J. Kissel, S. Dwyer, E. Hall, K. Arai, K. Izumi

I'm embarrassed to say I'm overwhelmed by the wealth of open loop gain transfer functions (OLGTFs) that have been taken recently. But, there's also a ton of stuff to explain, so I summarize comparisons and information from the 3 OLGTFs that were taken prior to this weekend here. More to come on this past weekend's new data.

Summary Points: 
- With a "streamlined" matlab model (similar in content to, but separate from the Noise Budget DARM loop model) we can predict the following DARM OLGTFs (measured between 5 and 300 [Hz]):
2015-03-10, Prior to DARM Loop Shape Modification LHO aLOG 17153
2015-04-02, Post DARM loop modification LHO aLOG 17642
2015-04-06, Post DCPD Analog Electronics Compensation Correction LHO aLOG 17710
to within 10% in magnitude and 5 [deg] in phase (between 5 and 300 [Hz]), with the following uncertainties (determined by the standard deviation of the model parameters for these three comparisons):
     - DC optical gain of 1.1e6 +/- 8%
     - residual, [unknown / unaccounted for] time delay of 93 +/- 30 [us]
- The DCPD Analog Electronics Compensation confusingly did *not* affect the frequency dependence of the OLGTF between 2015-04-02 and 2015-04-06, even to the 10-20% level Koji suggests. As of now, based on these measurements alone, I argue that the lack of discernible change in the OLGTF suggests that we do *not* need to make any correction to our CAL-CS front end calibration.
- Just because I can model the open loop gain TFs to this uncertainty level does *not* mean the overall DARM calibration has this uncertainty. We still have a (potentially) large variation in ESD actuation coefficient due to charge, a (potentially) large uncertainty in the DARM coupled cavity pole frequency, a (potentially) large optical gain fluctuation from lock to lock, and (potentially) large discrepancy between the real actuation strength and what we've measured, and all things of which we haven't realized.

Detail Points:
--------
- Kiwamu had put together a "simple" model of the DARM loop when he'd updated the DELTA L EXTERNAL calibration in the CAL-CS front-end filters after the second-to-last time the DARM loop shape was changed (see LHO aLOG 17151). As he mentions in his aLOG, this code lives here:
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER7/H1/Scripts/DARM_OLTFGTF_LHOaLOG17153.m
That model had included
    Actuation Function
    - The QUAD SS Model that have the current foton filter file's damping filters engaged with gains that are hard-coded into the generate_QUAD_Model_Production function to gather the necessary damped SUS transfer functions in [m/N], i.e. the output of 
    /ligo/svncommon/SusSVN/sus/trunk/QUAD/Common/MatlabTools/QuadModel_Production/generate_QUAD_Model_Production.m
    using the 
    /opt/rtcds/lho/h1/chans/H1SUSETMX.txt
    foton file.
    - An assumed DAC gain of 2^18 / 20 [V/ct].
    - The UIM analog electronics chain using 
    /ligo/svncommon/SusSVN/sus/trunk/Common/MatlabTools/make_OSEM_filter_model.m
    all parameters of which are "as designed" and not measured. This turns the [N] of drive at the UIM into [ct] of drive at the output of the ETMX_L1_LOCK_L bank.
    - The ESD analog electronics chain using a simple, linearized model of 2*alpha*Vbias*40^2, where 40 is the range of the DAC, Vbias is the bias voltage, in units of the DAC [V], and alpha is the force coefficient. He uses the force coefficient that has been confirmed by measurement to be (2.0 * 1.417)e-10 = 2.834e-10 [N/V^2]. (see LHO aLOG 16843) 
    - The ESD driver's single pole filter
    - The correct hierarchical filters from the current foton file (same as above), with known gains grabbed from conlog.
    The DARM filter
    - Loaded in from the H1OMC foton file from the filter archive,
    /opt/rtcds/lho/h1/chans/filter_archive/h1omc/H1OMC_1110098950.txt,
    with known gains from conlog.

