Summary of the PSL trips from 2015-5-1 to 2015-5-3 during the LHO mini run.  Every instance of the PSL tripping was due to the same interlock, H1:PSL-IL_DCHILFLOW, tripping with no apparent loss in coolant flow for the diode chiller, H1:PSL-OSC_DCHILFLOW.  The first three trips on 2015-5-3 were during the long interlock trip that Nutsinee reported in alog 18187.  Data for the other PSL trips over the last 10 days have been reported in alogs 18083 and 18134.  All times UTC.

Using 0100pdt on Saturday morning as an okay time to check the ~middle of the 10 hour lock stretch during the run.  No large coherence with DARM_CTRL for any of the three controlling pressures for the HEPI Pump Controller Servos.  Everything is below ~0.6 and most all just look like noise.

Attached are power spectra of the sum signals of the 4 IR QPDs that are on the ETM Trans Mon tables (in-vac). Each Trans Mon has 2 QPDs (labeled A & B). Also included in the plot is a spectrum of QPD_B from the L1 Y-arm. As discussed in LLO log entry (hmm, LLO log is down), the L1 Y-arm QPDs show broad noise peaks at 30 Hz, 60 Hz, 90 Hz; these peaks show up in DARM and are believed to be caused by scattered light at the end station (the L1 X-arm QPDs do not show these noise peaks).

The good news is that the H1 TransMon QPDs do not show anything like the scattered light noise peaks seen in the L1 Y-arm, and in general the H1 QPD spectra are lower than the L1 spectra (all channels are normalized to unity for a single arm lock). The RMS of the X-arm transmitted power fluctuations is about 30/10,000 = 0.3%; about 1% pk-pk.

The bad news is that there is something wrong with QPD_A on the Y-arm. It shows an elevated 1/f noise above a few Hertz. This is presumably related to the QPD 'clipping' problem reported by Keita in entry 18204. Looks like some electronics problem to me. On the other hand, the X-arm QPD_A is anomolous in another way: its average value is about 30% lower than the others (see table below).

For reference, the average values of the QPD NSUM channels were:

Laser Status: 
SysStat is good
Front End power is 31.4W (should be around 30 W)
FRONTEND WATCH is RED
HPO WATCH is RED

PMC:
It has been locked 0 day, 23 hr 54 minutes (should be days/weeks)
Reflected power is 2.0 Watts and PowerSum = 24.3 Watts.
(Reflected Power should be <= 10% of PowerSum)

FSS:
It has been locked for 5 h and 4 min (should be days/weeks)
TPD[V] = ~1.1V (should be 1.3 - 1.6)

ISS:
The diffracted power is around 8.5% (should be around 7%)
Last saturation event was 22 h and 57 minutes ago (should be days/weeks)

Attached are the series of plots: ASDs, Coherences, and TFs; for and between the three LVEA SEI STS2 instruments.

Last week I moved the STS2-B (ITMY) to concrete (References for it are the old unit on vinyl under the igloo.)

The current traces attached are from this morning at 0130pdt.  I had a problem with the calibration and units before, but getting that straight hasn't made answers to all the questions clear.

The three Z ASD are right on top of one another to below 20mHz.  The Y DOF ASDs are similar but they diverge below 40mHz.  For the X DOF, the HAM2 instrument seems the outlier diverting from the other ASDs as high as 90mHz whereas ITMY and HAM5 are hand in hand until 20mHz.

The Coherences look very good on Z, other DOFs are here and there.  Maybe as expect too, the Z TFs look great, and the other DOFs are 'it depends.'

I think we can say that the removed STS2 should go in for overhaul and the HAM2 machine should be huddle tested with one of the others.

Apparently I haven't aloged it last week, but oplevs recive the IR scatter from the arm. It's not a big deal, I'm writing this just for the record.

Attached shows one 7W lock when ETMY OPLEV was not working (no light). As soon as IR resonates in the arm, ETMY oplev segments jump up  and the SUM goes to 560 counts (left and middle row). If the oplev laser was alive, this 560 counts would have been added on top of about 30k counts. Fortunately this is mostly common for all four segments, and the effect on the angle readout, when the oplev laser is alive, would have been about  0.03% of the full range, or about 0.03 urad.

The same thing happens to ETMX (right bottom) except that the oplev laser was alive and that the scatter increased the oplev SUM by only 360 counts.

For ITMs the SUM due to the arm scattering seems to be abount an order of magnitude smaller than ETMs, but the oplev power itself is also smaller (3000 to 4000 counts).

(Update: See Peter's alog.)

I looked at the lock stretch from last night and the IR QPDs on TMSY still show the sign of clipping though the saturation was fixed.

