Evan, Stefan

With the winds calming down again, we did some more SR3 alignment work:
- We noticed that for SCR1_Y AS B 36 I is still the best signal. It has
   - less "phase lag", presumably due to a reduced coupling to the BS. This allows us to do a high bandwith loop.
   - a small enough offset that servoing it to zero makes sense for reducing build-up fluctuations.
- Thus we closed the yaw loop with a UGF of 3.3Hz. Engaging it is in the Guardian.
- We tried to play the same game for the pitch loop, with less sucess.
   - all signals have some RF offset.
   - none of the signals seem to have low enough "phase lag" for a high BW loop. We should make sure this phase lag is not due to some broken whitening filter.
- Thus for now we left pitch in the configuration described in alog 15769.

Evan is now also updating the WFS relieve.

We will leave DRMI locked for the night.

I went into the PSL to check out possibilities for redoing the top periscope piezo mirror mount, which I think is responsible for the 250 Hz peak in DARM at LLO (Link). The secondary purpose was to check the recovery time for a 10 minute incursion. The IMC did not loose lock but suffered intensity spikes beginning when I went in, and quickly dissapating so that they were gone by an hour after I left. The plots show MC2 TRANS and ISS_AOM_DRIVER_MON in an overview and a zoom into one of the intensity spikes. The zoom suggests ISS oscillations. The step in MC2 TRANS was when Evan, seeing the spikes, shut down the gaurdian. 

Robert, Evan

Elli, Thomas, Stefan

- We found that the DRMI build-up fluctuations reported in alog 15765 were mostly due to a small offset in the WFS locking point for the SRC (feed back to SRM yesterday, switched to SR3 today).
- We fine-tweaked the input matrix mixing signals from AS36 A (orthogonal to the BS signal) and AS36 B (I&Q), such that we maximize the SR3 signal and get a good locking-point offset.
  The matrix is:
    AS A RF36I -0.45
    AS A RF36Q  0.89
    AS B RF36I  1.1
    AS B RF36Q -0.77
  This was found for pitch. Yaw was confirmed to be close, but wind prevented further fine-tuning. Using this significantly reduced the build-up fluctuations.

- Next we commissioned the a high BW loop for SR3. The filters are
    PIT: zpk([0.06+i*0.815;0.06-i*0.815;0.3+i*3.25;0.3-i*3.25],[0.3+i*2.87;0.3-i*2.87;11.1111+i*38.4258;11.1111-i*38.4258],1,"n")
    YAW: zpk([0.13+i*1.24;0.13-i*1.24;0.15+i*2.88;0.15-i*2.88],[0.15+i*2.48;0.15-i*2.48;11.1111+i*38.4258;11.1111-i*38.4258],1,"n")
  They were successfully tested up to a UGF of 6Hz using an optical lever. However, on the WFS we could not go that high because there was significant cross-talk from the other loops.
  Thomas will attach a measured transfer function.

- We left the feed-back on SR3 (the guardian sets this up), but with maybe 10 times lower BW.

- We also noticed that the high BW WFS cause more violent lock losses. We thus put (generous) limiters to all the top stages.

Unfortunately the winds are at 60mph again, so we won't leave it locked tonight.

I have reconfigured conlog to remove the constantly noisy H1:ALS-Y_VCO_TUNEOFS and the 2 disconnected channels. Details are:

+ H1:ALS-X_WFS_AUTOC_SWITCH

+ H1:ALS-Y_WFS_AUTOC_SWITCH

- H1:ALS-X_WFS_AUTOC_SWTCH

- H1:ALS-Y_VCO_TUNEOFS

- H1:ALS-Y_WFS_AUTOC_SWTCH

inserted 2 pv names

deleted 3 pv names

model restarts logged for Fri 19/Dec/2014
2014_12_19 11:28 h1fw1
2014_12_19 14:48 h1hpiham3
2014_12_19 14:49 h1isiham3

h1fw1 unexpected restart, SEI HAM3 restarted to see if it would fix a problem. Conlog frequently changing channels report attached.

Stefan, Kiwamu,

We did some more ASC optimizations tonight in DRMI. We are leaving the DRMI locked overnight to see what drfits on a time scale of hours.

Here is a list of what we did:

• High bandwidth PR3 and PRM ASC loops were engaged. Both use the M3 bottom stage with an almost 1/f open-loop shape.
  • PR3 loops = 6 Hz UGF,
  • PRM loops = 1 Hz UGF (going above this UGF causes instability at 10 Hz for some unknown reason )
• Off-loading to top stage on PRM, PR3 and BS are newly implemented. The top stages have an integrator so that they keep the DC value when the DRMI drops lock.
• IM4 pointing slow loop is newly engaged. It uses ASC-POP_B. The output matrix is diagonalized with an off-diagonal element for PRM.
  • for pitch output matrix, IM4 = 1 and PRM=22.
  • for yaw output matrix, IM4 = 1 and PRM = 129.
  • The servo points to a non-zero point on POP_B as we were not sure whether it was a good idea to servo it to zero without confirming the arm pointing. In addition, we saw the build-up dropping when we went further away from the nominal offset point, which is another reason why we did not servo it to zero. For now, we put an offset in ASC-POP_B_PIT(YAW)_OFFSET such that we don't loose the current IM4 pointing.
• We moved SR3 (which is one of the uncontrolled mirrors) to see what signal responds to it. It seems that REFL_B_45I is sensitive to this mirror, but currently SRM is suppressing this sensor with a slow bandwidth. Stefan will look into this mirror during the weekend.

