I arrived to the PI experience that Patrick was having and tried my hand at damping to no avail. This seems to have been plaguing his shift. Diag main was complaining that Nominal ring heater settings for ETMY was 'Off". I read Sheila's aLog about turning them on but trending back to a time when we were having somewhat decent lock stretches (around 10/10) I decided to try turning the ETMY heaters off and see what hatches. Repeating the same process that Patrick was dealing with didn't seem  thatit would get me any further than he had gotten. I'll be consulting commissioners soon on this matter.

I kept losing lock from NLN at 26 W after a fairly constant amount of time. Each time ETMY would saturate and the whole DARM spectrum would jump up for a while before hand. I have begun to suspect that it might be related to a fairly broad hump seen in Terra's PI DTT template that grows in height and width as the lock progresses. It is centered somewhere around 15008 Hz and the peak grows from around 100 to 10000 before the lock loss. I tried sitting at DC_READOUT and then INCREASE_POWER and playing around with a bunch of PI settings, assuming it was related to either mode 18 or mode 26. I tried various filters in the H1SUSPROCPI_PI_PROC_COMPUTE_MODE26_BP filter bank, different phases and gains and even turned off and back on the entire PI output to ETMY (H1:SUS-ETMY_PI_ESD_DRIVER_PI_DAMP_SWITCH). Nothing really seemed to have any effect and it eventually broke lock again.

Relocking has been fairly robust. The IR transmission at CHECK_IR has been kind of poor towards the end of the shift, but it doesn't seem to hinder further locking.

At the beginning of the last lock at NLN I changed the TCS ITMX CO2 power by a small amount per Sheila's request.

07:40 UTC NLN at 26 W
07:50 UTC Damped PI mode 27 by flipping sign of gain
07:56 UTC Played around with damping PI mode 18 and 26. Not sure if they just came down on their own.
08:10 UTC Damped PI mode 27 by flipping sign of gain
09:05 UTC Lock loss. EY constantly saturating and PI modes 9, 18 and 26 ringing up. Attempts to damp these by changing their phases did not seem to help.
09:30 UTC Lock loss immediately upon reaching DC_READOUT. IFO got that far without intervention. OMC SUS and HAM6 ISI tripped.
09:35 UTC X arm IR transmission is ~ .4 at CHECK_IR. Able to bring it to ~ .7 by adjusting H1:ALS-C_COMM_VCO_CONTROLS_SETFREQUENCYOFFSET from 0 to ~ -156. This dropped Y arm transmission. Brought back by moving H1:ALS-C_DIFF_PLL_CTRL_OFFSET.
10:00 UTC Pausing at ROLL_MODE_DAMPING. Waiting for ITM roll modes to damp.
10:12 UTC DC_READOUT_TRANSITION. Stable here.
10:13 UTC DC_READOUT.
10:17 UTC Stable at DC_READOUT. Moving on.
10:25 UTC NLN at 26 W
10:35 UTC Flipped sign of PI mode 27 for third time since NLN.
10:57 UTC Flipped sign of PI mode 27 again
11:18:50 UTC Changed TCS ITMX CO2 power using rotation stage. Changed requested power from 0.200 W to 0.201 W. 0.195 W measured out at 42.2733 deg changed to 0.195 - 0.196 W measured out at 42.3040 deg.
11:24 UTC EY saturating again
11:25 UTC Tried dropping power to 10 W by going to manual -> adjust power -> auto, power request through guardian. Lock loss. Peak on PI DTT at 15008.9 got really broad. HAM6 ISI and OMC SUS tripped.
11:45 UTC Having hard time on CHECK_IR getting stable transmission. Moving on.
12:06 UTC Pausing at DC_READOUT.
12:12 UTC Stable. Moving on. Various large optics saturating until reaching ~ NOISE_TUNINGS.
12:20 UTC NLN at 25.9 W
12:22 UTC Changed TCS ITMX CO2 power using rotation stage:
req .200 W -> .198 W
meas .196 W -> .194 W
meas 42.2800 deg -> 42.2483 deg

12:30 UTC Flipped sign of PI mode 27 gain
12:46 UTC Flipped sign of PI mode 27 gain
13:18 UTC Lock loss.
13:46 UTC Pausing at DC_READOUT. Played around with various settings for mode 18 and 26. 15008 Hz line seemed to come down a little, but not sure it was anything I did.
14:12 UTC Going to INCREASE_POWER.
Sitting at INCREASE_POWER trying lots of different things to damp mode 26. No effect.

