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.

This is the first charge measurements after changing the sign of bias voltage applied to ESD (See alog 19821). At July, 21 and before ESD bias voltage was: 
ETMX (H1:SUS-ETMX_L3_LOCK_INBIAS) 9.5 
ETMY (H1:SUS-ETMY_L3_LOCK_INBIAS) -9.5
Now:
H1:SUS-ETMX_L3_LOCK_INBIAS -9.5
H1:SUS-ETMY_L3_LOCK_INBIAS +9.5

Plots are in attachment. Voltage is more or less the same, and it's early enough to consider the tendencies.

- TJ, Locking Operator, Cheryl, Operator Operator

- morning:

• See Jeff's alog for activitities 8AM-10AM.
• Locking 10AM to about noon, then too much glitching from beam tub cleaning to run full IFO and use DARM.

- afternoon: investigations by commissioners/others

- activities - short term

• PRX, Shiela
• HAM6, Jim
• charge, Leo

• cabling in electronics room, Filiberto

• Beckoff, Daniel

- activities - all day

• beam tube cleaning
• Kyle, Earnest: visits to all outbuildings, including entries into VEA's

EY, entry at 1:25PM, stayed 15 minutes

EX, entry at 2:15PM, stayed 15 minutes

CS LVEA, entry at 3:15PM, stayed 30 minutes

• WP5376
• WP5377
• WP5378
• WP5379
• WP5380

Currently commissioners have the IFO.

to help with getting the glitch rates, I'm running a script every minute which performs a DIAG clear on the models which are showing this issue. These models are: IOP-SUS[EX,EY], SUS-ETM[X,Y], IOP-SEI-E[X,Y], ALS-E[X,Y], ISC-E[X,Y].

Yesterday I started a cut-down version of this script which only cleared the ALS and ISC errors, however not every SUS glitch prodcues a remote IPC receive error so this was under counting.

We have noticed that in the past 20 hours only EY has glitched. We at still seeing two different types of IOP-SUS glitches either with or without a TIM bit setting.

On Monday, numerous ODC threshold values were changed, so says SDF.  See attached snapshot of these diffs.  I've asked around, but can't find who did made these changes...  Anyone know?  Are the new settings the best values to capture or do we need to revert?

The  BSC's and HAM's have been handling payload watchdog trips differently for a while. The HAM's watch the SUS watchdog and do a running 10 second sum on IPC errors, so if the SUS model goes down for 10 seconds, the ISI will shut off. The BSC's have not been as smart. They watched the SUS watchdogs, but when they received a single IPC error, they would just trip. This is because the logic was incorrectly converting from an error rate. This wasn't an issue until recently because IPC errors were rare, but for now, the end station SUS computers are producing occasional IPC errors. Today, JeffK walked Hugh and I through importing the appropriate SEI library part to fix this. All BSC's have been modified at the top level, and all models compiled, we will wait until tomorrow to restart. We also cleaned up some redundant stuff on the top level. To wrap up, Hugh commit the changes to the SVN. Attached screens show the changes. Unfortunately, I didn't get a before shot,  but the changes are a lot cleaner. We should get many fewer end station trips after the models are restarted.

Patrick, Daniel

Accidently stopped when we logged out of the controls account. It automatically restarted when we logged back in. The settings appear to be back, so no burtrestore has been done. However this is something to check if a problem arises.

Summary

A lower-estimate of absorption in the end test masses was measured using the end-station HWS cameras.  This can be used to get a lower estimate of absorption in the test masses.  I only got 30mins of data with the interferometer locked at 3W, we should repeat this measurement for a longer lock stretch to get a better idea of the absorption in the end test masses.  The current measurement gives an absorption of 230ppb in ETMY and 130ppb in ETMX.  Becasue we only measured for a 35min lock stretch, this will be an underestimate of the true test mass absorption.  Also, the ETMY HWS measurement looks untrustworthy, so it would be worth checking the PZT off sets.

