Krishna, Michael,

We left Seattle at 10 AM and reached LHO at 2ish PM. Hugh helped us unload the BRS-2 vacuum can and other parts into the 'loading bay' at the Y-End-station. Tomorrow morning, we will clean them and move them in and begin assembly, which is expected to take 2-3 days and commissioing/debugging may take a week. We will try to complete activities in the VEA by mid-day to minimize impact on commissioining.

1545 - 1600 hrs. local -> To and from Y-mid 

Exhaust check valve bypass opened, LN2 at exhaust after 3:39 mins with LLCV bypass open 1/2 turn 

Next CP3 over-fill to be Fri. before 4:00 pm hrs. local 

Following the grouting of the HAM5&6 HEPI piers, and in light of JeffK's work untangling my designs (in LHO alog 26002), I wanted to review the design of the HAM 4/5 S0-1 feedforward. To do this I took a new set of measurements for HAM's 4 and 5 so I could see how similar the different transfer functions were. The measurements I took were: the transmissibility from the FF L4Cs on St0 to the St1 GS13s with the ISI in both damped and isolated states, and the actuator to GS13 tfs in both the isolated and damped states. I got all 24 measurments for HAM4, but I only got the all of the Z measurements for HAM5, so I looked at that dof filter design.

Jumping straight to the punchline (first plot, calibrated ground and GS13 spectra for HAM4) I have a new Z FF filter that does a lot better and makes more sense, installed on HAMs 4&5, and I'm working on similar redesigns for the remaining dofs. The two traces to really look at are brown and light blue, the GS13 measured displacement with the old and new FF filters. Compared to dark blue (FF off), the old FF filter mostly improved motion between 20 and 30 hz and only worked well with a gain of .5, something I couldn't explain when I installed it. The new filter works better from a few hz to almost 60 hz.

The second plot is the transmissibilties for HAM 4 (blue) and 5 (green) in both damped (solid) and isolated(dashed) states. The damped states are very similar, though I'm not sure why there is a gain difference. The Isolated tf's are more different, but probably it's probably due to some differences in the feedback loops, I should probably take a look at that.

The third plot is the stiffness tf, color key is the same, HAM 4 (blue) and 5 (green) in both damped (solid) and isolated(dashed) states. Again the damped states are similar, the isolated measurments are a little more different. Importantly, the differences are consistent with the transmissibility measurements, which means the filter design ends up looking the same between the chambers, as shown in my next plot.

The fourth plot is the ideal filter design for HAMs 4&5. This is done following the process outlined in JeffK's 26002 alog, where the ideal filter is roughly speaking the transmissibility over the stiffness. One of the other things I wanted to look at was  what state the ISI needed to be in when designing the filter, as I thought that I had found in the past that the ISI needed to be isolated for both the transmissibility measurment and the stiffness measurement. It looks like it doesn't much matter as far as the final filter design is concerned. The isolated design is a little different at a few hz, though it's hard to see because the data is crappy. The data is much cleaner with the damped transfer functions. UGF's for this loop are on the order of 35hz, so feedback is not doing a lot at 10 hz, that probably explains why the isolated and damped filters end up looking the same, and why they differ more at lower frequency. Also nice to see that the filters for HAM 4 & 5 should be the same, regardless of the either ISI's state. The cleaner data for the damped configuration is a strong argument for using that configuration for my future redesigns.

The fifth plot is a comparison of the HAM4 ideal filters(blue and green), the old filter (red), and the new filter (black). You can see that the black line matches green and blue very well between 10 and ~40 hz, but red only matches well in phase right at about 25 hz. This explains why the old filter only did well at 20-30hz. The gain mismatch at 25hz also explains why the old filter needed a gain of .5 to work. The new filter works well from a few hz up to almost 60 hz, with a gain of 1.

I still have my data and the script that I used for the orginal design, Jeff rehashes it in his log. I still don't understand the differences, what I screwed up originally. I think the approach used both times was the same, but I clearly did something wrong the first time around. I'm in the process of repeating this for the other dofs.

The last plot is HAM5, comparing the old FF filter to the new. Red, blue green are with the new filter, brown, pink and light blue are with the old filter.

I, for some unknown reason, never added the INIT_ALIGN.adl to the sitemap.  I added it under ASC-->Init Align. This screen is to help operators/commissioners with initial alignment (see alog 24943)

Jeff Bartlet, Jim Batch

Original dust monitor IOC's have been killed and new IOC's to support the gt521s dust monitors have been started at EX, EY, and LVEA.  Work will continue today to install correct autoBurt.req files and revise the instructions for starting the IOC's.  Jeff will be installing some new dust monitors today.  

I did a common CO2 test with the fully locked interferometer. Unfortunately the interferometer could not stay locked due to the SRC1 and 2 pitch loops running away.

The interferometer was fully locked with 8 W PSL (10 W was not stable and in fact it lost lock once due to the angular instability 26208). ASC loops were all closed. No LSC feedforward engaged. DARM line was injected at 331.9 Hz monitoring the cavity pole and optical gain. The line was provided by the LSC lockin oscillator and not by Pcal Y.

• CO2X 240 mW -> 640 mW
• CO2Y  0 mW -> 400 mW

Since it lost lock, I set the CO2s back to nominal. I will check the data later.

Something is wrong with ITMX HWS. I need help from experts.

