Guardian just spent 40+ minutes in ENGAGE_ASC_PART3 state. DSOFT and CSOFT kept switiching back and forth between "ON:INPUT" and "OFF:FM2". I set the ISC_LOCK to manual and skipped to the next step, lost lock shortly of course. Now I'm stuck at ENGAGE_ASC_PART2 with Guardian message "POP A has a large offset. Align by hand." but abs(ASC-POP_A_PIT_IN1) and abs(ASC-POP_A_YAW_IN1) is already less than 1 (conditions for the Guardian to move on to the next state). Still trying to figure out what to do.

The low frequency sensitivity (below 50 Hz) was coherent with CHARD PIT and YAW. I tried to retune the A2L, first using Hang's script: I had to fix a bug in the function call (number of steps passed as double instead of integer). The script ran, but made the coupling much worse. So I tried to measure by hand the couplings, injecting lines at 21 Hz. A the end of the day I got a performance similar to what I could get reverting to the A2L coefficients of one day ago. So I reverted to the old coefficients.

At 0:53 LT I reduced CHARD PIT and YAW gains by 20 dB, and as expecetd the noise got better. However, the low frequency is non stationary.

The first plot shows the situation at the beginning of a full power, low noise lock. The ISS second loop is closed. After the re-tuningof the IMC offsets, the periscope peaks are no more visible in either the in-loop or out-of-loop ISS second loop signals.  This is very good.

However, the first plot shows that the peaks were, at that time, still visible in the DARM spectrum, together with some coherence with the periscope accelerometer. So, there is residual beam jitter that does not generate intensity noise anymore, but that is transmitted to the IFO input and couples to the OMC transmitted power.

The second plot shows the situation after a while we were locked in low noise. The peaks are no more visible in DARM: so something in the IFO drifted in the right direction (probably some thermally induced drift) and now jitter is no more converted by an IFO misalignment into intensity noise. This is something interesting to investigate in the future over long lock stretches.

ALL TIMES IN UTC

• 22:01 Kiwamu out to LVEA to measure ALS Diff PLL electronics next to the PSL enclosure.

• 22:03 Gabriele has taken the mode cleaner for measurements.

• 22:35 Kiwamu out of LVEA

• 23:33 Sigg, Stefan and Robert out to the PSL to connect a cable for RIN strain measurements WP#5434. Robert will be monitoring the environmental entry procedure from outside the enclosure.

• 23:45 Kiwamu back out to the floor to measure next to the PSL again

• 01:00 Sigg, Stefan and Robert back from PSL. temps monitored by me in dataviewer. Temp dropped by a few degrees as expected 73F to 69F. Everything remains normal.

• 01:40  we’ll try locking now. Winds around 35mph

• 02:15 TCAC members start arriving for tonight’s outreach event

• 03:39 IFO fully locked at NOMINAL_LOW_NOISE

• 03:40 Lockloss. Will attempt relock at DC_READOUT

• Dale called to inform me that the Star Party is over and that some late comers may show up.

Summary:

• The beginning of the night was slow with high winds. IFO hadn’t been locked all day because of the high winds.After a couple of hours I began locking and had to contend with a troublesome Y-Arm.

• Input_Align gave me trouble so Sheila and I tried increasing gains and decreasing trigger times to no avail. So we moved on with the other alignments.

• The IFO came into full Nominal_Low_Noise lock for a few minutes. Lockloss most likely due to poor initial alignment done while the wind was still about 30mph.

• We re-did Initial Alignment.

• subsequent attempts to lock resulted in loss, mostly at Engage_ASC. Sheila edited guardian in a way that I believe breaks up the engaging of the ASC loops into different times rather than all at once.

• Shift ends in about 30 minutes. IFO locked at Nominal_Low_Noise/22.1W for about 45 minutes now @ 60mpc. Wind has calmed to about 20mph.

Ed, Gabriele, Sheila

We had three locklosses in a row while engaging ASC.  I've rearranged the ASC_ENGAGE state in the gaurdian, breaking it into three separate states.  

