Evan, Sheila,

Many things were tripped this morning after the earthquake in Nepal, (ISIs, HEPIs, and suspensions).  most of this went smoothly.  I had trouble untripping HAM5, the screen shot I attach is the collection of screens that I was looking at when I was confused, from these I thought that the watchdog was untripped, but that was untrue, in the ISI watchdog screen the small box aroud the rouge watchdog was red.  Maybe this could be more obvious, say if the watchdog indicator on the ISI overview screen was red when the rouge watchdog was tripped, and if the reset all button really reset all the watchdogs.  That might have save Jeff and Jim from a flurry of saturday morning texts in the future.  Jeff logged in and reset the rouge watchdog.  

Also, the PSL was tripped this morning about 16 UTC (not at the same time as the earthquake), it might have been a flow sensor problem.  After turning the laser on we weren't able to open the HPO external shutter from the beckhoff computer, we came to the control room and found that the flow sensor was red, we reset that but still weren't able to open the shutter from the control room.  We went back into the diode room and were able to reset the shutter from there.  

After the PSL came back SYS_DIAG said that the NPRO noise eater was oscillating, but we think that it is not.  The attached screenshot shows 100 days of the NPRO ROO readback, this number is around -500 when the noise eater is osciallating,  Each time that the laser tripps and is turnd on again this readback is high for a while before settling down.  We changed the tolerance on the readback to 50 counts from 10 counts in the SYS_DIAG test.

In order to check whether we have messed up the camera positions, I locked the interferometer and brought it to a recycling gain of 40 by steering ITMs. It seems that the ITMX camera position remained good while the ITMY camera postion was completly off for some reason. I updated the ITMY camera position.

pit: 302 -> 180

yaw: 434.3 -> 391

Kiwamu, Elli

Yesterday after removing the lexan viewport covers from all of the ITM cameras, we focused the ITMX_green and ITMY_green cameras and looked at the images of the ALS beams on the ITMS when ALS is locked.  We noticed that the picture on ITMY is a fairly  diffuse beam with few point scatterers, while the image on ITMX is mostly point scatterers. 

We wondered if these images showed a real difference in the ITMs or whether there was a difference in the cameras, for example maybe there is a smudge on the IMTY_Green camera lens which makes the beam look more diffuse than the ITMX_Green beam.  So today we refocused the ITMy_Spool and ITMx_Spool cameras, which are usually focused in IR but which have no color filters on them, to green.  This way we have a second pair of cameras looking at the ITMs.  The saw the same difference in pattern (ITMy diffuse beam, ITMx many point scatterers)  with the ITMX_Spool and ITMY_Spool cameras.  This might mean there are more point scatterers around the center of ITMX than around ITMy.

We tried looking at the pixel sum of these cameras to compare the relative brightness of the scattered light.  Comparing images taken with the same settings, the pixel sum is higher on ITMX_Green than for ITMY_Green (eg 1,550,000 counts on ITMY_Green vs 960,000 counts on ITMX_Green when counts on ALS-C_TRY_A_LF are 1050 and on ALS-C_TRX_A_LF 1370, with camera settings exposure=100000microsecods, analog gain=100, image type = mono12.).  The IMTY_Spool camera pixel sum = 845,000 and ITMX_Spool =186,500.  THis is a factor of 4 difference between the intensity on the ITM spool cameras, which we can't explain.  We expected them to be roughly the same!

6.2mag quake off the Canadian coast had everything tripped and down

07:00 Cris and Karen into the LVEA

08:05 Hugh out to LVEA to fool with FF seismometer

08:25 Hugh out of LVEA

08:37 Buba to EY to check instrument air pressure transducer.

09:00 Fil to EY to assess AA/AI swap job

09:12 Bubba laeving EY. Inst Air alarm reset

11:28 Travis heading into LVEA to look for parts

11:32 Kiwamu out to help Ellie adjust cameras

11:40 Travis out of the LVEA

~12:00 Patrick restarted Beckhoff Ethercat; Rotation stages/PSL Env. etc

Scott L. Ed P. Chris S.

Yesterday the crew cleaned 82 meters ending 12 meters north of HNW-4-012.

Today the crew cleaned 61 meters ending 13.7 meters north of HNW-4-015. The crew also serviced the generator today.

