These are the past 10 days trends.

After a measurement of charge on each ETM yesterday, I took a few more on each today.  Attached show the results trended with the measurements taken in April and Jan of this year.  There appears to be more charge on the ETMs than in previous measurements, although there is quite a spread in the measurements.  The ion pumps at the end stations are valved in.

I updated the SUS Drift Monitor with values from a shortish lock stretch last night, 1116855522.  In addition, I updated the threshold updating script to widen the thresholds for PR2 and BS per Betsy's suggestion.  The IMs and OMs are still showing alarm, but we assume they will come back to green during a lock.  As part of the background to get the Drift Monitor back to functional, we (TJ at the keyboard and Betsy, Hugh, and myself in the peanut gallery) reassigned the alarm severity states (.HSV, .LSV, .LLSV, .HHSV) to their appropriate values (MINOR, MINOR, MAJOR, MAJOR respectively).  At sometime during the past month, these values were lost (i.e. NO_ALARM), presumably during some bootfest. 

We need to update the appropriate database such that these values are not lost during bootfests in the future.

Rick, Peter, Jason, Jeff B.

   A series of apparent glitches and dropouts of the PSL chiller water flow caused the PSL to shut down several times. We swapped out the online chiller (Gromit) with the backup chiller (Wallace) from 05/07/15 until 05/20/15. During this time, we replaced Gromit’s Central Chiller Controllers (for both the Crystal and Diode chillers). The older turbine flow sensors, which were flagged as the source of the PSL shut downs, were also replaced with new vortex flow sensors.

   After the upgrades, we swapped Gromit back in as the online chiller and put Wallace into backup. Gromit has been running for the past 8 days without any glitches or dropouts. The turbine flow sensors in Wallace will be replaced by new vortex flow sensors. 

   The Di-Water cartridges in both chillers have not been replaced in sometime, and there was concern for their proper functioning. The attached plots show the 180 and 30-day trends for the flow rates and the conductivity of the Di-cartridge’s for both chillers. 

   The Diode chiller is functioning within operational parameters. The conductance ranges between 4 and 7 µs/cm (the low/high set points) during a 14 to 15 day period. The flow rate is very steady at 21 l/min. The fluctuations at the right of the plots are when Gromit and Wallace were swapped on 05/07 and then swapped back on 05/20. The conductance appears to be normal, although we need a longer periods of data to reconfirm the previous trends. The flow rate appears to have climbed from 21 l/min to around 30 l/min. The flows through the diodes are all normal. This appears to be a calibration issue with the new vortex flow sensors. 

   The data for the Crystal chiller appears to have the same patterns as the Diode chiller, with two notable exceptions. (1) The conductance rise and regeneration period is three to four months (vs 14 to 15 days for the Diode chiller) and (2) the flow rate for the Crystal chiller has dropped from 18 l/min to 10 l/min. Again, this is likely to be a calibration issue as the flows through the PSL components are all in normal ranges.
 
   We will discuss this calibration question with the laser group in Germany. 

The BRS was very rung up this morning so I went to investigate. It looks like the damper may have caused the BRS to ring up.

People were at End X yesterday but left around 1230 pst, where as the BRS didnt start to dramatically ring up till around 1900 pst. The damper seemed to be on before the large amplitudes seen on both the INMON and the DRIFTMON. Siesmometers aren't showing any signs of an earthquake within the past 24 hours, so that seems to be be out.

I went to EX to turn OFF the damper by uncommenting the line of code, and adjust the damper masses (about 75 degrees out of position). I left the damper OFF to allow the BRS to ring down on its own like we have done previousily.

Screenshots attached: 1st - A 4.5 hour view around the event. 2nd - 24 hour trend. In the 2nd, you can see when people were at EX and the damper seemed to relax the signals back down to normal where they stayed for a little over 4 hours before everything picked up again.

DarkhanT, RickS

We are running a short (hour or two) test at Yend.

The Rx PD assembly is back in the Rx module.  The outer beam is blocked inside the Tx module so only the inner (upper) beam is reflecting from the ETM into the Rx PD assembly.

We are trying to identify the source of variations we have seen in the received power, but not in the transmitted power.

Dan, Evan, Sheila

Tonight we started to look at the angle to length couplings of our test masses.  We injected lines into pitch and yaw on the PUMs, and adjusted the A2L gains to minimize them.  Using the math in the 40 meter alog and Jax's alog, we can estimate the miscentering from these measurements

After we had adjusted these, we saw an improvement in the spectrum below 20 Hz.  The line in the attached screen shot at 16.6 Hz with sidebands at half a hertz are the excitation.  Keep in mind that this is on the new ESD driver and we haven't redone the calibration yet, but clearly this improved the noise below 20 Hz.  