All the modifications and new loops are coded in not only in the ISC_DRMI guardian but also ISC_DOF guardian so that they do not mess up the initial alignment WFSing.

Last night I tried a new loop topology for the OMC alignment servos, using the inputs to the OMC SUS that were added to the model a few weeks ago.

The idea here is to diagonalize the DC alignment in HAM6, using OM1 and OM2 for the centering on the AS WFS, and use OM3 and the OMC SUS for the centering into the OMC.

I measured the sensing matrix for OM3,OMCS {P,Y} --> OMC-ASC ANG,POS {X,Y}, took the inverse, and used this for the output matrix (DOF2TT).  This kind of worked; I was able to close all four loops and engage the AS WFS DC centering in parallel.  But the centering on the OMC wasn't very stable, and turning on the integrators caused an instability in the yaw loops.  I think the problem is that we're using loops designed for the tip-tilts to actuate on a 2-stage suspension; a better approach is to invert the OMC SUS --> OMC QPD transfer function and put this into the OMCSUS ASC filter banks.  But, my earlier fear that the OMCSUS actuation was too weak doesn't appear to be true.  This scheme should work once we account for the complications in the OMC SUS transfer function.

A screenshot of the output matrix from ANG,POS --> OM3, OMCS is attached.  You can see that the OMCS is 1000x weaker than the tip-tilt.  For now I have reverted to the old configuration, which uses OM1 and OM2.

After I reverted back I noticed that the dither loops had developed an instability!  They were stable as recently as 10 days ago, according to conlog nothing had changed.  We'll need to investigate the dither alignment chain in the new year.

[Mackenzie, Eleanor, Paul]

This afternoon we got the PLL aux laser measurement up and running, and fortunately this happened to coincide with a locked DRMI. 

We were initially able to observe the FSR dips, as we had seen them previously. We decided since we had the benefit of a locked DRMI we would try adding the clipping objects in the aux laser input path, and also in front of the REFL AIR B diode that was used to detect the beat note between the aux laser reflected from the PRM and the PSL beam reflected from the PRM. 

We observed new features in the transfer function, which are likely candidates for higher-order mode resonances. Attached are two preliminary plots of sweeps close to two FSR HG00 resonances.

A very quick calculation of the PRC one-way Gouy phase from these data is as follows:

HG00 peak resonance frequency - HG10 peak resonance frequency = 0.3MHz.

Fraction of FSR = 0.3/2.6 = 0.1154.

Convert to degrees one way Gouy phase: 0.1154*180 = 20.77degrees.

With the ITMs that are currently installed, we expect a one-way Gouy phase in the PRC of about 18 degrees (with no ITM thermal lensing). Design value accounting for thermal lens in ITMs from 18W input power and 0.5ppm absorption on the ITM HR surface is 25 degrees. 

Worth noting is that the DRMI was locked during this measurement, not the PRMI. It's not clear to me yet how this affects the results – maybe not much. Also, evidence for the additional peaks really being due to HOMs is the repeated resonance a further 3MHz away from the HG00 resonance, which I expect is the HG11+HG20+HG02 mode resonance. More precise analysis and measurements to follow. 

J. Kissel, K. Venkateswara, K. Izumi, J. Warner

While Kiwamu was trying to lock the Michelson, several things went wrong, but it uncovered a flaw in the new gain switching of the GS13s that has been implemented in the Guardian (see LHO aLOG 15537. Here's what happened.
(1) Kiwamu incorrectly brought up the BSC ISI in "fully isolated," which turns on stage 2 isolation loops, and switches the GS13s to high-gain mode.
(2) As expected, while trying to acquire MICH lock, impulses sent to the SUS BS kick the cage as well, which is attached to the BS ISI ST2, and trips the ST2 on the GS13s watchdog.
(3) We then reset the watchdog, and switched to "isolated damped," and this triggered the new guardian feature to *start* switching the GS13s back to low gain, but with MICH still trying to lock, impulses would still trip the watchdog before guardian had the chance to switch *all* of the GS13s gains. 
(4) This, trigger-happy watchdog resetting, and guardian half transitioning, caused a nasty loop of guardian sloshing the GS13 gains back and forth between high and low, which, with MICH impulses, continued to trip the watchdog.

