yesterday Jamie, Jim and myself discussed the ramp down issues which were reported by Jenne in alog 30258 Link

here are some notes we made describing the problem.

In the figure attached, the diaggui program running on the workstation sends commands over the network to the model's awgtpman process (running on the general core on the front end machine). Inside this process there are three components of the excitation; the excitation itself, an optional user-supplied filter and an output gain stage. The output of the gain stage is sent, via shared memory, the the front end model which writes the excitation signal into the EXC input of the appropriate filter module.

When diaggui completes its measurement or the user presses the abort button, the excitation is ramped down to zero amplitude over the user supplied ramp-time. Normally at this point the output of the gain stage is also zero. The excitation is then stopped, and the EXC input to the filtermodule is zeroed.

In Jenne's case the filter running on the awgtpman rang up even with the excitation writing zero to it. This meant that at the conclusion of the excitation ramp down the output of the gain stage was non-zero, resulting in a sharp step to zero when the excitation was stopped.

Assuming that at the conclusion of the measurement (or if the measurement is aborted) it does not matter whether the excitation ramp-down does or does not go through the filter, then one solution is to ramp the excitation down by ramping the gain to zero. This ensures the output of the gain stage is zero when the exitation is stopped. Jim is reviewing if this is possible and how much programming time this change would take.

We came up with a short term solution in cases where the filter does not zero in the ramp down time. It is possible to run awggui to the excitation test point in order to manually control the gain stage, and diaggui to the same excitation test point to control the excitation. In such case, when the excitation should be stopped the user can ramp the gain down to zero using awggui and then abort the diaggui measurement.

We think this must be set up in advance of the measurement, with awggui started first. The awggui configuration should set the frequency as non-zero (e.g. 1Hz) and the amplitude as zero. When we tried running awggui after diaggui had been started we got errors.

Title:  10/07/2016, Day Shift 15:00 – 23:00 (08:00 - 16:00) All times in UTC (PT)
State of H1: IFO is unlocked.  Wind is mostly a Fresh Breeze with gusts up to Near Gale (19 to 38mph). Seismic is slightly elevated but well below the 0.5 line. Microseism is elevated at the corner stations. Unsuccessful locking and the look of the spots indicate an initial alignment is in order. 	   
Outgoing Operator: N/A
 
Activity Log: All Times in UTC (PT)

15:40 (08:40) HFD driving inspection along Y Arm
16:05 (09:05) Evan – LVEA to check REFL9 signal chain
16:18 (09:18) Robert - Into LVEA setting up to look at tables 
16:30 (09:30) Evan – Out of the LVEA
16:35 (09:35) Robert – Out of the LVEA
17:54 (10:54) Richard & Daniel – In CER working on RF9 & RF45 problem
18:05 (11:05) Marc - Going to Mid-Y to recover parts
18:22 (11:22) Marc – Back from Mid-Y
20:08 (13:08) Chandra – Going to CP3 for overfill
20:19 (13:19) Peter & Dave – Going into CER
22:19 (15:19) Robert – Going into LVEA
22:35 (15:35) Robert – Out of LVEA
23:00 (16:00) Turn over to Travis


Shift Details: 10/07/2016, Day Shift 15:00 – 23:00 (08:00 –16:00) All times in UTC (PT)
Support: Daniel, Peter, Kiwamu, Terra               
Incoming Operator: Patrick

Shift Summary:  After commissioners finished working on the REFL9 signal chain through an initial alignment. Locking has been very difficult. 
   First – Trouble with the ISS First Loop. There was an oscillation at 1.6KHz, which was flipping the ISS lock on/off. Kiwamu put the ISS into Manual Mode and was toggling the First Loop on/off until the First Loop came on with no oscillations. This has happened before but not very often and not for some time.  
   Second – When going from DC_READOUT to INCREASE_POWER PI Mode18 would start to ring up very quickly. Twice the lock was broken before I could suppress the ring up. On the third lock, Mode18 started to ring up during RESONANCE. This time was able to damp it before breaking lock, but could not suppress the mode. Spoke with PI Help Desk – Conclusion the mode was rung up past the system’s ability to damp it. The fix was to set the gain to zero and wait for the mode to ring down low enough to where the damping can work. Once things had settled down will bring the gain back on and work with phase to further suppress the mode.      

In relation to Sheila's investigation on the increased noise in the aux length loops, I ran BruCO on the loop error signals LSC-PRCL_IN1, LSC-SRCL_IN1, LSC-MICH_IN1.