As a part of  the camera alignment study (alog 18033), I noticed that the ASC loops for green X reacted so slow that it took about several minutes to converge. See the attached screenshot. This is a time series when I turned on the ALS X green ASC loops. I was watching the ALS COMM beatnote strength at the same time as a position-sensitive sensor. I suspected that the camera loop (DOF3) is the one which is so slow, but increasing the gain of this loop told me that the UGF is already close to the 0.5 Hz mechanical resonance (10-sih dB away from instability in gain). Perhaps some kind of cross coupling between the loops exist and may be slowing them down. I am not sure how critical this is in terms of the recycling gain, but if one does not wait for these loops to settle, certainly the alignment will not be repeatable.

I've been trying for a while to get feedforward running on HAM's 4&5, but not having much luck. Originally, I just tried copying the filter we are using on the BSC's, only because it was there, and the test was quick and easy. And not the right answer, as (kind of) expected. In order to design a proper filter, I've taken measurements as outlined in Brian Lantz's SEI log 682. Two measurments are needed, 1. a driven tf from the FF path to the ISI GS-13's and 2. a passive tf between the St0 (or HEPI) L4C's and the St1 GS-13's. First attachment is the driven tf for Y on HAM4, second picture is of 2 passive tf's between the ISI GS-13s and St0 L4C's (in blue) and between the ISI GS-13s and the HPI L4C's (in red). The filter should be a fit of the ratio between the passive tf and the driven tf (so green / blue (OR red), depending on the path you choose). Third attachment is plot of these ratios, blue is St0 FF, red is for HPI FF. I've tried a number of filters and so far the best I've gotten is a small improvement between 20 and 25 hz, and at best, no worse any where else. Fourth attachments is of my fits to the St0 feedforward. I've tried closer fits and they didn't work either.

Just to make sure I wasn't totally missing something I tried doing the same for the BSC's and was at least able to get something that worked (fifth plot is the performance, last plot is the design). A work in progress.

I realigned the beam into the ISS array. The QPD signals are close to zero.

For reference, here are the DC values read by the slow signals for 3.3W input power:

I didn't check the jitter to RIN coupling as we did in the past, so the alignment might not be the optimal one yet.

In addition, it seems that PD8 has some problems, since the spectrum is clearly noisier.

J. Kissel

The CAL-CS front-end model is where the infrastructure for the calibration (i.e. inverting the DARM actuation function such that a waveform calibrated into strain can be injected into the DARM loop in the correct DARM [ct] units), so I'm looking at what I need in order to fill the one filter bank that we'll use for this inversion. I've used the DARM open loop gain TF model (described in LHO aLOG 17951) to demonstrate (a) what the actuation function model looks like and (b) how simple it *could* be to invert it.

In summary, we can get a ~5%, 3 [deg] frequency-dependent fidelity of the full model between 10 - 2000 [Hz] if we simply use a
1.03e-13 [m/ct] * (1 [Hz] / freq)^2
model for the magnitude, and a
-1 * 176 [us] delay
model for the phase. Huh! 

Recall that 1.03e-13 [m/ct] has a +/- 26% uncertainty because we're as of yet unable to discern the difference between optical gain fluctuations and ESD strength changes from fluctuations in charge (again, see LHO aLOG 17951 for discussion).

I'll discuss with the LLO injection team to see what they'd implemented for ER6, where they've rolled off the *inverse* of this filter, and discuss the path forward, so we can get something installed by the mini-run.

Done around 12:14 to see if it might help resolve rotation stage issues.

Mike, Jeff, Jim, Dave:

Jim has built the h1hwinj1 server. This is a Scientific Linux 6.5 rack-mounted machine in the MSR with software installed as requested by the hardware injection group. Eric Thrane, Ed Daw, Peter Shawhan, Michael Landry and Jeff Kissel are commissioning this machine between now and the 5/1,2 mini run.

Attached are ASD comparing the Old (troublesome) STS2-B and the newly repaired STS2 temporarily in place in the beer garden.  The current traces are from ~0130pdt--looks like a quiet time based on the PEM traces.

When I compare these to the plots (calibrations in meters) in 18007 from Wednesday AM, I observe the following:

Strong coherences are moving to lower frequencies in all DOFs.

Unity transfer function for X DOF too is moving down in frequency.  The Y & Z TFs look pretty similar.

Maybe this means these signals are getting more stable.  However, the Z signal of the Old & New STS2-B still don't look like the A & C units, is this an indication of the vinyl difference?

