Last night I measured the change in spherical power in ETMX during a 50 minute, 25.5W lock stretch (Started ~23 Jul, 00:05:00 UTC) using the same method last night's measurement,  see alog 19835.  The change in spherical power was 20 microdiopters, which means 21.2mW of power was absorbed.  According to the ASC_TR_X_A/B PDs the power in the arm was 132kW (+/- 15%), which puts the absorption in the ETMX at 160(24)ppb.  The absorption of this optic is 330ppb, according to the galaxy website, so our measurment does not agree with this previous value.

Attached is a plot of ETMX and ETMY spherical power change during this lock stretch.  There are some big glitches in the HWS spherical power, which correspond to where I briefly closed the green beam shutters. The ETMY spherical power looks dodgy.  I will adjust the misalignment of the green beam onto the ETMY and see if we can get a decent measurement.

Things that probably happened, but of no impact to the IFO:

- WP5377 - Bubba, fan, LSB

Things that happened:

- EY to check SUS ESD cables, Andres, started 8:34AM, done 10AM, no cables changed

- WP5379 - JeffK, SUS and SEI IPC - done 9:00AM

- HEPI EY transition, Jim, started 9AM, done 10:49AM

- HEPI, Hugh, to EY, started 10AM, done 10:49AM

- ETMX charge measurement, Leo, started 9:50AM, done 10:54

- HEPI blend filters, Jim, EX, done 10:55

- WP5381 - Richard, Vault Seismometer, started 9AM, done 10:43AM

- High Bay door opened, Andres, 11:10AM

- WP5378 - Daniel, Beckoff, started 9AM, done 11:25

- PEM, mid-Y and EY, Vinney, started 10:46AM - done 11:34AM

- WP5350, Jason, PSL PMC, PMC and FSS electronics, Done 12:30

- TCS, Nutsinee, TCSX HWS align, started 10:50AM, Done 12:30

- WP5376 - Jonathan, CDS EPICS Gateway, started 8:24AM - assumed done

- ETMY charge measurement, Leo, started 10:50AM - assumed done

- ETMX PCAL, Sudarchan, started 9:58, Done 12:57PM

- WP5380  - JeffK, CAL-CS, started 12:54PM, done 12:57PM

- DAQ NDS0 full reboot, Dave - currently in process

Things that are waiting for a window of opportunity:

- WP5349, Filiberto, LVEA Cosmic Ray Detector, started 8:37AM, still work to do if there's a window, ~1 hour

- Low ESD at ETMX, Filiberto, still work to do if there's a window, ~30 minutes

Because of the clipping on both edges (left and right) on the first mirror, this is as pretty as it's gonna get. An in-air solution that could possibly be done is to replace the first few mirrors with larger ones. The Hartmann plate is put back on.

Richard M. Vinny Roma,

This morning we pulled our wagon of toys out to the vault to installed the STS-2 seismometer and return the Magnetometer coils to the vault.  After getting lost in the desert we were able to locate the Vault.  The seismometer was installed and cabled.  We know there are signal problems but that can be addressed later.  Getting all the material out to the vault before it got too hot was the goal for today.  After Gerardo powered up the battery charge we had power to the fiboxes and Vault so signals to the mid station.  I was able to confirm the cabling for y and z channels but not x as it is railed at the mid station.  I will continue to work on this system to get all of the signals working.  Probably will need another excursion to the vault to push the centering servo button.

Thank to Vinny for all his help.  I would still be out in the desert had he not helped.

On Tuesday the fluid level in the EndY HEPI Reservoir was found to be 1/2" lower in just one week.  As I suspected, a leaking schrader valve was the problem.  All seven accumulators on the EndY system are at the same pressure as last week except the one on PRESS2 at the pump station.  It was exactly zero.  After charging, the saliva test showed a very suttle leak and tightening the schrader valve was repeatedly not successful.  The valve was replaced and it seems to be holding now.

This accumulator is charged to 78 psi and losing this one unit is responsible for the entire 1/2" fluid drop.  I can imagine the relation between accumulator pressure and fluid level in the reservoir is maybe not linear.  But maybe close, so at the ends, to maintain the spec of 60-93% accumulator charge, a fluid drop of only ~3/16" could be too much.  But this would be the case if it is only one accumulator.  Many could be at 80% say and we might hit the 1/4" fluid drop threshold.

Let's make this easy: if there is no observed fluid drop, the accumulators are likely fine.  If the level drop is more than 1/8", that is likely outside the typical temperature fluctuations and the system should be checked for actual fluid leaks and accumulator charge loss.