SRCL

The BruCo report can be found here:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_srcl_1159781057/

Beside some expected coherences, there are quite some ASC signals that are coherent in the 10 to 100 Hz region. Of course, it might as well be that the angular signals are polluted by the LSC control.

• as for PRCL, the IMC WFS has significant coherence all over the frequencies(fig 1 and 2)
• ASC-AS_B_RF36_Q_PIT (fig 3) below 70 Hz
• in the region between 10 and 70 Hz, there is coherence with ASC_OMC_B_PIT (fig. 4)
• finally, there is some coherence with LSC-REFL_A_LF (fig. 5)

In relation to Sheila's investigation on the increased noise in the aux length loops, I ran BruCO on the loop error signals LSC-PRCL_IN1, LSC-SRCL_IN1, LSC-MICH_IN1.

PRCL

The BruCo report can be found here:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_prcl_1159781057/

Beside some expected coherences, there are quite some ASC signals that are coherent in the 10 to 100 Hz region. Of course, it might as well be that the angular signals are polluted by the LSC control.

• ASC-PRC1_P (fig 1) below 70 Hz
• ASC-AS_B_RF45_Q_YAW (fig 2) mostly between 20 and 40 Hz
• ASC-REFL_A_RF9_I_PIT (fig 3) is similar to the previous one, but it also shows some more coherence at the jitter peaks
• ASC-REFL_A_RF45_I_YAW (fig 4) mostly above 30 Hz and up to 100 Hz
• In addition there is some interesting coherence with input beam pointing loops and IMC WFS (fig 5, 6 and 7). In particular the IMC WFS signal shows a lot of coherence everywhere between 10 and 1000 Hz, including the jitter peaks
• Finally, there is good coherence with ASC-POP_X_RF_I_SUM (fig 8), but I'm not sure what this signal is

Just for now. It's outputing 2M of useless data every minute (since green lights are shuttered for the most part). I'm saving disk space for the cornor station HWS. For those you might care, I took a new reference centroid when the IFO is cool ish with arms locked in green.

1:15pm local

Took 21 sec. to overfill CP3 with 1/2 turn open on bypass LLCV. Left bypass exhaust valve open.

Next fill due Monday. 

Attached is a rough trend of the amount of water we have added to the TCSY chiller over the last week in order to keep it "topped off".  There is ~kinda a downward trend, which may indicate we are finally getting to the point where the system is "full".  Recall, Wed Sept 28th the system ran dry due to a leak at the chiller.  At that time the chiller was refilled with ~5L of water.  We have since added another 5L of water (~300mL at a time over the last week).  The reservoir holds 7.2L and the piping probably takes a few more L so, maybe we are still clearing out air leaks in the whole stsyem...

We'll just slowly filling and watching for another few days and replot.

Evan, Daniel

17:12:30 UTC Oct 7 2016:

• RF modulation off for 9 and 45 MHz
• 45 dB whitening gain compensated by a filter gain of 0.0056
• 1 stage of whitening, compensated
• V/ct filter engaged, referred to TNC ouptut of 2-chn demod board
• Dark

17:16:30 UTC Oct 7 2016:

• same input configuration
• 29 mA of photocurrent

17:18:30 UTC Oct 7 2016:

• turn DC centering of REFL WFS on

17:24:30 UTC Oct 7 2016:

• turn DC centering off again
• 14.8 mA of photocurrent

17:32:00 UTC Oct 7 2016:

• 9 MHz modulation on
• 14.8 mA of photocurrent
• DC values: 9I = 3.7 mV; 9Q = 9.5mV

17:34:30 UTC Oct 7 2016:

• 9 MHz modulation on
• 29 mA of photocurrent
• DC values: 9I = +7.2 mV; 9Q = +18.1mV

18:06:30 UTC Oct 7 2016:

• 9 MHz and 45 MHz modulation on
• 29 mA of photocurrent
• DC values: 45I = –14.3 mV; 45Q = +62 mV

SEI: All OK – Working on ESs sensor correction
SUS: No Report
CDS Ele: All OK
CDS Swt: All OK – Fixed problem with bad commissioning frame effecting NDS
PSL: All OK – PSL has been running since the Diode controller swap
TCS: No Report
VAC: All OK – Kyle planning for the 5 day RGA bake out at End-X

There was only a short, not very good lock, after the DBB signal started to be acquired. I used ten minutes of data from GPS 1159862777 to compute the coherence between DARM (CAL-DELTAL) and the DBB QPD signals.

The first plot shows that the most coherent signal is Q1Y.

