Craig, Sheila, Jenne, Travis
There is still at least one problem with the rotation stage, that sometimes it goes the wrong way when it first starts moving.
The attached screenshot shows our first attempt at increasing the power since the vent, the rotation stage velocity and request are correctly set to 22 Watts and a velocity of 10, before the rotation stage starts moving. When the rotation stage starts moving, you can see a drop in the input power (which happens faster than the normal rotation stage motion), the normalization (PSL-POWER_SCALE_OFFSET) is lowered by the guardian to adjust for this, but we loose lock anyway. After the lock is lost the rotation stage proceeds at a reasonable pace to 20Watts, and the normalization follows correctly.
This is not a new bug, we've had random locklosses like this for some time, but it is a bug that remains after last week's rotation stage fix.
[Travis, Craig, Jenne, Ross]
Somehow using the faster rotation stage velocity (RS_VELOCITY=100) is making things funny, so when we try to change the laser power after using the faster velocity, we have this problem where the laser power dips before increasing. So, we've changed the PSL power guardian so that the "fast" velocity is the same RS_VELOCITY=10 as the "slow" velocity. This seems to have fixed things.
It seems like the rotation stage still has the problem that the minimimum power angle drifts, tonight we have seen it change by 2 degrees after being rotated several times, and then change again after only being rotated once.
Changes as measured by OSEM values: last IMC lock before laser work to stable IMC lock today
April 4th | April 22 | diff (urad) | |
MC1 p | -27 | -13.5 | +13.5 |
MC1 y | -1044 | -1036 | +8 |
MC2 p | 500 | 504 | +4 |
MC2 y | -688 | -686 | +2 |
MC3 p | -895 | -895 | 0 |
MC3 y | -1027 | -1018 | +9 |
IM4 Trans p | -0.425 | -0.490 | -0.065 |
IM4 Trans y | 0.103 | 0.081 | -0.022 |
I worked on the IMs (IM1-4) this morning, and have verified that they are aligned to the April 4th values, so cannot account for the change in IM4 Trans.
The alignments of MC1-3 follow the alignment of the IMC input beam, so while the alignment changes for these optics are bigger than what we typically see, after the laser work they are not unexpected.
This morning I measured the AOM drive voltage as a function of "offset slider %", and also the amount of diffracted light both with and without the digital support loop. All measurements were taken with the HEPA fans running. With no diffracted light, the maximum output voltage on PDA was (-9.6,-9.3) V and on PDB was (-9.65,-9.4) V. No saturations were observed with the incident power at this level. Attached are the spectra and transfer function measured. The relative power noise is about a factor of 10 higher than it should be. In the spectrum is a peak at ~1 kHz, the source of which is unknown, but is probably related to the problems mentioned by Keita. Pushing the gain higher seems to increase the noise beyond 10 kHz. The noise at frequencies below 100 Hz is significantly higher than with the low power mode. At low frequencies the transfer function is not as clean as the measured result in the low power mode. I am not sure but this might be related to the linearisation of the AOM drive.
Attached are the plots for the AOM drive voltage and diffracted power as a function of the offset slider. With the current settings with the offset slider at 6%, we are diffracting ~4.5 W. The plotted and reported diffraction percentage on the MEDM screen needs to be recalibrated.
The attached trend shows that while Peter was working this morning, analog PD outputs that are used for ISS (i.e. "filt" outputs that are monitored by PSL-ISS_PDA_OUT and PDB) were railing all the time.
Analog "DC" outputs might have been OK but they're not used for ISS.
There was about 3 minutes window where the PDs are less severely railing. Almost (but not quite) in the same window, NPRO noise eater monitor was smaller than usual. But during O1 NEMON was always about 28. I don't know what this means.
Following up on Kiwamu's LSC model change, and in preparation for closing the ISS 3rd loop, I made a loop filter.
The idea is to make an ISS loop which sends the arm power signals (TRX and TRY) to the ISS 1st loop error point to prevent radiation pressure driven instabilities. This loop only need to have gain around 0.5Hz (near the suspention pitch mode), so the open loop TF can be a peak around 0.5Hz with upper and lower UGFs a factor of 5 or so away (see figure 1). The assumed plant transfer function is the interferometer coupled cavity pole aroud 0.7Hz, and the (yet to be realized) anti-aliasing filter (SR560 AC-coupled and with a pole at 10Hz, see figure 2). The control CDS filter is shown in figure 3.
During relocking effort, for no apparent reason ISS went crazy several times (attached left), oscillating at about 1.6kHz (attached right). This is not unlike 2.5kHz oscillation reported in alog 26666, but the frequency is different.
This is not FSS though FSS is affected by this, as the refcav was once knocked out of lock during the oscillation but the oscillation in ISS continued. It seems that FSS is affected because there's simply too much intensity noise (attached right top cyan and right bottom shows the refcav transmission DC).
HPO output itself seems to be fine (right top, brown trace), so this really sounds like something that happens in ISS.
Anyway, when this happens, do the following.
Another FYI.
Left is when ISS was NOT oscillating. Bumpy structures at about 1k and 4k seem to be from HPO (left top, brown). Lower than 1kHz, out-of-loop sensor (PDA) is not much coherent with second loop 1-4 SUM. This shows nothing new, but there's a lot of sensing noise in first loop sensors. Noise eater was at its usual (28 or so).
Middle is when it was oscillating and it's not that interesting. The oscillation was causing so much noise in the intensity that all sensors agree with each other. Again noise eater was as usual.
Right is when it was oscillating. The oscillation shows up in many things, and the channel that showed the highest coherence in non-intensity channels was PMC mixer. This could just be that the PMC lock point was thrown off in one direction because of huge intensity noise, causing a large intensity-to-PDH coupling, or this could be that the PMC is locked a bit off to the shoulder.
