no restarts reported. Conlog frequently changing channels report attached.
Alexa, Sheila, Stefan
We made a little bit of progress in DRMI alignment today.
- First we ran the SRY cavity, and commissioned a pointing loop from the ASC_AS_C quad to SRM and SR2.
- We used M1 (top mass) actuation because we needed the range, so we switched both SRM and SR2 to MO angular actuation.
- We then carefully tuned the output matrix such that we don't rely on the WFS to keep SR2 and SRM aligned relative to each other.
- The output matrix is:
SRM SR2
PIT -7.08 1.00
YAW 7.12 1.00
Note that this matrix will likely change if we switch M2 actuation.
- Then we successfully used this pointing loop in DRMI, even without any SRC WFS running.
- The gains were H1:ASC-SRC2_Y_GAIN = 1, H1:ASC-SRC2_P_GAIN = 1, and the input matrix is also 1 (H1:ASC-INMATRIX_P_7_27 and H1:ASC-INMATRIX_Y_7_27).
- Next we re-phased the AS 36 and AS45 diodes using a freely swinging Michelson. A snapshot of all four diodes is attached.
- Then we started looking into the SRC WFS again:
- After many failed trials, we noted that one of the biggest signals for the SRM is AS_A_RF36_Q. But we already used this for the BS.
- However when driving the BS we found that it has a different demod phase: The BS signal is maximized for the mix
0.89*I + 0.45*Q (all of AS_A_RF36). The same mix was measured for both PIT and YAW.
Thus we switched the BS to this mix.
- Finally, for controlling the SRM, we found two signals: AS_A_RF36_Q from before, and AS_B_RF36_I.
- Because AS_B_RF36_I is more what I expected, I left the SRM on that one.
Not done yet:
Adding all this to the Guardian.
I added the SRC2 feedback to SRM, SR2 to the "SRM ALIGN" part of the ISC_DOF guardian. These are also in the DRMI guardian now. The SRC1 feedback to SRM is also in the guardian but for now I have left the gain to 0; the old gains are commented out. In the DRMI guardian, "OFFLOAD_DRMI_ASC" now only offloads the PRC, and MICH wfs since its only works for feedback to M2. I have added an "OFFLOAD_SR2_ALIGNMENT" and "OFFLOAD_SRM_ALIGNMENT" which should offload the M1 stages; this was copied over from ISC_DOF guardian and I have not tested it in this configuration.
[Mackenzie, Paul]
Yesterday we had trouble getting a large enough beat signal between the aux laser and the main PSL. After discussions with Dave O., Stefan and Daniel, we were convinced that the aux laser was not operating monochromatically. This can apparently occur if the aux laser is close to a "mode hop" region when we bring its frequency close to the PSL frequency using the temperature control. We then end up observing the beat frequency between the PSL and one of the "parasitic" modes of the aux laser, which has a much smaller amplitude than the main mode.
On Daniel's advice, we adjusted the diode input current as well as temperature, in order to give us an additional frequency control option that affected the proximity to the mode hopping region differently to the temperature. After some searching around, we suddenly observed a forest of peaks, with one especially large peak.
This forest appears to have been a combination of a) saturation of the 1811 AC output exciting harmonics of the base beat frequency and b) contributions from RF sidebands of the PSL light. We reduced the power on the 1811 using the filter wheel (we ended up using the OD 2.5 filter), resulting in the spectrum shown in the attached figure. The VCO offset frequency was 20MHz. Interestingly, the beat between aux laser and 9, 45MHz sidebands are quite visible.
The dominant beat frequency now registers a -22dBm signal at the AC PD output on the spectrum analyzer, even with the power on the PD attenuated such that the DC output from the PD produced by the PSL beam is less than 1mV (the PSL beam is the weaker of the two beams at the PD). This may still seem a little weak, but it is much better than yesterday, when we had ~-50dBm AC on a ~100mV DC signal.
After some adjustment of the servo box gains, we were able to achieve stable PLL locks. There is no slow temperature servo path included yet, so the PZT on the aux laser will go out of range rapidly if the temperature dial is not adjusted by hand. By adjusting the temperature dial, it was possible to keep the PLL locked for tens of minutes.
Next, we switched the frequency reference for the PLL offset from the Marconi VCO to the swept sine output of the network analyzer. This presents a new challenge, because now not only does the aux laser have to phase lock to the PSL, but it also has to track the offset frequency generated by the NA. After playing around with IF BW, sweep ranges, source power etc., we were eventually able to get the aux laser to reliably phase lock to the PSL and track the NA frequency through a ~2MHz frequency range (almost enough for a full PRC sweep). We convinced ourselves that the PLL was locked and tracking the NA frequency by observing the TF from NA drive signal to 1811 AC output. When the PLL is locked, the TF is flat, high, and smooth, since the 1811 AC output is coherent with the NA signal at the same frequency. When the PLL is unlocked, the same TF is many decades smaller.