    The Sensing Function
    - Assuming the Actuation and DARM DC gains are correct, the remaining scale factor needed to match the OLGTF model to the measurement is what is used for the interferometer's optical gain, in [m/ct]
    - A single-pole zpk filter, with the pole at 389 [Hz]

    Time Delay
    - An overall true time-delay to account for *all* the high frequency behavior like anti-imaging and anti-aliasing filters.

I've used this model as a template to get started, but I've made the following changes to (a) be able to compare many OLGTFs against the model that best represents the DARM loop at that time, and (b) include the now-better-known high-frequency effects:
(1) Pulled out the hard-coded parameters of the model, and put them in a separate function identified by their GPS time,
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER7/H1/Scripts/
H1DARMparams_1109994128.m
H1DARMparams_1111998876.m
H1DARMparams_1112399129.m
(2) I've modified the filter files chosen such that both the OMC *and* the SUS are pulling from the filter archive, not the live data. This will be come relevant later when we track changes in UIM / TST crossover, or when we begin using all stages like LLO has.
(3) I've now included both the analog and digital anti-aliasing in the sensing function, and the analog and digital anti-imaging in the actuation function. The digital AA and AI filters are the same, from the function
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/S7/Common/MatlabTools/iopdownsamplingfilters.m
and the analog AA and AI filters are the same, taken from .mat file inherited from the 40m, which has been pruned and now lives in
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/S7/Common/MatlabTools/analog_65k_AAAI_filter_response.mat

(4) I've included the known time delays:
Sensing: 1 IOP Computation Cycle (65k) + 1 OMC Computation Cycle (16k)
Actuation:1 SUS Computation Cycle (16k) + 3-Cycle IOP Error Checking (65k) + 1 IOP Computation Cycle (65k) + Zero-order Hold Delay (1/2 a 65k cycle)
(which total 205 [us]) and created a new parameter for the "unknown" time delay, which is fit to make the high-frequency phase flat.

Known remaining flaws in the model:
- Mismatch in digital compensation for analog whitening or pre-amps of the DCPDs -- but this should now be *much* better than before (see LHO aLOG 17650)
- Mismatch in digital compensation for analog whitening of the SUS UIM coil driver and now the ETMY ESD Driver filter 
    -- Measurements have shown that the UIM driver agrees quite well with the model (see LHO aLOG 4495), but this hasn't been confirmed for these SUS individually and/or after their increase in range (Integration Issue 762).
    -- The "temporary" ESD low-noise filters (E1500164) were compensated with their designed poles and zeros, I don't know how well they're matched.
- The model uses 389 [Hz] for the DARM coupled-cavity pole, but this is a modelled value from the L1 IFO's losses (see LHO aLOG 15923). Our losses are larger, so we expect our cavity pole frequency to be higher. More to come from Paul and Daniel on this. The data out to 1 [kHz] from over the weekend should also help with getting a measured confirmation.

This model is a function which takes in the parameter files, is called 
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER7/H1/Scripts/H1DARMmodel_preER7.m,
and returns the modelled and measured open loop gain as well as every single possible thing you could possibly ever want out of the model in a parameter structure (including the things that are independently computed in the model itself, like the full actuation function and the full sensing function).
This model can then be looped over, which I've done with the function
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER7/H1/Scripts/CompareDARMOLGTFs.m

I *hope* that this makes it much easier to compare a new DARM OLGTF against others as we take them.

Scott L. Ed P. Chris S.

The crew cleaned 70 meters from last single door to mid station on X-1. Crevice tool cleaning remaining on that section. 

Beam tube pressures monitored by control room operator during cleaning operations.  

Last week I tried exporting some of the blend filters mods that I had developed at ETMX, but found that at least one of the blends didn't work. Today I worked on figuring out why.  I started by doing an ugly hack of Jeff's plot_current_blends script so I could look at the original LLO  blends in complementary form. When I used the hack to look at what I had installed, it became immediately clear why my blend didn't work. In the attached image, I show the complementary version of the "bad" blend (solid lines) and a "good" blend. The good blend is what is currently running on st2 on all of the BSC's in X,Y,Z and RZ. It's a modification of a 250 mhz blend that we stole from LLO (they run a similar blend). The bad blend is a modified version of the 01_28 blend we use on the HAM ISI's. You can see that at .4 hz I managed to introduce a notch ( in the solid red line) that did all kinds of band things to the plant.

