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.

The information we received from Hanford ops indicated that hauling would not occur on day shift or swing shift today, 12/19.  The 1-3Hz seismic trace during the day today looks pretty noisy, however, as if hauling is occurring.  I'll pursue this next week -- perhaps there's other activity underway nearby.  No hauling is scheduled for the weekend.  Next week the drivers are scheduled to work day and swing on Monday and Tuesday and then go out for the remainder of the week and the weekend.  I suspect that they'll use a similar schedule during the week of Jan 1.   

Kyle, Gerardo, Bubba -> Door 

Kyle -> Annulus 

Will begin "rough" pumping X-end first thing Monday morning

F. Matichard, H. Radkins, J. Warner, K. Venkateswara

Due to the problems described in 15690, Z sensor correction to the corner station BSC HEPIs was causing excess tilts at low frequencies. Based on directions from Fabrice, Hugh and I ran tilt decoupling measurements described in 15726 and fixed this to some extent. The pdf attachment (BS_HEPI_Tilt_Decoupling.pdf) shows the effect of the tilt decoupling at the Beamsplitter. The measurements show the X, Y  CPS signals with no sensor correction, with sensor correction and finally with sensor correciton and tilt decoupling. There is still room for improvement and a more careful and longer measurement might reduce this further.

For the moment this seems to be good enough to keep MICH locked with perhaps some improvement in the MICH_OUT as seen in the image attached (MICH_OUT.png). The benefit of the Z sensor correction can be seen in the second image (BS_Zsensor_Correction.png). The improvement is not as significant as some of the other chambers. We should investigate more to see what limits the subtraction.

Edit: I made a mistake in the labeling of the lines. The blue and green labels are switched and so are the blue/cyan and pink labels. In summary, the sensor correction increased x and y motion by a factor of ~10 and ~40 respectively and tilt decoupling reduced it by a factor of ~3 and ~8. A more careful/longer approach may reduce it to the original levels.

Betsy, Travis, Jason, Rick

First Contact was peeled from the ETM surface this morning.  No First Contact remnants were observed on the surface.  

Particulate counts, using the "Green Lantern," were in the 2-5 particles per square inch range, down from the 5-10 particles per square inch seen before applying the first contact.

The composite image attached below contains six images.  The upper row of three were taken before applying the First Contact and the lower row of three were taken after the First Contact was removed.

For all images, the surface of the ETM was illuminated with a green LED flashlight.  For the four images on the left the flashlight was held by hand.  For the two in the right, the flashlight was set in the Arm Cavity Baffle in an effort to make the illumination the same for both images.

Fabrice Krishna Hugh.

Krishna was suspecting that RX tilting on ITMY and the BS was impacting the HEPI Z Sensor correction results.  Sure enough, when checked it was most coupled on the BS Z to RX and next on ITMY HEPI Z to RX.  The other couplings, that is, HEPI Z to RY, and for ITMY both HEPI Z to RX & RY, where less by about a factor of 10.

The Measurement

HEPI Z is driven with a 0.001 to .1 band pass excitation (see attachment 1) looking for coherence with ISI Stage1 T240 X & Y.

The HEPI is in normal configuration, Lvl1 position loops but with sensor correction off.

The ISI Stage1 all dofs are put into high blend (T750) and its sensor correction is also off.

Once a baseline of the existing HEPI Z to ISI Stage1 T240 to RX & RY coupling is established as seen by the T240 Y & X, the HEPI is then Tilted in RX & RY with a smaller magnitude but similar bandpass to see the actual tilt of the ISI Stage1 when HEPI is tilted.  The Decoupling factor is computed by the ratio of the former to the latter: RX_z/RX_rx.  This correction goes into the IPS Align matrix.

Results

See attachment 2 for ITMY.  The left three plots are the TF data for inline tilt on ITMY, this is the Y direction caused by RX; the three right plots are for the crossline tilt RY showing on X. The first step is shown in blue: the area below 0.1 to 0.01hz with good coherence is our tilt coupling.  Notice on the right side, there is poor coherence and the TF magnitude is 10x smaller than the tilt in the Ydirection seen on the left side.

The green traces are the direct tilt measurement HEPI RX(RY) to ISI RX(RY).  Picking a few magnitude points from the blue & green traces in the area of interest and averaging the ratios gives the decoupling factor blue/green= 0.23/46(e.g.) == -0.0049 with the sign coming from the phase which are ~180 out of phase.

The brown trace (only on the left side) shows the reduction with the decoupling factor in the matrix (see last attachment) when the first measurement is repeated. (I failed to save the coherence for this but it was reduced just above 0.8 from the near 1 at the start (blue.)  This indicates there may be more improvement to be made but it will be time consuming and may not be worth it.  The improvement though is clear, about a factor of 10.

Time constraints (commissioners) prevented a brown results curve measurement for the Z to RY tilting but I have the data to calculate the ratio.  We expect the improvement to be minimal as the coupling is already low.