Each time the NA reaches the end of a sweep and flips back to the start frequency, the lock drops. I'm not sure there's much we can do about that. It would help to have the slow path enabled though, in order to compensate for slow drifts of the aux laser frequency away from the PSL frequency.
Next we plan to try some PRC sweeps if there is PRMI locked time available. For this, we will take the TF from NA drive signal to one of the REFL AIR broadband detectors, with the PRMI locked and the PLL locked. Depending on how that goes, we may pursue the slow temperature feedback development.
With a subcarrier you can measure the strength of each individual RF sideband---with upper and lower sidebands separated around the VCO frequency. The ratio you see here between RF sideband amplitude and carrier is a direct measurement of the modulation depth.
Great point, what a convenient way to measure the modulation depth! It's also probably a lot more precise that the OSA.
When we get the PLL going again later today I'll save the data from the spectrum analyzer so we can do a more careful analysis.
(Doug C and Suresh D.)
This afternoon we replaced the glitchy diode laser (Sl. No. 193) in the BS optical lever with a repaired and thermally stabilised laser (Sl. No. 130-1) which was under observation in HAM3 oplev. The attached plots show the improved performance due to the repairs and stabilisation.
Things to note:
1) Broadband noise injection into pitch has disappeared after swapping the lasers
2) Constant glitching and consequent broadband injection of noise into yaw signals has disappeared after swapping.
3) The RIN has dropped by an order of magnitude at all frequencies
4) The spectrum is stable and does not oscillate between stable and unstable regimes as the temperature in the LVEA changes due to the airconditioners.
Please note that the laser is still approaching a stable operating condition and is under observation for a futher 24 hrs. However its performance over the past six hours is satisfactory.
Distinguishing glitch and operator initiated actions in PIT and YAW signals:
We can distinguish the glitch and operator actions by looking at their spectral signatures. A glitch would cause a rise in spectral amplitude right across the entire frequency range. This would then appear as a white line running vertically (across all frequencies) in the spectrogram. Where as an operator initiated action would have a subsequent suspension damping motion at low frequencies (only).
We can see examples of both in the PIT spectrogram. There are no glitches in the red trace (the spectrogram for that is in bottom panel). This was after about 7PM and folks had already started using the BS oplev for damping. So their initial alignment efforts show up as small steps with an associated low frequency spectral signature.
The blue trace has the classic glitch related signals showing up in pitch. They can be seen starting at 1.3 hrs and going on till 1.4 hrs. I dont think anyone was using the IFO at that time. Since the BS oplev is used for local damping continuously, it is likely that the gliches kicked the optic and caused the activity we see around that time.
The picture is more messy in the case of YAW as we can see from the blue trace and its associated spectrogram (middle panel). The yaw signal seems to be continuously affected by the glitching however the event we saw in pitch at 1.3 hrs can also be seen in yaw. Once again there is no operator related activity in the blue trace while the red trace shows some steps which have an associated low frequency spectral signature (bottom panel). I concluded that they were associated with the initial alignment activity which was going on at that time.
I looked at whether the improvement in the laser quality has resulted in an actual improvement in the BS local damping. There is a tangible improvement in YAW.
1) The Spectrogram of YAW motion shows that the injection of broadband noise into the optic motion in YAW due to glitching has disappeared after the swapping of lasers
2) the Coherence between the witness channel and Oplev channel in YAW shows that we can now extend the servo bandwidth to about 10Hz reliably.
3) The spectrum of yaw motion dropped by a factor of two in the range 1 to 20 Hz. This probably has nothing to do with the laser per se. Probably the pier motion decreased between the two data segments.
Performance check after a week of operation
To see if the laser is still operating safely within the glitch free region, I checked the 1s trend over the past two days. The laser power has a slow drift of about 1% in a day. This is probably a LVEA average temperature related effect. The long term spectrum shows a 1/f shape down to 10^-4 Hz.
And to see the broad band noise I looked at raw signal over the past four hours (256 samples/sec)
The 4hr stretch of raw data spans a period when the oplevs were not used for first 1.4 hour stretch and then were turned on. We can see the suspension resonances damp in the witness channels.
The spectrograms show that there is broad band noise in the optic motion, but it is not due to the laser glitching.
