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Reports until 13:41, Tuesday 04 March 2014
H1 CDS
david.barker@LIGO.ORG - posted 13:41, Tuesday 04 March 2014 (10497)
Summary of model restarts during today's maintenance

Today's restarts tested my new model restart logger. Here are the contents of the file /opt/rtcds/lho/h1/data/startlog/2014/03/04/2014_03_04_model_start.log

 

2014_03_04 09:53 h1susitmy

2014_03_04 09:58 h1iscey

2014_03_04 11:46 h1isibs

2014_03_04 12:24 h1isiitmy

2014_03_04 12:25 h1isietmy

2014_03_04 12:44 h1lsc

2014_03_04 12:47 h1pemmx

2014_03_04 12:54 h1isiitmx

2014_03_04 13:10 h1isietmx

 
and not logged by the system yet:
2014_03_04 13:11 h1dc0
2014_03_04 12:24 h1isiitmy
2014_03_04 12:25 h1isietmy
2014_03_04 12:44 h1lsc
2014_03_04 12:47 h1pemmx
2014_03_04 12:54 h1isiitmx
2014_03_04 13:10 h1isietmx
2014_03_04 09:53 h1susitmy
2014_03_04 09:58 h1iscey
2014_03_04 11:46 h1isibs
2014_03_04 12:24 h1isiitmy
2014_03_04 12:25 h1isietmy
2014_03_04 12:44 h1lsc
2014_03_04 12:47 h1pemmx
2014_03_04 12:54 h1isiitmx
2014_03_04 13:10 h1isietmx
H1 DAQ (CDS)
david.barker@LIGO.ORG - posted 13:35, Tuesday 04 March 2014 - last comment - 13:43, Tuesday 04 March 2014(10496)
DAQ restart, resyncing to new models, added one channel to DMT Broadcaster

13:11PST performed DAQ restart. Was not a clean restart, the following frontends required a restart of their mx data stream: susauxex, susex, pemmx, susauxey, iscey, sush2b, sush56, susauxb123, susauxh34, susauxh56. As normal, h1psl DAQ flags went red/green during these resyncs.

DAQ restart was needed due to new models on: h1susitmy, h1iscey, h1isibs, h1isiitmy, hisietmx, h1lsc, h1isiitmx, h1isietmx.

DMT broadcaster was reconfigured to add one new channel: H1:PSL-PERISCOPE_A_DC_POWERMON

Comments related to this report
david.barker@LIGO.ORG - 13:43, Tuesday 04 March 2014 (10498)

h1broadcaster was very slow to come back from the DAQ restart. We manually restarted it and it eventually started. No errors were seen to explain this.

H1 SEI
sebastien.biscans@LIGO.ORG - posted 13:20, Tuesday 04 March 2014 (10495)
BSC-ISI models/scripts/MEDM screens successfully updated

The models (master and local models), scripts and MEDM screens have been updated to support new changes made by the Stanford crew (see update list DCC T1400012).

Everything went well and has been committed.

H1 SUS (ISC)
jeffrey.kissel@LIGO.ORG - posted 13:18, Tuesday 04 March 2014 - last comment - 13:18, Tuesday 04 March 2014(10493)
H1 SUS ETMX PUM/L2 Coils Balanced
J. Kissel, A. Pele

Following the same procedure outlined in LHO aLOGs 9453 and 9079, Arnaud and I balanced the coils on the PUM stage of H1 SUS ETMX. The final balanced gains in the L2_COILOUTF bank are

H1 SUS ETMX
Channel     Balanced COILOUTF Gain
L2 UL            +1.034
L2 LL            -1.014
L2 UR            -0.986
L2 LR            +0.966

The precision to which we could balance the coils was limited by the day-time ground motion (we saw an almost instantaneous loss in SNR once the day-time 1-10 [Hz] noise increased around 8:30a PT), but we believe the obtained values are good to within +/- 0.5%.

This balancing has reduced the L3 P and Y caused by a L2 pringle excitation at 4 [Hz] by
   DOF                  Reduction Factor @ 4.0 [Hz]
    P                          > 6.0      (peak below the noise, and totally incoherent)
    Y                          > 7.3      (peak below the noise, and only ~60% coherent)
The first attachment shows the result from which these values were obtained, comparing the optical lever ASD at 4 [Hz] driven from L2 at the same amplitude for both balanced and unbalanced configurations.
Non-image files attached to this report
Comments related to this report
jeffrey.kissel@LIGO.ORG - 13:18, Tuesday 04 March 2014 (10494)
Measurement Details
-------------------

Coil Driver Configuration:
State = -2, with all COILOUTF compensation filters turned off
This is the configuration which gets the most drive to the coils, given that the analog driver in this "acquire" configuration has [z:p] = [1.35:80.5], see LLO aLOG 4495).

