bubba.gateley@LIGO.ORG - posted 10:00, Thursday 15 January 2015 (16091)
Mid Station Chillers
I have turned off the Mid station chillers.
I have turned off the Mid station chillers.
ISS AOM Diffracted power was up ~11.3%. REFSIGNAL was also set to ~2.13 from the ~2.23 that It was set to yesterday to maintain roughly 7.5% diff. This morning I adjusted it back down to ~7.1% with a REFSIGNAL of -2.25. Is the Diff Power purposely being raised during commissioning at night?
We have had at least three incidents today where MC1 and MC3 both tripped, we haven't had time to investigate why but this is a new phenomenon.
Kyle and Gerardo were operating the large Genie manlift at BSC3 on Wednesday and I believe also used the overhead crane in that region in order to replace a failed annulus ion pump. Were the trips related to excess motion?
Sheila, Kiwamu, Alexa, Evan, Nergis
After locking the x-arm in green (alog) and testing for the x-arm losses (alog), we repeated our usual initial alignment procedure. Some comments:
We were able to lock ALS COMM very easily; however, we had difficulties locking DIFF. At first we thought we had found our culprit: LSC-DARM had FM10 engaged, which should not have been; the LSC-DARM filters should be FM5, FM7, FM8 with FM3 turned on later. Even after we noticed this, we still could not lock DIFF. As soon as the DIFF engages (even with gain's of 1, relative to the nominal 400), we would immediatly lose lock. We ensured that the ETMX ESD was working by sending in an excitation to the bottom stage in both pitch and yaw; this was successful and we did not see any large Y2P or P2Y coupling. We did not take L1, L3 crossovers, which we should do tomorrow. We also had trouble getting the DIFF PLL in range -- the old guardian tidal scripts the Nick wrote have been decommissioned, and we were not yet ready to implent Daniel's new tidal feedback, so we were left to using an ezcaservo in the test offset. This did not work very well, and limited us from figuring out what was wrong with DIFF. It's possible that there are still some more inccorect filter/gains setting.
Elli, Nergis, Daniel, Evan
Today we did a preliminary measurement of the Schnupp asymmetry to be 9.0cm +/- 1cm. We injescted a beam from the auxiliary laser on IOT2R which can be offset in frequency from the main laser. We measured the power of this beam at the AS port using a 1611 photodiode on ISCT6. With the michelson locked to a bright fringe, we measured the variation of auxiliary laser power with frequency at the AS port. Due to the Schnupp asymmetry, the power should change as the auxiliary laser offset from the carrier increases as cos(scnupp_assymetry*2*pi*f_offset/c).
By fitting a curve to our measured data, we can get an estimate of the Schnupp asymmetry. I did a fit using least squares fitting to a quadratic to get 9.0cm +/-1cm Schnupp asymmetry. The measured data and curve fitting codes are attached. Evan hopes that we can reduce our error estimet by doing the curve fitting more elegantly.
Summary
Attached are two plots showing the measured data, along with least-squares fits (using scipy.optimize.curve_fit). The horizontal axis is the detuning frequency of the aux laser from the PSL (and the sign is arbitrary). The vertical axis is rf power of the AS port beat note, as measured with an HP4396 (so these watts are electrical, not optical).
For both the upper and lower fringes, I've fit to a quadratic using the formula a(f−h)2 + k (the "vertex" form), where f is the detuning frequency. For the lower fringe, I find the minimum-power frequency occurs at f− = −840(3) MHz, and for the upper fringe I find f+ = 815(4) MHz. The uncertainties come entirely from the fitting routine; I have not included the measurement uncertainties (which we estimate to be 0.5 dBm or so). The Schnupp asymmetry is then found via the formula 2π(f+ − f−) LS / c = π; with this I find LS = 90.6(3) mm, where the errors come from the fit alone. I believe the difference between this uncertainty (<1%) and the uncertainty reported above (11%) is that the above analysis involves some covariances in the fitted parameters, and these must be accounted for when propagating the uncertainty forward to the Schnupp asymmetry.
