Yesterday, I implemented length to angle decoupling filters for the three stages of SRM. The L1toY3 decoupling was tested and results show an improvement of ~10dB at low frequencies, and few dBs above .8Hz. Plot attached in screenshot shows the L1toY3 transfer function without (blue) and with (red) compensation. The 2nd pdf attached shows the measurement, and the fitting used for this particular filter design. The other pdfs show the design for the rest of them.

The method used was :

1. Measured cross coupling transfer functions from one stage to test mass using the script Matlab_tfs.m (started with LHO_Matlab_TFs under /ligo/svncommon/SusSVN/sus/trunk/Common/MatlabTools/SchroederPhaseTools/).
   Measurements were done with the suspension damped and the ISIs damped. The three stages of MC2 SRM and SR2 should be already measured (dates can be found in the spreadsheet attached in previous alog). Only SRM M3 tf needs to be retaken since a chunk of data was missing for the pitch drive of M3 stage.
2. Plotted the measurements to make sure they worked using plothsts_matlabtfs_cross_levels.m under /ligo/svncommon/SusSVN/sus/trunk/HSTS/Common/MatlabTools/
3. Fitted L2P/P2P for pitch decoupling and L2Y/Y2Y for yaw decoupling using Keita's awesome fitting script, and a wrapper called fitting_for_decoupling.m under /ligo/svncommon/SusSVN/sus/trunk/HSTS/Common/MatlabTools
4. Installed filters in foton with autoquack. The filters are installed in two filterbanks : FM1 for {L2P or L2Y} and FM2 for {1/P2P or 1/Y2Y}, and gain should be -1. When the number of zeros of the decoupling filter is higher than the number of poles, script will warn you that a low pass roll off should be added in foton. The new filters need to be saved with foton before being loaded.
5. Tested the filters taking a white noise tf with/without the filter. Template can be found for the L1toY3 coupling of SRM under  /ligo/svncommon/SusSVN/sus/trunk/HSTS/H1/SRM/SAGM1/Data/2014-08-22_SRM_decoupling_L2Y_test.xml

TO DO :

• Check stability/performances of other SRM filters using the template of step 6.
• Design and install filters on three stages of MC2 and top/bottom stage of SR2 (middle mass cross coupling is too high because of the non functioning osem actuator)
• Make a safe.snap when happy with a configuration
• Work on getting the coherence with the matlab tf script
• Take a safe.snap with the filters installed Jeff and I realized that the step response looked like the filter was unstable (we looked at L1toP3 and L1toY3 of SRM) even though the transfer function didn't show instability.

J. Kissel, K. Venkateswara

We were able to take overnight measurement with everything working smoothly. I have analysed 35000 seconds of data starting from ~7 PM to ~5 AM this morning. The first file shows a similar plot as I had posted yesterday. The subtraction is done a bit differently:
Yesterdays subtraction -
Residual = BRSout  +  T240X * (w/g)

This simply accounts for the inertial angular acceleration measured by the bar and assumes d = 0.

Todays subtraction - 
Residual = BRSout  +  T240X * (w/g) + T240X * ( 1/w * M * d * g/I)

where BRSout is the BRS output (in rad), T240X is the velocity output, w is angular frequency (2 pi f), M is the total mass of the balance (4.2 kg), d is the distance between CoM and the suspension point ( (39 +/- 5) microns), g is 9.8 m/s^2, and I is the moment of inertia of the beam (0.59 kg m^2).
This subtraction accounts for inertial angular acceleration and horizontal acceleration coupling based on an estimate of d, which is explained below.

The second file shows the raw T240X displacement output and the tilt-subtracted output.

The third file shows the angular acceleration measured by the bar. This is similar to the first plot, but rotated by f^2. This makes the effect of various terms a bit clearer. The first plot shows the influence of inertial angular acceleration and the horizontal acceleration coupling. This allowed me to estimate d by varying it until the green curve lined up with the blue at low frequencies. In the next plot I added the residual and the autocollimator noise. Note that the residual is worse below ~8 mHz due to the influence of the low-frequency high-pass filters which mess up the phase.

