J. Kissel

While updating the DARM loop model, in order to compare with the measured loop (from LHO aLOG 45714), I found two things:
    (1) That the ETMX_L3_DRIVEALIGN_L2L gain had changed from -40 to -80, and
    (2) That the loop model was over estimating the measured DARM OLG TF  by a factor of two.

This lead me down a small rabbit hole, in which I found Peter Fritschel's brief entry from early in November (LHO aLOG 45193), which states that "we've reduced the ETMX bias voltage from -430 V_ESD (/40 = 10.75 V_DAC) to -218 V_ESD (/40 = 5.45 V_DAC)". 
However, this was permanent change implemented in guardian / the ETMX bias path in a sneaky way:
    (a) the H1:SUS-ETMX_L3_LOCK_INBIAS is now zero (the bias record was moved from INBIAS to the BIAS_OFFSET so we can use the ramping of the OFFSET)
    (b) the H1:SUS-ETMX_L3_LOCK_BIAS_OFFSET is -9.3 (V_DAC * 40 V/V = 372 V_ESD), and
    (c) the H1:SUS-ETMX_L3_LOCK_BIAS_GAIN is 0.5
    (d) the ETMX_L3_DRIVEALIGN_L2L gain is -80 (where it used to be 40)
such that the output is (including the cnts2V filter gain of 2^18 / 20 = 13107.2) = -60948.5 18-bit DAC counts = -4.65 V_DAC = 186 V_ESD. 
Remember also -- 
    (e) we compensate the fact that we have a 20 bit DAC by dividing the requested DAC counts by 4 in the ESDOUTF banks. 

#TangledWebsWoven.

Before I figured out the mystery, however, I was allowed some time to measure the actuation strength of the L3 stage with the PCAL system (we need this for ER13 anyways) to help me. See the 1st and 2nd attached results. They report that the actuation strength is now 2.149e-11 N/V^2, or 2.294e-12 N/ct_18bitDAC, which is half the value measured in October (LHO aLOG 44690), before we switched to a 20 bit DAC (which doesn't affect the estimate because of (e)), and before the above sneaky bias voltage reduction (a-d).

The problem for the calibration group to fix: yet again we've been out-smarted by the ISC team in its infinite ways of setting a  single number. 
The DARM loop model does not yet include (c), and because of (e) we haven't yet updated the model DAC gain from an 18 to 20 bit DAC gain thinking we could get away with ignoring it after the ESDOUTF compensation.
So -- I can make the DARM loop model work by 
     (i) accurately changing the ETMX_L3_DRIVEALIGN_L2L gain at -80
     (ii) leaving the model DAC gain at 2^18/20 V
     (iii) incorrectly leaving the bias voltage at -9.3 V_DAC (= 372 V_ESD)
     (iv) reducing the physical actuation strength of the ESD by a factor of 2 from 4.1303e-11 to 2.149e-11 N/V^2

3rd attached result is this DARM Open Loop Gain model vs. measurement.

L3 / TST Actuation Function Measurements:
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/MeasurementsFullIFOActuationTFs/
    2018-12-05_H1SUSETMX_L3_PCAL2DARM_5min.xml
    2018-12-05_H1SUSETMX_L3_iEXC2DARM_5min.xml

Data Processing scripts that makes the attached plots:
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/Scripts$
    DARMOLGTFs/process_darmolg_20181205.py
    FullIFOActuationTFs/process_actuationmeas_20181205.py
    FullIFOSensingTFs/process_sensingmeas_20181205.py

New DARM loop Model that informs the attached final 3rd plot:
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/params
    modelparams_H1_20181205.py

Danny, Dan

There is a weak point absorber on ETMX we saw in the 20W power up today. This seems significantly weaker than the current ITMY absorbers. The first image shows the point absorber and ifo beam heating, the cross marks the center of the beam heating. By choosing a reference 350s later over the same timeframe we can extract the ifo beam heating only, as shown in the second image.

Recently (at least since we started using the new SOFT offsets for the new TCS pre-loading) the OMC alignment dither loops ran away during power-up to 20W, leading to an OMC-SUS saturation. So we dug a little deeper:

- The loop that runs away during power-up to 20W is H1:OMC-ASC_ANG_Y_OUTPUT, driven by dither lines.
- So we set the QPD offsets to match the dither alignment at low power (2W), and increased the power running on the QPD for OMC alignment. That worked fine and did not saturate the OMC SUS.
- Indeed the QPD OMC alignment produced 5% higher optical gain at 20W (!, that does translate into range - 80Mpc at 20W into the interferometer).
- We switch back and forth between QPD alignment and dither alignment (stopping short of saturating the OMC SUS), and repeatably saw more optical gain on the QPDs
- Just to verify that it is not a dither SNR problem, we increased the dither line strengh. This just confirment that the dither alignment has an offset (i.e. pulls us away place with less optical gain).