TITLE: 10/21 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Lock Acquisition
INCOMING OPERATOR: Patrick
SHIFT SUMMARY: Flipped the gain sign and added -60deg to 4735Hz damping filter (added to Guardian). The mode hasn't caused us any trouble tonight (as mentioned in alog30713). Lockloss multiple times at DC Readout. I found that sitting at DC_READOUT_TRANSITION for a while helps (unclear to me why -- all the control signal looks fine). Had trouble locking FSS many times tonight. Every unsuccessful FSS lock seems to cause the noise eater to complain (and also kills ISS and PMC). I ended up locking FSS in the LVEA near the PSL where I can easily toggle noise eater. A successful trick seems to be locking FSS first, and the rest (ISS, PMC) will follow. Just keep hitting ON button on the auto lock until it stays on. Had no problem locking PRMI/DRMI last time I tried (besides alignment issue). Watch out for PI Mode27. The damping phase changes constantly.  

- Guardian is now able to go to low noise at any power (see alog 30730)

- While the ISS isn't touched in the Guardian, its gain needs to be set for the final power:
  25W: H1:PSL-ISS_SECONDLOOP_GAIN = 13dB
  50W: H1:PSL-ISS_SECONDLOOP_GAIN = 7dB
 

- At 25W I did a quick SRCFF tuning (no filter - just gain to -0.55) (now in guardian). This produced a broad notch in the SCR coupling around 80ishHz. Attached is a residual coherence plot.

- Next I tried a number of things to attached the noise below 100Hz:

   - Moved both compensation plates by 100urad in PIT and YAW. Moving them fast clearly produces scatter shelfs, but there was no obvious noide difference when the CPs were parked at a new location.

  - Turned off the ESD bias on ETMX, ITMX and ITMY (no obvious effect)

  - Added 20000cts of ESD EY offsets in pringle-shape to avoid zero-crossing (no obvious effect)

  - Noticed that ITM L3 STATE REQUEST was 1 (LP off) - I am not sure the switch does anything on the ITMs, but I changed it to 2 (LP on) (no effect)

  - Slightly lowered the HARD ASC loop bandwiths. The shelf just below 25 Hz is from the ASC and scales accordingly.

  - Temporarily tunrned off the 40ish Hz cal lines to make sure they don't introduce non-linear noise (they don't).

  - While I didn't close the SCR1_Y loop, I did look at the AS_A_RF36_I_YAW signal - it looked like a perfectly fine signal  and we could use it again at 25W.

  - Just remembered that we are still on the POP_X WFS (with POP beam diverter open). We should switch back to REFL.

Attached is a noise spectrum. Sensmon claims 60Mpc, but the 331Hz peak is actually 8% high, so I guess we are closer to 65Mpc.

Here is a look at our spectrum with 4 changes made:

We were back at the TCS settings from late July.  (This was before I changed the ring heater back to 1.5 W total to go back to early July). 

27 Watts

DBB unplugged

PMC realigned

The noise lump is still here, although not as bad as it was yesterday.  Most of the peaks are smaller but some new peaks have appeared. 

At around 3:30 UTC I set both upper and lower ring heaters on ETMY to 0.75W, this reverts us to the settings we had in early and mid July, and the first part of ER9. This was changed to 0.54 July 23rd.

It also means that now the two arms have the same ring heater settings:

ITM: 0.5 Watts total

ETM 1.5 Watts total

From the shell command line:

ezcareadpast.py H1:ASC-PRC1_Y_GAIN 1161131166
 

Or in pyhton:

import ezcareadpast as e
value=e.ezcareadpast('H1:ASC-PRC1_Y_GAIN',1161131166)
 

enough said...