This happened because I was designing in foton (blind), and couldn't see the complementarity of the blends from there. I thought I was safe because I was making small adjustments and was trying minimize any phase wobbles around the blend frequency. Turns out that is not enough. I think fixing the complementarity will be relatively simple,  the first image in my alog  17790 shows why I would like to get this to work, roughly an order of magnitude reduction at 1 hz, with some low frequency injection.

The amazing part is this blend runs on ITMY and ETMX.

The 2 attached pdf's are the original blends (1st pdf) and modified blends (2nd pdf) for both stages X, Z, RY, RZ , shown in both installed and complementary versions.

The successful mods I made are adding elliptical filters to the St1 90 mhz Z blend (alog 17702), a more effective elliptical to the St2 250 blends (alog 17488) and an elliptical to 750mhz St1 RZ cps blend. I haven't found the to do much good, but it doesn't do any harm that I've seen.

Kyle, Gerardo 

We switched HAM5/6 annulus pumping over to the small annulus ion pumps and removed the pump carts -> The 500 l/s "main" ion pump was valved into HAM6 but we are leaving the turbo pump pumping in parallel with it over night 


- Commissioners -

HAM6 high voltages components (picomotors, PZT and fast shutter) can be left energized/enabled without monitoring HAM6 pump curve now.

Went through an initial alignment after the PSL incursion, but had issues getting the full interferometer to lock up.  Commissioners had a few attempts which have come close to DC Readout this afternoon, but H1 dropped out at various steps.   They're continuing to get H1 locked UP.

Summary of Day's Activities:

• 8:51:  Jodi to Ymid
• 8:52-9:10:  jeff/andres in Cleaning Area
• 9:10:  fiber work going on in MSR & VPW room
• 9:16 Gerardo heading out to HAM6 for Pump work (switching on Ion Pumps).  Will leave pump cart hooked up until they are happy with Ion Pumps.
• 9:20 Filiberto:  Powering ON Fast Shutter [& Shutter toggle ENABLED] & PZTs in Electonics room
• 9:18 Hugh investigating HAM6 ISI
• 9:28-11:42 Peter/Ed working on FSS ("for an hour")
• 10:30 Jim W trying out L1 Blend Filters on a HAM (~1hr)
• 1:30-2:00:  Gerardo valving out pump cart (and will see if Ion Pumps are happy)
• Dale with big tour after 1pm
• 3:00 Mike/Fred/Richard tour out to the H1 Elec Room

Today, I restored the ITM misaligned TEST_OFFSET and TEST_GAINs which I found to be showing as diffs in SDF - Sheila had been playing with them last week but said they should be restored.  Snapshots of the ITMy "was" and "now" (aka good) values are attached.

Turned ITM R0 OPTICALIGN zeroed offsets and inputs off - these are never used and are just confusing when found on.

Cleaned out BIO/COIL/TEST_SW2 and LOCK_SW2 changes like has been ongoing across all SUSes.

Rolf, Jim, Dave:

after removing the LSC RFM receive errors completely last week, I noticed that the ASC is getting receive errors from the ALS models at the end stations at a very low rate.

The rate of error is one every 8 to 10 hours. The return of the errors can be tracked back to the ALS model changes made last Tuesday 07apr2015 during maintenance. A trend of the ALS CPU usage shows a difference in signature (attached plot shows last 2 weeks of trends) starting last tuesday.

To remind everyone, when the end station ISC was split, the ALS is the "slow" component, so RFM errors would not be entirely unexpected from this sender.

An understanding of beam tube motion as a function of wind speed is important in predicting scattering noise from the beam tube baffles and in deciding if we need to re-insulate the beam tube. This data was taken during the windstorm on Apr. 11, 2015 at baffle #96 (near the power maximum for the diffracted light from the pattern on the original optics), near the first double doors towards the CS from MY. Figure 1 is a photo of the accelerometers attached to the beam tube, and Figures 2-4 show the motion along the different axes at 3 different wind speeds (9, 18 and 24 MPH). As a first guess I would expect peak amplitudes to increase roughly with wind speed to the 3/2 power (wind power goes as the cube), and, very roughly, it seems consistent.