On the left column you have X QPD SUM(B)/SUM(A) data (top), which is basically just a solid flat line after the IR resonates in the arm over a large change in the IR alignment.

The top right plot for Y QPD SUM ratio has the same scale as the top left, it goes up and down in low power lock and then steps up when the power was increased. Even during the 10W lock, the ratio was not as stable as X.

It's not like Y beam is particularly moving larger than X.

J. Kissel

Now that the mini-run is complete, I've reverted the "nominal" ISC_LOCK guardian state back to LSC_FF (I'd changed it to the mini-run state of "LOWNOISE_ESD_ETMY" on Friday, see LHO aLOG 18145). I've reloaded the guardian code change, and confirmed that the "nominal" box is now surrounding the LSC_FF state; see attached.

SEI
nothing planned

SUS
nothing planned

CDS
continue preparations for chassis swap
possible RCG upgrade on Tuesday

FAC
starting repair of wall around patio area
wet paint all around building
expecting delivery from Sunbelt

PSL
trips appear to all be related to flow sensor

VAC
preparation for vent of end stations in June
need to run pump cart at Y end for 24 hours to bakeout RGA, possibly Tuesday

This morning AOM diffracted power was up to ~ 13% with a refsignal setting of -2.00 . I've adjusted the Diff power to ~ 8.5% -> refsignal = -2.05

Summary

Today I wanted to see if increasing the bandwidth of the SRC ASC loops could make the 90 Hz SRCL coupling into DARM go away or become more stationary. I cranked up the bandwidth of the AS_C loop, but saw no improvement. We should try cranking further, or else try cranking the bandwidth on the AS36I loop.

Details

I was able to bring the interferometer to dc readout at 10 W with a recycling gain of 39 W/W. To get there, I had to turn on the ITM oplev damping again to avoid 0.4 Hz instability during power-up (and sometimes during the last steps of the CARM reduction sequence). I was able to engage the MICH, SRCL, and dETM yaw boosts without issue.

Then I tried increasing the bandwidth of the AS_C pointing loops. I was able to increase the gain by a factor of 30 just fine (2 ct/ct to 60 ct/ct, pitch and yaw), which gave a ugf of about 250 mHz as measured by step response. This means that the original bandwidth was less than 10 mHz, since the loop is 1/f below the suspension resonances. Correspondingly, the low-frequency angular motion seen by AS_C is suppressed by a factor of 30 or so, and the rms angular motion seen by AS_C is reduced by a factor of 4 in pitch and some small factor in yaw. Based on the attached spectra, it seems like we would have to push the bandwidth up to several hertz in order to see any further improvement in the rms. Anyway, after doing this I did not see any improvement in the stationarity of the SRCL coupling aroung 90 Hz.

I attempted to repeat this exercise with the AS36I loops, since Gabriele had previously found that the pitch loop was the dominant signal modulating the SRCL/DARM coupling once dETM yaw was adequately suppressed. However, I could not increase the loop gains by more than a factor of 4 before they went unstable (this was the case even when I engaged the same HSTS compensation filter as used for the AS_C loops). This factor of 4 was not enough to give a noticeable improvement in the spectra of AS36I pitch and yaw, since these loops are also slow (<100 mHz, just based on watching the loops' responses to transients).

I came in and found the PSL had tripped about 6 hours ago. It is again correlated with some flipping of the diode chiller flow monitor bit. After the trip, the bit flips for about 40 s before returning to the OK (1) state.

When I went to reset it, both chillers were on. The diode chiller has been holding steady at 20.5 lpm or so for the past hour (not sure about further back in time).

To answer Jeff's question about the wind, I looked at the ten hour lock, and the three hour lock starting about 23:30 UTC (ignoring the stochastic injection). I wrote a custom script to make the plots, since I couldn't get sensemon range from NDS. I've done a 3-minute median filter on the wind and range minute trends to smooth them out a bit.

The first plot shows the wind and range for the first lock. Around 12:30 UTC, the spectrogram (second plot) shows a big increase in the noise, and there's a corresponding decrease in the range. I think this is unrelated to the wind, and will be investigated elsewhere, so I've cut this lock off about 320 minutes in (third plot). The fourth plot is the scatter of the wind versus the range. A simple fit gives a value of 8.4 Mpc at zero with an 0.03 Mpc decrease per MPH of wind. The fifth and sixth plots are this repeated for the other lock, starting after the stochastic injection ends. The fit is 9.0 Mpc at zero with an 0.01 Mpc decrease per Mpc of wind.

I've attched the script I used. It needs a cache file for data of type H-SenseMonitor_CAL_H1_M called snsw.lcf. There's some values hard-coded, but it should be obvious what to change.

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.