Given that this accumulator is before the second laminar flow resistor and the 3rd accumulator on the pump station, and, remember there are two more accumulators at the chamber before the HEPI Actuators, I suspect this one accumulator loss will have had little affect on PS pressure fluctuations coupling into platform motion.  But, that will be determined by data rather than supposition--so data to come.

The serial port of the Trimble Thunderbolt E GPS has been connected to the second port of the serial concentrator. (The third port doesn't seem to work.) The default baud rate is 9600 8N1 which is what we are using in the EtherCAT terminal as well.

Attached are the new auto-generated screens. An error will be generated, if the GPS is not synchronized.

GPS user's guide: E1500318

To fix the problem of accidental PUM/ESD crossovers near the violin mode resonances, the PUM is now rolled off more aggressively above the crossover (see attachment of EY L2 LOCK FM6 vs FM7, where grey is old and purple new).

Previously, the PUM had an f² plant inversion out to about 600 Hz. It is now more like 300 Hz. There is also a broad notch around the first violin mode just to make sure that we do not have an accidental crossover there.

DARM OLTF attached (blue and red are essentially part of the same measurement). The high end of the phase bubble has flattened out a bit.

The PUM/ESD crossover was remeasured and was found to be satisfactory (attachment). Additionally, the rms drives to the three stages seem to be acceptable as well (attachment), although these were taken during low seismic activity.

The guardian request and state was DOWN when I arrived.

I had some trouble with tuning the VCO to manually find the IR resonance in the CHECK_IR state. The wiki instructions said to use the LSC overview screen but should have said the ALS overview screen. Ed has updated them. I think I was also using the wrong slider. I was using the 'Tune Ofs (V)' slider and it was fighting me. I think I was supposed to use the 'Set Off (Hz)' slider. I will confirm this with commissioners and add this to the wiki.

It eventually reached DRMI_LOCKED twice. In both instances it lost lock on its way to ENGAGE_ASC. The first time was from PREP_TR_CARM. The second time was from CARM_ON_TR.

Dave, Daniel

(I meant to post this a couple of weeks ago but hadn't gotten around to it.) I compared ~2 hours of the 1PPS signal from the old GPS clock installed in EY to the aLIGO Timing Distribution System's 1PPS signal and found, as expected, a near-constant time difference of order 100 ns (likely attributable to antenna and 1PPS cable length). The jitter, which is the more important feature, was nicely contained to 3 clock cycles, with a standard deviation of no more than two clock cycles (the narrow bands in the histogram are due to the comparator's measuring time difference based on clock cycles).

The 1PPS signal was present from precisely 6-23 19:52:34 UTC (12:52:34 local) to 6-23 21:52:29 UTC (2:52:29 local), a total of just under 2 hours. I'll follow this up with a long-term timeseries and histogram showing the time differences between aLIGO Timing Distribution and the new GPS clocks installed at both end stations.

We observed broadband coherence of OMC_DC_SUM with ASC_AS_C_LF_SUM and ASC_A_RF36_PIT. We made some numbers and plots, using the 64kHz version of the channels.

First the measurements we made on OCXO oscillator:
- ASC_AS_C sees a RIN of about 5e-7/rtHz above 100Hz (either from H1:ASC-AS_C_SUM_OUT_DQ or from H1:IOP-ASC0_MADC6_TP_CH11). The same is true for its segment 1.
- The calculated shot noise RIN at 20mA (quantum efficiency 0.87) detected is 4.0e-9/rtHz.
- The 4.0e-9/rtHz agrees with DCPD_NULL_OUT_DQ's prediction (8.0e-8 mA/rtHz/20mA).
- DCPD_SUM_OUT_DQ sees a slightly elevated RIN of 4.6e-9/rtHz (9.2e-8 mA/rtHz/20mA).

- The RIN in DCPDA (H1:IOP-LSC0_MADC0_TP_CH12, corrected for the whitening) is about 5.9e-8 mA/rtHz, or RIN = 5.9e-9/rtHz at 20mA/2diodes (~15pm DARM offset)...
- ...or about 3.3e-8 mA/rtHz or 1.2e-8/rtHz at 5.7mA/2diodes (~8pm DARM offset).

- ASC-AS_C_SEG1 (H1:IOP-ASC0_MADC6_TP_CH11) and OMC-DCPD_A (H1:IOP-LSC0_MADC0_TP_CH12) shows a coherence of 0.053 at 20mA, suggesting a white noise floor a factor of 0.23 below shot noise.
- At 5.7mA the same coherence is about 0.13, i.e. the white noise floor is a factor of 0.39 below shot noise.
- These two measurements are in plot 1.