The top panel shows the laser spectrogram and it does not show any broadband noise.
Conclusion:
The laser is performing well, without glitches. All the action we see in the Pitch and Yaw is associated with either human intervention or lock loss events which have kicked the optic.
After looking at the oplev spectra with the OL damping loops on and off, I turned down the yaw gain from 650 ct/ct to 500 ct/ct to reduce the amount of extra noise injected between 1 and 10 Hz. The pitch gain is still 300 ct/ct.
In the attached plot, blue is the spectrum without damping, and red is the spectrum with the new damping gain.
Betsy, Travis, Rick
After Jim finished locking the ISI this afternoon, Travis hopped in the chamber. Using the Green LED flashlight (part of the "green lantern" kit) he immediately identified the 3 spots on the HR surface of the ETMy that last week's pcal images highlighted - 2 fairly large chunks of FirstContact (FC) remnants and one quite small one. I also went into the chamber and with green and white flashlights we then identified the ring observed at 3" diameter around the center of the optic also due to previous FC sheets. The 3 macroscopic remnants near the center of the optics look very similar to remnants we have observed on other failed FC sheet pulls, and were likely left on there from the March cleaning FC sheet, and not from the original sheet. Why Margot and I missed them in March is beyond me.
We then:
Installed the ACB locking brackets and dropped the ACB down such that it was partially swung back. (We did not use the wedge, but instead just let it hang in it's free and open state. This allowed pcal to still see the optic but also gave enough clearance to attach the green lantern and also to paint FC.)
Installed the Green Lantern on the ETMy structure and reinspected the optic. Again the large FC remnants lit up well. However, the ring feature did not show up under this lighting condition. (The flashlights were better for this. The ring feature looked more like a staining or clouding that started at the 3" ring boundary and spread ~uniformly outward towards the edge of the optic. There did not appear to be large macroscopic contaminants or FC remnants at this 3" ring boundary.
Rick took a few pcal photos (see attached) of the remnants and the ring using the green lantern and the green flashlight.
We secured the ETM TM with TFE rails on the EQ stops around the barrel of the optic.
We proceeded to paint FC onto the HR surface, making a nice thick coating after a few layers were applied - this took ~45 mins. Note, we only observed "spider webs" on the FC sheet/brush toward the end of the 45 min and they were more noticeable around the TFE rail that was nearest the HR face which was likely charged and attracting or even causing(?) the webs.
Set the PETG cap on the face of the optic.
Tomorrow we plan to come in mid morning and then catch up with Richard/Fil to make the ESD connector swap midday. After that, we can pull the FC and hopefully see that we have removed the remnants and improved the ring feature.
The first image shows the ETM surface illuminated with the "Green Lantern." In the second image it is illuminated with a green LED flashlight. The third, zoomed image is illuminated with both the green lantern and the green flashlight and shows the large first contact remnants (the two bright vertical objects with ragged edges and the smaller object to the left), as well as the edge of the "ring feature" identified with the ~3" window in the first contact that was applied previously. Although the two vertical objects are roughly aligned with the edge of the ETM telescope baffle in the background, this photo and in-chamber visual inspection clearly showed that they are debris on the front surface of the ETM.
A few images of the process of painting the First Contact on the ETM HR surface attached below. The last image shows the PETG cover in place to slow the drying of the First Contact.
F. Matichard, K. Venkateswara
This is related to Sheila's alog (15607), where they had trouble locking MICH_DARK. This was being caused by excessive RZ motion as described in the comment to that post.
Ideally, we should not even need Z to RZ subtraction and a simple position sensor loop ought to be sufficient to hold RZ constant. We will test this configuration soon and look at other chambers as well.
Currently, the RZ loop is engaged on the Beamsplitter.
I have made new snap files for h1iscey, h1iscex, h1asc, h1susetmx. Betsy had recently done h1susetmy, so I did not repeat it.
Kyle, Gerardo- Venting activities Kyle, Gerardo, Bubba, Betsy- BSC10 door removal activities
[Peter K., Alexa, Paul, Mackenzie]
(Written by Mackenzie, on Paul's login)
This morning we went into the PSL to set up the RFAM measurement and try to finalize the IO table layout.
We found that IO_AB_W1, which sends the beam to IO_AB_PD1 and IO_AB_PD3, was substituted previously with a temporary 1" HR mirror, so we located and installed the correct AR 2" window. We placed IO_AB_PD3 in transmission of IO_AB_W1 and placed IO_AB_PD1 (the RF 1811 PD) in reflection of the window. IO_AB_PD3 is saturating right now even at the lowest gain setting, so we'll have to attenuate that beam more somehow.
