Dan, Kiwamu,

We had trouble locking the interferometer tonight and therefore did not reach full lock.

It seems that the recycling gain is very low for some reason tonight. It seems as low as 19. Therefore the CARM reduction did not work as intended. In fact, REFL_LF dropped below 40% or less even when we were at the CARM_15PM state. Every time when we moved onto CARM_10PM it lead to lock loss. Not good. We even tried to transition to TR_REFL mutilple times by skipping a few CARM reduction steps since the REFL9 seemed passing the turn-around point. However this did not work either. Sad.

We co-aligned both red and green light in the Y arm in order to improve the recycling gain, but this did not seem to help. I am thinking of starting from the baffle PDs tomorrow in both arms just to make sure alignment is reasonable. In the course of the Y arm alignment tonight, we had to realign the ALS diff beatnote once because it went lower than -10 dBm.

PRC2 ASC loop still does not work only in yaw as reported by Dan (alog 18109).

There was a cabling error for the ETMX ESD DAC signals and this was the reason why we could not untrip the ESD driver. This is now fixed.

I drove down to EX and investigated the issue and found out that calbe #85 (see D1992741-v8) was conected to a wrong input of the AI chasis (S1102380). This must have been introduced today during the AA/AI chasis activity (see alog 18117). Since Stuart's medm screen (alog 17585) relies on the ability to see the analog signals, it was not able to tell whether the ESD driver was on or off even though the binary switches have been functional. I connected the cable back to the correct position which is the first slot (ch1-4) from the left on the front panel of the AI chasis. This fixed the issue -- now we can untrip and drive the ESD.

Seemingly due to some flow sensor issues. I reset the flow sensor indicator back to green in the control room. Then I reset the interlock and restarted the frontend from the diode room.

Nutsinee, Greg
Alignment continued in two parts today. We first aligned the SLED beams to the irises on the table while waiting for a green beam to return. Once we got a green beam we attempted to align the SLEDs to the green beam. The Y side looks like it could use some continued refinement, while the X side continued to give us fits until the commissioner asked to give him back the interferometer. 

Kyle, Gerardo 

Today we wanted to quantify the gas load "contribution" of the known leaking all-metal 2.5" Vent/Purge valve at the X-end station.  

SETUP 
X-end open to BT (GV19, GV20 open)
Main Turbo backed only by the leak detector (no parallel pumping)
 

RESULTS 
LD helium baseline < 10-10 torr*L/sec before valving turbo into X-end volume
Helium background signal = 3 x 10-8 torr*L/sec after valving turbo into X-end volume 
Valved-out IP12 
Removed NW50 blank from closed Vent/Purge 2.5" all-metal valve (i.e. vented air side of closed metal valve) 
X-end pressure responded by rising to low 10-7 torr 
Sprayed audible flow of helium on air side of closed valve while monitoring helium signal 
Helium signal rose rapidly then leveled-off and peaked at 2 x 10-5 torr*L/sec (signal peaked after ~10 seconds of spraying but I continued spraying until ~30 seconds) 
Spent the next few hours pumping system with the turbo pump to remove introduced helium.  We also added an O-ring valve in series with the leaking valve and evacuated the air side of this valve 

CONCLUSION 
Traditionally we have only used the vendor supplied hand knobs to open/close these Vent/Purge 2.5" metal valves (1 per isolate-able volume).  The allowable torque specs far exceed what can be applied using these knobs.  As such, our valves are likely under-torqued as a rule and, as was demonstrated yesterday, this leak could likely be eliminated by tighing this valve using a wrench.  As this particular valve has a "gappy" conflat joint on the vacuum side, we didn't want to "fix" it using a wrench (long lever) while we are open to the BT and while commissioning time is at a premium.  The main take away is that all of our poor pressure level at the X-end can be attributed to this under-torqued metal valve and that we have no reason to suspect GV19 or GV20.

J. Kissel, M. Landry

We've confirmed that hardware injection signals can go from each hardware excitation point that will be accessed by the non-blind and blind hardware injection team all the way out to the ETM SUS. We've done so with a 1 [Hz] sine wave awggui excitation from each of the injection filter banks. It turns out awggui can't request a gain of less than 1e-6, so each of our excitations which passed through the new inverse actuation filter (LHO aLOG 18115) were, shall we say... ridiculously large. But, at least it passed the signal chain test.

We'll work on getting unit-full text files of physical waveforms from the search groups (that are of amplitudes ~1e-21 or 1e-22 in strain instead of 1e-6) tomorrow. 

