jeffrey.bartlett@LIGO.ORG - posted 09:22, Thursday 18 December 2014 (15710)
End-X Laser Safe
Richard transitioned End-X to laser safe.
Richard transitioned End-X to laser safe.
model restarts logged for Wed 17/Dec/2014
2014_12_17 04:41 h1fw0
one unexpected restart. Conlog frequently changing channels report attached.
[Mackenzie, Paul]
We took some initial sweeps of the PRC with the aux laser this afternoon with the PRMI locked on sidebands. We'll save most of the analysis for later, but just as a quick update, I've attached data from sweeps around two FSRs which are 20 FSRs apart, as well as a full FSR sweep. Just estimating the peak frequencies of these sweeps gives a rough FSR estimate of 2.6005MHz, or 57.6413m for the PRC length. We'll increase the frequency resolution on subsequent scans, and take more data from FSRs over a greater frequency range for the Schnupp measurement. In the end we'll do some fitting rather than just guessing peak frequencies too. More to come later.
Dan, Fil, Thomas
We made a quick modification to the ASC-AS_C transimpedance board today, so that the HAM6 fast shutter threshold can be set for 1W of light into the chamber. The modification was a swap of R23, from 1.24k ohm to 422 ohm. This changes the gain on the SUM_OUT channel on the back of the chassis, that's used for the fast shutter logic.
ASC-AS_C gets 2.5% of the light into HAM6, so we'd like to set the threshold at 25mW. The input to the shutter controller rails at 2V. The QPD transimpedance is 1000 ohms, the quantum efficiency is probably about 80%, and the new resistor changes the final gain stage to 422/4.99k = 0.0845. So, the correct shutter threshold is 0.025*1000*0.8*0.0845 = 1.7 volts.
This modification only affects the signal path to the shutter controller; it doesn't change the signal path that is acquired by the ASC front end. So the ASC-AS_C sum that you see on the MEDM screen hasn't changed. (The input to the HAM6 shutter controller is recorded by the channel H1:SYS-MOTION_C_SHUTTER_G_TRIGGER_VOLTS.)
Something seems odd here. The QPD amp single ended sum output (D1001974) is designed to accommodate the full design dynamic range of the QPD (10mA per quadrant)by use of the R3 = 1.24k and to produce 10V at the sum output during this full scale optical input. The shutter controller (D1102312) photodiode input is a unity gain receiver, although for some bizarre reason, this design only operates on +5V for all the opamps. The correct way to fix this dynamic range problem should have been by lowering R13 from 10k to 2k thus preserving best SNR on the QPD sum output. Also, I see no mention of serial numbers here. Hopefully the eTraveler's are being updated as this is the only way to track such changes at the board and chassis level.
Stefan, ThomasV, Kiwamu,
Tonight we continued working on the BS high bandwidth loops (see previous alog 15662). We successfully engaged both pitch and yaw loops with unconditionally stable 1/f open loop shapes.
We also worked on PR3 loop a bit as well.
(BS high bandwidth loops)
Even though we had success yesterday on the BS loop, we were not satisfied with the loop shape as there was multiple UGFs. Today we tried inverting the BS M2 stage plant so that we can nicely have a 1/f open-loop shape. We studied the plant inversion using the oplev damping paths at the beginning and PRMI. Later on we applied the resultant inversion plant in the actual DRMI ASC loops. Here are the inversion filters we used as a starting point:
Note that the lower resonance in Y-to-Y has a mismatch both frequency and Q. With these inversion plant filters in, we then modified the location of the resonances as well as their Qs of the inversion filters as we observed instability in the loops. In particular, we tended to slightly lower the resonant frequencies and Qs such that the phase of the open-loops go up in order to prevent them from small phase margin. The actual resultant inversion filters are written in the foton files.
We did a simple in PRMI where we ramped up the overall gain of two loops from 0 to the nominal in a minute to see if there is unstable region. As expected, we did not see instability at all. So the loop is unconditionally stable with opelv damping loops off. Then we applied the new inversion fitter in DRMI with the new AS_Q input matrix. This went pretty smooth. The attached is the nominal open loop transfer functions for both pitch and yaw. They are currently set to 7 Hz. The whole setup is coded in guardian. ISC_DRMI.
(PR3 ASC loops)
We briefly closed the PR3 ASC loops using REFL_B9_I. There was large coherence between the power build-up and PR3 angular motion. For now we made a low bandwidth loop, but tomorrow we should commission a high bandwidth loop as there was fast residual angular motion.
(Pointing DOF)
We also quickly checked if the POP QPDs are sensitive to a pointing DOF. We moved IM4 and let PRM and PR3 follow the IM4 pointing to see if we can see it on the POP QPDs. And we confirmed that_POP_B QPD was sensitive to the pointing DOF.
(Some guardian update for SRC2 loops)
The setup for the SRC1 and SRC2 loops are now coded in the guardian as well. This is something reported in alog 15638,
I launched an overnight measurement for Alexa at 8:21:33 UTC (or 0:21:33 local)
I had to restart this because I had forgotten to enable the modulation on the IFR -- second try started at 08:32, or GPS = 1102926745.
