LASER IS ON
- Output Power = 28.6 W
- Watchdog is active
- System status is good
PMC
- Locked for 4 days, 7 hours
- Refl Power = 1.2 W, Trans Power = 10.2 W
FSS
- Ref Cav locked for 11 hours
- Alignment is OK, PD threshold = .96 Volts
ISS
- 12% diffracted power
- Saturated 14 hours ago.
PRY is locked (POPAIR_B_RF_18_I is around -0.14) and Yuta's measurement started. I'll leave it going overnight.
Alexa, Sheila
Tonight we decided to try to charachterize the coupling of alingment fluctuations to the error between the arm resonance and the ALS COMM lock point. We did this using the normalized PDH error signal. The frequency dependence of this spectrum is unclear- if we were staying on resonance we would just have the cavity pole, but the transfer function of the transmitted light will change as we move over the resonance. So to make a good calibration we need to lock well enough to stay on resonance. (This is why we have been trying the AO the last few nights). For tonight we concentrated on low frequency noise that is dominating our RMS, where the frqeuency dependence won't matter anyway.
We put a 1 Hz excitation onto ETMX pitch, making it large enough to see the second harmonic. We measured the spectrum of our REFL_DC_BIAS error signal when COMM was locked, and the op lev spectrum with and without the excitations. The attached screenshot shows the spectrum with and without the excitation.
Measuring the peaks due to the excitation we estimated the coupling coefficient with excitations of 2 different amplitudes, 1.7kHz/urad and 1.5kHz/urad. We also can esitmate the quadratic coupling from this data, we got 159Hz/(urad)^2 and 170 Hz/(urad)^2
Attached is a plot of linear and quadratic projections based on the Oplev data (up to 4Hz) into the REFL_DC_BIAS path. It can explain all the noise around the pitch resonance (which is most of the RMS), but not elsewhere. We had wondered if the coupling was nonlinear and some of our unexplained noise from 1 Hz-50Hz (or below 0.3Hz) was upconverted angular fluctuations. Our measurement suggests that this is not the case.
We were planning to repeat this measurement for ITMX, but so far we have been prevented by and earthquake.
At 1 Hz we have 748Hz/0.49urad OpLev motion for ITMX. (saved as references 26-29 in sheila.dwyer/ALS/HIFOX/COMM/NormalizedPDHSpectrumMarch10.xml)
The ITM oplev is much noisier than ETMX, and I was not able to get a good measurement of the quadratic coupling. In the attached plot I assuemd that the pitch coupling to frequency is the same as Yaw, and plot projections for ETM+ITM pitch and YAW, and the total. The total is high above 1 Hz because of the extra noise on the ITMX oplev, but alignment fluctuations do seem to explain all of this noise at low frequencies (not really a suprise).
We don't really need any nonlinear couplings to explain most of the noise we have, a linear coupling explains most of it.
Since no ISI transfer functions will be running tonight, ETMY overnight transfer functions were started to assess for rubbing on opsws6.
This morning I was able to take some transfer functions on the ETMX :
Top mass to test mass yaw to yaw transfer function : It was saved under /SusSVN/sus/trunkQUAD/H1/ETMX/SAGM0/Data/2014-03-03_H1SUSETMX_M0_PtoPY_WhiteNoise_0p1to10Hz.xml. Coherence is good until 4Hz.
Tested top mass to test mass pitch to pitch transfer function driving through the invP2P filter. The TF looks as a nice single pendulum below 1Hz, but looses coherence afterwards, cf attached plot.
Top mass length to test mass pitch transfer function driving through the L2P decoupling filter. It doesn't seem stable, so this one shouldn't be used for now.
Left to do for ETMX is the UIM pitch/yaw to test mass pitch/yaw transfer function, as well as y2y fitting.
ETMX chamber tripped after Arnaud clicked on a wrong button on the Quad (thanks Arnaud! 
).
After resetting the targets on the ISI, we can clearly see that the ISI didn't come back to the same position in ST1-RZ and ST1-RY.
My understanding is that this phenomena had appeared at LLO in the past. The solution chosen is to restore the previous alignment in RZ only. This fix seems good enough for now.
Targets ST1
| Before trip | After trip | |
| X | 45888.9 | 47062.6 |
| Y | 10684.4 | 7705.4 |
| Z | -22890.4 | -22874.7 |
| RX | 39593.4 | 38039.6 |
| RY | -2575.4 | -5903.7 |
| RZ | 6475.0 | 21741.5 |
Targets ST1
| Before trip | After trip | |
| X | 4542.3 | 4508.7 |
| Y | 282.9 | 442.8 |
| Z | -11459.7 | -11162.3 |
| RX | 10185.6 | 10178 |
| RY | 7344.8 | 7306 |
| RZ | 6746.1 | 5717.4 |
After SUS team was gone, we went in the BSC10 to check a potential rubbing issue that has been bothering SEI.