Details

The EMT HWS cameras use the green als beam to measure the curvature change of the ETMs.  We want a single reflection of the green beam off of the ETM, we cannot take this measurement when the green beam is resonant in the arm cavity.  The green beam is usually shuttered and not present in the interferometer once the interferometer has reache DC_READOUT.  To take a measurement with the HWS, once the interferometer is at DC_READOUT and the green beam is shuttered and no longer used,  we re-open the ALS shutters and mislalign the green PZTs enough that the HWS sees no return beam from the ITM, only seeing a single bounce off of the ETM.  I choose the PZT misalignment offsets as stated in alog 17860.  Pictures of the HWS camera images are attached.  Both cameras measure 22 centroids.  The X-end image does not show a nice round beam, I may have to adjust the PZT alignment offset settings for this arm.

HWS reference centroids were taken before any locking started, with green PZTs in same misaligned state as we use when taking a measurement.

The ALS X/Y PZT2 are misaligned with type 'fixed', and with misalignment offsets:

H1:ALS-X_PZT2_PIT_MISALIGN_BIAS=15500

H1:ALS-X_PZT2_YAW_MISALIGN_BIAS=8300

H1:ALS-Y_PZT2_PIT_MISALIGN_BIAS=16100

H1:ALS-Y_PZT2_YAW_MISALIGN_BIAS=12000

The change in the spherical power of ETMY was 30udopters and ETMX was 11udiopters over a 35 minute lock stretch at 25.3W input power.  For a change in spherical power of 1udiopter, 1.06mW of power is absorbed, according to Aidan's model of the test mass absorption (LLO alog 14634).  The input power was 1.7W into the IMC, assuming 0.88 IMC-Faraday throughput efficency, 45 recycling gain, 280 arm cavity gain, 50:50 splitting ratio at BS, then 25.3*0.88*45*.50*280=140.3kW stored in the arms.  Absorbed power/stored arm power = optical absorption.  (Arm cavity gain is calculated using G_arm=(t_ITM/(1-r_ITM*r_ETM)).^2, where r_ETM=sqrt(1-TETM-L) and L=120ppm=loss in the arm. )  The arm power can also be caclulated using the four ASC_TR QPDs, which agree with the calulation using IMC input power, the variation between the four QPDs puts the uncertainty of the arm power at 15%.

Attached is a dataviewer plot of the HWS spherical power output during a 30min lock at 25W.  The shutters are opened when the shutter value=0.  I have calculated an absorption value for both test masses, but the spherical power inn the ETMY is growing in the wrong direction.  Either there is a sign error in a model or script somewhere, or this HWS is not set up correctly currently.  I will investigate this.

This measurement assumes the test masses have had enough time to reach thermal equilibrum, which actually takes longer than 30 mins.  This means that the absorption measurement is an underestimate.  It would be desirable to get a measurement of a lock stretch of >1hr.  The HWS measurement itself is quite noisy.

Hannah, Stefan

We were investigating some noise in the 70-100Hz range. Following up with Gabriele's alog (19756) we decided to check the RF36 channels and their coherence with the OMC-DCPD. ASC-AS_A_RF36_I_PIT and ASC-AS_B_RF36_I_YAW do appear to have some increased coherence in this range, but they also have a broadband coherence from 100 to at least 900Hz. We're still working to find a theory to explain this.

There are also some peaks in the coherence between PSL-ISS and the OMC-DCPD. However, the AS RF36 channels do not seem to correlate with peaks in intensity noise, suggesting some other source of noise.

We will investigate the higher frequencies during the next lock.

J. Kissel, B. Weaver

Betsy and I have updated the end-station SUSAUX top-level models to include Stuart's new library block for the HV and LV ESD analog readback monitors, as per WP 5373, ECR E1400232, II 859.
with the changes as described in LHO aLOG 18819, and obeying wiring diagram D1400177 , specifically p11.

They been compiled against RCG 2.9.5, we'll wait for Dave to confirm that we want 2.9.5 or 2.9.6, and will install later in the morning, as per today's schedule (LHO aLOG 19770).

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)