[Paco, Anchal, Radhika]
We tried to debug why the XARM green laser isn't catching lock with the arm cavity. First I tried to improve alignment:
- Aligned the arm cavity axes by maximizing IR transmission.
- Adjusted M1 and M2 steering mirrors to align the X green beam into the arm. GTRX reached ~0.3.
- At the vertex table, I adjusted the lens in the GTRX path to focus the beam onto the DCPD. This increased GTRX to ~0.7.
- Visually I confirmed that TEM00 of the green laser was flashing in the arm cavity, fairly centered. But it was not catching lock.
We suspected the XARM AUX PZT might be damaged/unresponsive. Paco, Anchal, and I fed several frequency signals to the PZT and looked for a peak in the AUX-PSL beatnote spectra at the expected frequency. We confirmed that the X-arm AUX PZT is responsive up to 12 kHz (limited by ADC samping rate). We have no reason to suspect the PZT wouldn't be responsive at the PDH modulation frequency of 231 kHz.
- Investigate PDH servo box / error signal.
c1hpc has option of dithering BS now (sending excitation to BS LSC port to c1sus over IPC). This is available for demodulating BHDC and BH55 signals. Also BS is a possible feedback point, however, we would stick to using LSC screen for any MICH locking.
c1sus underwent 2 changes. All suspension models were upgraded to the new suspension model (see 40m/16938 and 40m/17165). Now the channel data rates are set in simulink model and activateDQ script is not doing anything for any of the suspension models.
Changed the BHD BS transmissivity to 0.56.
As was noted before. The LO phase sensitivity plot vs LO phase from the previous elog shows the optimal sensitivity at each LO phase. That means that the optimal demodulation phase might change as a function of LO phase. Attachment 1 shows the previous plot and a plot showing the optimal modulation phase for some of the methods. When double demodulation is involved I optimize one modulation and show the optimal demodulation angle of the second. As can be seen, optimal audio demodulation angles don't change as a function of LO phase.
Additionally, as expected maybe, for the single RF sideband methods that nominally should not have worked at nominal LO phase (angle in which BHD Diff is most sensitive to MICH), the optimal demodulation angle changes quite a bit around the nominal LO phase.
Fixed demodulation angle
Attachment 2 shows the LO phase sensitivity in the single 55MHZ sideband method when we fix the demodulation angle. -23.88 is the demod angle optimal for nominal LO phase. 66.12 is 90 degrees away from that. -75.21 is the is the demod angle optimal for LO phase at the amplitude quadrature and 14.78 is 90 degrees away from that. It can be seen that fixing the demod angle can be mostly harmless.
Effect of MICH offset
The simulations were run with 0 MICH offset. Attachment 3 shows the LO phase sensitivity of the different methods when MICH offset is introduced together with the optimal demod angle. As expected the single RF SB methods are sensitive to this offset while the double demod methods are not since they are not relying on DC fields.
[Yehonathan, Yuta, Paco]
We would like to estimate:
We picked up the following I/O chassis components from Downs CDS testing lab:
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.
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 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.
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.
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.