Regarding the RFAM measurement, we were able to see the carrier with 45 MHz and 9 MHz sidebands on the OSA. The resolution was not great, and some of the sidebands were lost in the noise floor. Volker had previously performed this measurement, but needed an amplifier to boost the signal onto the EOM to see the sidebands well. We intend to go back in later today or tomorrow with an amplifier and try again. When we slowed the OSA scan down to try to resolve the peaks better, we found that the carrier peak was quite distorted (see attached pic). Maybe something to do with PZT non-linearity, we're not sure yet. Another attached pic shows the visible 45MHz sidebands along with two carrier FSRs.
We looked at the RFPD spectrum, and were only able to see 9MHz sidebands. For some reason neither the 24MHz or 45MHz sidebands were visible. We had assumed RFAM/PM would be consistent between different sideband frequencies, but this doesn't seem to be the case. Again, we will know better once we get the amplifier in place.
Alexa, Peter K., Paul, Mackenize
We have begun the set up for the RFAM measurement in the PSL enclosure.
First we aligned the OSA and attached it to an oscilliscope. We could see the carrier and 45MHz sidebands, but only sort of see one of the 9 MHz sidebands. After we set this up we remembered an email from Volker indicating we must add an amplifier to the EOM in order to better see the sidebands from the OSA. We will do this when we return to the PSL enclosure. At the moment we have a beam dumb in front of the OSA until we continue.
Second we placed an 1811 PD on the table. The PSL layout indiciates that IO-AB_PD1 should be a 1811; however this was not installed on the table. Instead we had found IO-AB_PD3 in the postion of PD1 and the wedge IO_AB_W1 was actually a HR mirror. We moved PD3 to its specified location and put the proper wedge (2025-45P) on the table. We placed the 1811 as specified and connected it to a spectrum analyzer. We could only see the 9 MHz and not the 45 MHz sideband ?? Also PD3 is conntected to H1:PSL-EOM_A_DC_POWER, which reads 2.22 (not sure what this is calibrated in); we noticed we are actually saturating this PD even though we are at this lowest gain setting of the PD.
07:50 Karen in LVEA
08:00 EY VENT TODAY
08:50 I'm covering for Travis today, apparently :)
08:51 Kyle requested picomotor drives be disabled at EY
08:59 Bubba into LVEA
09:04 Switched ESD bias to ETMY L3 off
09:19 Ellie out to LVEA
09:23 Aaron out to LVEA
09:49 Fil out to LVEA
10:25 Compressed air alarm at Mid-X. John and Kyle notified
10:49 Corey out to LVEA - squeezer bay
12:24 Hugh to EY to lock HEPI
12:57 Betsy and Travis will be goin into the LVEA and then to EY - EY control will be turned over to Betsy after the vent for optic cleaning.
13:20 Fil and Essence out in the LVEA
13:22 Jeff at EX to check out contamination stuff13:25 Kyle getting ready to start Kobelco for at HAM1
13:40 Corey back out to squeezer bay
13:43 Cris to EX to stock garb
14:00 Jeff back from EX
14:29 posted PSL report
15:24 Suresh and Doug out of LVEA - replacing BSC3 op Lev LASER
15:35 Cyrus out to LVEA to check on a couple of vacuum computer
15:49 Cyrus out of LVEA
15:51 Dick out to ISC R1
16:00 Jeff maybe out to EY
I did this back 7 February, the numbers still look like they work well.
See the attached where I measure the tilt with the previous values and bracketed values around the good number. The blue traces are the original values and the green and red traces are with the vlues offset a bit. Still looks like the old values are the best. The first attachment is the inline measurements (drive Y) with the second attachment showing the croosline measurement (drive X.)
Laser Status: SysStat is good Output power is 29.3 W (should be around 30 W) FRONTEND WATCH is GREEN HPO WATCH is RED PMC: It has been locked 4day, 22hr 0minutes (should be days/weeks) Reflected power is 2.9 Watts and PowerSum = 25.8 Watts. (Reflected Power should be <= 10% of PowerSum) FSS: It has been locked for 0h and 35 min (should be days/weeks) Threshold on transmitted photo-detector PD = 1.74V (should be 0.9V) ISS: The diffracted power is around 7% (should be 5-15%) Last saturation event was h and 16minutes ago (should be days/weeks) There was a group of four working in the enclosure today taking RFAM measurements causing some grief to the normal stability of things.
Since the platform was tripped (at the end of my locking up the HEPI) I turned the pump down to get zero pressure readings. I use these to define the AOFF so the sensors don't have that zero bias offset. Pump back on within a few minutes and servoing on 70psi differential pressure.