Demodulator filters used:
SIG band pass: BP4.0Hz = butter("BandPass",2,3.5,4.0)
DEMOD I & Q low-pass: CLP50mHz = cheby1("LowPass",2,3,0.05)

Demodulator Drive Parameters
 Freq [Hz]     Amp [ct]     Sin [ct]    Cos [ct]
 4.0          125000         10000     10000
 4.0          125000         10000     10000
Note -- we started off at 6 [Hz], but was not able to get enough SNR with a half-hour's worth of effort, so we moved down to 4 [Hz]. Again, we want to stay away from any suspension resonances that might complicate the signal, but get the frequency high-enough that we get lots of cycles inside the 50 [mHz] band pass.

SEI Configuration:
HPI: Level 1 Isolation, "Pos" position sensor only blend filters
ST1: Level 3 Isolation, "TCrappy" blend filters (in all DOFs)
ST2: Level 3 Isolation, "TStart" blend filters (in all DOFs)
Note -- we had started around 7:30a PT this morning, but the day-time ~1-10 [Hz] noise quickly started to create a lot of excess noise at our drive frequency. We played around with the ST2 blend configuration until we found something we'd liked. I'm not sure that it makes sense -- the TCrappy filters have a factor of 2e-4 displacement sensor isolation at 1 [Hz], where the TStart only has a factor of 0.3 -- but the SNR was clearly better with TStart on ST2. (see LHO aLOG 10408 for blend filter details).

Resulting Demod Phases:
Measured using a 300 second average of the demodulated signals, i.e.
tdsavg 300 H1:SUS-ETMX_LKIN_P_DEMOD_I_OUT H1:SUS-ETMX_LKIN_P_DEMOD_Q_OUT H1:SUS-ETMX_LKIN_Y_DEMOD_I_OUT H1:SUS-ETMX_LKIN_Y_DEMOD_Q_OUT
H1 ETMX L2
     Demod Phase [deg]          Unbalanced Value [ct]    Balanced Value [ct]
P       145              I         +1.385 pm ~0.5           -0.12 pm ~0.75
                         Q         -0.064 pm ~0.5           -0.08 pm ~0.75
Y       153              I         +1.027 pm ~0.2           -0.09 pm ~0.25
                         Q          0.054 pm ~0.2            0.08 pm ~0.25

To perturb the PIT or YAW balancing by 1%:
/ligo/svncommon/SusSVN/sus/trunk/Common/PythonTools/perturbcoilbalance_fourosem.py H1 ETMX L2 [PIT/YAW] 0.01

Exact balanced values:
Measured using a simple command line caget, i.e.
caget H1:SUS-ETMX_L2_COILOUTF_UL_GAIN H1:SUS-ETMX_L2_COILOUTF_LL_GAIN H1:SUS-ETMX_L2_COILOUTF_UR_GAIN H1:SUS-ETMX_L2_COILOUTF_LR_GAIN
H1 ETMX L2
 Coil     COILOUTF Gain
UL         1.03422
LL        -1.01374
UR        -0.98575
LR         0.96623
Of course, these values are set at arbitrary precession, they're rounded to the above quoted precession (a) because the measurement uncertainty is no better than 0.5%, and (b) the MEDM screen does not display out to higher precession, so further precision would not be visible.
H1 SEI
hugh.radkins@LIGO.ORG - posted 11:03, Tuesday 04 March 2014 (10492)
WBSC9 SEI HEPI Parker leak under control

I checked the amount of fluid that has oozed from the H1 ETMX H2 Parker valve since 25 Feb.  It is maybe a couple teaspoons so we are safe for a few weeks before I need to clean it up again.

H1 CDS (ISC)
david.barker@LIGO.ORG - posted 10:12, Tuesday 04 March 2014 (10490)
h1iscey model rebuilt and restarted

As part of WP4476 I rebuilt, installed and restarted h1iscey. Its safe.snap showed no "cannot connect" errors, but it is out of date and has only about 50% of the channels defined.