ENGAGE_ASC part1 does the set up, turns on CHARD, checks the recylcing gain.  If the recycling gain is OK, it engages PRC2 and INP1, other wise it gives a message to align by hand and will not move on.  This logic was in the old state, but it did not stop to wait for by hand alingment.  Once the recyclcing gain is high enough, the guardian will engage PR2 and INP1, so the user may want to pause the gaurdian if aligning by hand. 

ENGAGE_ASC_PART2 increases the gain for the SRC loops, this part used to be done after engaging PRC1 but we tested this and it is fine.  Then it checks the POP offsets, and if they are small enough it engages the PRC1 loop.  Otherwise it gives the user a message again, and keeps checking the offsets.  It will move on if the drop below the threshold, so if you are aligning by hand you may want to pause the guardian. 

ENGAGE_ASC_PART3 engages the SOFT loops.  There is a place hoder here to check the offsets and not engage if they are too large.  I put this in because sometimes we are loosing lock when engaging these loops, however based on the last lockloss it wasn't obvious how to set a threshold, so currently there is no check, they will always be turned on.  As we collect some data while running next week we can look at these locklosses and set an appropriate threshold.  

The main motivation for doing this is because the checks that we had previously written weren't really being used (the guardian would move on, just leaving the PRC loops off, but this might not be obvious to the user).  A secondary benefit is fewer blocking calls so that we will check for locklosses in places where we used to miss them.  

We tested this once, but did parts of the PART2 state by pasting into the command line.  The only untested change is turning on the ITM offloading to the top mass in when we first turn on DHARD.  Now we are both turning on the offloading and setting it to the full gain in the state DARM_WFS.  (lines 1052 to 1056 used to be near the end of the engage ASC state).  #guardbomb

The other thing to note is that the OFFLOAD_ALIGNMENT state generators are no longer requestable.  I've been slowly trying to reduce the number of requestable states so that we have options that we need in the drop down menu, and fewer options that shouldn't be used. 

Our X arm green WFS took extremely long to converge (up to 8 minutes.)  While it was too windy to lock this afternoon gabriele and I increased the gain of ALS-X_WFS_DOF_1 and 2 by a factor of 3, now things should be faster.  A factor of 10 gain was too much, the loops became unstable.

We probably have not been waiting long enough for these loops to converge while doing inital alingment, hopefully things will go better now that they are a little higher gain.  However, it is still a good idea to watch the control signals to see when the converge.  Ed has put templates called XARM_GREEN_WFS and YARM_GREEN_WFS in ops/Templates/StripTools that can be used for this.  

J. Kissel, J. Driggers, C. Cahillane, K. Izumi

I've taken the data that we took last Sunday of the ALS DIFF PLL Open Loop Gain TF and Boosts (from LHO aLOG 20363), built a model of the loop. Given the precision of the measurement, I can make a model the reporoduces the boost filters and the PLL OLGTF to within 1% and 1 [deg]. The most important outcome of this is the ability to characterize the frequency dependence of the low-pass filter just before the VCO. The nominally z:p = 40:1.6 VCO Filter is actually a z:p = 1.05:40 Hz filter. This means that, in using the ALS DILL PLL CTRL signal, prior estimates of overall actuation strength of the QUADs (i.e. LHO aLOH 18711) was over estimated by (1.6-1.05)/1.6 = 34%. This potentially explains some of the discrepancy we saw when comparing the three methos, PCAL, Free Swinging Michelson, and ALS DIFF VCO in LHO aLOG 18767.

Of course, as you know, we plan remeasure all methods and make the comparison again.