To make a long story short, the Beam Rotation Sensor works as expected. The subtraction scheme we showed above is easily implementable and presently gives a factor of ~5 improvement in displacement noise below 0.1 Hz down to ~10 mHz. The d offset is larger than I expected which was due to the inaccuracies in the transfer function measurement scheme. Still, it does not present any difficulties in doing the subtraction. If we have to open up the vacuum can for whatever reason in the future, we can correct it easily.

We have learnt many lessons and if we get the opportunity to do this again, we will do better. We have some ideas for implementing a simple damping scheme to remotely damp the balance, which we will try out at UW. 

I have had a great time installing/commissioning the tiltmeter and would like to thank everybody at LHO for all the asistance. The atmosphere and energy here is terrific and I hope to be back here soon :)



edit: The matlab file I used for the above analysis is : /ligo/home/controls/tmp/BRSanalyze.m
It is very badly written and I will add comments, polish it and upload it soon.

Last night Kiwamu and I put the pop beam on the pop analog camera.  This camera is input 25 in the MSR camera big black box, I have sent it to output 29 which is the white cable on CB7-050-005 (the cable that goes to the monitors in the front of the control room). 

Now we can watch our michelson fringing.

J. Kissel, J. Warner

Jim unlocked the ISI and we installed damping loops on the H1 HAM6 ISI (such that we could run SUS close-out TFs). The damping loop install went poorly, but eventually we got it to work in an odd configuration. Below is the chronology.

- I installed a copy of HAM4 damping filters using straight copy and paste from foton.
- Tried turning loops on, got immediate trip. Repeated just to be sure, with the same result.
- Checked HAM6 ISI DAMP filters against HAM4 filters in foton, confirmed they're identical
- Checked Basis Transformation matrices, confirmed they're identical to HAM4, and they match T1000388.
- Confirmed with foton that the actuator compensation filters were installed and correct (i.e. they match HAM4).
- Confirmed with foton that the GS13 calibration filters were installed and correct (i.e. they match HAM4).
- Confirmed that all signs along the chain, in the GS13INF, DAMP, and OUTF filters were the same as in HAM4.
- Checked that gain switching on GS13s was functional, and that were were in low gain.
- Tried closing loops again, still unstable.
- Jim installed HAM6 damping filters using the "normal" Matlab quack method from commission scripts that were designed from an old set of plant data.
- Confirmed with foton they installed correctly and showed very little difference between HAM4's filters.
- Tried them, still unstable.
- Noticed that all corner station ISIs had ADC saturations on CDS overview screen. Found it to be STSA (i.e. the one by HAM2) which was railed, and being piped to every ISI and HPI front end.
- Went out to racks, re-zeroed STSA, saturations disappeared, still no change in behavior. Damping loops still unstable.
- Turned down / off purge are in HAM six. Amplitude of GS13 motion went down, but still the loops were unstable.
- Performed the radical -- flipped the sign of loops in the DAMP filter bank, AND IT WORKED.

We can't think of any reason that there would be a sign flip in the chain, but for now, we leave it and move on checking out SUS.

yesterday we noticed that ITMX has been tripping, it seems to happen within a minute or so of becoming fully isolated.  HEPI seems to have position loops running, there is no feedback from ISC to the suspension or HEPI.  The last few trips have been just stage 2, actuator trips.  It looks like something is ringing up.

The stage 2 blends were on Tbetter expect RZ, which was on Tcrappy for the two trips plotted in the first screenshot attached.  I've tried setting stage 2 blends to start, this also caused a trip which is the second attached screenshot.

Now I have set the guardian to isolated_damped, so that stage 1 is isolated and stage 2 is damped.  So far its not tripped. 