The new autoBurt.req has 15,666 entries. The safe.snap has 7,095 and the latest hourly autoburt has 8,520. So I'll keep it with the safe.snap restoration for now.

WP closeout waiting for DAQ restart and safe.snap update.

H1 CDS (SUS)
david.barker@LIGO.ORG - posted 10:06, Tuesday 04 March 2014 (10489)
h1susitmy reverted to non-Hardware watchdog code

h1susitmy has been running a special HWWD test version built against RCG trunk since Jan 9th and did not get upgraded to RCG2.8.3 last Tuesday. Today I reverted the h1susitmy.mdl file back to the original code, compiled against 2.8.3 and restarted the model. The safe.snap is out of date, 673 PVs are not connecting. I burt restored the system to 9am today (local time).

Waiting on a DAC restart to close out WP 4475

H1 DAQ (CDS)
james.batch@LIGO.ORG - posted 09:50, Tuesday 04 March 2014 (10488)
Change default NDS server back to h1nds1
Since the h1fw1 system has been stable for several days, the default NDS server has been changed back to h1nds1.  This should only affect new logins or new processes started from new shells or by opening desktop icons.
H1 SEI
sebastien.biscans@LIGO.ORG - posted 09:43, Tuesday 04 March 2014 (10487)
HAM-ISI - BLEND_SWITCH_ALL screen fixed

The HAM-ISI BLEND_SWITCH_ALL screen wasn't working properly at LHO: it was impossible to switch all the blends at once (white screen).

This issue has been fixed by the Stanford crew (see Hugo's SEI log: https://alog.ligo-la.caltech.edu/SEI/index.php?callRep=391)

I've 'svn up' and everything works fine now.

H1 ISC
keita.kawabe@LIGO.ORG - posted 09:27, Tuesday 04 March 2014 (10486)
Green WFS trend from last night

Attached is the 18 hours trend of the X arm WFS from last night.  Seems like it's doing something sensible. Happy periods are indicated by pink arrows at the bottom left.

Images attached to this report
H1 General
andres.ramirez@LIGO.ORG - posted 09:11, Tuesday 04 March 2014 (10485)
PSL Check
PSL Check:
Laser Status: 
SysStat is good
Output power is 28.7 W (should be around 30 W)
FRONTEND WATCH is Active
HPO WATCH is red

PMC:
It has been locked 2 days, 15 hr 39 minutes (should be days/weeks)
Reflected power is 1.2 Watts  and PowerSum = 11.9 Watts.
(Reflected Power should be <= 10% of PowerSum)

FSS:
It has been locked for 0 d 9 h and 51 min (should be days/weeks)
Threshold on transmitted photo-detector PD = 0.55 V (should be 0.9V)

ISS:
The diffracted power is around 1.5 % (should be 5-15%)
Last saturation event was 0 d, 10 h and 1 minutes ago (should be days/weeks)
H1 ISC
keita.kawabe@LIGO.ORG - posted 22:17, Monday 03 March 2014 (10483)
Green WFS today (Alexa, Keita)

After Sheila and Alexa realigned the arm by hand (arm transmission ALS-C_TRX_LF_OUT about 700cts), we removed the dark offset of WFS demode output, confirned that RFAM is negligible by misaligning the ITM but aligning the ETM, then centered and engaged WFS, but it did not converge.

We had to refine alignment further (760 cts transmission), disable the PDH off-loading to the ETM (the length to angle coupling is large even at low DC),  recenter the WFS, engaged WFS, wait for a while, hold the WFS output, recenter the WFS, and it worked with all except one DOF (DOF2 PIT, which is the soft mode PIT).

For now the hard mode sensor for PIT and YAW are WFSB and WFSA, respectively, while the soft mode sensors for PIT and YAW are WFSB and WFSA. The WFSA and WFSB seem to be highly degenerate for PIT, and that's probably why it's very difficult to make both DOF1 and DOF2 PIT at the same time.

Anyway, after three DOFs are engaged the transmission went up to 860+ cts maximum. We left the arm with WFS on.

Note that it's still with very small bandwidth (basically just DC).