I have created a new CDS Overview MEDM screen customized more for CDS sysadmin rather than OPS. It is very similar to the CDS overview with the following differences:

• size has been reduced so the model names are readable on most screens
• the overflow bit is not shown
• the excitation bit is a different shade of green

The purpose of the screen is that any non-green indicator shows a possible problem which can be resolved by software means (unlike overflows which require system level intervention). The screen is called H1CDS_ENG_STATE_WORD_CUSTOM.adl and is accessible from the CDS block of the SITEMAP (ENG OVERVIEW selection).

Evan, Sheila

We have been able to lock the IFO at 10 Watts with a recycling gain of 37.  We also think that we can probably improve our inital alingment scheme by adding a servo from POP A to PR3 durring the INput align step.  We've closed loops around ITMX from the TRX QPDs, these were stable for almost an hour before we dropped the lock for other reasons, and helped keep the X arm build up stable as we increased the power.  

Variation on Inital Alingment 

At the beginning of the evening, our alignment resulted in a rather low recycling gain (15 or something) which resulted in difficulty locking.  This was probably because the ITM camera references would have moved 18033.  We have now gone through an initial alignment with some extra steps which brought us back to a decent recycling gain (35 before any manual adjustment or full lock ASC).  

• First we locked the X arm with both green and IR, and ran two green WFS loops (ETM and TMS), green ITMX camera loop, and the input align WFS loops (REFL WFS to IM4+PR2).  In this configuration Evan moved PR3 to bring the spot position on POP A close to zero, which is the position it was in during a high recycling gain lock last night.  (0.05 Yaw, -0.08 PIT).  This move also increased the COMM beatnote strength, to above 4 dBm.  After this we set the green ITM camera reference again. 
• Then we used this input beam and with the Y arm optics misaligned steered the BS to get red light on the ETMY baffle PDs.  This was a rather different location than what we found in october 14321. We did this by hand since we have never set the gains and phases correctly to use the ditherAlign script for the BS.

• After this we locked the Y arm on green and IR, with green WFS running on the ETM and TMS.  We moved the ITM to maximize the red build up in the arm, and let green WFS take care of the ETM.  After this, we reset the ITMY green camera reference.  Ideally, we would have used red WFS to 
• After that we checked MICH dark which was misaligned by about 0.6 urad, we adjusted the BS to get a nice dark port.  
• Then we did the rest of our initial alignment scheme as usual, PRM ALIGN and SRC align. 

 This resulted in a recycling gain of about 35, so it seems like this was a sucsesful approach at least once.  If there is time for some day time commissioning tomorrow, it would probably be helpful to add to the INPUT align state a loop which actuates on PR3 to center the beam on POP A.  Commissioning the dither Align script for the BS to ETMY baffle PDs might also be helpful, but this is a lower priority because we aren't sure that step is necessary.  

Since we have seen this week that many things (CARM offset reduction, violin and roll mode damping, and ASC error signals, possible radiation pressure instability on the ITMs) change when we go from a bad recycling gain to a good one, it seems like we will want to improve our initial alignment scheme enough to consistently bring us to a high enough recycling gain that we can use consistent settings for lock acquisition.  

Avoiding oscillations durring power up

We ran into the oscillation in ITM pitch which we think is due to mis centering and radiation pressure on the ITMs several times tonight.  It seems like we are more stable when the recycling gain is high, we have also slowed down the final CARM offset reduction and the power increase.  

Closing ITM loops

We were able to close loops around ITMX from the QPD error signals we found last night. Here are settings:

DSOFT P (ITMX P) error signal 1.71 TRX A -1 TRX B FM offset 0.08, FM2,3,4 gain -700,000, top mass offloading on

DSOFT Y (ITMX Y) error signal 1.84 TRX A -1 TRX B FM offset -0.1, FM2,3,4,6 gain 600,000, top mass offloading on

both of these loops respond in a 2-3 seconds.  

DARM OLG

Evan made a measurement of the DARM OLG, this was when we still on ETMX, DC readout with low frequency boost, and a recycling gain of 35.  11 Watts input power. 

Now a large earthquake has tripped most of the seismic platforms.  

Evan, Sheila

We have been slowly stepping up the input power tonight, and we see the power drop when we request increased power.  Here is an example, from 4-24-15 9:35 UTC.  The top left panel shows the power which Evan requested, the bottom left panel shows the actual cmd position, which approriately goes in the same direction consistently when the requested power increases. The right two panels show the problem, that the readback of the actual rotation stage position goes in the wrong direction briefly when a new comand is sent.  This is a real decrease in power, the lower right panel shows that the power monitor PD sees these power decreases.