Details:
------------------------------------
Here're the final answer numbers of the model:
                                                   Traditionally Quoted "Nominal" Values            This Model's Fit Values
Phase Frequency Discriminator (PFD)                        z:p = (none):(0Hz)                   z:p = (none):(0Hz, 450kHz)
Voltage Contolled Oscillator (VCO)                         z:p = 40Hz:1.6Hz                     z:p = 40Hz:1.05Hz
Phase Locking Loop (PLL) Control Common Gain               26 [dB]                                                     25.5 [dB]
Phase Locking Loop (PLL) Control Boost Filter 1            z:p:k = 20kHz:2kHz:0dB               z:p:k = 1.9kHz:1.89kHz:0dB
Phase Locking Loop (PLL) Control Boost Filter 2            z:p:k = 2kHz:40Hz:0dB                z:p:k = 1.95kHz:38.55Hz:-0.2dB

------
Attached are figures demonstrating the progression and precision of the model.
pg1 : The final answer, showing the model of the ALS DIFF PLL Open Loop Gain TF from 0.1 Hz to 1e6 Hz.
pg2 : PLL Control Boost Filter 1; a comparison between measurement, model with fit parameters, and nominal parameters
pg3 : PLL Control Boost Filter 2; a comparison between measurement, model with fit parameters, and nominal parameters
pg4 : PLL OLGTF, with out the boosts engaged
pg5 : PLL OLGTF, with boosts engaged
pg6 : A comparison between fit residuals and nominal residuals with measurement.
pg7 : A confirmation that the closed loop gain, G / 1+G, of the ALS DIFF PLL is indeed 1.0 to better than 0.1% out to 1 kHz.

------
Perhaps it is of interest for the scrutinous to focus on pg 6, where I compare the residuals, and it'll illustrate my motivations for the fit paramaters, and my quoting that we trust their values to such high precision.
Question 1: Why d'you think the magnitude uncertainty is less that 1%, when clearly the boost OLG measurement residual falls by 15% with frequency below 1 kHz, and the unboosted measurement residual falls by 10% with frequency below 100 Hz?
     Recall that at these frequencies, below 1 kHz and 100 Hz for the boosted and unboosted measurements, respectively there is a rediculous amount of loop suppression. As such, given that the phase residual holds up well to fitted poles, and has little affect on the magnitude residual, I suspect that the measurement magnitude drops with frequency as the suppression increases due to very-small, non-linear, in-loop voltage affects.

Question 2: Why do you think there's an 450 kHz pole in the PFD when you've only measured up to 100 kHz?
     I played around with the very-high-frequency response for a while. Of course, a pole is the only high-frequency tool one has to affect the magnitude residual, and 450 kHz was a good balance between the fitted time delay, and the frequency of the pole. Both the 800 [ns] and 450 kHz pole are "plausible." Inside the PFD, there is a fast chip, that the data sheet claims is good up to 100 kHz, but that doesn't mean much, because you don't know what rolloff filter was chosen. 800 [ns] would correspond to a few hundred meters of cable length difference, so it's not that. But if I see a consistent ~230 [ns] delay in the indepednent measurements of the boost filters, it's not crazy to think that the whole phase-locking-loop accrues 800 [ns].

------
The analysis script that built this model is commited to the CAL SVN here:
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER8/H1/Scripts/ALSDIFF/ALSDIFFModel_PreER8.m
and the plots live here:
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER8/H1/Results/ALSDIFF/2015-08-09_H1ALSDIFF_PLL*.pdf

In order to determine how sensitive we are to activities at the site, and to help set rules for the O1 run, I injected human disturbances as recorded in the table below. DetChar, can you run these times to see if there are events detected in DARM for these activities? My timing should be good to within a second.

Daniel, Stefan

Puzzled by Evan's elog on the still persisting broadband noise (alog 20524), we hooked up the pre-EOM driver 45MHz RIN monitor again (plot 1)

- Interestingly, the out-of-loop RIN monitor is still coherent with the pre-EOM driver input (just 38 dB lower), although there is a sign flip below ~2.5kHz (plot 2 shows the transfer function).

There is some suspicion that motion of the HAM1 table is contributing to CHARD noise. I learned today that LLO is using some inertial isolation on their HAM1 HEPI platform (i.e. they are blending L4Cs & IPSs, and use that signal for feedback control). I've started looking in to doing this here, but I wanted to see what kind of gains we could maybe expect from such a scheme. The two attached plots are (first image) LH0's HAM1 L4Cs versus our ground, and (second image) LLO's HAM1 L4C's versus their ground. A few points:

  1. X at low frequencies at both sites sucks. I suspected sensor correction, my third image is an on/off comparison. X is a lot better with it off (blue is sensor correction off, red is on, green and brown are the grounds). We are getting hammered by wind right now but the performance is equally bad without sensor correction). I remember turning HAM1 sensor correction on a while ago, and did a measurement where I thought it was making an improvement at the time, so I'm not sure what happened here. Y is not as bad, but I've turned it off as well.