So, we are forced to conclude that the simple dither alignment somehow is affected by non-arm carrier light. It might be time to revive the idea of a beacon alignment.

For now I commented out the dine in the OMC_LOCK guardian that switches to dither alignment.

The Yarm camera copy script is frozen.  Thankfully DiagMain warned us, so DaveB can fix it before he heads home for the day.  We don't need it now since we have a nice ~80Mpc 20W lock, but we'll need it for our next initial alignment.

17:00 Chandra to HAM6/HAM1

19:00 Nutsinee to ISCT6

20:00 Danny TJ to EX

23:00 Danny TJ to EY

J. Kissel

I've gather a new measurement suite for the DARM loop / Sensing Function -- Results are attach, and sensing function parameters are quoted below.
The interferometer conditions during the measurement:
   - 20 W input power
   - DARM actuator configuration: EY L1, EY L2, EX L3. EX L3 ESD Bias set to -4.65 volts at the (20 bit) DAC, or -4.65 * 40 V_ESD/V_DAC = -186 V at the ESD Bias Electrode
   - all modern (red) ASC loops were engaged including SRC (36 MHz BS control, 72 MHz SRC control). 
   - let the IFO thermalize for ~30 minutes or so before I began taking the measurement. 
   - all calibration lines were OFF (PCAL and SUS).

The optical gain is consistent with what has recently been done to match PCAL calibration lines to DELTAL EXTERNAL (i.e. adjusting the inverse sensing function gain from 1.0 to 1.1).
This is the first quality measurement of the H1 IFO's SRC detuning since we replaced ITMX and the ETMs between O2 and O3 -- and results look good -- the optical spring frequency appears to have been reduced from between ~6-8 Hz (depending on the alignment and thermal state of the IFO) to f_s = 3.6 +/- 0.1 Hz (informed by only one measurement, 68% C.I.). The Q remains unresolved (though we expect the Q to be very close to critically coupled at ~1/2).

More details below.

The processed results based on today's measurements for the sensing function parameters are as follows:

Parameter                              | Quantiles (0.15, 0.50, 0.84)
---------------------------------------------------------------------
Cavity gain, H_c (ct/m)                | 3.245e+06, 3.249e+06, 3.253e+06
Cavity pole, f_cc (Hz)                 | 423.7, 425.2, 426.8
Detuned SRC spring frequency, f_s (Hz) | 3.441, 3.603, 3.758
Detuned SRC spring quality factor, Q_s | 30.71, 23.81, 19.41
Residual time delay, tau_c (usec)      | -2.499, -1.806, -1.112

See previous values (that informed what is currently installed and calibrating DELTAL_EXTERNAL) in LHO aLOG 44364.
Specifically, I draw your attention to the optical gain ratio of (previous / current) = 3.552e6 ./ 3.249e+06 = 1.093 ~~ 1.1, which is what's installed currently in the CAL-CS GAIN field.

If we so chose to update the sensing function filters in the CAL-CS model (probably not yet), those filters should be:
Inverse Sensing FOTON values:
H1:CAL-CS_DARM_ERR Bank
SRCD2N: zpk([425.2376;3.5282;-3.6796],[0.1;0.1;7000],1,"n")gain(1298.18)
Gain: gain(3.078e-07)

Inverse Sensing without cavity pole FOTON values for CFTD path:
H1:CAL-CS_DARM_CFTD_ERR Bank
SRCD2N: zpk([3.5282;-3.6796],[0.1;0.1],1,"n")gain(1298.18)
Gain: gain(3.078e-07)

Data was taken with the templates:
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/Measurements/FullIFOSensingTFs
2018-12-05_H1DARM_OLGTF_23to800Hz_10min.xml
2018-12-05_H1_PCAL2DARM_TF_23to800Hz_2min.xml

Results were processed and produced with
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/Scripts/FullIFOSensingTFs$ python3.5 process_sensingmeas_20181205.py


And updated DARM loop model comparison to come -- but we know we at least need to make the updates described in LHO aLOG 44667.

J. Kissel (in concurrence with others in the control room)

Upon investigating parameters for the DARM Loop Model, I found that the ETMY ESD Bias was ON. While some previous noise investigations have indicated that the bias doesn't impact the noise (e.g. LHO aLOG 45113), it seems bad practice (due to general charging concerns) to leave this on. Thus, I've turned OFF the ETMY ESD bias, and captured that in the SDF system (in the "safe" snap) so it sticks. Note that the HV driver is still *on*, we're just not requesting it to drive any voltage. The binary switches are in the configuration where the the low-voltage (LV) output is selected, the high-voltage input to the LV driver is disconnected, and the LV driver's low-pass filter is engaged.