- Taking the last two statements together, we predict a coherent noise of
  - 5.9e-8 mA/rtHz *0.23 = 1.4e-8 mA/rtHz at 20mA/2diodes (~15pm DARM offset)  (RIN of coherent noise = 1.4e-9/rtHz) - The pure shot noise part is thus 5.7e-8 mA/rtHz
  - 3.3e-8 mA/rtHz *0.39 = 1.3e-8 mA/rtHz at 5.7mA/2diodes (~8pm DARM offset)  (RIN of coherent noise = 4.5e-9/rtHz) - The pure shot noise part is thus 3.0e-8 mA/rtHz.

- AS_C calibration:
 - 200V/W (see alog 15431)
 - quantum efficiency 0.8 (see alog 15431)
 - 0.25% of the HAM 6 light (see alog 15431)
 - We have 39200cts in the AS_C_SUM. Thus we have
   - 39200cts / (1638.4cts/V) * 10^(-36/40) (whitening) / (200V/W) = 1.89mW and AS_C. (shot noi
   - 1.89mW/0.025 = 76mW entering HAM6. I.e. we have slightly more sideband power than carrier power (Carrier: 27mW in OMC transmission).
   - Shot noise level on AS_C_SUM is at 2.0e-8 mA/rtHz, corresponding to a RIN of 1.6e-8/rtHz. I.e. the coherent noise seen at 5e-7/rtHz is high above the shot noise. Dark noise TBD.
   - The light entering HAM 6 has a white noise of 5e-7/rtHz*76mW = 3.8e-5 mW/rtHz 
    

Bottom line:
 -We have ~1.4e-8mA/rtHz, or 1.9e-8mW/rtHz of coherent white noise on each DCPD.
 -It corresponds to 3.8e-5mW/rtHz before the OMC, i.e. the the OMC seems to attenuate this component by 2000.
 -This noise stays at the same level (in mW/rtHz) for different DCPD offsets.


Next, we switched back to the IFR for testing. plot 2 shows the same coherences (all at 5.7mA / 8pm DARM offset), but on the IFR. Interestingly now AS_C and AS_A_RF36 start seeing different noise below 2kHz. We convinced our selfs that the higher excess noise seen in AS_A_RF36 is indeed oscillator phase noise from the IFR - so that is clearly out of the picture once of the OCXO. (Evan will shortly log the oscillator phase noise predictions.)


64k Channel list:
H1:IOP-LSC0_MADC0_TP_CH12:     OMC-DCPD_A  (used in plot)
H1:IOP-LSC0_MADC0_TP_CH13:     OMC-DCPD_B
H1:IOP-LSC0_MADC1_TP_CH20:     REFLAIR_A_RF9_Q
H1:IOP-LSC0_MADC1_TP_CH21:     REFLAIR_A_RF9_I
H1:IOP-LSC0_MADC1_TP_CH22:     REFLAIR_A_RF45_Q
H1:IOP-LSC0_MADC1_TP_CH23:     REFLAIR_A_RF45_I
H1:IOP-LSC0_MADC1_TP_CH28:     REFL_A_RF9_Q
H1:IOP-LSC0_MADC1_TP_CH29:     REFL_A_RF9_I
H1:IOP-LSC0_MADC1_TP_CH30:     REFL_A_RF45_Q
H1:IOP-LSC0_MADC1_TP_CH31:     REFL_A_RF45_I


H1:IOP-ASC0_MADC4_TP_CH8:      ASC-AS_A_RF36_I1
H1:IOP-ASC0_MADC4_TP_CH9:      ASC-AS_A_RF36_Q1
H1:IOP-ASC0_MADC4_TP_CH10:     ASC-AS_A_RF36_I2
H1:IOP-ASC0_MADC4_TP_CH11:     ASC-AS_A_RF36_Q2
H1:IOP-ASC0_MADC4_TP_CH12:     ASC-AS_A_RF36_I3
H1:IOP-ASC0_MADC4_TP_CH13:     ASC-AS_A_RF36_Q3   (used in plot)
H1:IOP-ASC0_MADC4_TP_CH14:     ASC-AS_A_RF36_I4
H1:IOP-ASC0_MADC4_TP_CH15:     ASC-AS_A_RF36_Q4

H1:IOP-ASC0_MADC6_TP_CH11:     ASC-AS_C_SEG1  (used in plot)
H1:IOP-ASC0_MADC6_TP_CH10:     ASC-AS_C_SEG2
H1:IOP-ASC0_MADC6_TP_CH9:      ASC-AS_C_SEG3
H1:IOP-ASC0_MADC6_TP_CH8:      ASC-AS_C_SEG4

I was running an ASC OLTF swept-sine template with a request for a 10 s rampdown time.

