estimate sqrt(g/len). I then added Q = 3 F2A filters into FM1 output filter of LO1, LO2, AS1 and AS4 suspensions in anticipation of BHD locking scheme work.
I added the pypi package "restoreEpics" to the donatella clone under test. This is required by some of Anchal's scripts that turn on F2A filters as well as other recovery stages during some measurements.
I checked the LSC rack to evaluate what we might need to generate 44 MHz rf in the hypothetical case we go from BH55 to BH44 (a.k.a. double RF demod scheme). There is an 11 MHz LO port labeled +16 dBm (measured 9 Vpp ~ 23 dBm actually) on the left hand side. Furthermore, there is an unused 55 MHz port labeled "Spare 55 LO". I checked this output to be 1.67 Vpp ~ +8.4 dBm. Anyways the 55 MHz doesn't look very nice; after checking it on the spectrum analyzer it seems like lower frequency peaks are polluting it so it may be worth checking the BH55 LO (labeled REFL 55) signal to see if it's better. Anyways we seem to have the two minimum LOs needed to synthesize 44 MHz in case we move forward with BH44.
We confirmed the noisy 55 MHz is shared between AS55, BH55 and any other 55 MHz LOs. Looking more closely at the spectrum we saw the most prominent peaks at 11.06 MHz and 29.5 MHz (IMC and PMC nominal PM freqs). This 55 MHz LO is coming all the way from the RF distribution box near the IOO rack. According to this diagram, this 55 MHz LO should have gone through a bandpass filter; interestingly, checking the RF generation box spare 55 MHz the output is *cleaner* and displays ~ 17 dBm level... ??? Will continue investigating when we actually need this RF.
In Attachment 1, I give a plan for the proposed path of AS beam into the IMC WFS heads to use them temporarily as AS WFS. Paths shown in orange are the existing MC REFL path, red for the existing AS path, cyan for the proposed AS path, and yellow for the existing IFO refl path. We plan to overlap AS beam to the same path by installing the following new optics on the table:
I request people to go through this plan and find out if there are any possible issues and give suggestions.
PS: Thanks JC for the photos. I got it from foteee google photos. It would be nice if these are also put into the 40m wiki page for photos of optical tables.
RXA: Looks good. I'm not sure if ND filters can handle the 1 W MC reflection, so perhaps add another flipper there. It would be good if you can measure the power on the WFS with a power meter so we know what to put there. Ideally we would match the existing power levels there or get into the 0.1-10 mW range.
I tried locking single arm this morning, but I was unable to because the triggers were set to lock strictly to MICH. Anchal explained this to me and helped me out. I figured this information would be useful and should be logged somewhere. In red, this is accessed through the IFO --> Configure. Choosing X Arm and Y Arm will change the triggers on the C1LSC page for the single arm locking (In the Black Box.)
Many changes have been done to c1hpc to support dual demodulation at audio frequencies. We moved away with ASS style of lockin setup as the number of connections and screens required would become very large. Instead now, the demodulation is done for a selected oscillator, on a selected signal. Similarly, the demodulated signal can be further demodulated for another selected oscillator. Please familarize yourself with new screen and test the new model. The previous version of the model is kept as backup alogn with all it's medm screens, so nothing is lost. Shown as an example in the screenshot, AS1 and BS oscillators can be turned on, and BHDC_DIFF signal can be demodulated first with BS and next with AS oscillator to get the signal.
All incondescent lightsbulbs have been switched over to LED.
Electrical came by today to see the lights. The issue may be the switches, but they will come by tomorrow to solve the issue. A couple light bulbs were noticed to be out, but they no longer have incandescent lights. . . only LED. I figured this would be preffered because of the reduction on noise. I would prefer to go ahead and ask to change all the incandescent bulbs to LED bulbs. Are there any objections to this?
After swapping out the HDD on donatella, I noticed that the display resolution was stuck on 700x400 and could not be changed. To fix this issue, I edited `/etc/apt/sources.list` to include the following:
deb http://ftp.us.debian.org/debian/ testing main non-free contrib
deb-src http://ftp.us.debian.org/debian/ testing main non-free contrib
deb http://ftp.us.debian.org/debian/ testing main non-free contrib
deb-src http://ftp.us.debian.org/debian/ testing main non-free contrib
to make `non-free` packages available in our repository, then I ran:
sudo apt-get update
sudo apt-get install firmware-amd-graphics
sudo apt-get update
sudo apt-get install firmware-amd-graphics
After the installation was complete, I did a reboot and the problem was fixed.
I picked up the 950 nm laser that Koji tested before and restored the Jenne laser (may long it live).
I changed a couple of things; first I took out the old laser from the hose and noted the new laser has a shorter fiber patch cable, so I replaced the hose with a flexible fiber jacket I found around the X arm storage. I also added a 14 pin DIP socket so the laser is now always showing its part no. and is easy to install/uninstall. Last but not least I replaced the black insulating material right at the output of the laser package because it was decaying badly and spread a bunch of dusty residue all over the place. I used some foam instead. See various attachments for visual support.