Also -- while I was in there, I unmonitored the distracting "inputs to the violin mode damping filters" for all 4 quads which are controlled by guardian. There are 40 of them, so they pollute the check against the safe.snap and OBSERVE.snap SDF file when looking for other problems.

Following on from the Monday Log, thought it prudent to look closer at the V1 sensor.  Plot one of that alog suggested the V1 and possibly the H1 sensors were outliers.

The first attachment here shows high and low gain responses during quiet ground motion times.  You'd expect the signals to be the same unless the GM is different.  All sensors show differences at lower frequencies with V1 starting to diverge at 150 mHz.  Below about 70mHz, the other two vertical traces diverge while the horizontal stays similar to as low as 40mHz.

The second attachment shows all High Gain responses between quiet and large EQ times.  On this plot, the before noted problem of the V1 sensor is not presenting itself, that is, all the vertical signals look similar well below 10mHz.  Does this suggest the V1 low gain signal path has issues?  Otherwise, why would not all the vertical sensors reflect the same GM condition...?

• Initial alignment: Tried first to just lock, but arm powers were low in both green and red (both X and Y), and I was having to move all 3 suspensions to get something reasonable, so it seemed worth it to just do a quick alignment.
• SRCL mode hop offset - put back into guardian yesterday afternoon (forgot to alog)
• Locked to Increase_power, then fast lockloss
  • Barely got to 20W, the lost lock.  OMC SUS was saturating, as were test masses. 
  • See first figure (with "Lockloss1" in the title).  Looks like something happens in MCL (CARM), then other LSC loops get a kick quickly after that.
• Locked, increased only to 10W.  OMC SUS started saturating from ASC after about 2 min.  Held ASC loops by turning master input gain to 0 for all 4 loops, and also reduced gain of the PosY and AngY loops to 0.2 from 0.4 and 0.35 to reduce signal sent to OMC. 
  • Walked up to 20W (sat at 10W for a few min, then 13W, then 16W, then 18W, then 20W).  MCL looks similar to last lockloss, but other LSC loops don't have same kick.  MCL "buzzed" a few times in the last seconds before lockloss at 164.9Hz, not a nice sine wave, looks like something is saturated or slew rate limited or something.
  • MCL seems also to have a ring up near the very end at 183Hz.
  • See 2nd and 3rd figures (with "Lockloss2" in the title) for the buzzing and the MCL ring up.
• Shutter failed the auto-check, but looking at AS_C sum vs. AS_A sum, it's clear that the fast shutter closed appropriately after the lockloss. 
  • The lockloss this happened for the AS power fluctuated up and then back down, before lockloss and the full power going to AS (and the shutter closing).  So, I wonder if our auto-checker gets confused when the power fluctuates just before lockloss.
• ISS AC coupling wasn't working, as a result of Stefan's guardian work yesterday (now fixed), but this seems to have been our problem.  Now able to get to nom low noise!
• Running A2L, then on to a day of noise hunting / calibration time-dependent correction work.

Came in a little early to run ETM Charge Measurements before Maintenance & followed the usual procedure. 

Log:  (Times in PDT)

• 7:20 Begin prep work for measurement
• 7:40 Began measurement (& went out to transition LVEA to SAFE)
• 8:22 Canceled out of measurements due to conflicting Maintenance activity.  So basically acquired 3-full data files (and a 4th data file was bad because I canceled out of it.)

Notes on the procedure/measurements:

• Step 1c: (HV values)  For both ETMs, the HV values remained less than 5V (vs the ~200V mentioned in procedure).  This is with multiple toggles of the HV ON/OFF button.  (NOTE:  ETMx actually did eventually get up to ~175V.)
• General Prep Note:  ETMx & ETMy look different.  ETMx ESD Coil outputs all have values, on order of 50k (vs. ETMy whose similar channels are all zero).  I don't look at these screens enough, but maybe this is due to how we use the ESD on ETMx and how ETMy continues to have a bad ESD (i.e. the LR).  I've attached a screenshot of both ETMs to show what I observe.   Again, this just may be normal, but for someone who doesn't put an eye on these screens often, it was just something I noticed.
• For ETMx measurement (see attached), the 2nd data file had errors, so I only had (2)  good measurements. 
• For ETMy measurement (see attached), had 3 good measurements (all with a "flat" LR which is due to our ill ESD).
• Matlab note:  Since I run this from my account, whenever I run the ESD_Analyse measurement, I select to "Change Folder" vs "Add to Path" when Matlab asks.
• Long Tred Plot (see attached) note:  made stop time:  2018,12,04,18,00,0
  • This gave me only plots for ETMx (see attached).
  • ETMx ESD Charge Eff Bias Trend showed only the Mean data point for my measurement.
  • ETMX ESD Actuatioon Strength Trend showed all the data points at 0.