I attach a plot of one of the WD trip, which clearly shows that the V3 GS13 had failed to have its gain switched to low. 

We should 
(a) look the new code to make sure there isn't a bad loophole regarding the GS13 gain switching when transitioning from "fully isolated" to "isolated damped"
(b) look for ways to increase the switching speed, or add a pause / check that the switch has occured on all GS13s before proceeding with the transition
(c) remember that these are physical, several thousand pound systems -- if you have to reset watchdogs repeatedly something is wrong and you don't know why, don't just blindly continue to mash the reset button, figure out what's wrong, or do what Kiwamu did and ask an expert!

#justwait

Thomas, Stefan, Jeff, Kiwamu, Elli

Continuing along the same line as yesterday's work on PR3 (alog 15727), we have designed high-bandwidth (<10Hz) actuation filters for the PRM.  These filters are applied to H1ASC-PRC1P and H1ASC-PRC1Y in the central part of the ASC WFS servo.

The filters added to ASC WFS central are called 'PRM^-1' and are:
H1:ASC-PRC1_P:   zpk([0.2+i+0.9;0.2-i*0.9;0.05+i*3.41;0.05-i*3.41],
                [0;0.2+i*2.75;0.2-i*2.75;0.125+i*9.99922;0.125-i*9.99922],1,"n")
H1:ASC-PRC1_Y:     zpk([0.04+i*1.08;0.04-i*1.08;0.1+i*2.08;0.1-i*2.08;0.05+i*3.43;0.05-i*3.43],
                [0;0.15+i*1.8;0.15-i*1.8;0.05+i*3.3;0.05-i*3.3],1,"n")
Some old unused filters were also removed.

Low-pass filters called 'RLP17' were added to the PRM M3 locking filters in pitch and yaw:
H1:SUS-PRM_M3_LOCK_P:  zpk([4+i*119.933;4-i*119.933],[6.78887+i*13.9134;6.788887-i*13.9134],1,"n")
H1:SUS-PRM_M3_LOCK_y:  zpk([4+i*119.933;4-i*119.933],[6.78887+i*13.9134;6.788887-i*13.9134],1,"n")

Fabrice, Hugh, Dave:

we restarted the models h1isiham3 and h1hpiham3 as part of the seismic investigation of this chamber. No new filters, code or daq configuration were applied, this was a simple restart.

LVEA: Laser Hazard
Observation Bit: Commissioning  

08:00 Cris – Delivering garb to End-X
08:40 Doug – OpLev work at HAM4
08:51 Kyle & Gerardo – Roughing BSC10
09:00 Betsy, Travis, & Rick – At End-X
09:10 Fabrice – BS & HAM3 Testing
09:13 Filiberto & Aaron – PEM cabling work in the Beer Garden
09:30 Karen – Going to End-Y
09:55 Kyle & Gerardo – Back from End-Y
10:18 Jim – Going to End-X to unlock HEPI & ISI
10:30 Shutdown dust monitor at HAM1
10:36 Karen – Back from End-Y
10:40 Dale – High School tour in control room
11:19 Dave – Going to End-Y to adjust cameras
11:21 Jim – Back from End-X
11:45 Betsy, Travis, & Rick – Back from End-X
12:50 Jim – Going to End-X to unlock HEPI
12:52 Filiberto – PEM and cabling work in Beer Garden and along spool arms
13:50 Dave – At End-X to adjust cameras
14:02 Kyle, Gerardo, & Bubba – End-X Install West door, connect pump cart and pump annulus
14:05 Dave – Back from End-X
14:44 Filiberto – Out of the LVEA
14:47 Dave – Restarting HAM3 models
15:28 Rick – Taking Mike R. and friend on tour of LVEA
15:40 Kyle, Gerardo, & Bubba – Finished with BSC9 door install, started pumping annulus 

Jim, Hugh, Krishna, Jeff, Fabrice:

We keep investigating the sensor corrction issue on HAM3. What we found yesterday is that it depends on which blends are engaged. We can't explain why yet. We did additional tests today:

- we turned off all CPSs of all HAM-ISI and BSC-ISI in the corner station. No change.

- we checked the jumpers of all HAM3 CPS boards. All good.

- we tried to apply large offset in case it would reduce some kind of cable touching/rubbing (+/-400 um in HEPI Z, and +/-400 um in ISI X,Y, Z). No change.

Finally, we tried to do the Z sensor correction to HEPI. In the plot attached:

- Red curves is HAM3 ISI isolated, no sensor correction

- Green Curve, we turn ON the sensor correction in X and Y to the HAM-ISI

- Blue Curve, we also turn on Z sensor correction to ISI. The 0.6 HZ peak shows up. For some reason it also reduces X at the microseism.

- Brown, we do the Z sensor correction to HEPI instada of ISI. The peak is still there in the CPS, but not in the GS13. It's unclear why.

The last configuration looks good from the GS13s,  but it's unclear yet how good it is for the cavity. More info on that is coming.