Daniel, Sheila, Keita

This morning Peter King realinged the PMC again. The attached plot shows the PMC HV mon recorded yesterday afternoon, and now after the alingment, the peaks have gone down by about a factor of 3, and the noise in the ISS first loop out of loop PD also decreased.  We can further reduce the peaks in the HV mon by increasing the loop gain to 27dB.  We saw the loop start to oscillate with a gain of 30dB, which might explain the braodband noise in DARM we saw when we went to 30dB the other night. (30682)

In the attached plot, LSC-EXTRA_AI_1, which is calibrated into volts at the ADC.  There is a SR560 with a 10 Hz high pass and a gain of 100 between the monitor point and the AI input, so combined with the 1/50 gain of the monitor, 1 V here is 2 Volts applied to the PZT.  The PZT is a custom made PZT, PI PAHH-0013, the capacitance is 63nF, travels 4um/kV.  We have a 3.3k resistor, so the pole is about 770 Hz.  So to calibrate this channel into meters:  V LSC_EXTRA *2(Volts to PZT/Volts LSC_Extra)*4um/kV= 8e3pm/Volt, with a pole at 770 Hz. 

The measurement from yesterday was made in full lock, with the ISS second loop at full bandwidth (PDB is out of loop).  This morning's measurements were made without the ISS second loop on. 

after being stable since 11am Wednesday, h1fw0 restarted itself at 16:24 PDT Friday afternoon. This did not look quite like a slow-disk error, but I decided to do a pre-emptive power cycle of the h1ldasgw0 solaris computer before the weekend break. Sequence was:

• h1fw0: stop monit
• h1fw0: stop daqd
• h1fw0: umount /ldas-h1-frames
• h1fw0: power off
• h1ldasgw0: power off
• h1ldasgw0: power on, wait about 10 mins
• h1ldasgw0: mount /ldas-h1-frames
• h1ldasgw0: source /etc/dfs/dsftab.qfs
• h1fw0: power off, wait for everything to auto start

460 day trend shows IM3 moved in yaw and what looks like a corresponding move by IM4 yaw of about 50urad.

IM4's yaw history:

• July 2015, about -610urad
• Aug-Nov 2015, about -590urad
• a brief stint at -575
• Nov 2015 to Sept 2016 a climb from -630 to -610
• Sept 2016, a move to -540urad, a change of 50urad, that could be in response to the move of IM3

[JimW, Jenne]

We were really struggling to lock PRMI.  When it would catch for a second or two, we could see on dataviewer somewhat slow oscillations before it would lose lock.  This indicated that maybe the gain was too low.  So, we put a factor of 2 more gain, and it seems to be okay so far.  

- Started with checking the ISC guardians into svn.

- Designed a set of arm ASC filters for 25W using the following simple interpolation for the filter zeroes and Qs:
   f^2 = (f_0)^2  + [(f_50)^2-(f_0)^2]*P/50W  (Frequency squared should be linear in power, with the offset given by the stand-alone suspension.)  
   Q  =interp1([f_0,f_50],[Q_0,Q_50],f,'linear')  (Linear interpolation for the Q's between the stand-alone frequency and 50W frequency)
  The same procedure was applied to both resonences in each transfer function. The detailed frequencies and Qs are in the attachement.
   Looking at Jenne's full model, this should be relatively close to the truth.

- Then I rewrote the LOWNOISE_ASC guardian state to choose the new 25W filters below 40W, and the old 50W filters above 45W.

- We'll test all this as soon as the IFO is back.

2:20 pm local

Took 90 sec. to overfill CP3 by doubling the LLCV setting to 34% open rather than cracking the bypass valve. I am dissatisfied with the TC readings. Temps never registered below 0degC. But there is still a decent delta.

On Monday I'll fill the same way and allow LN2 to exhaust a little longer to see if the TCs eventually read appropriate temps. 

I connected the second SR560 to the HPO injection lock HV monitor with the same setting as the PMC length PZT monitor. Blue is the injection lock, red is the PMC length PZT.

Known peaks in PMC PZT, i.e. 240Hz, 320, 480, 600 and 1kHz are all much more prominent in the injection lock feedback.

Unsurprisingly, opening/closing DBB shutters, plugging off the shutter cables, turning off HV of DBB, and completely powering off the DBB crate didn't affect the peak height of the PMC PZT as well as injection lock. (green and brown are when the DBB crate was fully powered and the shutters were closed, red and blue are with the DBB crate totally powered off and the shutter cables disconnected.)

