Kiwamu, Sheila, Evan, Lisa, Daniel, Elli, Dave O., Dan, Alexa

On December 3rd 2014, 3:01 UTC we had the IR resonanting in all the cavities. MICH, PRCL, and SRCL were still on the 3f signals; DARM was on AS 45Q and CARM was on REFL 9 I at 0 pm. This is what we did:

• We started with CARM controlled by sqrt(TRX+TRY) and DARM by AS 45 Q.
• With the CARM offset at -15, we measured the UGFs of the DRMI loops: PRCL ~80 Hz, MICH ~ 10 Hz, and SRCL ~ 20 Hz (this was with the reduced gain as Lisa noted in the last alog)
• We then compared the TFs between the normalized REFL9 I signal and the sqrt(TRX+TRY) signal. With a gain of -40, the TF was relatively flat (see TRvsREFL_CARM.pdf)
• We also measured the CARM UGF with the CARM offset at -15 and found that the UGF was ~90 Hz with zero phase margin. We turned up the REFLBIAS gain from 0.8 to 1.5; this brought the UGF to 150 Hz with 25 degree phase margin. We also measured DARM at this point and found the UGF of 16 Hz, with a phase margin of 40 deg.
• With a CARM offset of -15.5 we set the normalized REFL 9I offset such that the output was zero, and then adjusted the input matrix to tranistion from sqrt(TRX+TRY) to the normalied REFL 9I into the REFLBIAS input. Finally, we zeroed the offset. We stayed locked for about 12 min. We repeated this and Evan adjusted the offset around to ensure that we were actually at a maximum power build up in the arm.
• As we locked, REFL LF power went from 75mW to 33mW, and TR QPD sum went from 4 to 143 counts. Meanwhile, ASAIR LF stayed constant. We are missing build up in the arm, and the next step will be to investigate this.
• With CARM on REFL was also took several more transfer functions. The CARM TF looked flat around the UGF. We need to improve this loop. Evan will make an attachement with these pdfs. We also need to transition REFL 9I to the analog signal in the summing node board.
• This is all in the guardian now.
• I have attached a picture for good measure.

This morning, after my failed attempt to engage the new LLO-imported filters on the SR3 damping loops, Evan managed to be successful.  Attached is spectra of the SR3 OPLEV PIT and YAW signals comparing the original state of the SR3 (LHO filters and gains, OL damping enabled) with engaging the filters.  Note, I increased the gain to compliment the LLO ones a few hours after we switched the filters and added new spectra.   It does not apear that the new loop filtering and gain are helping, but instead hindering.  Hmm...  I've since dropped the gains back to the original LHO values, and leave it to the commissioners to flip back the filters if they see fit.

Today the fire protection water tank was filled which required the well pump to be switched over to a manual mode. After the tank was filled I was unable to switch the well pump back to the "auto mode" therefore I manually turned the well pump off. The domestic water tank is completely full and there should be sufficient water through the night. We will address this issue in the morning.

I was checking on the HTTS today and noticed that the lockin oscillators for RM1 & 2 were enabled.  It looks like these have been exciting the optics for the last three months.  The plot attached shows the amplitude and frequencies; RM1 was a few Hz, RM2 was a few mHz.  I've zeroed the amplitudes.

Sheila was asking about extra glinting showing up in HAM5 somewhere between the SRM and SR3 suspensions which sit almost side-by-side when viewed face-on from HAM4.  I've dug through the log and have reposted below some HAM5 pics which confirm that

1) the SR3 HR baffle location and orientation look to match the L1 HAM5 position, and the specified mechanical layout drawings of HAM5 (phew)

lho log 12599 pic

2) the baffle does not appear to completely block the line-of-sight to the left edge of the SR3 suspension cage which appears to be light up

llo log 7180 HAM5 pic

I also confirmed that according to E1200145, the SRM, SR2, and SR3 optics all have a vertical wedge, so no secondary back reflections in the cavity should be propogating from the SR optics along the yaw axis.

Although she was specifically asking about light just to the left of the SR3 optic, there are light splashes above the optic on the SUS cage and below the optic on the HAM table, outside of the baffle frame.  It is difficult to see the right edge of the baffle and cage with the existing camera view.  I supect this is just the low power, non-gaussian tail of the beam which the cameras are very sensitive to.  Will have to watch to see if this correlates to anything bad the commissioners see twitching around in the cameras.