From the EXCMON of the drive channel, it seems that this rampdown did not happen. Rather, the excitatation continued at full strength for about 10 s and then cut off abruptly.

Tonight we have a nice example of one of the particularly troubling lockloss types that we have.  

In light of the recent ASC improvement, we are now curious about how stable the DARM coupled cavity pole is as a function of time.

In order to monitor it in a casual way, I set up a lockin demodulator like I did before (alog 18436), but this time with a Pcal line.

I set up a realtime demodulator in the LSC front end for a new Pcal line that Evan added last night (alog 19823). It uses demodulator 1 of osc 3 and a Pcal line at 325.1 Hz. The demodulation phase was adjusted such that the estimated cavity pole becomes roughly 350 Hz although I did not measure the actual DARM cavity pole via an open loop measurement. This will introduce some bias in the estimated cavity pole, but I think this is fine for now because we are interested in the stability rather than the absolute value. I then edited the ISC_LOCK guardian so that it does not send the OSC 3 excitation to the ETM suspensions any more. The attached is a screen shot of the demodulator setting.

Looking at the spectrum of the demodulated real and imaginary parts, I see that the fluctuation are coming from flat sensing noise (i.e. shot noise). Because of that, a longer integration time would improve the precision of the measurement. I empirically set the integration time (or the cut off frequency of the low pass filters) to 0.03 Hz or 33 sec in order to get a few percent precision. We might try a higher excitation amplitude at some point because I would like to know if there is a fast-varying component at around 1 Hz where some suspension fluctuation may matter. Also, I briefly looked at other Pcal lines of 331.9, 534 and 540 Hz in the frequency domain with a resolution of 0.003 Hz and saw no side-lobes around them, indicating that their performances are also limited by shot noise.

Jenne, Hang

We did some more tests on the al2 decoupling for BS. Pitch worked fine, but yaw was mysterious. The fits looked quite bad. We suspected that it might be due to MICH FF, but did not see any significant improvement in the measurement without MICH FF (LinFit_BS_yaw1437625900.png). Lots of mysteries...

J. Kissel, for the everyone

Since we're running out of Tuesdays before O1 / ER8 to do "invasive" activities that have been traditionally lumped into the term "maintenance," we'll be performing a several of these activities tomorrow morning (Thursday 7.23). The idea is that Tuesdays are typically swamped/confused by CDS Software maintenance, and much IFO hardware and electronics tuning needs CDS up-and-running. We intend to start these activities after the operator training period ends (at 09:00) and complete all activities by 12:00 PT, and recover the IFO with great vigor, ASAP, as though it were a Tuesday.

There are several activities in the list below which are still "maybes" because the associated electronics were not known to be ready at the time of this aLOG, but those task leaders in question were working hard on having the electronics ready today, and we'll reassess in the morning.

 (All times Local/Pacific)
09:00 ETMY HEPI Pump Accumulator repair 1 hour (H. Radkins)
          To fix problem found on Tuesday (see LHO aLOG 19796) 
      PSL PMC alignment adjustment 2 hours (J. Oberling, P. King, PSL OPS)
          To address that the reflected power has drifted above 10% over 
          the past few months 
      Cosmic Ray Detector Commissioning 1 hour (R. McCarthy, V. Roma, J. Palamos)   
          To finish cabling up and testing functionality of CRD installed 
          on Tuesday (see LHO aLOG 19804)
      BSC-ISI Front-end Model Restarts 1 hour (H. Radkins, J. Warner, J. Kissel)
          To install SUS payload watchdog fix (LHO aLOG 19842)

10:00 Add new EPICs channels to CAL-CS model 30 min (J. Kissel)
          To support storage of reference calibration filter values at 
          calibration line frequencies for tracking slow time dependence
          of interferometer response. (See T1500377)
      Investigate ETMX PCAL Reflection PD clipping 2 hours (S. Karki, D. Tuyenbayev, R. Savage, T. Sadecki)
          To solve problems seen in variability of ETMX PCAL calibration. (see LHO aLOG 19025)
      Add GPS serial port to Corner-Station Beckhoff PLC 30 min (D. Sigg)
          To add more diagnostic signals for the recently-installed 
          external GPS clock reference (see LHO aLOG 19782)