More details
Instead of using the vertex form for the parabola, one can fit using the formula af2 + bf + c (the "standard" form). The minimum-power frequency is then f = −b/(2a). I ran a fit using this functional form, and for the upper fringe frequency I found a = 1.54e-4, b = -0.241, and c = 1.03e2. The nominal value of f+ is then 815 MHz. To find the uncertainty, I examined the covariance matrix of the fit parameters:
| Cov | a | b | c |
|---|---|---|---|
| a | 2.28e-10 | -3.74e-07 | 1.51e-04 |
| b | -3.74e-07 | 6.15e-04 | -0.250 |
| c | 1.51e-04 | -0.250 | 102 |
To find the variance var(f), we need the variances var(a) and var(b), as well as the covariance cov(a, b); the formula to find var(f) is then given in this Wikipedia article. Applying this formula gives an uncertainty [i.e., sqrt(var(f))] of 4 MHz, in agreement with the fit to the vertex form. If instead cov(a, b) is left out, I find that the reported uncertainty is much larger (114 MHz), and more in line with the larger uncertainty reported earlier.
The code I've used is attached.
Sheila, Keita, Nergis, Evan, Alexa
With our beloved x-arm back, we began the alignment process:
1. Aligned TMSX with ITMX baffled PDs (and ETMX misaligned). For reference:
| Volts | Gain | TMSX (P,Y) | |
| ITMX PD1 | 2.3 | 0dB | (-16,-245) |
| ITMX PD4 | 2.4 | 0dB | (52,-306) |
2. Aligned ITMX with the ETMX baffle PDs (and ETMX misaligned). Again, for reference:
| Volts | Gain | ITMX (P,Y) | |
| ETMX PD1 | -0.87 | 0dB | (6,-24) |
| ETMX PD4 | -0.85 | 0dB | (49.9,13.5) |
Yes, the ETMX baffle PDs have a negative voltage!!
3. We realigned ETMX by hand. We had to increase the max pitch PV limit from 440 to 500. We hope those were set arbitrarily; the DAC was not saturating with these higher slider values. We were able to lock the x-arm on green to a buildup of 1.4-sih, which is good.
Unfortunately the green wfs servo did not wok and would misalign the arm. We did have to turn on the ITMX ISC_INF_LOCK and MO_LOCK, and TMSX M1_LOCK filters. Unfortunately this was not the culprit. It appeared that the wfs error signal had an offset, but we did li. We want to continue with locking.
We found that TMSX had the gains for the M1 lock filters both in the filter bank gain setting and in the cal filter which was engaged. Once we set the filter bank gains to 1, the WFS worked fine. We've captured safe.snaps of both TMSX and ITMX with the configuration where the WFS were working.
Alexa, Sheila, Nergis, Evan
We took a quick measurement of the X arm loss using the same technique as LHO#15919. For ASAIR_A_LF, we have Pon = 1267(5) ct, Poff = 1293(3) ct, giving an equivalent loss of 78(18) ppm for the ETM.
Today I spent sometimes setting up the calibration filters for LSC DARM in h1oaf. It should be functional now.
What I did:
Also, the second attached png is a screen shot of the latest DARM calibration setup. This is set up for a single ETM configuration where either ETMX or ETMY is not in use. If one wants to feed DARM back to both ETMs, an extra factor of two should be added somewhere. Note that the L1 (UIM) stage currently has a gain of 0.5 as shown in the screen shot n order to simulate the digital gain in SUS-ETMX_L1_LOCK_L_GAIN.
Following the RCG2.9 upgrade yesterday, I have created SDF files for the following systems: IOP, PEM, SUSAUX, TCS, CAL, PSL, ODC. In each case I have made all channels monitored, and removed the obsolete FEC-nn_GRD_[ALH,SP,RB] channels from the safe.snap sdf file. Modified files have been commited to SVN with the exception of CAL (I get an svn error with this working directory).
Latest SDF_OVERVIEW MEDM screen shot attached. All monitored systems are now green for channel matching.
S. Biscans, J. Kissel, N. Mazumder, H. Paris, H. Radkins, B. Shapiro, J. Warner
After an extremely productive two weeks -- thanks to the new years present of Narwita, Seb, Hugo, and Brett all arriving within the same few days -- I figure it would be good assess where the LHO SEI team's priorities lie from here on. In particular, what *other* things that we could be doing to improve *all* the platforms instead of continuing to bang our head against the HAM3-0.6-[Hz]-feature wall. Here're the remaining activities, sort of prioritized, and split into "Improve the chamber noise performance" and "improve the maintainability / extensibility" groups.