7:00-8:00 Cris and Karen in LVEA

8:17 Fil and Ed to EX AA/AI work

8:21 Richard and TJ to EY AA/AI work

8:52 Karen to MY

9:37 Kyle and Gerardo to EX

9:49 Karen done at MY

10:35 Fil and Ed done

10:39 Kyle and Gerardo to LVEA, then EX

12:00 Greg and Nutsinee to LVEA

13:13 Greg and Nutsinee done

15:52 Kyle and Gerardo done

Due to high traffic in the X end today, the BRS was rung up pretty high. SYS_DIAG showed the BRS rung up as well as the damper out of range. Jim w. and I decided that it would be best for it to settle with the damper off. So, I went to EX and turned the BRS Damper OFF and will leave it commented out until it settles down.  When I went to go inspect the masses I found that they were about 45 degrees off, aligned with the tube, so I moved them back to their North-East and South-West positions.

SEI running TFs on ITMy, BS, and ETMx ISIs

AA/AI work at both end stations

RGA work at EY

Leak checking ongoing at EX

J. Kissel

I've installed the first cut of the inverse actuation filter for the hardware injection team, based on the model shown in LHO aLOG 18050, but originally described in detail, with uncertainties in LHO aLOG 17951 and LHO aLOG 18039. Exactly the same filters have been installed in both the HARDWARE and BLND filter banks.

Design Details:
%%%%%%%%%%%%%%
I've divided the filter into two banks: 
- FM1 "Inv.Act" = the "main" [ct/m] inverse actuation function described below, and 
- FM10 "m_per_strain" = a gain-only filter that is equivalent to the mean IFO arm length of mean([3994.4704 3994.4692]) =  3994.47 [m]

For the "main" [ct/m] inverse actuation function I
- saw that the model parameters of the past six actuation functions we've reconstructed show results that are virtually identical above 20 [Hz], (see pg 1 of attached .pdf)
- grabbed the latest one of these actuation function models from Apr 15 2015 (parameters from H1DARMparams_1113119652.m),
- inverted it, and
- compared/"fit" it against a simple zpk filter that I knew I could easily hand-implement in foton (see pg 2 of the attached .pdf)

I ended up with the following filter:
Matlab Notation:
    toyModel.poles_Hz = [pair(4e3,51) 6e3];
    toyModel.zeros_Hz = [0.01 0.01];
    toyModel.gain     = 5.98e9;
Foton Design String:
    zpk([0.01;0.01],[2517.28+i*3108.58;2517.28-i*3108.58;6000],1,"n")gain(9.51664e+08)
where the gain has been normalized to match the real model at ~100 [Hz] in matlab, and forced to match the matlab at 99.54 [Hz] in foton (see gain forcing in 2015-04-29_H1DARMINJ_FotonDesign_and_MEDM.png). 
Bode plots of these filters implemented in foton can be found in the last two pages of the attached .pdf.

HOWEVER
You'll notice that the "real" model of the inverse actuation function (a) goes to infinity at high frequency, and (b) has phase behavior equivalent to that of a time *advance*. As such, I've made the following design choices / approximations with this simple model of the inverse actuation:
- Without the ability to make higher-than-Nyquist frequency poles, or to have a filter with more zeros than poles, I've rolled off the function at ~5 [kHz] with the above design (note the pair of poles with some complex phase in between is to tweak up the magnitude to achieve good fidelity reproduction out to 2 [kHz]).
- Of course, we must also, unfortunately have *casual* filters in the front end. As such, I compute the amount of time *advance* we need to reconstruct the phase response reasonably well. This is ~250 [us]. or 4.1 16384 [Hz] cycles.

I'M HOPING that the hardware injection team has this ability, to merely time-shift or "mis"-time-stamp their injection at the sub-millisecond time precision, or some how program the injection to happen 4 clock cycles "in the future." We'll be discussing this on the HW INJ call tomorrow to be sure.

Comments on Accuracy and Precision
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Recall from LHO aLOG 18039, that we are confident in the frequency dependence of the open loop gain to +/- 2.5% in magnitude and 1 [deg] between 15 and 700 [Hz] (and probably out to several [kHz], we just don't have any measurements to that high a frequency yet). However, the uncertainty in the overall scale factor is still ~26% (because we haven't yet discerned the scale factor uncertainty between optical gain fluctuations of the sensing function and ESD actuation strength varying due to charge fluctuations).

As such, I would assign the same uncertainty to the inverse actuation function alone, in addition to the residuals between the real model and this simple fit to it. These residuals are less than 1% and 0.5 [deg] between 15 - 1500 [Hz]. In summary, the 1-sigma, 68% confidence intervals are
Overall Scale: 26%, Frequency Dependence: 2.7%, 1 [deg] between 15 and 700 [Hz] (but likely out to 2 [kHz])

Per Work permit 5173

A continuation of the work done yesterday.  Today the Seismic and Suspension AA/AI chassis at bot EX and EY were swapped for V6 chassis.  All Chassis in the electronics room have been addressed at this time and are V6.

The pressure at XEND has stepped up to 1e-7 due to the leak testing activity. No cause for alarm as this appears to be the purge valve leaking. More info to come later today.

Here are plots from yesterday, again around 0130pdt like previous posts: Monday, Friday (18046), and Wednesday (18007.)