Earlier in the evening we were having difficuulty powering up because of a pitch instability at the main suspension resonant frequency that showed up in all the test masses.  We moved the QPD offsets for pitch back to what they were may 15th, (they had been changed last tuesday).  We then remeasured the miscentering for pitch only, things were a little bit better.  Once we increased the power to 17 Watts, the IFO was stable and we repeated some of the measurements.  We were able to power up to 23 Watts without seeing the instability twice, but lost the lock quickly for other reasons.

- commissioners had the IFO, working on EY

- Rick and crew returned from EY(?) early in the shift

- currently an instabillity is preventing the IFO from going beyond 10W

K. Izumi, S. Karki, J. Kissel, R. Savage, D. Tuyenbayev

Lots more work done today -- still a fire hose of measurements that we're furiously trying to understand quickly enough to make a statement about them and/or use them in our loop models, but we're falling behind the analyzing / documenting as expected.

What we accomplished today:
J. Kissel, S. Karki
Finished measurements of ETMX PCAL electronics, as had been done for ETMY yesterday (AA and AI data finished being processed, still need to process full-chain measurements; both end station's work need aLOGs)

K. Izumi, J. Kissel
Gathered Free-Swinging Michelson calibration of ETMY L2 stage between 2 and 7 [Hz] (by the usual daisy chain of measurements), tried to get L3 stage but it's just too weak -- will have to do an ETMX to ETMY propogation using the full IFO. (measurement processed, needs aLOG for procedure and results)

K. Izumi
Gathered data for calibration of ETMY L2 stage using ALS DIFF VCO (preliminary aLOG is LHO aLOG 18656, but still needs process and results aLOG)

R. Savage, D. Tuyenbayev
Compared response of standard ETMY PCAL PDs against other broadband PDs to check for high-frequency frequency dependence. Still needs more time (and an aLOG).

R. Savage, D. Tuyenbayev, J. Kissel
Begun looking at changes to be made to CAL-CS model and PCAL models. Accidentally updated ${userapps}/cal/common/models/ and found new library parts which need new connections and IPC at the top level that we don't know the details about.

Goals for tomorrow:
B. Weaver
Measure ETM charge

R. Savage, D. Tuyenbayev
Continue at EY, and move to EX comparing high frequency response of PDs.

J. Kissel, K. Izumi
Measure Simple Michelson Technique again, but propagate to stronger ETMX this time (and get all three stages), then lock of DARM to propagate from ETMX to ETMY (again all three stages)

J. Kissel, R. Savage, D. Tuyenbayev
Call up J. Betzwieser and S. Kandashamy and figure out what the heck they've done to the CAL-CS and PCAL library parts, so that we can absorb the changes and have functional front end models.

Jeff, Kiwamu,

In addition to the classic free-swing-Michelson technique, we did another calibration of the ETM responses using the ALS diff VCO.

We locked ALS diff and drove various stages of ETMs. The plan is to take out the loop suppression by using a measured open loop transfer function and calibrate data into meters through the known VCO calibration. The data and results will come later. A conclusion from todays's calibration is that the calibration of the ETMY ESD in the low voltage configuration is difficult to measure since the strength is so weak. So for the reason, we ended up measuring only the ETMY L2 stage and ETMX L3 stage. Sigh. In order to get a reliable calibration on ETMY ESD, we probably need the DARM loop closed in fully locked interferometer and need to make a comparison between well-calibrated ETMX ESD and ETMY ESD.

Adrew Lundgren has written a script that can be easily used to identify which suspensions saturate in which order in a lockloss.  The script is in USERAPPS/sys/common/scripts/ and should work for LLO as well.   The script is called with a time which can be either a gps time or any format that tconvert accepts, it checks for suspension MASTER_OUT_DQ channels that go above 2^17 for 10 seconds before or after the time given.  This may be integrated with the summary pages and/or the graphical lockloss tool soon, but now it is ready to go from the command line.  For now it is not checking things like RMs, OMs, IMs, but they can be added if anyone wants them. 

Thanks to Andy for putting this together so quickly, and to Jamie, Johnathan Hanks, and Greg Mendell for helping to get it running here.  

Keita, Kiwamu, Daniel, Elli

We have measured the SRC length to be 56.013+/-0.0035m.  This is 4.8+/-3.5mm longer than the design SRC length of 56.008m.   
This result is consistent with an earlier measurement of the LHO SRC length of 56.015(+/-.005)m (alog17451).  (This earlier measurement which was considered questionable due to signal-to noise issues and a lack of SRMI angular control.)