I was careful, testing the connections with a cheap LED to validate the setup before I connected the laser-- this made everything smooth and I finished the work by verifying the laser is outputting light at the other end of the fiber 1x2 coupler. The PD testing with Jenne's resucitated laser should proceed normally now.
I don't think you need to record the excitations. They are just sine waves. The amplitude you can read off from the OSC screen. You just have to have the BEAT channel recorded and you can demod it to get the calibration. If the BEAT channel is calibrated in Hz, and you know the 40m arm length, then you're all done.
Basically, only the DARM line was recorded (DQ channs) so I modified the c1cal to store the SIG_OUT and DEMOD_I_IN1 channels for both BEATX and BEATY cal signals. This means I need to repeat this measurement. In the meantime I am also going to try and rerun calibrate the BEAT HZ transfer function.
We are doing this attempt again in following configuration:
PST: 2022-12-01 20:44:23.982114 PST
UTC: 2022-12-02 04:44:23.982114 UTC
PST: 2022-12-02 14:32:29.547603 PST
UTC: 2022-12-02 22:32:29.547603 UTC
I took a transfer function measurement of the XEND PDH servo box, from servo input to piezo output [Attachment 1]. The servo gain knob was set to 10. The swept sine input was 50 mVpp, as to not saturate the servo components. I toggled the local boost on/off for these measurements. With the boost on, coherence was lost from ~100Hz-10kHz, and the saturation light indicators were flashing. I will retake this measurement shortly.
Atachment 2 is from a previous measurement of this PDH servo TF, found here. For this measurement, boost was off and the gain knob was set to 2.0. (If there is a more recent measurement than 2010, please point me to it.)
I've turned off HEPA fan and all lights at:
PST: 2022-12-03 10:13:03.184705 PST
UTC: 2022-12-03 18:13:03.184705 UTC
Today I did a lot of steps to eventually reach to WFS locking stably for long times and improving and keeping the IMC transmission counts to 14400. I think the main culprit in thw WFS loop going unstable was the offset value set on MC_TRANS_PIT filter module (C1:IOO-MC_TRANS_PIT_OFFSET). This value was roughly correct in magnitude but opposite in sign, which created a big offset in MC_TRANS PIT error signal which would integrate by the loops and misalign the mode cleaner.
WFS offsets tuning
WFS loops UGF tuning
OLTF measurements were done using this diaggui file. The measurement file got deleted by me by mistake, so I recreated the template. Thankfully, I had saved the pdf of the measurements, but I do not have same measurement results in the git repo.
Another five mode cleaner alignment controllers were tested last night (remotely), running in tandem with the standard controller. As before, c1ioo was burt restored to Oct 28 and the MC TRANS PIT/YAW 80dB gain filters were disabled before the test. Each test consisted of five minutes with pitch alignment uncontrolled, five minutes with the standard controller only, and twenty minutes with both controllers enabled.
The first four tests went smoothly, but the last controller (goldfish_short) repeatedly broke the lock. Eventually I got it running with an output gain of 0.5, strong enough to see the misbehavior without unlocking the mode cleaner.
GPS times for each phase of testing were the following:
Today, I worked on WFS loop output matrix for PIT DOFs.
Sun Dec 4 17:36:32 2022 AG: IMC lock is holding as strong as before. None of the control signals or error signals seem to be increasing monotonously over the last one hour. I'll continue monitoring the lock.
Mon Dec 5 11:11:08 2022 AG: IMC was locked all night for past 18 hours. See attachment 4 for the minute trend.
Just a few minutes ago, all models on FE c1sus2 crashed. I'm attaching some important files that can be helpful in investigating this. CDS upgrade team, please take a look.
I fixed this by running following on c1sus2:
Also reply to: 40m/17255
I ran the toggleWFSoffsets.py script to generate a step response of the WFS loops in operation. Attachment 1 shows the diaggui measured time response following the parameters mentioned in 40m/17255. There are few things to quickly note from this measurement without doing detailed analysis:
To get out the UGF of the loops from the step responses, I need to read this into python and apply the same filters and analyze time constants. I still have to do this part, but I thought I'll put out the result before spending more time on this.
I took transfer function measurement of WFS2 SEG4 photodiode between 1 MHz to 100 MHz in a linear sweep.
Relative to 29.5 MHz, teh photodiode response is:
I'm throwing in an extra number at the end as I found a peak at this frequency as well. This means to use these WFS heads for arm ASC, we need to have 10 times more light for 11 MHz and roughly 100 times more light for 55 MHz. According to Gautam's thesis Table A.1 and this elog post, the modulation depth for 11 MHz is 0.193 and for 55 MHz is 0.243 in comparison to 0.1 for 29.5 MHz., so the sideband TEM00 light available for beating against carrier TEM01/TEM10 is roughly twice as much for single arm ASC. That would mean we would have 5 times less error signal for 11 MHz and 40 times less error signal for 55 MHz. These are rough calculations ofcourse.