Here are the original Slider Values (which I returned to after the measurement):

ETMx:

• Pit:  102.2
• Yaw:  -128.4

ETMy:

• Pit:  136.3
• Yaw:  -124.0

Attached a transfer function from yesterday and today along with the pump laser output.

Basically when we had >840mW, something  was noisy and EOM couldn't handle it.

Now that we're down to 770-780mW the loop behaves okay again.

This is the laser output and green production out of the SHG (1day)

SHG scan looked fine. There was no obvious multimode or misalignment yesterday.

We had >840mW yesterday with less green production out of the SHG compared to today. Funny.

The transmission of green from the coupler to SQZT6 also has dropped to 20%. I was able to recover some yesterday with the two pick-off mirrors before the coupler but once the power started to fluctuate it's difficult to do any optimization. I'm still hopeful that this is an alignment drift issue. Would be nice to install additional picomotors there.

Probably this is a readback problem and thus not that important, but there's a bump at around 10kHz in dark noise of IOP channels of LSC-REFL_A_RF9_I_IN1 and Q_IN1, coherence is large between these two channels, and both the shape of the bump and the coherence are dependent on whitening gain.

In the attached, TP_CH28 and 29 correspond to RF9_Q_IN1 and I_IN1 respectively.

Red/blue is with 12dB of whitening gain, green/brown 45dB, pink/cyan 0dB, all with two stages of whitening filters. I don't understand this.

It seems to be a small effect and these digital signals are not used for control, but we need to check if this is present in channels that are actually used for control and on the same whitening board (H1:IOP-LSC0_MADC1_TP24=POP_A_RF9_Q, TP25=I, TP26=POP_A_RF45_Q, TP27=I, TP30=REFL_A_RF45_Q, TP31=I).

Keita, Stefan

We re-centered the green QPD offsets in full-lock (2W but with 20W soft offsets) and physically moved the Green camera back to the screen center.  (work permit 7985 with Chandra's verbal approval).

J. Oberling, R. Schofield

At Robert's request I lowered the flow rates of the PSL cooling circuits by ever so slightly opening the bypass valve in the chiller room.  Our target was to get the flows close to 1.5 lpm.  In the past, the flow meters were happy with flows at this level (unlike when we were running with a flow closer to 1.0 lpm and the meters became very glitchy).  Robert will assess how this small change effects PSL table motion; I will keep an eye on the flow meter readings to see if they become glitchy again.

Flow rates before change:

• 35W FE: 1.7 lpm
• 70W Amp: 2.2 lpm
• Power Meter: 1.7 lpm

Flow rates after change:

• 35W FE: 1.5 lpm
• 70W Amp: 1.7 lpm
• Power Meter: 1.5 lpm

Danny, Craig, Dan Brown

We had a long lock run in low noise tonight. During this we were adjusting the PRC1 offset resulting in some slight alignment drifts of the BS and ITMs (45623). You can see the affect this has on the HWS spherical power here. The alignment offsets started around -3000 seconds on the time axis, first in pitch and then in yaw.

This drift was enough to see how the self heating spot moves relative to the HWS probe beam: ITMY before and after. The red cross is where the IFO beam was before the vent. The other thing to notice is that by choosing the reference time for when the point absorbers have heated up we can get the wavefront distortion without them included, so we see the broader absorption. We also ramped the CO2 heater to get a position of the CO2 relative to the interferometer beam, which is noticeably offset.

We did the same alignment shift images for ITMX, before and after. For ITMX the self heating spot wasn't in a bad position to begin with, however with the new offsets it's become misaligned to the HWS probe beam, so we need to do some picoing.

Lastly, we ramped CO2Y up and down to find the position on HWSY but also to see how the PRC gain and noise was affects. Turning the CO2Y power up 2X resulted in the ASC becoming unstable and noise increased at low frequencies, PRC gain didn't really change. Turning it down 1/2X did the same, DHARD yaw became unstable and we lost lock. We did notice a high frequency bump appearing at several kHz, similar to the frequency noise bump when changing the CO2 laser significantly. More investigation needed on that though. When HWSX is sorted out again we'll run some better comm and diff CO2 tuning.