Improve The Chamber Noise Performance:
All Chambers Benefit to IFO
- ST 01 L4C Feed Forward (all 6 DOFs), improve 1 to 10 [Hz] performance
- Sensor correction gain matching (all 3 DOFs), improve 0.08 to 3 [Hz] performance
BSCs Only
- Z to RZ subtraction, reduce BSC optic's yaw below 0.08 [Hz]
- Implement Slow MICH, reduce MICH velocity, improving lock acquisition
- Finish ITM HEPI Z to RX/RY Tilt Decoupling, reduce BSC optic's yaw below 0.08 [Hz]
HAMs Only
- HAMs 2,3,4,5 Isolation Loop Gain Increase improve 0.5 [Hz] to 20 [Hz] performance
- Continue HAM3 0.6 [Hz] feature investigation improve 0.6 [Hz] performance
Improve the Maintainability / Extensibility:
- BSC-ISI Noise Budget Model
- HAM-ISI Noise Budget Model
- HEPI Noise Budget Model
- Assess guardian vs. watchdog robustness of bringing all chambers to OFFLINE from FULLY_ISOLATED
- Put MATCH OUTPUT channels on Sensor Correction overview screen
- Storing more than just RZ on HEPI alignment
- Hook IOP SWWD signals up to ISI USER watchdog
- Install HEPI saturable integrators
- Remove HEPI / ST0 L4C Sensor Correction path from ISI models
- Differential Pump Pressure signals are noisy possibly from poor electrical grounding
- Switch ETMX to using differential pressure signal
- Assess whether switching to differential pressure affects platform noise performance
Removed one of the PEM AA chassis to troubleshoot some bad channels. Troubleshooting/repairs is taking longer than expected but should have the unit back in service sometime tomorrow morning. D1001421 Serial Number S1001053.
Unit has been repaired and reinstalled.
Kyle and Gerardo opened the XEND to the beam tube today.
The turbo was valved out, the ion pump valved in, and the gate valve to the tube/80K pump opened.
Plot attached. The pressure has fallen from 1e-6 to 8e-8 and is still moving the right way.
The clean room remains on at X-end, righ above BSC9, clean room will be dealt with by facilities tomorrow.
(Kyle R, Gerardo M)
Removed and replaced the annulus ion pump.
NOTE:
Currently there is a pump cart pumping this annulus system, will remain there until system pressure is down enough to turn on the ion pump.
J. Kissel, K. Izumi Kiwamu is making sure the online calibration filtering (currently in the "OAF" model, will eventually be in the "CAL" model) is reasonably up-to-date. In doing so, we discovered that the two ETMs have different damping loop filters installed and ON. Most filter modules are as expected, according to the original, low noise, Level 2.1 quad design (see LGO aLOG 6760). However, in FM3 of the L and Y banks of both ETMX and ETMY, there are filters called "resg1" and "+12dB" respectively. They are ON only in ETMX. After a little digging down memory lane, we recalled that in attempts to get ALS DIFF up and running last time (see e.g. LHO aLOG 15025), before we lost the arms, we had copied over LLO's damping filters' differences at the time -- described in detail in LHO aLOG 14959. However, as indicated in LHO aLOG 15037, having the filters constantly ON never got captured in any sort of configuration control, because ALS and LSC control was bouncing between using ETMX and ETMY depending on the functional-state and state-of-confusion for each test mass. We have now turned both FM3's of L and Y filter banks ON, and changed the DAMP_STATE_?_GOOD state to match the current state with those ON. We have not yet captured a new safe.snap in this configuration, but we'll do so ASAP. A note -- the ITMs do NOT have these "bonus" LLO filters installed, so FM3 is therefore OFF.
Replaced bad projector lamp on left side projector in control room. NOTE: The lamp socket internal to the projector has badly overheated and the plastic mount that holds the socket pins has lost it's integrity. If you smell smoke in the control room, this projector should be powered off. This seems to be a common problem with these projectors.