H1 AOS
yuta.michimura@LIGO.ORG - posted 21:33, Monday 03 March 2014 - last comment - 10:27, Tuesday 04 March 2014(10482)
Calibrated PRM actuation function and PRY signal challenge (factor of 2)

I calibrated PRM actuation transfer function measured in alog #10450.
Measured PRY error signal is smaller by factor of 2 from the calculation and suspension model. This means that demodulation phase is off by 60 deg, or PRY modematch(including misalignment) is 50%, or suspension model is off by factor of 2 (or combination of all of them).

[Motivation]
We wanted to check the PRCL loop signal chain (We have done this for MICH loop already; see alog #10213).
Also, we need calibrated actuation TF for designing the compensation filter which does not saturate DAC.

[Method]
1. Made PRY simulink model (It lives in /ligo/svncommon/NbSVN/aligonoisebudget/trunk/PRMI/H1).

2. Change optical gain from PRM motion to REFLAIR_A_RF45_I to match the measured OLTF (which was measured in alog #10450).

3. Use this optical gain to calibrate PRM actuation transfer function.


[Result]
1. OLTF_PRCL_1077847156.png: OLTF compared with model and measured. Flat gain is fitted in the model and this gives the optical gain. The measured optical gain was 1.3e3 W/m.

2. From the REFLAIR signal chain in alog #10213, calibration factor for REFLAIR_A_RF45_I_ERR in PRY is 3.4e11 counts/m.

3. ActTF_PRM_1077847156.png: Calibrated PRM actuation transfer function. Red curve is plotted using zpk from LISO fitting of the measured TF (alog #10450) and divided by 3.4e11 counts/m for calibration. Blue/Cyan curve is from the suspension model using /ligo/svncommon/SusSVN/sus/trunk/Common/MatlabTools/TripleModel_Production/generate_Triple_Model_Production.m and calibrated using the numbers from ./MatlabTools/make_OSEM_filter_model.m (or LIGO-T1000061). M3 and M2 crossover and measurement look healthy. Note that the overall gain of the measurement agrees with model just because we don't have independent measurement of the optical gain. Even so, crossover frequency doesn't change.


[Discussion on optical gain]
Theoretical expression for PDH signal is

dPmod/dL = 2*8*pi/lambda*Peff*J0(beta)*J1(beta)*(t1**2*r2)/(1-r1*r2)

With

Effective input power: Peff = 7.3 uW * 4 /Tprm**2 = 0.032 W  (alog #10213; incident power on REFLAIR_A was 7.4uW when PRM and ITMY is misaligned)
Modulation depth beta=0.07 (alog #9395)
Amplitude reflectivity/transmissivity of PRM: t1 = sqrt(0.03)
Amplitude reflectivity of BS/ITMY compound: r2 = rBS*rBS*rITMY = 0.50

This gives dPmod/dL = 3.1e3 W/m (+/- ~10%). Here, Pmod is RF modulation amplitude of laser power, and dL is one-way length change of PRC, which equals to PRM motion. (Optickle gives 1.5e3 W/m since Optickle assumes demodulation gain of 1/2).

Even if I include the loss of the cable we measured(alog #10213), theoretical value is 2.5e3 W/m (= 3.1e3 W/m * 0.81), or 6.5e11 counts/m at I_ERR. This is factor of 2 larger than the measured.

Since theoretical value assumes perfect modematching and demodulation phase, actual value might be smaller. Also, note that measured optical gain is derived from the model which assumes that suspension model is acurate enough.

[How to solve this challenge]
 - Calibrate BS actuation transfer function using simple Michelson, and compare it using the measurement done in PRY. This will be an independent measurement of PRY optical gain.
 - Measure PRY modematching

Images attached to this report
Comments related to this report
yuta.michimura@LIGO.ORG - 10:27, Tuesday 04 March 2014 (10491)

From OLTF measurement in simple Michelson, we know that the BS suspension model is quite accurate (within ~10%; see alog #10127).
So, by comparing the actuation transfer function model and measurements done in PRY (alog #10450), we can estimate PRY optical gain independent of PRM suspension model.
Attached is the comparison of the measurement and model. This gives calibration factor for REFLAIR_A_RF45_I_ERR in PRY to be 4.3e11 counts/m.
This is different by factor of 1.3 from estimation using PRM.

This means that PRM suspension model is off by ~30% or calibration factor changed during BS measurement and PRM measurement. Still, 4.3e11 counts/m is significantly smaller than the theoretical value calculated above.