The second plot shows the transfer function from Q1Y (in arbitrary units, not sure about the calibration) to CAL-DELTAL (properly calibrated in meters, including the de-whitening filter). The shape is quite smooth, and it looks like a monothonic increase like f for most of the range. The low frequency noise of the IFO was quite bad, so I could only measure coherence above 100 Hz. Hopefully this will be improved in future locks.

However, I could fit the measured transfer function between Q1Y and CAL-DELTAL with a 3rd order model. The fit is shown in the third plot: the result is reasonably good.

I then converted the model into a IRR filter and computed the time-domain subtraction of the Q1Y signal from DARM. The result is quite good, most of the bump has disappeared, see the 4th plot for a comparison of the spectra and the 5th plot for the residual (basically null) coherence of the subtracted DARM with DBB signals.

Of course, we'll have to check in future locks how much this coupling changes over time and how hard it is to compensate for this change.

Trying to check where the laser power went to.  From the attached plots, the drop in laser power
is not easily explained by a power drop in the laser diodes.  So my suspicion is that there's a
small resonator alignment change.  Perhaps not all that surprising given the temperature change
of the laser due to being off for a few days.

Just a quick report. Broadband noise in 200-1000 Hz was also visible at a mid-high input power of 27 W.

I did not insert the cutoff filters in the hard ASC loops. ISS 2nd loop was fully engaged with a gain of 19 dB and the boost on. TCS was held at the lock acquisition settings, i.e. [CO2X CO2Y] = [500 mW 1000 mW]. The period when the interferometer was low-ish noise is in 8:15 - 8:25 UTC which was followed by lockloss due to me failing to handle PI mode 27.

Terra, Travis, Kiwamu,

Here are some unexpected issues that we addressed tonight.

• AS36 -> SRM
  • As mentioned earlier (30295), we had stability issue with the AS36 -> SRM loop in the DRMI state with the arms held off resonance.
  • One immediate human error we found was an integrator not engaged in DC3 pitch loop.
  • However, engaging the integrator in DC3P did not improve the behavir of the loop running away.
  • In the end, we changed the input matrix. AS36BI: +2 --> +1.
  • This solved the issue. Not sure why we had to change the input matrix.
• AS WFS DC and fast shutter
  • At one point, we ran into a situation where ISC_LOCK did not proceed because the shutter guardian reported a failure in a shutter test.
  • This was found to be a failure report from the dark test in which the light level on AS WFSs A and B were checked with the shutter closed.
  • In the end, we found that the AS WFS DC signals now had a slower low pass filter (a 2nd order butterworth at 1 Hz in FM1), which was too slow to give a low enough light level. This used to be a 2nd order butterworth at 5 Hz yesterday.
  • We re-installed the 5 Hz BLP in FM2 and edited the FAST_SHUTTER and ISC_LOCK guardians so that it uses FM2 when in test.
  • It worked once.
• AS90 jumped multiple times
  • We witnessed a funny behavior of AS90 a few times tonight.
  • It suddenly changes its level by a few % or so when DRMI was in lock with the arms helf off resonance.
  • Times to look at are around 2:13:19 UTC and 3:30:00 UTC.
  • DRMI did not lose lock.

Jonathan, Jim, Dan, Dave

Jim W reported data errors from 06:14PDT this morning in the full frame. We found that the commissioning frame file for this time is correct on the LDAS QFS file system, but corrupt when NFS exported by the h1ldasgw2 NFS server machine to the nds machines. This is a relatively new solaris server installed this summer to take read-only exports away from h1ldasgw0 when h1fw0 was unstable.

I've opened an FRS for this #6370

Investigation is continuing, including a full characterization of the problem.

(Corey, Jason on phone)

Last night, Nutsinee came in early for her OWL shift & just before midnight the PSL tripped.  We opted to leave it tripped for the night to wait for Jason to walk us through recovery procedure.  Atleast for now, we always want to run through this procedure with one of our PSL people (Jason or Peter K).  Here are my rough notes:

• Control Room PSL card (in key box) just passed its 7-year expiration date on Fri
• Remote login (with Jason)
• Went through a few steps in procedure and during a 5-min wait, I went out to Fill the low Crystal Chiller.
  • Both Chillers were on (but not chilling).  The Crystal Chiller (on top) had a "Flow sensor 1" error (but Jason says this is a generic error).
  • The cap blew off and was on the floor
  • Topped off with 375mL Laboratory Water
• Continued with procedure with Jason
• Once laser back, worked on restoring PSL systems via medm.
• Had to RESET the Noise Eater (toggle switch to OFF [for ~5sec], then ON).  This switch is at the "NPRO box" which is the Innolight box on the right most elec cabinet outside of the PSL Room; has the sticker:  "AdvLIGO observatory No3" on it.)
• Then brought everything back (actually the PMC, FSS & IMC came back on their own.  Had minor actions to bring back the ISS).
• Last task is to wait 30min to hit the LRA button (can't remember what Jason said this stood for) & then ENABLE the Oscillator & Frontend WatchDogs.
• Closed out Remote Login interface.
• Time on phone with Jason:  ~60min

Now on to "Aligning" on Observatory Mode!