07:16 Cris into LVEA
08:06 Karen into LVEA
08:10 Jim B. reconfiguring fw0
08:46 Corey to squeezer bay for 3IFO ISCT work
09:21 Filiberto, Aaron and Sudarshan to end X to power up magnetometers
09:37 DAQ restart
10:03 Gerardo to H2 PSL laser enclosure to work on OFI
10:09 Dick G. to ISC rack 2 to test RF signals
10:36 Betsy taking transfer functions on SR3
10:37 Karen cleaning at mid Y
10:38 Keita to end Y to check cross cabling of green WFS
11:07 Dick G. done
11:30 Karen leaving mid Y
12:06 Corey out of LVEA
12:26 Aaron and Filiberto done, Sudarshan still checking channels
12:34 Sudarshan back
12:35 Keita done
12:56 Gerardo done
13:15 Let truck with portable toilets through gate
13:19 Dan and Rob working on ISCT6
13:32 DAQ restart
14:07 Dan and Rob back

Made programming change to one half of pump -> Will duplicate change on remaining half of pump tomorrow -> IP4 was at wrong HV value for pressure conditions -> Previous change attempts either not saved(?) or entry error(?)

I have completed a full set of measurements checking for basic coherence of input/output of the Aux Channels for every suspension. Suspect channels were retested a number of days later. Those that failed in the same manner were labled as "bad" or "failed". Those that changed, either significantly or marginally were left to question. Below is a crude spreadsheet that illustrates my findings so far. The measurement technique is noted on the spreadsheet. 

All /trend/minute_raw files have been moved to /frames/trend/minute_raw/minute_raw_1101489341, and a new /trend/minute_raw directory has been created to accumulate new data.  The h1nds0 nds server has been reconfigured to read the /frames/trend/minute_raw/minute_raw_1101489341 files as old data.  

Testing has been performed to check availability of old and new data, across file boundaries.

This concludes WP 4955

Alexa, Kiwamu, Lisa

Most of the day was lost in ALS land. We manage to start locking at 2am. Our success was pretty well correlated with Kiwamu changing the Y end VCO offset slider from -0.263 to -5.526 such as the X VCO goes away from the negative railing point when DIFF is locked. This was done because, even if the HEPI relief was on, we were seeing that at least some of the ALS lock losses were due to the X VCO railing (to be investigated).

After that, we worked on ASC during the CARM offset reduction. 

So far we have been using AS_B_45Q for DHARD until CARM offset = -12, then we were opening it because we suspected that this signal was flipping sign when reducing the CARM offset further. Tonight we indeed established that by measuring the response to ETMX steps by comparing CARM offset -8 and -13. At the same time we checked the AS_A_45Q response, which is still sensitive to DHARD but it does not change sign.
After measuring the relative gains, we transitioned from AS_B to AS_A at -13 CARM offset, and then we kept the loop closed while reducing the offset down to -16.

Some parameters:

 - AS_A input matrix elements are +2e-6 for both P and Y (ugf ~50mHz).

 - We also reduced the SRCL gain by a factor of 2 (from -30 to -15) at CARM offset -15, and that reduced the broad gain peaking we were seeing in the SRCL spectrum at 70 Hz (we didn't really make any measurement).

We are not updating the Guardian, as this needs further testing.

Data: Dec 3, 11.15 UTC locking start, lost lock at 11.56 UTC while transitioning to -16

J. Kissel

In summary:
(1) Turn on X, Y, and Z sensor correction for HAMs 2 and 5, using the standard Hua Filter scheme (see T1200285), with tuned gains.
(2) Use LLO's M1 OSEM Damping filters and gains.
(3) Turn off optical lever damping so we don't have worry about maintaining optical levers to as great care.

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This continues (and hopefully resolves) the study of why PR3 and SR3 (both HLTSs) are angularly noisy, began by Kiwamu (see LHO aLOG 15048), and continued in a prior aLOG by me (see LHO aLOG 15154). I had started today thinking that I would do the usual full modeling suite, and this time include the optical lever damping. But after a little bit of exploring, I found that the L1 HLTS, H1 PR3, and H1 SR3 were using in various, completely different damping schemes, the performance of the optical levers are radically different, so a noise projection would be difficult, and the L1 vs. H1 HAM ISIs perform significantly different. So, since a "representative" model seemed impossible, as did the thought of making an individual model for all four suspensions and comparing, I've just spent the time gathering proof of what we need to do to make them much better. Once we get all of the above three steps completed *then* I'll make a full model suite of the performance.