Note that BS changes PRY length by sqrt(2) * (BS longitudinal motion). Attached plot is counts (at H1:SUS-BS_M3_ISCINF_L_IN1) to PRY length change, not counts to BS longitudinal motion.

Images attached to this comment
H1 AOS
yuta.michimura@LIGO.ORG - posted 19:45, Monday 03 March 2014 (10481)
PRCL and MICH coupling investigation in PRMI

Stefan, Kiwamu, Yuta

Dip at ~13Hz in PRCL OLTF (see alog #10441) was from 40 Hz bandstop filter in PRM_M2_LOCK_L filter bank. When we turned this filter off, PRCL OLTF got much better. We still need a diagonalization of output matrix since we currently use only the BS to lock MICH. To do this, we measured BS and PRM actuation transfer functions (see alog #10450 for more detail) because they have different frequency response. We are now trying to make a conpensation filter to balance BS and PRM actuation from this measurement.

[PRCL and MICH OLTF]
OLTFs after removing the 40Hz bandstop filter are attached. The bandstop filter at 40Hz had -30 deg of phase and it seems like this filter was to blame for PRCL OLTF dip at ~13Hz. This filter was removed.
Demodulation phase of REFLAIR_A was re-tuned to 146.2 deg from 142.7 deg (H1:LSC-REFLAIR_A_RF45_PHASE_R) by minimizing the PRCL to MICH coupling. The LSC guardian is updated accordingly.
MICH to PRCL coupling is unavoidable in the current configuration.

The gain of the MICH to PRCL coupling was fitted with model with coupling at sensing matrix. The parameters I used to fit was 1. optical gain of BS to MICH error signal, 2. BS to PRCL, 3. PR2/PRM to PRCL, and 4. demodulation phase. The parameters I got to fit the measured curve was:

        BS     PR2+PRM
REFL_Q  1.8e2    0
REFL_I -4.9e5  -1.9e6    W/m

and demod phase of -17 deg (when perfect, it will be 0 deg).
But I think it is unlikely that the demod phase is off by 17 deg. So, we need actual sensing matrix measurement after output matrix diagonalization.
 

Images attached to this report
H1 ISC
stefan.ballmer@LIGO.ORG - posted 19:08, Monday 03 March 2014 (10480)
Observation intent bit
Fred, Jamie, Stefan

I was asked to install an "observation intend" bit that will be included in the interferometer state vector (ODC master). For now this is only intended to report that the IMC is ready.

What I did:
- Updated masks for the guardian input to ODC -right now there are only two bits: operator intent and guardian intend. The keep-alive is currently not used.
- Updated the IMC guardian to turn on its bit when it is done locking the IMC, and turn it off when it detects a lock loss.
- Added a user button on the Guardian main screen to report the operator intent (snap short).

With this, the H1 ODC master (H1:ODC-MASTER_CHANNEL_OUT_DQ) reports when the mode cleaner is locked, Guardian thinks so too, and a human being set the operator intent bit (or forgot to unset it...).

Obviously it will only be as good as the commissioners using it.





Images attached to this report
H1 SUS
brett.shapiro@LIGO.ORG - posted 18:47, Monday 03 March 2014 - last comment - 23:50, Monday 03 March 2014(10476)
Quad model wire length study
I have been investigating the wire length values used in the matlab model since the model fitting code results on ETMY from https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=10089 found a discrepancy in the UIM to PUM wire length. The value given by the model parameter file quadopt_fiber.m for this length is 
     330.8 mm. 
However, the model fitting code converged to 
     340.0 mm +- 2 mm.
About 9 mm longer.

I started investigating this discrepancy by looking at the drawings of the wire jig and the PUM assembly. Since the UIM to PUM wire is a loop, the equivalent length between the UIM and PUM needs to be backed out from these drawings. From these drawings, I calculate the length of wire between the UIM blade tip clamp and the PUM prism is 
     337.61 mm. 
The attached pdf, PUMwireLoopLength.pdf, contains the calculations and references for this number. The limiting assumption for this calculation is likely to be that the wire has an infinitely sharp bending radius going around the prism. In reality, a finite bending radius exists, which will tend to make this calculation a slight overestimate.