As I wrote yesterday (26185), because the HWS codes were not running, I had restarted both ITMX and ITMY HWS codes. Today I checked the output, in particular the spherical power, and noticed that the noise level was way too high (+/- 200 uD !). I restarted the code with a new reference image to see if it helps, but it actually made the noise level worse. Now it fluctuates as big as 0.03 uD. Looking at the camera image itself, I saw a beam on the center and assumed that it was the right one. Also I steered the ITMX compesantion plate (which is now intentionally steered by approximately 500 urad due to the green view port issue, 26164) back to the zero-offset angle, but this did not help at all. The laser power has dropped to 1.1 mW which used to 1.4 mW on March 1st (25806), but I believe that this should not increase the noise level such drastically.

One suspicious thing I found is the number of centroids which now reads only 65. In the past it was 400. In summary, I have no idea what has gone wrong.

[Stefan, Sheila, Jenne, Kiwamu, Hang]

Tonight ended up being a night of retuning the PRC2 loops, to make them sensible.  Now they have UGFs around 2 Hz, rather than ~20mHz. 

The thought was that perhaps this 0.4Hz oscillation that we regularly see is a result of not holding the PRC2 loops tight enough. If the PRC isn't following the motion of the SOFT loops (which move when we power up due to radiation pressure), then we're getting a modulation in the amount of power coupled in to the arms from the PRC.  This power modulation makes the SOFT oscillation even worse.  If we force the PRC to follow the arm pointing, then we won't have this power modulation, so we will hopefully only have to deal with "regular" angular instabilities.

In the end, we tuned the shape of the PRC2 pitch and yaw loops while sitting at ASC_PART3 by compensating the PR3 suspension resonances.  This made the loops beautifully stable, so we cranked up the gain.  For the PRC2_Pit loop, we use the new shape (although low gain) for DRMI_ASC.  For the PRC2_Yaw loop, we use the old loop shape and gain during DRMI_ASC, and then use the new loop shape for the main ENGAGE_ASC steps.  Recall that all DRMI ASC loops except for MICH are turned off after offloading the alignments, and are left off for the carm offset reduction sequence.  Also, during DRMI_ASC, the PRC2 loops actuate on PR2, while they actuate on PR3 in the final state, so it's not quite as weird as it sounds to be using different shapes at different states.

See the attached PRC2 open loop measurements for the OLG after our retuning and gain increases.  All of these sequences have been added to the guardian. 

Now however, when we try to go from 12W to 15W, we see an oscillation in PRC1 Yaw.  We should probably retune the PRC1 loops, including actuating on the lower mass in addition to the top mass of the PRM (right now we only push on the top mass).  We leave this for another day. 

ASC plan for tomorrow:  Run Hang's A2L script, and find SOFT offsets that put us at our actuation nodes.  Hopefully this will reduce the angular effects of increasing the power, and help us get back to 20W.

* Alog title courtesy Stefan

Corey, Daniel, Stefan

We moved one of the two AS56/45 WFS from the AS port in-air table (ISCT6) to the REFL port in-air table (ISCT1). (Serial number S1300512)

The WFS was connected to the RF cables for the REFLAIR B WFS, and powered by the third slot on the WFS interface chassis.

One thing to note (again) is that those 5-channel RF connetors are impossible to plug in - in fact the only way to guarantee that all connecions are good is to remove both the connector backshell and the WFS box cover, and idividually checking that every channel pin and shield makes a good contact. Corey has some pictures of this.

Also, we quickly wanted to check the RF transfer functions from test in to each channel, but they looked broken. The chain definitely needs to be checked out again.

John, Chandra

Connected aux pumping carts to the following annuli:

1. HAM 7/8, with secondary turbo
   Pressure:  3.4e-5 Torr
2. HAM 11/12, with secondary turbo
   Pressure:  9.5e-5 Torr
3. HAM 9, no secondary turbo
   Pressure:  7.0e-4 Torr

Still need to connect BSC4 annulus. 

Two annuli systems are leaking, based on the attached plot of diagonal gauge PT-140. Leak rate (O) e-3 Torr-l/s.

re aLog 26140

Here are snaps of 0-120hz spectra for HAMs 2 thru 6 with the reference traces from 13 March (before the switch last week,) and the current traces from this morning at 3am.  Not even really suttle differences so I'd say at least no harm done from the switch to the common timing source.

During O1 run we have monitored slow variations in the DARM actuation and sensing functions with several ~35 Hz and a ~350 Hz line at both observatories.

Systematics in the actuation function mostly affect systematic errors at frequencies below UGF, while systematics in the sensing mostly show up at higher frequencies.

Variation in the DARM sensing is parametrized with an overall sensing gain κ_C and a cavity pole frequency f_C. Most dramatic changes in both of these parameters appear in the beginning of locks, which could be a result of changing of cavity modes due to thermal heating of test masses and possibly some other effects.

Variation in the DARM actuation is parametrized with κ_TST and κ_PU. The κ_TST is a scalar gain factor of the ESD driver actuation which drives only the TST stage. We believe that it changes mostly due to charge accumulation on the surface of an ETM. The κ_PU is a scalar gain factor of the actuation functions of the upper stages PUM and UIM. The coil-drivers as used to for actuation of these stages. We do not believe that κ_PU should change over time, but monitoring it helps to make sure that we do not miss any slow variations that we did not account for.

Time-frequency plots of the known time-depedent systematics in the overall DARM response function calculated from κ_TST, κ_PU, κ_C and f_C in O1 run are attached.

Update: replaced figures (portrait -> landscape orientation) for convenience.