Method:
See alog 18263 DRMI was locked with wavefront sensors on for alignment control.  An auxiliary NPRO on IOT2R was sent into the interferometer through the back of IM4.  The Aux laser was coaligned with the PSL using the PSL transmission through IM4 onto IOT2R, and the prompt reflection of the Aux laser onto IM4. The auxiliary laser frequency was locked at a frequency offsets to the PSL using a PLL, and this frequency offset was swept to measure the Aux laser power reflected from DRMI as a function of frequency.

The DRMI reflection coefficient is a function of frequency because Mich reflectivivty varies with frequency. This is due to the 8.9cm Schnupp asymmetry, and Michelson reflectiviy = cos(2*pi*f//c*ScnuppAsymmetry). When DRMI is locked, the PSL light is totally reflected from Mich, and DRMI reflectivity looks the same as the PRC reflectivity.  At 842.7 MHz offset from the PSL frequency, Mich transmissivity is 100%, and DRMI looks like a cavity between the PRM and SRM mirrors and with the length of SRC+PRC combined.  As the PRC length is already known (alog 10642), we can measure the DRMI reflectivity around 842.7MHz by sweeping the Aux laser through +/-842.7MHz offset from the PSL frequency.

The reflected  beatnote of the PSL and the Aux laser read out at relfair path. The frequencies of the transmission dips closest to +/-842MHz were fitted using a lorentzian function. The number of fsrs (N) between peaks at ~+842MHz and -842MHz were determined.  This determines the fsr and the length of the combined PRC/SRC cavity.

df=positive_peak_frequency-negative_peak_frequency
vfsr=N*df
LSRC=c/2/vfsr-LPRC;

Analysis:

Graphs of the reflected beatnote power vs aux laser frequecy offset are attached.  There is an 11MHz osciallation in the reflected power which is not yet explained.   The phase has had a linear phase term removed, but is not continous from sweep to sweep, perhapse due to small changes in the alignment of the aux laser to the psl over time.  There are peaks which appear every fsr, which I am assuming ar ehigher order modes, but I haven't looked closely at these yet.
Peaks were fitted at -842.14(0.02)MHz and +841.933(0.02)MHz, graphs attached.  
The number of fsrs between these peak frequencies is 1277.  (If the number of fsrs wer off by +/-1, the cavity length would differ by +/-10cm.  We had already estabilished from previous measurements that the SRC length is not off by this much.)
This corresponds to a combined PRC/SRC cavity vsfr=1.319MHz, and length=113.664(0.0027)m.  The PRC length was already measured by Evan et al (alog 10642) to 57.6508+/-0.0007m, so the SRC length is 56.013+/-0.0035m.
 

[Morning Meeting]

SUS BSC 1 2 3 down

[Safety Meeting]

DON'T GET HURT!

[Activities]

8:41 Jeff & Sudarshan to EX (Calibration work)

8:45-9:20 Richard & Fili in CER working ITMX SUS

9:35 Richard to SUS 2B power (Electronics room)

10:00 Jeff & Sudarshan temprary back

10:12 Jeff & Sudarshan back to EY

10:28 Richard back

10:46 Rick et al. to EY to measure transfer functions

11:48 Fred and a guest to LVEA

12:16 Fred back

12:42 Jeff & Sudarshan back

12:58 Jeff B. to optic room

14:08 Kyle rolled up receiving door

14:17 Kyle done, receiving door closed

Happy Calibration Day

Will taking some current measurements for SUS racks this morning, Richard noticed that the ±24V power supplies for HAM4/5 (ISI Coil Drivers) had some oscillation in the current meter. We power down the ISI coil drivers (HAM 4 and 5), and the oscillation in the current meter disappeared. We powered the ISI coil drivers back on and oscillation in the current meter is no longer present.

Evan, Kiwamu, Sheila, Jeff

We noticed that we weren't really driving ITMX PUM.  Evan and I went to the racks and saw that the DAC outputs were changing, but the LED that says DAC WD next to the DAC input was not lit and there was nothing coming out of the AI board.  This is probably why Dan was unable to damp ITMX violin modes last night.

Dan, Kiwamu, Evan

Summary

Tonight we worked on getting the interferometer back to its low-noise state. We are stable at 10 W, but there is some instability at higher powers.

Details

ITM steering

First, at 3 W we manually steered the ITMs to a good recycling gain (38 W/W), and then updated the TMS QPD offsets. We also locked the arms in green, adjusted the green QPD offsets for maximum buildup, and then updated the ITM camera references. Then we re-enabled the ITM loops in the guardian. This allowed us to power up all the way to 21 W without significant degredation of the recycling gain.