PSL Status NOTE:

• Have a Warning Red light under the Laser's HPO (not sure what this means).
• ISS Autolock is RED (not sure what this means either since the Autolock is ON & GREEN on the ISS screen).

BS horizontal wedge doesn't have any couterpart Y path. Any horizontal beam shift on the BS will cause MICH path difference because of this wedge.

(CPY has a horizontal wedge but it's a mirror image of CPX about BS HR surface. ITMY has a vertical wedge but again it's a mirror image of ITMX.)

This effect doesn't look small, and a rough calculation shows that the HPO jitter peaks from DBB (but not broad humps seen in DBB) are consistent with what we see in DARM.

----

In the attached cartoon, when the beam on the BS is shifted in Y direction by y (blue line), the optical single-trip distance from the beam spot on the BS to ITMX gets shorter than to ITMY by:

EQN1: MICH = n*yW*sqrt(2)/cos(theta) - yW*(1+tan(theta)) ~ 0.7896yW = 1.0E-3*y

where W=1.3E-3 rad is the wedge, n=1.4496 is the refractive index and theta=29.2deg=0.5096rad is the angle of refraction.

DARM will only see about (1-rI)/(1+rI) of MICH where rI is the amplitude reflectivity of the ITMs, which is sqrt(0.986):

EQN2: DARM=MICH*(1-rI)/(1+rI) = 3.5E-3*MICH ~ 3.5E-6 * y.

Because of this, DARM should have a flat coupling to YAW displacement on BS.

Instead of the displacement y, we'll use the displacement A which is just the displacement normalized by the beam radius on the BS (53.4mm):

EQN3: DARM=3.5E-6*53.4[mm]*A = 1.9E-7 [m] * A.

----

Now, let B be a normalized misalignment parameter out of HPO (i.e. HPO jitter), e.g. B=disp/waistRadius+ i* angle/divAngle. Note that abs(B) is conserved unless 01/00 mode ratio is altered.

PMC gives us 1.6% HOM01 suppression in amplitude (T0900616).

For IMC there's some difference for PIT and YAW due to additional sign flip on top of Gouy shift per round trip, but PIT suppression is about 0.5% and YAW is 0.4% in amplitude assuming that the common round trip Gouy shift is 102 deg.

For PRC, assuming carrier recycling gain of 30, PRM reflectivity of 97% and the round trip Gouy shift of 32.5 deg, HOM01 suppression is 5.7% in amplitude.

PMC, IMC and PRC combined, HOM01 suppression is 3.7e-6 for YAW, 4.6e-6 for PIT.

Though A cannot be known without knowing the Gouy shift from HPO to BS, since |B| is conserved except through cavities, we can set the upper bound on |B| using the HOM suppression through PMC, IMC and PRC as

EQN4: |A| < 3.7e-6 * |B|

therefore upper bound on DARM

EQN5: DARM < 7E-13 [m] * |B|.

DBB measurements of B are available in alog, e.g. alog 29754 (direct link to the HPO jitter plot is here).

If you look at 1kHz peak which does not appear in DBB RIN measurement, the peak height is somewhere between 5E-6 to 1E-5, and using EQN5 and these numbers,

EQN6: DARM < 3.5 to 7E-18 [m/sqrtHz] at 1kHz peak.

In DARM spectrum, 1kHz peak is visible at or somewhat above 1E-19 [m/sqrtHz], so it seems consistent with EQN5.

----

Caveats:

IF the broad noise in DBB jitter measurement is actually jitter,  assuming the same jitter coupling as the above, you should see the huge broad thing in DARM, which we do not.

This coupling only applies to YAW. As for PIT, there could be similar coupling mechanism if ITM wedges don't cancel with each other, but the imbalance is only 0.001 degree.

MICH is not the only thing that is modulated by this, SRCL and PRCL are simultaneously modulated. Full simulation might be useful.