  2. At 1 hz LHO is doing almost as well as LLO because our ground is quieter. Yay us.

  3. The real improvement would come between 1-10hz, where LLO is moving less by ~1.5 orders of magnitude. This will mean installing blends, which is an easy copy paste with foton. Or if LLO was nice they'd send a mat file with a zpk. It wil also mean that we would need to redesign the isolation loops for a UGF above where we want isolation. Right now they are probably 2hz loops, I would guess that LLO's are probably 10-15.

The 2 actions I want to do before 01 are:

      1. turn off X/Y sensor correction... which is done. I'll look at the filters and see if I can find whats wrong, but for now I would expect to leave this off. Z sensor correction seems to work fine.

      2. Install the LLO blends and see if they make things better at least a little better around 1 hz, and not make things worse at low frequency. I would like to do this Monday.

After that I can look at redesigning the isolation loops, or maybe just copy LLO's, but I would worry that the higher frequency parts of the plant may be different.

Summery:

So much wind...

Log:

Times in UTC (PST)

1505 (805) Ken done.

1515 (815) Jeff B done.

1524 (824) Ken to EY to work on lights, he will not be in the VEA.

1550 (850) Fil to CER.

1553 (853) Jeff B to EX to unplug dust monitor.

1615 (915) Ken done.

1621 (921) Jeff b done.

1637 (937) Bubba going down Yarm.

1804 (1104) Ellie, Fil going into the LVEA to look at ISCT4.

1820 (1120) Ellie, Fil back

2036 (1336) Andres to Ends for tmp sensor

2037 (1337) Kyle to Y28

2115 (1415) Kyle back

2221 (1521) Stefan to LVEA

Windy days are bad for locking, but good for other side activites. So I sat down to write a script that automatically tune the IMC aungular offsets to reduce to minimum the coupling of jitter to intensity noise. It basically follows the same procedure I performed manually earlier today. The script is attached to the elog entry. You can sae it and run it from terminal. it will open up a plot showing you the progress of the tuning. Run the script with the IMC locked, no IFO and ISS second loop open!

Here is what the script does

1. Turn on excitations on the PSL PZT at 101 Hz (pitch) and 153 Hz (yaw). The excitation is removed when the script exits (even if you kill it with CTRL+C)
2. Open up a window that shows you the progress of the tuning. There are three panels:
   1. Error signals for the tuning: real part of the transfer function of ISS_SECONDLOOP_SUM14 over excitations, both pitch and yaw. if the tuning is working, these two traces will be driven to zero
   2. Monitor of the band-limited RMS of ISS_SECONDLOOP_SUM14  in the 200-400 Hz region. this is where most of the PSL periscope noise sits, so if everything goes well you'll see this trace dropping down close to zero (typical values today when the alignment was good were 0.01-0.02 a.u.)
   3. Monitor of the IMC WFS offsets. The tuning acts on IMC-DOF_2_P_OFFSET and IMC-DOF_1_YAW_OFFSET, since those seem to be the most important offsets
3. After an intiial wait of 30 seconds, the script will start servoing the error signals to zero by changing the offsets. Basically, it reduces to minimum the coupling of the two PZT angular lines to the power transmited by the IMC (as seen by the ISS array)

The script has a built in check of the IMC power, and it doesn't change any offset if the IMC is not locked. There is no check on the convergence of the error signals, but the script terminates automatically after 10 minutes, which is typically more than enough to find the right offsets. However, you can terminate the script with CTRL+C when you're satisfied withe the results. The excitations will be automatically removed.

I tested the script several times with random starting offsets, and it worked all the times.