Raw data archive

Today's quest to increase the bandwidth of the FSS involved the following steps:

• removing both notches in the EOM path
• re-installing the original notch of 220 uH and 150 pF
• changing out the 150 pF cap for a 120 pF cap
• restoring the TTFSS back to its original configuration

The file NONOTCH1.TIF is the open loop transfer function with no notches installed.

Unfortunately the NPRO noise eater was oscillating for this measurement.

The file NONOTCH2.TIF is without the NPRO noise eater oscillating.  One can see

the ~760 kHz resonance that the notch was installed for originally.

The file 150PF.TIF is the open loop transfer function with just the one notch installed.

That notching being the one with 220 uH and 150 pF.  The unity gain frequency is a little

over 300 kHz here.

The file 120PF.TIF is the open loop transfer function with the 150 pF capacitor replaced by

a 120 pF capacitor.  The rationale being moving the notch frequency higher might still attenuate

the 760 kHz resonance enough and allow the gain to pushed a little higher.  This introduced

either another resonance or did not sufficiently suppress the 760 kHz one.

The file RESTORE1.TIF shows the open loop transfer function with the TTFSS restored to its

original state.

For all measurements the reference cavity transmission was ~1.45 V, the fast gain was 18 dB

and the common gain was 22 dB.

Ed, Peter
 

Many items are skewed since there is currently activity in the PSL this morning.

Laser Status: 
SysStat is good
Front End power is 31.7W (should be around 30 W)
FRONTEND WATCH is RED
HPO WATCH is RED

PMC:
It has been locked 18 minutes (should be days/weeks)
Reflected power is 1.8 Watts  and PowerSum = 24.2 Watts.
(Reflected Power should be <= 10% of PowerSum)

FSS:
It has been locked for 0 h and 18 min (should be days/weeks)
TPD[V] = 1.4V (min 0.9V)

ISS:
The diffracted power is around 11.7% (should be 5-9%)
Last saturation event was 0 h and 19 minutes ago (should be days/weeks)

HAM6 pumping continues, Kyle/Gerardo swapping annulus pumps

Jim working on updates ISI blend filters

CDS synchro/CPS work, vacuum maintenance for 3IFO, fiber installation between corner station and VPW

Investigating the trip on WHAM6 CPS, Friday night.  Mirky for now.  See the output drives fairly high (solid 100s touching 1000 on OUTF mons) with saturaions totalized over the weekend.  Cleared these and saw a few more shortly.

Took ISI and HEPI down to review free hanging position.  HEPI Deltas (Free Hang-Servo position) pretty small except Rz w/ ~24urads.  The ISI too had a larger than we left it Friday shift in Rz.  Of course, HEPI Rz can not affect ISI Rz.  The ISI Rz shifted about 9urads from Friday.  Recall, on Friday we had 70urad shift on Rx.  Maybe further temperature and pressure shifts are settling out.  The Reference Target Positions were reset to match the free hanging location.  The loops close fine and the OUTF drives are as expected, markedly smaller.

If alignment in HAM6 is an issue, use HEPI first for horizontal changes to keep the ISI drive reduced.

Commissioners - SDF shows that someone changed the P and Y Damping gain on Thur April 9th.  I couldn't find why in the alog...  See attached.  This maybe should be restored...?

Sheila, Alexa, Evan

Summary

We have recovered the usual low-noise locking state (except for the outstanding issue of the HAM6 centering scheme) and have turned up the power to 15 W.