[Fil Arnaud]

Few days ago I realized SRM top mass dials were moving more than usually, so I took a spectra this morning which shows noise at around 1700Hz for LF RT SD and T3 osems signals. Those four osems are using the same quadrupus cable from the flange to the sat box. The spectra compares those four osems with SR3 RT SR3 SD SRM T1 and T2, which shows a peak at 1700Hz but much less higher.
We tried powering down the AI chassis and the coil drivers several times, which didn't fix the issue. I don't recall we powered down the AA chassis, so that might be the next thing to try. 
To be fixed.
 

I increased the laser power incident on IMC from 2 W to 10 W. I readjusted the IMC locking parameters and updated the IMC guardian. The IMC now locks fine.

In attendance: Fred, Vern, Koji, Sigg, Krishna, Worden, Jason, Patrick, Warner, Kissel, Sudarshian?, Arnaud, Kuwami, Gerardo, Sheila, Fil Alexas

OpLev - HAMs 2&3 complete

HAM6 -cabling completed. ISI will be unlocked for J Kissel to run TF. Jim will run TF as well and Koji will attempt to get OMC locked today so that doors can begin to be reinstalled on Monday. North door will be first. Checking for ground loops needs to be done.

TiltMeter at End-X -complete. Communication regarding activities at End-X needs to be addressed. ie, technical cleaning crew frequency. Possibly some signage at the VEA door was mentioned.

End-Y -Measurements taken during green light exposure revealed that charging is NOT being caused by green LASER. The next step will be to investigate ION pump effects.

Visitors next week: Nic Smith will be here 8/26 through 9/10

model restarts logged for Thu 21/Aug/2014
2014_08_21 18:27 h1fw1

unexpected restart of h1fw1

- Kapton washers to prevent picomotor sticking were installed on the HAM6 picos in the morning.
- Cable grounding were checked with Dan after Jim's cable rerouting in the evening. (Entry below)

The last ISC task before puting the north door is alignment of the OMC leakage trans beam on the northwest viewport (emulator).
With 2W PSL input, corresponding to 3~4mW on the OMC, I expect 20uW transmitted when the OMC is locked and well aligned.
It is probably tough to find.

We might just barely be able to see this beam with a CCD + zoom lens. Otherwise, we need to rely on increasing the input power to 10W.

Dan, Koji

After Jim finished working on the seismic platform, we checked the HAM6 electronics for ground loops.  We re-discovered the grounding of the beam diverter shields in the vacuum, and found another short on the shield for the ASC-AS_C QPD.  The beam diverter grounds appear to be due to the cable connector on the diverters themselves, and I think I recall that we essentially resigned ourselves to living with them.  Koji fiddled with the cables and the connectors for the AS_C QPD and the ground loop went away; all of the ISC and tip-tilt connections to HAM6 are free of grounding issues.  (We did not check the OMC SUS cabling, should do this tomorrow.)

Once we finished with the ground loops we checked the dither for the OMC PZT was functional.  We set the dither frequency at 3.3kHz and toyed with the amplitude while trying to understand the LV readback on the OMC control screen.  The numbers didn't make much sense to us (we need to understand what's going on in the PZT driver board), but we verified that there was a signal coming out of the driver board and going into the vacuum.  Tomorrow we will try to lock the OMC.

When we looked at the low-voltage PZT drive with an SR785 we immediately noticed an 8Hz comb in the spectrum, which has been observed previously at LLO.  The comb is mostly at high frequency and seems to depend on the amplitude of the drive, but it's loud and messy and it's on the DAC input to the PZT driver board.  The attached plot is an amplitude spectrum of the signal from the AI chassis on the input to the driver; note the units are in amplitude, not amplitude spectral density, because we were trying to understand the calibration of the digital controls.  The amplitude of the dither in the plot may be much higher or much lower than what we ultimately use to control the OMC; at LLO they use 0.3V but we don't yet understand the calibration of our input signal.  An oscilloscope trace of the signal leaving the PZT driver and going into the vacuum looks very noisy, with many periodic sharp glitches of ~1microsecond duration that are presumably the source of the comb in the frequency domain.  (Note: the comb is also visible in the LV readback of the PZT drive, using DTT.)