The first attached plots show a comparison of IMC transmitted RIN before and after the script was run. The other plots show some examples of the plots generated by the script, showing the tuning in action.

Charge measurements was done on both ETMs.
It is early enough to discuss the new tendencies, but probably ETMY change the sign of charging after changing the bias sign on ETMY (see 20387).
Now (since Aug,10) both ETMX and ETMY Biases are -9.5V, 
Current results are in attachment.
Upd: Additional set of measurements was done at 12pm - 2pm (local). Windy, so the errors are large. New plots added. Script for gamma measurements debugged and tried on some of these measurements, results are not ready yet. 

(TJ writing as Nutsinee)

No locking happening today so far, gusts breaching 50mph.

Getting some good windy data though!

Scott L. Ed P. Rodney H.

8/13/15
The crew cleaned 59 meters of tube and bellows ending at HSW-2-006. All support tubes on Y-2 are vacuumed and capped. The water tank was also refilled.
Today was the last day for Rodney. 

8/14/15
Scott L. Ed P.
39.8 meters of tube and bellows cleaned ending at HSW-2-004. Both men had appointments in town and left at lunch. 

Chris S.(85%) Joe D.(60%)

Since 8/4 the guys have had various other chores, they also had to cut more metal into 10' lengths and since that date they have cleaned the existing seal joints, installed metal strips and caulked 500 meters of upper tube enclosure.

This brings the total installed to 1680 meters of enclosure on X-1. We are currently waiting on more metal to arrive. It has been ordered for 3 weeks.

This morning I retuned the IMC alignment WFS offsets to reduce the coupling of jitter into the ISS array.

The results

I could reduce to basically zero the coherence between the PSL periscope accelerometer and the ISS second loop signal, with the IMC locked and ISS second loop open. The first plot shows that the periscope noise between 100 and 700 Hz reduced down to the background noise of the signal. The two lines at 101 and 153 Hz are respectively a PZT pitch and yaw lines I was injecting.

The new offsets are

The procedure

Here is the procedure I used to tune the offsets, in details:

1. Inject a 101 Hz line in IMC-PZT_PIT_EXC with amplitude of 3 and a 153 Hz line in IMC-PZT_YAW_EXC with an amplitude of 3
2. I wrote three python scripts to monitor the jitter coupling (attached to this elog). The scripts demodulate_iss_pit.py and demodulate_iss_yaw.py gives you a real time plot of the demodulated amplitude of the excitations lines in the ISS power signal. Each plot contains the real and imaginary part of the ransfer function at the line. Those traces turned out to be a wonderful signal to tune the offsets. See in the second plot how the traces go to zero when the offsets are tuned. The third script online_blrms.py gives you another real time trace of the band-limited RMS of the ISS signal in the 200 to 400 Hz, thus measuring the noise due to the jitter peaks. Notice in the second plot how the noise reduced a lot when the yaw offset was tuned.
3. You can run the three scripts from any terminal, at the same time, and watch the traces as you change the offsets
4. Today the yaw offset was the worst one, so I tuned it first. here is some cross coupling between yaw and pitch, so chancing the yaw offset had an effect in pitch too. With a few iterations I converged to the final values above.

This entry is meant to survey the sensing noises of the OMC DCPDs before the EOM driver swap. However, other than the 45 MHz RFAM coupling, we have no reason to expect the couplings to change dramatically after the swap.

The DCPD sum and null data (and ISS intensity noise data) were collected from an undisturbed lock stretch on 2015-07-31.

Noise terms as follows:

• Shot noise
  • For 20.0 mA dc on the DCPD sum, we expect a shot noise of 8.0×10⁻⁸ mA/Hz^1/2.
• Dark noise
  • Dan and I measured this a few months ago. In full lock we use one stage of whitening, which amounts to a dark noise of 1.5×10⁻⁸ mA/Hz^1/2 or so above 100 Hz. We have at times experimented with two stages of whitening, but it requires some vigilance regarding the violin modes.
• Intensity noise
  • Coupling was measured à la Kiwamu by leaving the outer loop off and driving the inner-loop excitation point. For the noise estimation, I used the outer loop out-of-loop sensor. Since Sudarshan et al. previously found that this is artificially high, this estimation is an upper limit (though probably no more than a factor of 3, given Sudarshan's plot).
• Frequency noise [CARM sensing noise only]
  • Previously (i.e., when we locked CARM using the in-air REFL sensor), I estimated the coupling by looking at the TF in-vac REFL to DARM, and for the frequency noise estimation I used the noise of in-vac REFL as an upper limit for the frequency noise. Since we now lock with in-vac REFL, which has more light on it than in-air REFL does, I do not expect that the noise of in-air REFL is a particularly useful upper limit for the frequency noise.
  • Therefore, I have tried to instead estimate the sensing noise in CARM (from in-vac REFL, the summing-node board, the common-mode board, and PDH shot noise) in V/Hz^1/2 and propagate it (using the Izumi/Sigg expression) into a frequency noise in Hz/Hz^1/2. For the CARM optical TF I use 12.7 W/Hz at dc, with a pole at 0.48 Hz.
  • Then I have injected noise into CARM and looked at the TF from the residual of the excitation into DARM. This is the coupling TF needed to propagate the estimated sensing noise to DARM, assuming the CARM gain is high (this isn't quite true at high frequencies; the ugf is 17 kHz or so, and the gain does not exceed 20 dB until 3 kHz).
  • Since this includes sensing noise only (and not, for example, FSS noise), I have labeled it as a lower limit. In fact, the coherence between REFL 9Q and the DCPD sum is about 0.04 around 7 kHz, perhaps suggesting a frequency noise contribution of 2×10⁻⁸ mA/Hz^1/2 or so. More investigation required.
• Oscillator phase noise [not included here]
  • Stefan and I measured the coupling of the 9 MHz RF source into DARM, and using the expected performance of the OCXO estimated the noise in DARM should be 2.8×10⁻¹⁰ mA/Hz^1/2 at 1 kHz. This is quite low (and not shown on the plot).
  • This number should be replaced with Alexa's and Daniel's measurements of the phase noise. An even more satisfying number could be made by trying to measure the 9 MHz and 45 MHz phase noises in situ, closer to the EOM (e.g., at the output of the distribution system on the ISC rack).
• Oscillator amplitude noise [45 MHz only]
  • In this case we know that the 45 MHz RFAM is the dominant contributor (other than shot noise) to the DARM noise above a few hundred hertz. Here I use Stefan's estimate of the RFAM-induced photocurrent (1.8×10⁻⁸ mA/Hz^1/2), which (as he notes) is not enough to explain the excess between sum and null.
  • However, based on tonight's measurements using the new EOM driver readback, it seems that 45 MHz RFAM is enough to explain the excess. Perhaps Stefan's measurement is an underestimate, since it was done at the output of the distribution system and did not include the final rf amplifier before the EOM.
  • As for 9 MHz RFAM, Stefan and I made an estimate of the coupling from the 9 MHz source into DARM. Based on the specified performance of the OCXO, the expected noise in DARM is quite small. However, it would be better to look somewhere further downstream, as Stefan did (although I think he said the measurement was not that clean). This noise is not estimated in the plot.

The downward slope in the null at high frequencies is almost certainly some imperfect inversion of the AA filter, the uncompensated premap poles, or the downsampling filter.

ISC: Did some good work last night, changed ASC input matrix to a, hopefully, good setting.

CDS: PEM antennas, noise on tigger signals, Vault seismometer.

PSL: PMC work on Tuesday. OpLevs currently behaving.

VAC: Today they will be driving between Y28 and X28 and dropping off things.

Fac: Beam tube cleaning ongoing, front double doors do actually lock (see Bubba if you need instructions on how to lock properly)

Monday is the start of ER8, there will be 3 weeks till the O1.

Week 1 - Annealing. The intent is to bring the IFO to a stable operating state.

Week 2 - Calibration. Stability, stability, stability.

Week 3 - PEM injections and commissioning cleanup.

Then if all is well at both sites, O1.

(Please see JRPC site for a more detailed and accurate schedule)