Kyle, Bubba

Found the leak to be coming from the pump shaft -> Closed valve at pump inlet -> Using absorbent mats to soak up liquid (~1 gallon spill) -> Added water into chilled water system -> Will order pump replacement

The output from this booster pump supplies the Kobelco compressor, AHU3 hallway taps (no longer used) and the LVEA (no longer used) -> This chilled water branch "dead heads" (no flow) when the Kobelco compressor shuts down as the solenoid water valves close when the compressor is deenergized. 

Expect substantial 1-3Hz seismic noise from Hanford hauling on both day shift and swing shift today (11/7).  No Saturday activity is expected.  The daily numbers of truck trips in the current era are higher than S5 levels, especially on swing shift, and are comparable to or higher than S6 levels.  I drove to PNNL on Stevens in the middle of the day yesterday and saw nearly a dozen dumpster-carrying trucks traveling either north or south in a 10-minute span.   

3IFO:  inventorying OpLev; transferring SUSs from temp containers to permanent ones; working on viewports; SEI assy started; Mitchell packing masses; bifurcation preperation for LVEA started (to go into effect on Monday) see LIGO Document M1400342-v2

Commissioning: Will start @ 10:00 AM today

SEI: Nothing to report. Business as usual.

CDS: work @ EX to end at 10:00

SUS: couldn't hear what was said.

Diff Power seemed to be creeping towards the high 9% range. The REFSIGNAL voltage was set to -2.04 from -2.02. The result is 7.5% diff power.

Alexa, Evan

In preparation for locking DRMI with reduced power on REFLAIR_B, there is now a BS1-1064-90-2037-45P (90 % reflector at 45° for p-pol) ready to go on ISCT1. It is not yet in the beam path. There is also a dump ready to go.

There is maybe some confusion about the polarization state on the table. LHO#7032 says it's s-pol, but (1) at least a few of the 45° optics on the table are marked 45P, and (2) we initially tried to install BS1-1064-90-1025-45S (90 % reflector at 45° for s-pol), and we got 10 mW / 27 mW = 37 % transmission rather than the expected 10 % transmission. We should go out there with a PBS and see what's going on.

After installing the s-pol optic, we did some resteering of the yaw on the REFL-M3 mirror (see D1201103) in order to recenter the beam on the PD. When we removed the s-pol optic, we steered it back.

Betsy, Travis

Attached are the results from the first round of testing of this QUAD.  What we see:

1) Very poor coherence at low f which I had a hard time improving

2) Some cross coupling between T and R on the main chain

3) Some minor cross coupling between some P and L on the main chain

4) The 3rd L mode or 2nd P mode is split and the 2 are cross coupled on the reaction chain

2449.25 Hz line (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=14855) is visible in BS oplev PIT, but not in BS oplev YAW nor ITMX, ITMX, PR3, SR3, even when no LSC feedback goes to BS.

That line in OL signal becomes bigger when the IFO is in-lock even with the butterfly band stop, but the OL damp also seems to excite the motion at an amplitude that is comparable to the LSC signal through the band stop (attached right bottom).

Based on these observations, I moved the butterfly notch (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=14898) from M3 ISCINF to M2 coils so that everything is stopped (see the filter settings in the attached).

K. Venkateswara

Yesterday I had added a pre-amp to the temperature sensors on the Gnd_T240 and BRS. The gain increase should have been roughly 50 * 24/9 ~ 130. The attached trend seems to indicate this is correct as compared to the one in 14872.

The attached pdf shows the new ASD from last night. The noise seems to have only improved by ~2ish for the BRS and not much at all for the T240. A side by side comparison might differentiate sensor noise/pick-up/real temperature background though I suspect it is not real.

The ADC noise going to 0.5 mHz is described in Jeff's SEI alog: 614.