Around 9:30 we noticed IMC going out of lock with MC1 swinging hard. It seems like the coil output shut down.
It looks like the same situation as last Monday http://nodus.ligo.caltech.edu:8080/40m/17315.
Following that elog I restarted all the models by sshing into all computers and running
Then I burt restored all models to yesterday evening point doing following on rossa:
That seemed to have worked.
I also had to clear the WFS output to restore MC1 back to its place. Once the IMC got restored I turned the WFS again.
We have modified c1cal model to support sensing matrix measurements for BHD PDs on Friday last week.
c1cal model now can inject dither to LO1, LO2, AS1, and AS4, and demodulate BH55_I, BH55_Q, BHDC_SUM and BHDC_DIFF signals.
Related models, c1lsc, c1hpc, and c1sus2 are also modifed accordingly.
MEDM screens are also edited accordingly.
Attachments highlight the modifications.
We retook transfer function measurements of the XEND PDH servo box, this time setting the gain knob to 3.5 to avoid saturation. Once again I toggled the boost on/off. Attachment 1 shows the resulting bode plots, which now resemble the previous measurements circa 2010. This measurement along with the previous one suggest that setting the gain knob too high might affect the loop shape in an unpredictable way. With this accounted for, it seems the PDH servo box is functioning as expected.
Paco suggested that alignment could still be the primary reason why the XEND green laser is not catching lock. With the xarm cavity aligned with IR, I adjusted the M1 and M2 steering mirrors for the green laser, looking at the REFL PD output in an oscilloscope. Paco joined and was able to achieve better mode matching by adjusting mirrors and rotating the half-wave plate. At this point, we could see TEM00 consistently flashing. Green transmission also reached a value of 3, from around 0.5 that I was able to achieve previously (this channel is not normalized).
We broke the loop to make sure the demodulated signal looked as expected, and indeed it resembled a PDH error signal. After reconnecting the loop (with the gain knob set to 3.5), Paco lowered the REFL PD gain by 3 stages and I was able to raise the gain knob to 8 without the servo saturating. I turned boost on and toggled the servo inversion until the laser started to hold lock for a few seconds. The piezo output signal looked reasonable at this point, without clipping on either end.
After some final adjustments to the steering mirrors and the half-wave plate, the green laser can hold lock for around 5 seconds. However it's unclear why the loop isn't more stable, and more updates are to come.
I tested teh WFS demod board for possibility of demodulating 11 MHz or 55 MHz signal with it. It definitely has some bandpass filter inside as the response is very bad for 11 MHz and 55 MHz. See attached the ASD curves for the excitations seens on I and Q inputs of WFS1 Segment 2 when it was demodulated with a clock of different frequencies but same amplitude of 783.5 mVpp (this was measured output of 29.5 MHz signal from RF distribution board). See attachments 2-4 for mokulab settings. Note for 29.5 MHz case, I added an additional 10 dB attenuator to output 1.
The measurement required me to change signal power level to see a signal of atleast 10 SNR. If we take signal level of 29.5 MHz as reference, following are the responses at other frequencies:
Note that I and Q outputs are unbalanced as well for the two different demodulation frequencies.
This means that if we want to use the WFS demodulation boards as is, we'll need to amplify the photodiode signal by the above amounts to get same level of outputs. I stil need to see the DCC document of these board and if the LO is also bandpassed. In which case, we can probably amplify the LO to improve the demodulation at 11 and 55 MHz. THe beatnote time series for the measured data did not show an obvious sinusoidal oscillation, so I chose to not show a plot with just noise here.
Today we lock LO phase using audio+RF method in two variants: AS1+RF and MICH(BS)+RF. We measure the TFs and find that AS1 variant has a UGF ~ 17Hz and MICH variant has a UGF ~ 32Hz.
1. We lock MICH in the usual way using AS55. ITMs are aligned to make AS port dark. We use a single bounce and optimize mode-matching with LO beam by minimizing the BHDDC-A signal.
2. Using the new BHD Homodyne phase control MEDM screen we first try AS1. We put an elliptic filter with 80Hz corner frequency on the DEMOD1 filter bank. We find that the notch of that filter is at 281.768Hz and this is where we put the AS1 dither line.
AS1 is dithered with 20000 counts. We optimize the DEMOD1 demodulation angle by dithering LO1 at 27Hz and minimizing the Q quadrature in diaggui. We find that 45 degrees is the optimal demod angle. We lock the LO phase with a gain of ~ 45 and take the OLTF (attachment 1).
3. Next, we use MICH degree of freedom to lock LO phase. We dither BS with the same frequency as before with 4000 counts. Higher counts seem to put some offset on ASDC. As before we optimize the DEMOD1 demod angle and find it to be 115deg. We lock LO phase with a gain of 20 and take the OLTF (attachment 2).
We have spare WFS demods in a plastic box along the Y arm. So you don't need to modify the IMC demod boards, which we want to keep in the current state.