With the main laser down, it looks like some work effecting the oplevs must have happend over the last week, because some signals sit at 0 and then recover to typical levels.
I zoomed in on the Y axis to the sections of data that have reasonable signals.
Attached:
I am Closing this FAMIS (4672) task for Cheryl.
Kyle, Gerardo 0900 - 1100 hrs. local -> In and out of LVEA, used Main Crane to "fly" leak detector over YBM. Dissatisfied with the slow recovery of the HAM11/HAM12 annulus system, we decided to do some unscheduled (no work permit) helium leak testing -> We found a minor leak on a conflat which was mitigated by torquing the flange fasteners but were surprised to discover several very loose chamber flange bolts, i.e. we could visually see the bolt shanks between the flanges! In total we found (4) adjacent bolts on the flange connecting HAM11 to the OMC adapter spool to be very loose and (9) adjacent flange bolts that we could spin easily with our fingers on the flange connecting HAM12/septum/HAM11 -> these were torqued using twentieth century "old school" wrenches after we were unable to find a cell phone app. There are (3) pump carts running in the LVEA over the weekend, (2) at HAM11/HAM12 and (1) on the SW corner of BSC4.
Good catch! We visually inspected the CFFs on diagonal before pumping it down but did not physically touch each bolt.
The web page displaying detailed vacuum medm screens has been modified to show old and new medm screens for the site overview and LVEA. During the installation of new vacuum controls, some information is available on the old screens, some on the new. For the site overview and LVEA, the new system screens are shown to the right of the original screens. This is a temporary display change, once the new controls are installed the medm screens will be updated and the web page will be rearranged again.
Very nice! Thanks Jim, this is quite useful.
TITLE: 04/22 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: Got through initial alignment, then was immediately halted by ISC_LOCK trying to get the ETMX ESD to function. After finding the last remaining person on site (Kiwamu!), he agreed to drive to EX to try and reset the ESD driver. He discovered that it was not a problem with the ESD driver, but an issue with ISC_LOCK not checking all the channels it needed to to get the ESD up and running. Kiwamu edited the ISC_LOCK guardian to check that the requested DC bias was not zero. Then, just as I was starting to continue with locking, there was another 6.0 EQ in Ecuador (haven't they been through enough already?). Kiwamu suggested that with no one else here and the EQ ringing us up over 1 um/s, we should call it a night.
LOG:
23:51 Dave and Jim restarting SUS ETMX PI model
2:45 Kiwamu to EX looking at ESD driver (He noted that he was unable to open sitemap on one of the workstations at EX)
3:10 Kiwamu back
3:45 Calling it a night with the seismic plot going through the roof
Sheila, Matt, Jenne, Travis, Kiwamu
We went to ISCT1 because we were not finding the beatnote even when we moved PR3 back to its old alignment and we had aligned the X arm using WFS and the camera. It turned out that the COMM beatnote diode was saturated, so we reduced the power using the half waveplate and PBS in the SHG path. We realinged the beams, and ended up with a beatnote power of about 4dBm.
We might need to readjust this once we have a good alignment of the full IFO to get a good reference.
Also, it seems like we have less DC light on AS AIR, so we might need to adjust its alignment again. To get through the SRY alignment, I lowered the threshold for SRY triggering from 30 to 20.
Just FYI.
Even without ISS, during O1 the 1st loop diodes didn't rail, but they do now. The power on these diodes seems to be the same as before (I assume Peter and Jason adjusted them).
Attached left is the trend of the past 26 hours. ISS first loop was on at first, but is off right now. You can see that the first loop diodes seem to be railing without ISS.
Attached right show the same channels, but from O1 when ISS first loop was off (seems to be related to ISS investigation in alog 24171).
If you compare the DC level of PDA and PDB from O1 against the recent trend when ISS was on, it seems like the DC power on the diodes are the same as before. This is not a digital filter issue, there's no digital filter on these channels except a calibration factor, and the calibration factor didn't change in the filter file. Dewhite is applied after PDA and PDB output in PDA_REL and PDB_REL channels.
It should be noted, and it is my understanding, that the DC value as shown on the MEDM screen is not the actual DC value output by the PD; it is calculated based on the AC value. There are connections for the DC, but to my knowledge the actual measured DC values of the ISS PDA and PDB are not read into EPICS at all (I could be wrong on this, but this is how it was explained to me). When we set the DC value while in the enclosure we use a multimeter and measure the DC value directly off of the PD, and adjust it to ~10V using a HWP at the input to the ISS box. The last time we set the DC value it was set to ~9.7V on PDA.
To clear some confusion. Whitened output of PDA and PDB ("filt" output from ISS BOX) are whitened but DC-coupled.
PDA and PDB whitened output are measured by ADC and become H1:PSL-ISS_PDA and H1:PSL-ISS_PDB, which are plotted and reported in my entry. DC values of these are really DC values, though there is a factor of about 0.45 0.2 whitening "gain" in the ISS box.
The only channels I know of on the PSL_ISS MEDM screen that are supposed to have finite DC values despite being calculated from AC-coupled channels are band-limited linear spectral density (LSD) channels H1:PSL-ISS_PDA_LSD and H1:PSL-ISS_PDB_LSD.
Unfortunately PSL_ISS MEDM screen seems to have some mislabeling and this might have made people confused. RIN outputs (H1:PSL-ISS_PDA_REL_OUTPUT and PDB) are labeled "lsd" while band limited LSD (H1:PSL-ISS_PDA_LSD and PDB) are labeled "relative".
Fixed the MEDM.
"lsd" labels are now "ASD" for both PDA and PDB. Two numbers in each red circle were swapped so now "ASD" is LSD channel and "Relative" is REL channel.
DC is DC, AC is AC, "Relative" is AC.