After that, we were able to consistently engage the ASC with the guardian.

Power-up issues

However, we found that at 21 W the interferomter suddenly unlocks in a matter of minutes. There seems to be no instability in the arm or sideband buildups before the lockloss. We looked at OMC DCPD signals for signs of PI, but we did not see anything ringing up during any of our short high-power locks. Some times to look at are 02:29:50, 02:59:50, 04:57:30, 06:55:00, all 2015-05-26 UTC. But any of the other 21 W locklosses in the past 12 hours follow this pattern.

We measured the OLTFs of PRCL, MICH, SRCL, and DARM before and after powering up, but they all look fine and did not change with power. For CARM, we start at 3 W with a UGF of 14 kHz with 47° of phase. Then during power-up, the electronic gain is automatically adjusted to compensate for the increased optical gain. The algorithm for this was shooting a little high, so after power-up the UGF was more like 27 kHz with 30° of phase. This is probably fine, but we adjusted the algorithm anyway, so that the UGF is placed at 19 kHz, with 45° of phase. Anyway, this did not solve the lockloss issue.

We also tried locking at some lower powers. At 15 W the interferometer lasted for about 15 minutes before unlocking. At 10 W, the lock time seems to be indefinite (at least 90 minutes).

DARM crossover

Using FM9 in ETMY L1 LOCK L (zero at 2 Hz, pole at 5 Hz), we were able to push the L1 crossover from <1 Hz to 1.7 Hz by adjusting the filter gain from 0.16 to 0.31. Measurement attached, showing before and after. This is not included in the guardian. By pushing up the crossover, the rms drive to L2 decreases from >10000 ct to about 6000 ct or so.

Other

For the record, we did not notice any kicks to the yaw of IMC REFL tonight.

Sheila, Alexa, Evan

Summary

We have transitoned CARM from digital normalized REFLAIR9I to analog REFLAIR9I, with a 4 kHz bandwidth and 50 degrees of phase. An OLTF is attached [the last data point is spurious, so ignore it]. This lock started at about 2015-02-09 12:24:00 UTC. We are leaving the IFO locked.

There is plenty of phase to push the bandwidth higher, but we have encountered large offsets induced by switching on the common-mode and summing-node boards.

We can also improve the low-frequency fluctuations of the CARM error signal by introducing an integrator somewhere; we need more dc gain.

Details

Analog REFLAIR9I is plugged into input B2 on the summing-node board (SNB), with polarity "off". The output of B goes into input #2 on the common-mode board (CMB), with positive polarity. Digital normalized REFLAIR9I is plugged into input A1 on the SNB, with polarity "on". The output of A goes to input #1 on the CMB. [See LHO#16489 for a review.]

According to our reckoning, the shape of the digital CARM loop at the start of the transition is roughly 1/f above a few hertz. At a few hertz and below, it has a number of boosts and integrators which make it tricky to engineer a stable crossover with the analog signal.

Transition procedure is as follows, starting right after the guardian has brought the interferometer into resonance.

• With the B2 gain at 0 dB on the SNB, input B2 engaged on the SNB, and the input #2 gain at 0 dB on the CMB, we engage input #2.
• Step up B2 gain to 8 dB on the SNB.
• Turn off double integrator in digital CARM path (FM2 in REFLBIAS: it is two zeros at 2 Hz and two poles at 0.01 Hz).
• Step up B2 gain to 14 dB on the SNB.
• Remove zero-pole pair in digital CARM; it is a 1.6 Hz pole and 20 Hz zero. We remove this pair by engaging FM1 on REFLDCBIAS.
• Step up B2 gain to 17 dB on the SNB.
• Engage analog compensation filter in the CMB. It is a pole at 40 Hz and zero at 4 kHz.
• Ramp down digital CARM gain all the way to zero using the input matrix.
• Increase the analog CARM gain by 10 dB using the CMB slider. This is the point at which we saw disconcertingly large offset jumps. The total jump was 6 ct of REFLAIR_A_RF9_I_NORM. For comparison, the peak-to-peak fringing of this signal during digital CARM is 6 ct pkpk.
• We also saw a huge offset jump when turning off A1 on the SNB, which analogizes the digital CARM loop. In retrospect, this is probably because we had an integrated history on the output of this loop (since we turned the loop off at the LSC input matrix, not at the loop's output).
• To tune the error signal offset to zero, we have shifted around the common offset slider on the CMB

Also, the use of DHARD WFS (pitch and yaw) has removed the need for touching up the ETMs. However, since the AS36Q WFS feedback to the BS has not worked for the past couple of days, the BS had to be touched up by hand every so often.