I left DBB crate unpowered and shutter cables disconnected.

I left the injection lock monitor connected to the SR560 and the second LSC-EXTRA_AI channel.

Peter installed a cable running into the PSL and into the excitation port of the 9 MHz RF driver, so we can now excite 9 MHz RFAM with the DAC.

Summary:

There is a broad peak in the DARM spectrum around 5kHz which is consistent with the TEM10 being rung up at that frequency. 

• The transient behaviour is consistent with the simulated change in g-factor (and HOM spacing) of the cavity due to self-heating of the optics causing the ITM and ETM surface curvatures to change
• The observed peak in DARM shifted down in frequency after the ETMY ring heater values were changed (as expected).

Details:

The attached MATLAB file produces an animation that shows the DARM spectrum around 4700 - 5500 Hz. It updates this spectrum for 50s intervals around the time that the IFO is locked. Very quickly we see a broad peak (around 50Hz wide) form in DARM around 4900 Hz. This peak moves up in frequency as the lock is maintained.

I have the online simulation of the HOM spacing (frequency vs time) shown in the top plot. As the anmation steps forward in time, we can start to find the maxima of the broad peak in DARM. I've taken the location of these maxima and plotted them in the FREQ vs TIME plot (I've only picked the location of the maximum value of the broad peak and tried to exclude all times before the lock is acquired and the frequency starts to change). The transient behaviour is quite consistent with what the simulation predicts. 

The two figures correspond to two recent locks but different ETMY ring heater settings:

1. GPS TIME: 1160974817: ETMY RH = 0W
2. GPS TIME: 1161055457: ETMY RH = 1.1W (aLOG 30685)

After the ETMY ring heater is turned on and stabilizes, we expect the HOM frequency to shift down by about 60Hz, according to the simulation. We see a commensurate change in the location of the peak in DARM.

If this is the TEM10 mode in the arm, then what is ringing it up?

Time 2:

More to come ...

(Download and run the MATLAB file to see the animation).

Keita, Sheila, Kiwamu

This afternoon Keita and I did another test of opening and closing DBB shutters, since Keita realized that there are multiple shutters that matter.  The results are in the screen shot.  We only see two shutters on the PSL layout, (SH01 in the 35 W path to the DBB and SH02 in the 200W path) and on the photos documenting the table, but there must be a third shutter, perhaps inside the DBB box. We did not test switching to the 35W beam because that caused a lockloss last night. Apparently the shutters used here are Thorlabs SH05, which has an aluminum blade according the the thorlabs website. 

When changing between shutter states today we saw a broad band change in the DARM noise throughout our 200Hz-1kHz lump, (this is a little different from what we saw last night).  However, we saw 3 different noise states in DARM depending on the shutter requests, shown in the attachment.  

We guess that the shutter which is controlled by the epics channel "PSL-DBB_SHUTTER_DBB" is inside the DBB box itself and not on the layout.  It is hard to explain the table above.  For example, if no beam is selected, and both beams are really blocked before they reach the DBB, why would closing the shutter inside the DBB matter?  

Kiwmau and I went inside the PSL, placed beam dumps in the paths to the DBB.  We placed a "black hole" beam dump (no cone in the middle) in the HPO path (a 250 mW beam between M3 and M12 on the layout).  Looking at that beam with an IR card, we could see a corona around it, pictures will be attached to this alog.  This corona is scattered around, hitting the black baffle near the DBB apperature and other things.  We also placed a black glass beam dump upstream of the front end laser beam path the the DBB, just before the shutter. 

Update:

After waiting out the Japanese earthquake, we relocked.  The lump was smaller in the first moments of the lock.  After a few minutes the peaks reappeared, but the peaks still changed when we opened and closed the shutters, in a way that is repeatable although the plot is confusing since the overall level of noise was changing probably with the thermal state.  (each time we opened the shutter, things got worse than they had been).

We do not understand how changing the shutter state impacts the DARM noise, although we think we have ruled out scattered light.   Kiwamu thought that perhaps the change in the noise could be due to the change in the diffracted power when we move the shutter (see Keita's alog 30679). We tried a test of changing the diffracted power, which unlocked the IFO.  It could also be through the same electrical coupling that means the diffracted power changes when we open the shutter.