After backing off all EQ stops and making sure that the top mass is free, we've found that the top mass had ROLL tilt, and somewhat smaller PIT. We don't know where this came from, but in my experience TMS angle changes after transporting to the chamber.
We corrected the roll and PIT by moving top balance masses, roughly centered all BOSEMs (the only one that was left untouched is RT) and left it damped.
Note: While working with TMS yesterday, noticed that the TMS cartoon at the bottom left of the TMS screen (SUS_CUST_TMTS_OVERVIEW.adl) is backwards. The Side, F2, and Left BOSEMs are on the "front" end of the TMS. (Once I get better with medm-editing I can fix this.)
This morning while working on H1-SR3 the UR magnet/dumbbell was dislodged from the Optics mass. We have gathered up the tools and a replacement magnet/dumbbell assembly. We will attempt to glue a new magnet on tomorrow morning.
Andres & Jeff We attached the new Lower Wire Loop on H1-SR3. Set the pitch and roll of the Intermediate Mass using an optical level. Set the roll of the Optic using the optical level and lowered the Optic onto the new wire loop. The Optic is now suspended on the the new wire loop with almost zero pitch and roll.
Mitchell and I got the last corner of HEPI Actuaots attached. IAS was at the ready and noted a need to Yaw CW ~140urads. The SEI Dial Indicators suggested ~70 shift CCW from last IAS position. I thought they be better than that but at least they're in the same direction. I turned the HEPI DSCW Springs to compensate (1/4 Turn on every spring.) This put us about 20urads to go. We left it there and checked again after lunch and it looked maybe slightly better, a few urads, and this jived with some slight changes on the DIs.
The last time SEI did an elevation survey combined with the changes on the DIs since then suggest Elevation & Level of the optical table are 0.2mm high of nominal with just 0.2mm of level runout--at spec of 100urads.
With that I zero'd the HEPI Actuator IPS (Inductive Position Sensors) to less that 50 cts, most much less but it is mainly luck at that point. At the raw IPS there are 655cts/0.001" so comfortably under 0.0001". I also checked the gaps between the Actuator Plate and the Bellows Shields which form a range of motion limit and sensor protection mechanism, and these seemed mostly centered well enough. Range of motion and linearity tests will confirm if we are good there.
I'm sure Jason will put in an IAS log, otherwise, SEI/HEPI is good.
Attached are my leveling, DI readings, LoadCell numbers, Springs adjusting notes. Contact me anytime, if you want to talk about the vudoo
While Hugh and Mitchell were working on HEPI during this morning, Margot, Kate, and I did more cleaning inside of WBSC10. We wiped the ACB, viewports, and flooring again. We also wiped the barrel of the ERM more. We removed the ACB target and the ETMy-HR First Contact in order for IAS to continue alignment of the TMS through both the ACB and ETMy.
The floor in the tube nearest the purge port seems to have the most amount of particulate accumulation, although it hasn't had any cleaning attention like the BSC chamber has. We intend to take some samples and then clean it up.
This is a report about a small task that has been in Daniel's commissioning calendar for a long time (see for example alog 10451).
I checked the signals of REFL_A and compared them with the in-air ones to check if they are functional.
The signal levels seem reasonable and therefore I conclude that REFL_A is functional without a problem. See below for more details.
Comparison of the signal level:
Before doing anything, I adjusted the demod phase of REFL_A_RF45 which had not been set to a useful number. It is now set to be 5 deg. This maximized the PRY signal in the in-phase output. On the other hand, REFL_A_RF9 seemed already good and therefore I didn't change the demod phase. Then I locked the PRY and injected a 10 Hz excitation in order to compare the responses between the in-vac and in-air ones using dtt. Note that I only used the in-phase signals as the q-phases don't really give a good signal in this situation. At the same time, the DC power on the PDs were measured to be 14200 cnts and 8020 cnts at REFL and REFLAIR respectively. This means that the in-vac one should show a higher response by a factor of 1.77 due to the difference in the power falling on the diodes.
Unfortunately, I wasn't able to figure our whether S1300533 or S1300534 is in HAM1. So for now I use transimpedance gain of 600 and 730 Ohms for 9 MHz and 45 MHz respectively which should give us a coarse estimation of the signal levels.