Details

• Alexa and Sheila traced the ALS DIFF problems to the wrong coil state in ETMX L1; it was in low range mode, and hence saturating when DIFF engaged.
• IMC-F was saturating every 10 minutes or so. First we increased the UGF for the slow common feedback from 20 mHz to 40 mHz. That helped a little, but we had much more success by adjusting the settings for red tidal feedback. It now engages when each arm's TMS WFS B goes above 50 ct (with a 1 s holdoff), and disengages below 20 ct. This way, the tidal engages during the CARM reduction sequence, right before control of DARM is handed over from ALS DIFF to AS45Q. Excursions of IMC-F are now about 100 kHz pkpk (albeit with low wind).
• ITMX CO₂ laser heating was off. We turned it on to the usual 0.2 W.
• The OLTF gain for the dETM WFS seems to have increased; we had to turn down the filter module gains to 10 for pitch and 5 for yaw (whereas they used to be 14 and 21).
• The DARM optical gain appears to have changed. Our usual DARM ERR offset of 2e-5 ct, which previously gave something like 23 mA total from the two OMC DCPDs at 10 W PSL power, now gives more like 35 mA at 10 W PSL power. When we remeasured the DARM OLTF, we found that we needed a DARM filter module gain of 2000 ct/ct to achieve the same UGF as last week (compared to 1300 ct/ct that was used previously).
• Consequently, the DARM calibration was wrong. Using Kiwamu's script, I reckoned that the optical gain had to be increased from 9.09e-7 m/ct to 1.40e-6 m/ct (see attached plot and xml file). So I changed this value in CAL-CS_DARM_ERR FM5. That made the spectrum more resonable, but it seems that the high-frequency noise floor is still at or above the GWINC 10 W curve, even after bumping up the CARM gain. [Note that the old optical gain produced a phantasmagorical 50 Mpc lock stretch in the summary pages.]
• For 15 W, we closed the POP shutter on ISCT1, since POPAIR_A already has 25 mW dc at 10 W of PSL power.
• For 15 W, the DARM ERR offset was reduced to 1e-5 ct, giving 14.6 mA total dc on the OMC DCPDs. If (IF) the current calibration is correct, the DARM offset is about 12 pm. We could always bump this up to the 15 pm we were using previously.

As before, HV in HAM6 has been turned off for the night.

Here is a measurement of the DARM OLG with the ETMY linearization off.  It isn't changed significantly from when the linearization was on (blue reference). 

Note:  the calibration is off tpnioght, we have changed the DARM offset but haven't corrected the calibration for this so at the moment our sensmon range is nonsense.  More details about todays locking coming later. 

Alexa, Evan, Sheila, Koji

Koji, Evan and Alexa tested both the OMC PZT shutter and the fast shutter, realinged ISCT6, removed the ND filter from AS AIR and installed ND filters as beam dumps in the OMC refl path.  More details about that are coming in a latter alog.  

After Dave helped us get the h1boot back, we got a late start on trying to recover locking.  We got through the inital alingment procedure, evan set the whitening gain so that the signals out of AS AIR should be roughly similar to what they were before the change of OM1 and removal of the ND filter (he changed it from 42 dB to 15dB).  Some gains still had to be readjusted X arm IR locking gain was changed from 0.04 to 0.12, MICH dark locked gain was changed from -2000 to -1000.

We ran into a few problems along the way, the PSL noise eater was oscillating (and has been for a few days).  After togling the switch the ISS would not lock, we reset the reference level to get it locking again.  We also found a variety of settings which seem to have been wrong, the COMM PLL input was disabled, the DARM input was off, the SRM top stage length was on.  

We have been able to lock ALS COMM, but DIFF is not working.  We can engage it with a low gain, see that the PLL is kept in range, but we cannot turn the gain up. This is behavior similar to what happens when the ESD is not working, but we tried exicting the ESD in angle and watching the OpLev, we can see that it does respond.  

Also, the ETMY ESD has been tripping many times tonight, even though we have not tried to actuate on ETMY at all. 

As Kyle requested, we disabled the HV in HAM6. For the OMC PZT, we disabled the output of the 100 V Kepco supply. For the shutter, we flipped the HV enable/disable switch on the driver chassis next to HAM6.

For Jeff, we are leaving both arms locked in green with neither ALS COMM or DIFF locked.  The wind is not as high as it was forecast to be tonight.