For the earlier case (gain of 0.2 Volts/Kelvin), the ADC noise was a factor of ~2 below the measured noise floor at 10 mHz. In the present case, the ADC noise should be a factor of ~200 smaller than measured noise at 10 mHz.

VM server hosting alog, awiki, SVN, and CDS-Bugzilla hung overnight. I captured the crash dump screen and logs this morning then restarted host and guests. Services restored around 9AM PT.

no restarts reported

J. Kissel, S. Dwyer, A. Staley, N Smith

Continuing Shiela's investigations from last night (see LHO aLOG 14883), we put our heads together to figure out why we're having so much trouble with the ALS DIFF control. I attach plots comparing what is currently installed against when I last was involved with the ALS DIFF design (see G1400146, and the subsequent design that was used never got published, but was designed using ${SusSVN}/trunk/QUAD/Common/FilterDesign/HierarchicalControl/DARMmodel_ALS_20140428.m). Note this is also around the time that we increased the UIM driver strength by a factor of 4, and this WAS included in my 2014-04-28 design.

Some Comments and History that I think has caused in the current badness:
- After initial installation by Kiwamu (see LHO aLOG 11665), Stefan, Sheila and Kiwamu had lowered the UIM / TST crossover a bit, from 2-ish [Hz] to 1.5-ish [Hz] (see LHO aLOG 11899). From that entry, "These tweaks served to (1) to move the elliptic filter's gain peaking bump out of the way of the 10 [Hz] features in the input noise, and (2) roll off the low-frequency end of the test mass drive faster." These adjusted filters are shown on pg 3 and 4 of the attached, shown in solid lines. The dashed lines are the original filters. One can see there's a good amount of phase action and amplitude ripple around 10 [Hz]. The cross-over action happens over a wide frequency range from 0.6 to 20 [Hz].
- At the time, we were mystified why we were never able to get to the 15 [Hz] UGF I'd designed, but we moved on before figuring it out. With some finagling, one could only get the UGFs to 5 to 10 [Hz].
- Over the course of a few weeks, Stefan, Sheila, Arnaud, and Keita began to add tweaks and patches to the plant-inversion portion of the distributed hierarchical design. This is the source of the "invL2LNEW," "patch," "LISOfit" "invL2L1," "invL2L2," "MatchedinvL2L" filters that are now used. It's unclear if this completely solved the stability problems, but it tweaked the phase in the right regions enough to certainly help. Sometimes.
- This was followed by Arnaud pioneering the length-to-pitch decoupling filters, but those installs never really went well (see, e.g. LHO aLOGs 11952, 11849, 11832).
So -- as we left ALS DIFF before the summer vent, we could only ever get the UGF up to 5 to 10 [Hz], had trouble with its stability and cross-coupling to pitch, had installed a whole bunch of high-Q plant compensation filters. Indeed, these very-precise compensation filters were measured specifically for ETMX, and then copied and pasted over to ETMY (dubious).

- Quite a bit after this, after the summer vent, we (discovered / became confident) that the actuation strength or the ESDs were lower than I modeled by a factor of 2-to-4 (see, .e.g. LHO aLOG 12220) due to charge plaguing the electrostatic drive system. 
- Further, not only is it weaker by a factor of 2-4, but the strength of the ESD *varies* on the hour timescale because of continuous charge noise from ion pumps, requiring the cross-over between the UIM and TST to constantly need adjustment (needed both at LLO and LHO, but never really reported), and (I believe) occasionally moving the cross-over into instability.
- Further, further, because the charge on the quadrants evolve differently, which mean the length-to-pitch coupling is constantly evolving for this stage. We currently do not have *any* compensation for it (frequency dependent or independent).
- Distracted elsewhere, I never got back to modeling whether one could get a stable, 10 [Hz] UGF ALS DIFF loop, that did not saturate the SUS DACs. Not to mention, ground motion / SEI performance has evolved. As such, we haven't changed the cross-over of the distribution filters for the weaker, time-dependent, ESD drive.
- After finding that the highest vertical and roll modes were getting rung up with lock-acquisition, and saturating actuators, high-Q notches were added at 9 and 13 [Hz]. First to the DARM filter bank, and then moved to the UIM stage (LHO aLOG 14672). These are the "BandstopBR" that are now used in the UIM plant inversion filters. These cause substantial phase distortion near (a) the constantly evolving UIM / TST cross-over, and (b) the unity gain frequency of the loop depending on where they lived. NOTE: Sheila did NOT include these notches in her open loop gain plot (pg 1).