And then had to start it again, after I realized the REFL9_Q output was turned off...
1102928116
8:55:00 UTC
J. Kissel After Betsy and Travis successfully finished in-chamber close out (after LHO aLOG 15677), and Kyle, Gerardo, and Bubba have put the door back on (LHO aLOG 15696), I've taken H1 SUS ETMY Top2Top transfer functions on both main and reaction chains to confirm that the suspension is free and clear of rubbing. The transfer functions look spectacular. I'd call it ... wait for it ... a clean exit. I think the only other thing we should confirm before pump-down is that the ESD drive is functional by turning on the high-voltage driver, driving at ~5 [Hz] in angle, and checking optical lever for the signal, as has been done for the charging measurements. This would clear the work done by Filiberto and Richard also during this vent The new templates for this data set live here: 2014-12-18_0143_H1SUSETMY_M0_Mono_L_WhiteNoise.xml 2014-12-18_0143_H1SUSETMY_M0_Mono_P_WhiteNoise.xml 2014-12-18_0143_H1SUSETMY_M0_Mono_R_WhiteNoise.xml 2014-12-18_0143_H1SUSETMY_M0_Mono_T_WhiteNoise.xml 2014-12-18_0143_H1SUSETMY_M0_Mono_V_WhiteNoise.xml 2014-12-18_0143_H1SUSETMY_M0_Mono_Y_WhiteNoise.xml 2014-12-18_0203_H1SUSETMY_R0_L_WhiteNoise.xml 2014-12-18_0203_H1SUSETMY_R0_P_WhiteNoise.xml 2014-12-18_0203_H1SUSETMY_R0_R_WhiteNoise.xml 2014-12-18_0203_H1SUSETMY_R0_T_WhiteNoise.xml 2014-12-18_0203_H1SUSETMY_R0_V_WhiteNoise.xml 2014-12-18_0203_H1SUSETMY_R0_Y_WhiteNoise.xml
Travis, Betsy, Jason, Rick, Jim
After the noon SYS/COC/SUS telecon the chamber closeout went like this:
- Took particle counts in chamber - 20 - 0.5um size, 10 - 0.3u size, rest 0.
- Retidied the ESD cable loop after yesterdays fix which needed slack to pull out of the port.
- Blew all 4 of the large optical surfaces for 5-9 mins of N2 deionizing flow in an attempt to reduce charge.
- We attached the green lantern to the ETMy SUS and made a final count of particulate of ~2 particles per square inch.
- Took a few more pcal camera pix to compare with pix from before we attempted cleaning of the ETMy-HR.
- Released the ACB locking bracket and swung it back into place.
- Suspended the CP and the ERM, removing extra teflon payload.
- Reattached the QUAD witness plate holder now loaded with a new witness plate.
- Attached the new 1" vertical witness optic to its place on the side of the suspension frame.
- Removed all tool pans, optic covers, blowers, foil, etc. from the chamber.
- Asked Jim to unlock the ISI.
- Placed the new horizontal floor witness place and 1" vertical witness optic.
- Verified damping loops could enable on the ETMy.
- Took quick P and V TFs of the main and reaction chains.
- Called Bubba/Kyle/Gerardo to proceed with the door attachment.
Reminder the test of the ESD can be done after we have pumped down. 10-5 torr or lower.
Schedule for BSC9 Vent and ETMX Assessment and Cleaning
Approved work to be done:
The last step is at the time and discretion of the Vacuum crew.
Kyle, Gerardo, Bubba -> Installed HAM1 east door (every other bolt) -> Pumping annulus Kyle, Gerardo -> Closed GV20 -> Started slow vent of X-end Bubba -> Staged/Status prep for BSC9 West door removal slated for tomorrow morning Kyle, Gerardo, Bubba -> Installed BSC10 North door -> Not pumping BSC10 annulus or Y-end until others "sign-off" on readiness tomorrow
LVEA: Laser Hazard Observation Bit: Commissioning 06:15 Karen & Cris – Cleaning at End-Y 09:16 Elli & Thomas – In the LVEA working on HWS alignment 09:25 Hugh – Working on HAM3 CPSs 09:35 Aaron – In Beer Garden terminating cables 10:00 Jeff & Nutsinee – Tour of LVEA 10:15 Water sampling company on site to test water 10:26 Betsy & Travis – Going to End-Y 10:30 Kyle, Bubba, & Gerardo – HAM1 door install 11:08 Cris – Taking garb to End-X 11:40 Thomas & Elli – Out of the LVEA 12:08 HAM1 door installed 12:30 Dave & Jim – Going to End-Y to connect a HWD monitor cable 13:00 Manny – Dropping of parts at End-X 13:05 Shut down Picomotors at End-X to prep for vent 13:10 Kyle – Going to End-X to soft close GV20 for vent 13:30 Bubba – Going into the LVEA to gather tools for End-X Vent 13:32 Manny – Delivering parts to End-Y 14:00 Rick – Going to End-Y 14:30 Started venting BSC9 15:30 Robert – Going to beam enclosure just short of Mid-Y
Krishna, Sheila, Hugh, Fabrice:
We have been chasing large amplifications at low frequencies (in the range of 10mHz to 30mHz) caused by the Z zensor correction of HEPI, which is necessary to reduce the Z to RZ coupling on Stage 1. It looks like the Z HEPI inertial isolation is causing rotations (RX, RY), that are causing tilt signal in the Stage 1 horizontal seismometers, that couple to X and Y as we blend at 45 mHZ, and then shows up into the cavity signal.