Again (looking at the ASDs,) the Z channel looks like all the others and better for STS2-B (ITMY) compared to reference (old seismo.)  Also, the X axes all look good (similar) now (compared to Monday.)  Before it wasn't clear, maybe the seismic environment wasn't as benign as I thought.  For the Y DOF ASDs, HAM5 & ITMY sensors diverge below 20mHz but more telling, the HAM2 Y DOF goes off track from the other two around 70 or 80 mHz.  The traces also look differnt relative to the Noise trace, something has happened to the calibration I need to sus out.

The TFs I've presented before are a little too busy.  I'll rework their arrangement for the future.

Added 804 channels. Removed 918 channels.

2 channels remain unmonitored:
H1:SUS-SR2_LKIN_P_OSC_SW2R
H1:SUS-SR2_LKIN_Y_OSC_SW2R

Scott L. Ed P. Chris S. 

4/27/15 the crew worked on crevice and tube cleaning ending 2.3 meters north of HNW-4-016. Tested clean areas (posted on this report) and began moving lights and cords to the next section. Vacuumed support tubes and sprayed bleach/water solution.

4/28/15 continued vacuuming and began tube cleaning. Cleaned 55 meters ending 17.5 meters north of HNW-4-018.

J. Kissel

I've accepted a few changes in the SDF system, and chose to not monitor a few more before bringing the end station SEI and SUS systems to OFFLINE, in prep for their AA/AI chassis to be swapped out for v6. They are ready to go for the swap!

After Evan and Sheila made the first steps towards maintenance recovery I stuck around for a few hours working through the Guardian steps towards resonance.

In alignment, the PRC2 loop is not working in the DRMI state.  I reverted the input matrix from 1.0*REFLA_9I --> PRC2 to the settings we used last night, 0.5*(REFLA_9I + REFLB_9I) + 0.83*(REFLA_45I + REFLB_45I), but this didn't give us a good error signal either.  For this evening I commented out the loop from the DRMI Guardian and tweaked PR2 by hand, it worked well enough to move forward.  Oddly, it's only the yaw loop that looks bad.

The AQ45--> DARM matrix element needs to be re-tuned in the late stages of the CARM offset reduction.  We are losing lock at the 10picometer state -- the optical gain is increasing and DARM becomes unstable.  The DARM loop in the 15pm state is ok (40Hz ugf, 50deg margin).

Looks like the aperture mask on the ITMY green camera can be much more improved. See the attached picture. I removed the aperture for now as it occulted large fraction of the spot. I will tune up the mask tomorrow.

Kyle, Gerardo 

Our X-end pressure has been higher than nominal following activity in September 2014 which required cycling GV20 -> Data virtually mimics issue LLO had (has?) at their X-end station (see G1500110-v1).  As such, we had intended to spray helium on/in/around GV20 today but the VE configuration is not good (we are open to the BT) for the anticipated leak size and we also have been lead astray by the response of tightening the Vent/Purge valve which should have 1-liter of "rough" vacuum on the other side of its metal seal.

PT510B responded and the X-end pressure went down after we tightened the Vent/Purge valve -> Tightening this valve a little more resulted in a further pressure reduction -> I don't like looking at the visible "gap" on the conflat joint as I am torquing this valve knowing that we are open to the tube so we stopped and went looking for a torque wrench and the specs. for this valve -> We will continue this investigation as commissioners permit.

Evan, Dan, Sheila. Kiwamu

This afternoon we moved the picomotors on both transmon IR QPD sleds, although we moved Y much further than X.  This was to reduce the clipping and saturation Keita pointed out in 18077.  After that we excited TMSY in both pitch and yaw, and found error signals for the ITMs that are insensitive to TMS again. 

We have closed all the loops in full lock and things seem stable,  we were able to increase the power at 12:00 UTC on the 28th and saw that the recycling gain stayed stable.  We stopped at 6 Watts because the Y QPD is near saturation.  We should probably do more picoing (most of the light is on one quadrant), and reduce the whitening gain. 

The attached screenshot shows the settings we have now, the DSOFT and CSOFT loops could have gain of 1, but we were cautious. 

We had some difficulty turning on the ASC loops earlier tonight.  One thing that we noticed was that we were able to close INP1 each time, even when we didn't close PRC2 or CHARD (or SRC).  We also had trouble closing the CHARD PIT loop, although YAW was fine. Once we manualy adjusted the alignment to improve the recycling gain and closed the ITM loops, we closed CHARD PIT with no problems.  

We have left the ASC engage commented out in the guardian, because it is not working right now.  We also attempted earlier in the evening to take Keita's advice and manually aling the green PZT durring a full lock with good recycling gain.  We had difficulty getting the build ups high while minimizing the WFS signals, we adjusted the QPD offsets to keep the build ups high but this resulted in a bad recycling gain.  Probably a more thorough attempt is waranted. 

ETMX ESD tripping

Since saturday, the ETMX ESD has been tripping almost every lockloss.  We also need to toggle BO 4 to reset it, which is not required to reset ETMY.