Sheila, Kiwamu

We spent some time this evening to find the POP beam. We successfully found the POP beam and managed to extract it to ISCT1.

We realigned the down stream because we had touched PR3 to get the POP beam. Now REFL, POP and AS beams are all coming out of the chambers.

POP beam:

With the use of an analog camera, we became able to see the POP beam hitting the swiss cheese baffle in HAM2. It was too high and off toward left in the camera view. We temporarily placed the camera at 3 o'clock position at HAM3 spool. This allowed us for steering PR3 to get the POP beam coming out to ISCT1. Note that we could not see the spot with the GigE camera somehow.

We then placed an analog camera in the POP path on ISCT1. This is now blocking the POP beam opn the table, but serving as a reference. Also, touching ITMY, we got the Michelson fringing.

Re-alignment:

Since we touched PR3, we had to realign the downstream. We touched SR3 and SR2. We tried to center the beam on the left part of the SR2 baffle, but this resulted in DAC saturation in SR2 when centering the beam on SRM by steering SR2. So at the end, we gave up the centering of yaw of SR2 and brought it back to where it was. This released the DAC in SR2 as expected and we then could steer SR2 into SRM easily. We confirmed that the beam was hitting AS_A, _B and _C QPDs. The attached is the screenshot of the current alignment.

Since we are not super-confident with the SR3 alignment at this point. The HAM6 crews can feel free to revert the entire alignment, if they want to.

J. Kissel, K. Venkateswara

We did some very basic analysis of the data from the BRS_RY_OUT and the T240_X channels. The first attached plot shows the ASD of 5000 seconds of data from this afternoon. There was good coherence between the BRS and the T240X but there seemed to be a scale factor mismatch. The phase between the signals was very nearly zero. Since I believe BRS calibration is superior :P, I chose to apply a fudge factor of 0.62 to the T240X. To do the subtraction, I simply took the T240X velocity time-series data, differentiated once to convert to acceleration and divided by g. This was then subtracted from the BRS_RY_OUT time-series data, whose ASD is the light blue curve shown in the first plot labelled as 'simple subtraction'.

The second file shows an ASD plot of the raw T240X, the tilt-subtracted T240X and the T240 spec. in displacement units. Note that the weather was rather mild in the afternoon and the tilt noise can get much worse under high wind speeds.

12,185 process variables added
3,163 process variables removed
2,303 process variables are now unmonitored

Plot of pressure after 1 day on turbo pump, charge test is ongoing.

J. Kissel, K. Venkateswara, R. Schofield, S. Karki

Robert didn't believe that we can use our change in gravity gradient to damp the rung-up 8.8 [mHz] oscillations in the BRS, so we performed a demonstrative test in his presence. 

With Krishna himself as our test mass, he
(1) Waited for the balance to come to an equilibrium position,
(2) Moved in next to the North (+X) side of the sensor and squatted there. His approach created a bit of torque noise, but more importantly created a change in local gravity, changing the equilibrium position of the balance up because his squatted C.o.M. is slightly higher than the beam. 
(3) Stood up, increasing his center of mass much higher. This causes little-to-no tilt/torque and again changes the local gravity gradient shifting the DC equilibrium position of the oscillation to shift up. 
(4) Squatted back down, restoring his center of mass to the original location. Again there is a quick bit of torque noise as he squats, but one can see the DC equilibrium position has shifted back (roughly) to it's original location.
All of these changes in C.o.M. served to excite the 8.8 [mHz] mode, which is why you see the amplitude of motion increase at each change.

The first attachment is the time series of the tilt readout, and the second is pictures of the two positions.