Evan, Stefan Did some more WFS/camera loop work on both arms: - Added a 0.3Hz LP with a notch at the main pendulum modes into the WFS output filter modules. This allows for a ~3-5 times higher gain. - Carefully measured the output matrix for the camera loops (X and Y arm, yaw and pitch) by dragging the ETM around and letting the WFS follow. The new output matrix values are in the snaphots #3 below. With them the camera loop no longer relies on gain hierarchy - it's gain was increased ~x10. - Some gains were redistributed - see the attached snaps. - Cleaned up the arm Guardian. Removed all old slow feed-back stages, and instead added a state commanding Daniel's new setup. - Added a WFS relief step to the Guardian.
We noticed that the higher Camera gain can cause a too big kick during the WF engaging process. Thus we used the existing FM triggering to set up a 10 second delay. During those 10 seconds the DoF3 (P&Y) , i.e. the camera loops, have 20 times lower gain. This seems to take care of the engaging problem. The attached snapshot contains all elements that changed.
The experimentally measured output matrix to move TMS, ETM and ITM simultaneously to center the ITMX green camera (without misaligning the beam) is
X PIT: X YAW:
ITMX: 0.68 -0.43
ETMX: 1.00 1.00
TMSX: 1.43 1.00
Y PIT: Y YAW:
ITMY: 1.43 -1.23
ETMY: 1.00 1.00
TMSY: 1.54 1.15
The expected matrix would be
PIT:
ITM: 1.06 = -g1
ETM: 1.00
TMS: 1.00
YAW:
ITM: -1.06 = g1
ETM: 1.00
TMS: 1.00
This means that our angular actuation calibration is somewhat fishy...
For reference, the H1 installed optics radius of curvature are (from https://galaxy.ligo.caltech.edu/optics/, after coating measurements):
ETMX: ETM-08: RoC=2242m ± 2m, (LIGO-C1103233), g2= -0.7817
ITMX: ITM-03: RoC=1940m, (LIGO-C1103237), g1= -1.0590
X Arm length: L=3994.4704 m ± .3mm (alog 9626)
ETMY: ETM-12: RoC=2240 ± 2mm, (LIGO-C1103257), g2= -0.7832
ITMY: ITM-11: RoC=1939.4m, (LIGO-C1103255), g1= -1.0596
Y Arm length: L=3994.4691m ± .7mm (alog 11611)
SudarshanK, TravisS, EvanH, AlexaS, RickS Using the Pcal beam localization cameras at both end stations, we took images of the ETM surfaces under three conditions: IR and Green resonating; IR only resonating, and Green only resonating. Attached below are two composite images composed of four separate images taken with the same camera settings: Upper Left: Xarm Green Lower Left: Xarm IR Upper Right: Yarm Green Lower Right: Yarm IR The images in the first composite were taken with the following camera settings: F8, ISO 200, 30 second exposure, WB-cloudy. For the second composite image the aperture was F29 (~13 times less light) The Yend camera was re-focused for the IR-only images, but the Xend camera was not re-focused.
Thomas Abbott at LLO applied the Pcal beam localization analysis the the LHO ETMY image to calculate the position of the center of the optic in the image from last Friday. The image below contains lines that indicate the center of the optic using the Pcal image analysis.
Attached is a picture of the original FirstContact (FC) sheet, circa ~Jan 2014, showing the "IAS window" which is a thinner film of FC in the central 3" of the larger sheet. To me, the shape of the FC window looks similar to the 3" ring showing up in green on the recent optic photo above. SYS is working with us to get our cleaning game plan together in order to remove the ring. As well, they are investigating other possible scenarios of where the ring came from if not the window. Note, there was a full FC sheet re-cleaning in March that apparently did not remove all of the ring that was left behind apon the removal of the first sheet. To be continued...
I've attached an overlay of (a) the SolidWorks CAD view of ETMy along the PCal camera path and (b) the PCal camera image of H1 ETMy (scaled and rotated). Since SolidWorks does not diffract the image viewed through the ETM optic, I indicate the shift in the ETM Telescope Baffle aperture as well. Three of the 4 bright areas are along the ETM Telescope Input aperture/baffle edge (a coincidence?). (The upper one is red.) One of the 4 bright spots does not correspond to any feature in the CAD image and is likely a spot of residual First Contact. As subsequently shown by the zoomed in PCal image using the Green Lantern flashlight (green LED) after venting (see entry #15635), it is simply a coincidence that the two prominent bright areas appeared to be along the ETM Telescope baffle aperture edge.