Expected and measured ratios of the 9 MHz detectors:
Expected and measured ratios of the 45 MHz detectors:
Thomas Vo, Greg Grabeel After hearing that LLO had an alignment problem with SM1 and SM2 Thomas and I decided to look and see if we could get a visual confirmation on alignment. Taking the opportunity given by a soft valve close, we stuck a camera up to the viewports and took some pictures. One set of pictures is through the regular glass, and the other are through the Zinc Selenide. The pictures are a little blurry from the long exposure time needed to get anything to stand out, but it looks like we are still good for having the test masses in sight.
800 - Karen to EY
904 - Fil and Aaron at EY most of the day workign on cabling
930 - Betsy,Kate,Margot working EY
940 - Arnaud meas ETMX
945 - Kyle Soft close GV7
945 - Kiwamu and Yuta re-aligning ISC Table at HAM2
1301 - HFD onsite
1310 - Corey and Hugh to ETMY with IAS
Jeff, Sheila
Last night when Jeff brought the ISIs back after trips due to the first earthquake, he reset the target offsets as we have discussed doing from now on. This moved ETMX ISI RZ (yaw) by 16urad on stage 1, 12 urad on stage 2, RY (pit for TMS) by 3 urad on stage 1, and 2 urad on stage 2. This is at least the third time that we have reset the target values for ETMX, and the second time we have seen a large move. (25 urad seen in RZ in alogs 10596 10602)
If we had changes of less than a urad, either our dither alingment or WFS would be able to correct for that, if we had changes of less than about 5 urad we would still be able to find the baffle PDs easily to recover the alignment. 20 urad though is difficult to recover from. I (Sheila) would prefer waiting for T240s to settle than doing a random walk in alignment over 10s of urad.
We had a look at the other optics, and they don't seem to move that much. ITMX for example had no changes larger than 100nrad last night.
It seems like the solution proposed by Brian of keeping RZ and RY for the ETMs would solve this, but here is a plot to show what is going on.
We did a model restart of all the BSC-ISIs last Tuesday. By doing that, we restored the old target values stored into the snap files.
On ETMX, these old target values were huge compare to the natural position of the ISI. That explains why, when we reset the targets yesterday after the earthquake, the new location of the ISI is so different than last week.
If you compare the location of the ISI now with the location BEFORE the model restart, you can see that the difference is way smaller (a little big on RZ and Z though).
Assuming the frequency calibration of the network analyzer is accurate, we can compare the measured PRC length with the measured mode cleaner length. This was measured in alog 9679.
| Parameter | Value | Unit |
|---|---|---|
| FSRPRC | 2.600075 | MHz |
| LPRC | 57.6508 | m |
| FSRMC | 9.099173 | MHz |
| LMC | 16.473612 | m |
| FSRMC / 3.5 - FSRPRC | -306 | Hz |
| (1 - FSRMC / 3.5 FSRPRC) LPRC | 6.8 | mm |
Compared with the modeclaner, the power recycling cavity is about 7 mm too short. The other way around, the modecleaner is about 2 mm too long.
We hooked up the network analyzer to the timing comparator/frequency counter and set it to 40 MHz sharp at 0 dBm. The readback value was dead on, occasionally we would read 1 Hz higher. Conclusion: the frequency of the sweep is no more than 1 Hz off, even at 100 MHz.
I've redone the fits using both the magnitude and the phase. The fitting function is now the usual Fabry–Pérot reflectance function, with a complex magnitude to allow for global amplitude rescaling and global phase offset.
| Nominal FSR | Frequency (Hz) |
| −39.5 | −102 701 040 ± 200 |
| −39.5 | −102 700 900 ± 220 |
| −26.5 | −68 900 600 ± 180 |
| −12.5 | −32 500 080 ± 100 |
| 12.5 | 32 501 720 ± 110 |
| 26.5 | 68 903 940 ± 200 |
| 39.5 | 102 704 700 ± 200 |
The linear fit now gives an FSR of (2 600 073 ± 9) Hz. This is consistent with the previous fit, and anyway the total error is still dominated by some systematic, as seen by the fact that the residuals are excessively large.
Taking a systematic 400 Hz uncertainty on the residual for the 12.5 FSR measurement gives a systematic uncertainty of 32 Hz on the PRC FSR. Propagating foward gives (57.6508 ± 0.0007) m.
Measurement done at Mar 11, 13:50 UTC (6:50 local). Thank you Sheila!