Here's the details explaining how I can to these conclusions. They're supported by the first and only attachment.
(3) Turn off optical lever damping.
    Pages 1 and 2 of the attached show the wide variety of performance on the optical levers. Page 3 and 4 show the H1 the levers are in loop, but only with a bandwidth from 0.4 to 1 [Hz] (see design for SR3 in LHO aLOG 14719). There seems to be some effort toward rolling off the noise, but it seems quite unrelated to the actually noise performance of the levers at high frequency.
    LLO *had* used optical lever damping sporadically on L1 PR3, but they're currently not using it and haven't since Oct 17 2014. Given that the damping is so much strong and the input motion is so much smaller, this makes sense that its not needed. Further -- even with L1 SR3 aligned, the location to which, presumably, the optical lever has been centered -- the performance of the optical lever spectra is not limited by residual ground motion of the optic. So it's most certainly unusable for control. 
    Including optical levers in the local damping scheme complicates the remaining dynamics of the suspension (and perhaps more to the point, the subsequent modeling of it), and getting used to relying on them means they'll be left on and most certainly reinject noise above their bandwidth unless the loops are custom tailored to the ever-evolving optical lever noise. So if we can achieve the same level of local damping with the top mass OSEMs, and improve the performance of the ISIs, let's do it. 

(1) Turn on X, Y, and Z sensor correction for HAMs 2 and 5, using the standard Hua Filter scheme (see T1200285), with tuned gains.
    Pages 5 through 7 compare the performance of the HAM2 and HAM5 ISIs, highlighting the degrees of freedom which contribute to L, P and Y at the optic. 
    Remember, the L at the suspension point is the dominant contributor to L *and* P at the test mass, at all frequencies (see pgs 5 and 33 of the second attachment to LLO aLOG 7907). In turn, X and RY (for PR3) and Y and RX (for SR3) are the dominant contributors to L at the suspension point. Y at the optic is all Y at the susp. point, which is all RZ of the table.
    Though I'm not sure what the H1 HAMs have worse performance than the L1 HAMs between 2 and 8 [Hz] (that should be investigated further), I certainly know that the *drastic* difference between 0.3 [Hz] and 1 [Hz] is because LLO has sensor correction for all DOFs turned on. Poking around at LLO, I've found that the sensor correction is nothing particularly fancy -- it's just the standard Hua filter scheme, with a single, gain only Match filter at the output to tune better match STS gain to the displacement sensors (those gains are a correction of ~10-20%, matched to a ridiculously high precision [where its unclear if the precision is needed]). HAM2 uses the HAM2 STS (STS A), and HAM5 uses the HAM5 STS (STS C), as expected.
    At the first L and P resonances of the HLTS, there's a possibility for the following improvement if we get to LLO's level of isolation:
Frequency [Hz]   Table DOF      Performance Ratio
    0.64          HAM2 X       6.23 / 0.11 = 56.6
                  HAM5 Y       5.29 / 0.08 = 66.1 
    0.74          HAM2 X       1.87 / 0.03 = 62.3
                  HAM5 Y       1.42 / 0.02 = 71.0
and as we know by now, its these lowest resonance frequencies that dominate the RMS motion of the optic.
    All this being said, except for between 0.2 [Hz] and 0.6 [Hz], LLO is kicking the snot out of the "requirements." Nice job! I'm very confident that we can do just as well here at LHO. The trick will be to get the HAM2 and HAM3 sensor correction up at the same time, so that we don't introduce and relative low frequency noise in the recycling cavities.

    P.S. There're some pretty nasty sharp features and associated harmonics in the L1 HAM5 ISI's RX and RZ spectrum ... we should get that fixed -- they're obviously electronic, particularly ugly, and might affect pulsar searches.

(2) Use LLO's M1 OSEM Damping filters and gains.
    Pages 8 and 9 highlight the DRASTIC difference in damping loop filters. I hesitate to call the H1 HLTS filters a "design," because I know they were copied from the QUADs (hence the 0.43 [Hz] and 0.56 [Hz] resonant gains in the L and P filters, respectively). There's no reason at all we shouldn't just switch to the LLO design immediately -- these aren't under global control so we need not worry about changing any global control transfer functions, and though I haven't modeled it (yet) the increase in gain at just about all frequencies, especially what's focused at the *actual* first L and P modes of the HLTS. With the switch, we would get a factor of 16.2 increase in gain at 0.75 [Hz] in the L loop (which presumable will hit the same mode in P as well), and a factor of 44 increase in gain at the first, 1 [Hz], Y resonance.

With steps (1) and (2) complete, that means we can expect to improve the Y and P motion at the optic, at the main resonances by as much as three orders of magnitude.