The problem was mostly visible on the BS unit. We convinced ourself that Z to tilt was the problem by moving Stage 1 in high blend, which very significantly reduced the Mich amplification around 20 mHz (which exist only when the Z sensor correction is ON)
It seems that the excessive Z to tilt coupling in the BS was caused by off centered vertical position sensors (up to 24000counts). We recentered them by applying a HEPI vertical force. The Z to Mich coupling is now much lower. So I guess that the gain of the sensors was affected by the large offsets and thus creating excessive Z to RX and RY couplings.
Comparison with high blend configurations show that there is probably room to further reduce this coupling. We need the measure the Z to RX and RY coupling and apply corrections.
The plot attached shows the Mich Out signal:
- in the first box, HEPI Z sensor correction is ON, Stage 1 X abd Y are in low blend, the IPS are off centered. The low frequency amplication is huge.
- in the second box, HEPI Z sensor correction is ON, Stage 1 X abd Y are in high blend, the IPS are still off centered. The low frequency amplication is gone.
- in the third box, HEPI Z sensor correction is ON, Stage 1 X abd Y are in low blend, the IPS are re-centered. Our current understanding/aseumption is that the Z to RX and RY coupling on HEPI has been well reduced.
The latest configuration is likely the best compromize:
- good micro-seism atenuation thanks to the low blend on X and Y
- low vertical to pitch coupling thanks to the Z feedback
- little RZ amplification at the micro-seism thanks to the Z sensor correction to HEPI (that offloads Stage 1 Z drive at the micro-seism)
- amplification acceptable at very low frequency, now that the IPS have been re-centered. We'll try to further improve it.
An ASD plot of the MICH_OUT channel is attached under different configurations. The first (RED) is with no sensor correction on BS, ITMX and ITMY. The second (BLUE) is with X, Y sensor correction signals to all three BSCs. The third (GREEN) is with Z sensor correction to HEPI for the BS chamber, showing the large low frequency amplification. The fourth (BROWN) shows the MICH_OUT with the IPS recentered and same configuration as the third. Tilt-decoupling on HEPI ought to reduce the amplification further.
Z sensor correction has been turned OFF on BS and ITMY. X and Y sensor corrections seem to be working fine and can be left ON.
Could be that I'm missing something but it sounds to me like at least one of the IPS is not working properly (ie broken). They are supposed to be linear to within 0.1% over the full range (+/- 0.05 inches)
Thomas V, Elli
The ITMy and ITMx Hartmann wavefront sensors are now aligned to their respective SLEDS.
We took the HWS plates out and centered the SLED beam on the camera using the periscope mirrors and the final mirror before the HWS (pictures of the final alignment on the camera are included).
The ITMx image is a lot dimmer than the ITMy image, however the H1:TCS-ITMX_HWS_SLEDPOWERMON said 5mW whereas H1:TCS-ITMY_HWS_SLEDPOWERMON says 1.8 mW. We were watching to maximise image brightness as we made the adjustments so I don't know why ITMx image is so much dimmer.
We also observed some tarnishing or something on one of the HWS plates, picture attached. Some light wiping with an ipa wipe did not get it off, so we swapped the plate with a spare.
This morning, travis and I pulled the FC sheet that we applied to the ETMy yesterday. The patchy smudge mark and the large gooeyish particle that we induced yesterday were apparently picked up by this FC sheet. While there, we tested using the cotton tipped Q-tip on a portion of the ring around the edge of the optic (~1Inch in from bevel edge near the bottom). We used both DI water and also acetone, both chased with ~5 spot drag wiped of acetone using the pressure technique. Upon evaluating neither q-tip+ acetone drags seemed to improve the area since both swipes added to the streaking which the chasing acetone could not fully remove with 5 wipes.
Our cleaning efforts at EndY have focused on the three larger scattering objects on the surace (which were apparently removed) and the ~3" diameter "stain" associated with the thinner central window in a previous layer of First Contact (which we have not been very successful in removing. ) The composite image below includes six images. All were taken by illuminating the lower edge of the central "stain" feature with the green LED flashlight. The two on the left were taken before applying First Contact (note the large scattering objects are still on the surface). The middle two were taken after the first application and removal of First Contact. The two on the right were taken today, after the second application and removal of First Contact. It doesn't appear that we have significantly improved the "stain" feature.
(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.