Still, the value is close but not quite there. Upon further investigation of the other wire lengths given by the model, I noticed that all the wire lengths are a few mm off from the values determined by the wire jig in D060516. My assumption has always been that the parameter file requires values referenced from the wire clamps (given by the wire jig), as it does for the d's. Thus, either all these values are out of date, or my understanding is incorrect. In particular, quadopt_fiber.m gives the top two stages of wire lengths as

pend.ln = 449.192 mm
pend.l1 = 308.585 mm

In contrast, the wire jig gives these as 

pend.ln = 453.0 mm
pend.l1 = 305.8 mm

Since the model predicts the measured longitudinal modes very well with the UIM-PUM fitting correction, I made the assumption that pend.ln and pend.l1 are correct as listed in the parameter file. Therefore, my previous assumption that the model file requires clamp-clamp lengths is wrong. So I searched for an algorithm (by guess and check more or less) that would take the clamp-clamp wire jig lengths and convert them to the listed numbers in the parameter file. What I found was this:

pend.ln = (wire jig length) + pend.dm/pend.cn  = 449.208
pend.l1 = (wire jig length) + (pend.dn + pend.d0)/pend.c1 = 308.521

The pend.d values are the distances from the wire clamps to the centers of mass. The pend.c values are the cosines of the wire angle from the vertical. With this, both lengths are within 10s of microns from the current quadopt_fiber.m values. Thus, this algorithm means that the wire lengths as given by the parameter file reference the center lines of the masses rather than the wire clamp positions.

Following this center line to center line convention for the UIM to PUM length, rather than clamp to prism we get:

pend.l2 = (clamp to prism length) + (pend.d1 + pend.d2)/pend.c3 = 337.61 + (pend.d1 + pend.d2)/pend.c3 = 338.924 mm

This value is about 1.1 mm from the value determined by the model fitting code, and it fits quite comfortably in the fitting code's +-2 mm error bar.

So, the good news is that the value determined by the model fitting code is consistent with the other metal wires under the assumption that the parameter file is working with center line to center line distances rather than clamp to clamp distances. 

However, ssmake4pv2eMB5f_fiber.m, which compiles the parameter file appears to be assuming the values are in fact clamp-clamp. For example, near the bottom of the ssmake script, the pend.stage2 corrections have 

ln = ln - 2*flexn/cn;
l1 = l1 - 2*flex1/c1;
l2 = l2 - 2*flex2/c2;
l3 = l3 - 2*flex3/c3;

where flex is the distance between the wire clamp and the effective flexure point and ln is equal to pend.ln (and so forth). Thus, it seems these corrections are assuming the parameter file references the clamp positions, not the center line positions. Additionally, higher up in the script around line 285 the vertical heights of the masses are calculated as

pend.tln = sqrt(pend.ln^2 - (pend.nn0-pend.nn1)^2) + pend.dm;
pend.tl1 = sqrt(pend.l1^2 - (pend.n0-pend.n1)^2) + pend.dn + pend.d0;
pend.tl2 = sqrt(pend.l2^2 - (pend.n2-pend.n3)^2) + pend.d1 + pend.d2;
pend.tl3 = sqrt(pend.l3^2 - (pend.n4-pend.n5)^2) + pend.d3 + pend.d4;

where the tl's are the 'true' vertical heights of the centers of mass, the n parameters represent the horizontal distance from the centers of mass of the wire clamps, and the d's again represent the clamp to center of mass distances. So for the top wire for example, 

sqrt(pend.ln^2 - (pend.nn0-pend.nn1)^2)

gives the vertical length of the top wire, and 

+ pend.dn + pend.d0

accounts for the clamp to center line distances for the stage above and below the wire. Thus, it seems again that the ssmake file is expecting clamp-clamp wire lengths from the parameter file.

However, putting clamp-clamp lengths into the parameter file does not provide the correct frequencies. So, the wire length mystery goes on...
Non-image files attached to this report
Comments related to this report
mark.barton@LIGO.ORG - 23:50, Monday 03 March 2014 (10484)

The intent for the ssmake file is very definitely that, when pend.stage2=1, all wire lengths are interpreted as clamp-to-clamp, and all d distances are interpreted as "physical" d's, i.e., COM-to-clamp. (The current quadopt_fiber.m that is under discussion does set this flag correctly.) Moreover this behaviour has been checked against the equivalent Mathematica model both for this parameter set specifically and more generally.

H1 SUS
brett.shapiro@LIGO.ORG - posted 02:47, Friday 14 February 2014 - last comment - 18:50, Monday 03 March 2014(10089)
ETMY Modeling Results
Results of my visit to LHO this week for system identification of the ETMY.