So things we know now that should aide new design considerations:
- The ESD actuators are weaker by a factor of 2-4, and they vary in time. 
- So we need lots of gain margin both at the cross-over and the overall loop UGF.
- We should try to decrease the wide-frequency range impact of the UIM / TST distribution filters.
- We need 9 and 13 [Hz] notches in the length control path, because lock acquisition impulses cause them to ring up.
- Length-to-angle, though probably does not play a roll in the ALS DIFF loop stability at 10 [Hz], it does play a roll in the slow alignment fluctuations. In this case "slow" is both at 0.15 [Hz] as well as on the "DC drift," minute time-scale. It's unclear which stage is causing the problem.

  In order to see the effects of glitches in the BS oplev damping I requested that the servo be turned off for an hour yesterday.  
The attached figures show the effects of turning off the servo.
  
1) The spectrogram shows the relative change in the pitch, yaw and sum spectra when the servo is turned off at about 1900s and turned on again at about 5000s.
     1a) Note the low frequency kicks which both the pitch and yaw servos are introducing due to glitches in the laser power.  Stabilising the laser power may benefit this oplev.
 
2) The ASD plots show the change in the spectrum when the damping is turned off. 
     2a) The Yaw damping is good over a broad range of frequencies.
     2b) The pitch damping loop requires to be tuned further to reduce the servo bump between 2 - 6 Hz
     2c) The pitch loop also has slightly excess noise at low frequencies.

 [Hugh R.  Suresh D.]


     Yesterday we swapped out the HAM3 oplev laser (Sl. 122-1 was replaced by Sl. No. 199).  However the Sl# 199 which had behaved well in the lab for four days chose to go into wild 100% power drops when placed in LVEA.  The period between drop outs increased gradually as the laser approached thermal equilibrium (see the attached pic). However this was not a stable configuration so I brought it back to the lab and found that the problem was with the laser temperature servo.  The power drop outs went away after a bit of tweaking of the servo gains and the set point (which was too high).  

      The Sl#199 has been replaced back in the HAM3 oplev and I am monitoring its performance.  

K. Venkateswara

Sensor correction on X and Z at ETMX was left on last night. I turned it off this morning at 8 am as Filiberto and I were planning to work in the EX VEA. I modified the temperature sensors to take in +/-12V from the PEM power supply (thanks to Filiberto) and added a differential amplifier (with gain~50) to it.

In the afternoon, wind speeds were routinely hitting 50 mph. I've attached a pdf showing the ASD of the ground motion, BRS output and Stage 1 motion and some interesting coherences. Sensor correction was off in X and Z during this period.

Sensor correction has now been turned on and I will add plots of the result later.

This entry summarized the status of REFLAIR_B signals. REFLAIR_B is the broadband photodetector, D1002969, mounted in reflection of the interferometer which is responsible for measuring the 3f signals at 27 MHz and 136 MHz in DRMI. The 3f signals are relatively weak, especially at low modulation depth. This has lead to a low signal-to-noise ratio at sub milliampere photocurrent and distortion problems above a milliampere. The problem of saturation by out-of-band intermodulation products was recognized early on a LLO and fixed with a diplexer amplifier, D1300989.

The situation at LHO and LLO are essentially the same.