11:00 MAYBE PSL FSS Electronics Upgrade 1 hour (J. Oberling, P. King, PSL OPS)
          To increase the frequency of the high-pass on the fast/phase EOM actuator, 
          such that an IMC lock-loss is less inclined to saturate the fast/phase EOM
          actuator and *keep* the FSS railed in oscillation, i.e. to solve problems 
          seen after FSS tune-up and catastrophe on July 14 (LHO aLOG 19623
      MAYBE Cable up and commission EX LVLN ESD Driver (R. McCarthy, E. Hall, J. Kissel)
          To finish cabling up and testing functionality of driver that
          was installed on Tuesday LHO aLOG 19803

We have been sending the PRCL length to PRM M3 and M2.  Even with the modified driver we are using for M2, there is no frequency where we can get more actuation with M2 than either M1 or M3 has.  There have been a few problems related to this not great offlaoding.  Locklosses due to using up the M2 range, glitches when the drives were near 2^16 (alog 18983 ) and locklosses where a 20 second oscillation used up the M3 drive (alog 19464 ).  

We are now sending PRCL to both M3 and M1.  A screen shot of the measured crossover (currently around 0.5 Hz) is attached.  We are roughly compensating the suspension resonances at 1.4 and 2.8 Hz, just to prevent mulitple crossovers.  We are curently using a pole at 0.01 Hz, a susComp filter that compensates for the suspension resonances, 27 and 60Hz notches and an elliptic lowpass at 70 Hz.  It is probably possible to push the crossover up above the suspension resonances, as my original suspension compensation was designed to do, this didn't work, it might be that I accidentally used an undamped suspension model to design it.  

This is implemented in the ISC_DRMI guardian now, and is fine.  It works for PRX, but the gaurdian has not been updated yet so the old offloading will come on until that is done.  We can do the same for SRM soon.  

Fil, Evan

We screwed the 9 MHz OCXO source and the 9 MHz harmonic generator into ISC C4.

To do this, we had to first unscrew the IFR, remove its feet, and then screw it back in (the feet were blocking the slot for the OCXO).

We continue the charge measurements on ETMs.
Results for ETMX are consistent with negative trend, now the charge is from 10 to 20 [V] Effective Bias Voltage for all the quadrants.
Results for ETMY do not not show a significant trend (probably, the data are beginning to be consistent with positive trend). Charge is below the 10 [V] Effective Bias Voltage for all the quadrants.

Note:  We had positive bias on ETMX and negative bias on ETMY after discharging procedure. So it seems possible that charging is caused by the bias voltage.

Here is a summary of the brute force coherence report already posted in a previous comment to an elog entry describing the good sensitivity lock of last Friday.

Basically, there is no large coherence anywhere, except for the well known periscope peaks that are coherent with ISS signals, IMC angular signals and PSL periscope (figure 1-3)

At low frequency, there is coherence with SUS-ETMY_L3_ESDAMON_?? signals. This was not there in the past, so I guess this coherence is just due to a change in the control strategy. If I'm not mistaken, this signal is just a monitor of the correction sent to the ESD, so coherence with DARM is normal. Please correct me if wrong... (figure 4)

In the 10-30 Hz there is coherence with ASC-MICH_P (figure 5)

In the 10-70 Hz region one dominant source of noise is longitudinal control, since there is coherence with MICH and SRCL (figures 6-7). This noise is not dominant and still a factor of few from the measured sensitivity.

In the higher frequency region (above 100 Hz), there is coherence with ISS and PSL periscope as already pointed out, but there is also some coherence with AS signal: ASC-AS_A/B_DC_SUM, ASC-AS_A_RF36_I_PIT/YAW etc... Together with the main jitter peaks, there is a broadband noise floor at about 1e-10 m/rHz from 100 to 1000 Hz. This might be intensity noise or noise in high order modes that is not completely filtered by the OMC (figure 8).

Finally, a 90 Hz bump seems to be coherent with HAM5 signals (figure 9)

Jenne, Sheila, Evan

We locked at 10Watts with low noise, and redid the OMC excitations that Koji and I did in alog 17919.  We plotted the OMC L excitation against a model with a peak to peak motion of 36 um, and the result seems consistent with a reflectivity of 160e-7 that we measured on Friday by exciting the ISI.  This is slightly worse than what we measured in April.  

We made these excitations with the same amplitudes and frequencies that we used in April, but some of the velocities seem to be smaller.  Jenne is working on doing a more thourough comparision, but it seems that the scatter is better when we are exciting Yaw and Transverse, if a little worse for longitudnal.  

We used a frequency of 0.2 Hz for all excitations.