MOTIVATION:

Make better models for each particular suspension to aid control design and noise predictions.

The measured frequencies of the resonances are the most reliable data we have because they are not subject to errors in the sensors or actuators. There are also numerous resonances available for measurement, which can be used to adjust the model.

SETUP:

Resonance measurements were collected on ETMY main chain while on the test stand in the follow configuration with the following methods:
* full quad - top mass to top mass transfer functions using the OSEMs. This data was measured prior to my visit this week.
* triple hang - with the main chain top mass, reaction chain UIM and PUM masses locked on stops, spectra of the lower three main chain stages were measured with the UIM and PUM OSEMs and an optical lever on the test mass. No excitation is needed since the wind from the fans is more than enough. The process of locking the masses also misaligns the UIM and PUM OSEMs sufficiently that they are sensitive to vertical, roll, and transverse displacements of the stages. This allows us to measure more resonances with these OSEMs then we otherwise would. The optical lever isn't sensitive to any resonances the OSEMs miss, but it does add redundancy to help identify a forest of high Q pendulum resonances from spectra that include a lot of similarly shaped artifacts.
* double hang - with the main chain UIM and reaction chain PUM locked on stops, spectra of the main chain lower two stages were measured with the PUM OSEMs. In this case the optical lever would not stay in range, so the data is just the 4 PUM OSEMs.
* single hang - with the PUM on the teflon line stops, the test mass modes were measured with optically. This data was measured prior to my visit.

SUMMARY:

The data encompasses 56 resonance frequencies: 22 free quad, 16 triple hang, 12 double hang, and 6 single hang. See the attached plots and the summary of parameter changes below. In the attachment the black curves are the measured data, the blue the original model, and the red the new model. Pages 1-6 of the attachement show the diagonal top mass to top mass transfer functions. Pages 7-8 show L-P coupling and 9-10 T-R coupling. 11-13 are the frequencies of the triple, double, and single hangs respectively. 14 plots the mode frequency percent errors before the fit and 15 shows the same after the fit. The final page shows the convergence of the total error, where the error is calculated as

                  sum( [(measure mode - modeled mode)/(measured mode)]^2 ) 

The algorithm for fitting the data is Gauss-Newton, an approximation of Newton's method. The fitting code is on the svn at .../sus/trunk/QUAD/Common/MatlabTools/QuadModel_Fit/QuadPend_QuassNewton_fit_v2_H1ETMY.m.

Change in parameters from original model with the estimated convergence errors:
---------------------------------------
Inx (top mass roll inertia)                       : -1.0926 +- 2.6994 %
Iny (top mass pitch inertia)                    : 3.1636 +- 3.4396 %
Inz (top mass yaw inertia)                      : -0.86123 +- 0.65824 %
I1x (UIM roll inertia)                               : 3.9571 +- 0.77982 %
I1y (UIM pitch inertia)                             : 12.2729 +- 2.5078 %
I1z (UIM yaw inertia)                               : -0.10972 +- 0.55984 %
I2x (PUM roll inertia)                               : -2.9587 +- 0.85205 %
I2y (PUM pitch inertia)                            : 8.4597 +- 0.6904 %
I2z (PUM yaw inertia)                             : 0.011768 +- 0.3983 %
I3x (test mass roll inertia)                      : 2.2009 +- 0.77109 %
I3y (test mass pitch inertia)                    : -8.8738 +- 0.79819 %
I3z (test mass yaw inertia)                     : 0.44122 +- 0.5629 %
l2 (PUM wire loop length)                      : 8.6866 +- 1.1464 mm
l3 (fiber length)                                     : 22.1269 +- 2.6176 mm
kcn (top stage spring stiffness)              : 1.0719 +- 2.166 %
kc1 (top mass spring stiffness)              : 1.0935 +- 0.68178 %
kc2 (UIM spring stiffness)                      : 2.2795 +- 0.39067 %
kw3 (fiber bounce stiffness)                  : 9.4286 +- 0.4488 %
dn (top mass blade tip height)              : -0.20928 +- 0.303 mm
d1 (UIM blade tip height)                      : 1.8131 +- 0.56431 mm
d4 (effective fiber flexure at test mass): -4.8356 +- 0.23685 mm
---------------------------------------


DISCUSSION:

The fit of the original model was fairly descent already, except for pitch. The fit of the new model to this data is even better, especially for pitch. The worst mode frequency error decreases from 8.2% to 1.3%. Interestingly, even though only resonance frequencies were included in the fit, the shapes of the transfer functions (including zeros) all match well also. This goes for the cross coupling measurements as well. Note, the length to pitch measurement does not match the pitch to length. These should in theory be identical. Mismatches indicate measurement problems. Length to pitch has some low frequency notches that don't exist in pitch to length. Judging by the models (both before and after), I think it is likely that pitch to length is the more accurate measurement up to 4 Hz. I don't think we can believe either beyond 4 Hz. After the fit, the worst error in mode frequency corresponds to the first roll mode for both the free quad case and the triple hang case.

The inclusion of the extra resonance frequencies made a huge difference in the ability of the model to converge. In this case, a total of 21 parameters were floated. Normally, only a few at a time can be floated using just top mass data.

Many of the parameter changes produced by the fitting code seem quite reasonable. Some that are beyond what you would expect are the lengths of the fibers and the PUM wire loop. These changed by 22 mm and almost 9 mm respectively. Since the mass values are known, the only way to fit all 10 measured longitudinal modes is to adjust the wire lengths. This was achievable by floating both these wire/fiber lengths. I noticed that the default value in the original model for the PUM wire loop has the following comment: "% wire hang value - Mark Barton, 11/22/2011". I wonder if the entered value is no longer correct since the quad is not in the 'wire hang' configuration anymore. Regarding the fibers, the effective flexure length is rather complicated due to the geometry of the fibers. Perhaps some other error, like in fiber radius can mimic this. Note, the bounce mode stiffness moved by 9%.

The d4 change is also large. It is very likely this value is not physical because this parameter has significant degeneracy with both d3 and d2. Thus, the decrease of 5 mm could be spread out between all 3. d2 also has twice the sensitivity, so a small shift there can take up a fair bit of this 5 mm on its own. These degeneracies prevent the fitting code from floating these parameters simultaneously, so you simple have to pick one. d2 is sort of awkward because it is degenerate enough that it is difficult to float with either d3 or d4, but different enough that floating it instead of d3 or d4 yields different results.

DISCLAIMER:
As usual, the choice of parameters to float was made by experience and intuition. These parameter changes are not necessarily representative of reality. Though, with a fit that matches all 56 measurements to the 1% level, you might start to think that this thing is converging within some distance of reality.

COMPARISON WITH FUTURE MEASUREMENTS:
We should see how this new model holds up against L-P measurements at other stages and between stages.


NOTES:
The high frequency vertical and bounce modes were visible on the single hang and double hang measurements, but not the triple and free quad. If they were visible in all there would be 60 measured resonances. However, these modes are virtually the same from double hang to triple hang to free quad because they involve primarily displacement between the bottom two masses. Thus, the loss of information is negligible. In fact, we might be better off not including these extra bounce modes in case they emphasize bottom mass parameters over the upper masses since the same information would essentially be repeated 3 times.
Non-image files attached to this report
Comments related to this report
brett.shapiro@LIGO.ORG - 22:14, Monday 17 February 2014 (10125)
I found a typo in the model fitting code that explains the change in the fiber length. In the code the nominal d3 and d4 values, each 10 mm, were subtracted from the fiber length. The fitting code, doing what it is supposed to do, detected that the fiber length was incorrect and added 22 mm to compensate. The 2 mm difference is in the noise since the fiber length has a weak influence on the dynamics at the mm level. Note that the code did output a +-2.6 mm error bar for this fiber length change.

I'll take this as good news that the fitting code works.

The model fitting code has been updated on the svn with the bug fix.

The new parameter file is on the svn at:
/ligo/svncommon/SusSVN/sus/trunk/QUAD/Common/MatlabTools/QuadModel_Production/quadopt_fiber_H1ETMY.m
brett.shapiro@LIGO.ORG - 23:17, Monday 17 February 2014 (10126)
The following attachment shows that the new model is also a good match for L1ETMY.
Non-image files attached to this comment
brett.shapiro@LIGO.ORG - 18:50, Monday 03 March 2014 (10479)
A new alog entry at https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=10476
discusses the calculation of the UIM-PUM wire length required from the model based on the wire jig document and PUM drawings. These documents bring the wire length much closer to what the model fitting code found.
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