• LLO operates with 0.2 mA of photocurrent and can lock both the DRMI and the full interferometer. The signal-to-noise is not great and sensor noise dominates the 3f locking signals above 20 Hz. The modulation depth is three times the design value and will generate some excess light at the antisymmetric port.
• LHO operates around 4 mA of photocurrent and can lock DRMI with a better signal-to-noise ratio in the 3f locking signals. However, the signals have a strong dependency on the incident power, see here.

Koji has recently measured the second order intermodulation products of the RF chain in the broadband photodetector and found the second order intercept point to be rather low, around 30 dBm. This is maybe not too surprising considering these RF amplifiers are single transistors or Darlington configurations operated around a fixed DC working point. No specification of the IP2 is given in the datasheet.

This leads to the conclusion that 3f signals at LHO are predominantly due to intermodulation distortion in the RF amplifier chain and not due to the optical signals. This obviously works just fine for the DRMI, but probably doesn't give the required immunity to the carrier mode for full interferometer locking.

Possible solutions:

• Try to operate LHO at low photocurrent and re-optimize the DRMI locking signals.
• Removed the first amplifier stage from the broadband photodetector. This will remove 22 dB of gain and hopefully greatly reduce the RF distortion. The dark noise of the photodetector will increase by about 3 dB. At 27 MHz we should be shot noise limited with 0.2 mA of photocurrent. So, this should have little effect on the sensor noise. However, at 136 MHz the shot noise limited sensitivity is around 2 mA, so we should see a ~1 dB increase in the noise level.
• Get the 3f photodetector which is based on a tuned design into fabrication.

Increasing the modulation depth and reducing the photocurrent at the same time will not improve the situation, since the distortion depends on the absolute signal strengths of the individual RF lines. However, removing the first amplifier stage should give us enough room to further increase the modulation depth and improve the signal-to-noise ratio. Using a high modulation depth during locking may require an adjustable EOM driver, such as the, D0900760.

Alexa, Nic, Evan, Dan, Sheila

Tonight we went back to trying to get ALS DIFF working well.  We aren't sure what the problem is. 

First Nic checked that the gain of the 2 ESDs were the same.  The old X gain in L3 LOCK L was 0.2, the new one is 1.12 The old Y gain was 0.7 the new one is 0.384.  We also checked the crossover by using the green control signal. 

Attached are some plots, based on the suspension model that Jeff used to design the DIFF loop, and filters downloaded from foton. This is using none of the boosts for DIFF, which is how we have been running the last few nights without being able to use the ESD.  The two plots on the left are the cross overs for our loop, and the open loop.  We can use these plots to compare what we have now to what Jeff originally designed, (G1400146-v2)  We also copied the livingston filters, see alog (12590), their crossover is the third plot while their open loop (we added a scaling factor to get the right ugf) is the last plot on the right. 

Btoh ESDs are driving, but we seem unable to use them in the loop. 

K. Venkateswara

I had installed temperature sensors on BRS and GND_T240 yesterday as described in 14825. The first plot shows the trend over a day along with the PEM_VEA temperature sensor. The count to Kelvin conversion was expected to be 1.56e-3 K/count. This seems roughly consistent with the temperature of the T240. The BRS temperature sensor shows a lower magintude and a phase offset due to it's extra thermal shielding and larger mass.

The attached pdf shows the ASD of the temperature sensors and the coherence between them and their respective instruments. The temperature sensors are mostly limited by ADC noise. An op-amp based pre-amp of 50-100 gain would be useful. BRS_RY_Out shows a little bit of coherence near few mHz while T240 X, Y and Z show no coherence with the temperature sensor.

I wanted to try turning on HEPI sensor correction at EY this morning, but I've run into an issue. When I turn on just the new Mitt_sc filter no numbers come out of the outputs. However, when I turn on the filters associated with the fir sensor correction, numbers come out. Even when I just turn on the path, with no filters engaged, numbers come out of the output block. Something about engaging the sensor correction filter completely cuts the signal. I will try copying the filter to a different fm when I get a chance.