J. Kissel

Though we turned off the 1083.7 Hz calibration line last night (LHO aLOG 30476) because we were worried about range in the PCAL systems Optical Follower Servo (OFS) after increasing other calibration line amplitudes. However, as a quick test, I turned it back on. With the increased amplitude of other CAL lines, and this 1083.7 Hz line ON, the OFS does not saturate, so it appears we have enough range to run it all. I've also made a quick check of the calibration line harmonics to be sure those are not huge, and still well below the DARM sensitivity, and they are. Nice!

We want this line ON, so it serves as a clean reference for the optical gain while we perform the high frequency, long duration sweeps (i.e. LHO aLOG 30434).

I've accepted the change in the SDF system.

issues getting here:

• REFL WFS centering not coming on in Inital alignment for PRC and SRC, so in both cases those didn't complete until engaged by hand (guardian?)
• alignment
• POPA OFFSETS - Evan looks at these - not sure they're OK but in the end they seem to work
• ASC - Evan toggled PRC1_P on and off (3 seconds each) to save the lock and also allow PRC1 P to converge 
• POPA sum got noisy in ENGAGE SOFT LOOPS until I engaged the CHARD offset of 0.1 by hand in Engage Soft Loops, then the signal improved
• I set the ramp to 120 seconds, and at 120 seconds there's a kick that can be seen on CSOFT_P
• PI mode 2 rang up - easily damped
• PI mode 26 rang up and did a bouncing thing until I lowered the gain by half from -5000 to -2500, and then tuned the phase

Using the crystal chiller that is currently sitting in the mechanical room, the on/off flow rate
was recorded as a function of time.  The data is that reported via the RS-232 interface.  When
switched off, the flow rate drops to zero in 3.245 seconds.  This seems a lot slower than the
drop reported by EPICS, which seems to suggest the flow rate drops to zero in less than a second.

I'd like to go from PRMI to Lock DRMI 1F.

Locking issues this morning.

• could lock in green but not IR
• doing an alignment
• in Initial Alignment, REFL WFS centering is not coming on when it needs to, so PRM align and SRC align
• looks like a guardian issue, but haven't had time to look into it

Images attached show the filter banks that aren't being engaged, and where to find them on the ASC page (DC centering)

As expected, the jitter feed forward that was tuned yesterday evening was no more good. Using the same method described before, I retuned it and found comparable performances as yesterday.

Addition:

The second plot shows how the coherence between DARM and DBB Q1Y changed over time. Initially there was no feed forward, then it was switched on at about t=1 hour. At t=8 hours I retuned it as explained above. Beware that the coherence color scale tops at 0.6 and not at 1. It looks like the subtraction was getting worse, but not too bad after all.

TITLE: 10/13 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC

• Locked for 08:27. The BNS range seems to have steadily trended down despite the H1IFO_Range reading between 59 and 64MPc pretty consistently.
• PI was quiet all night.
• Intention bit set to Commissioning at 14:58 at Gabrieles request. 
• Dust monitors in the LVEA and the Ends were set to class 1000 alarm limits to eliminate the constant nagging.
• Handing of to Cheryl

• Locked at NLN 63.5MPc. Everything is stable. Intention bit is set
• mSei is up to 90%ile after an upward trend following what was described to me as some kind of explosion somewhere. EQ bands have also trended upwards to roughly .03uum/sec. Winds are calm.
• the Only saturation was EY over 2 hours ago.
• also, ongoing 300NM dust alarms sitewide

09:29:10 Intent Bit set to Observe 

First known case of crossing PI modes: over the course of a few hours, ETMX Mode18 crosses over the more stationary ETMY Mode26. Last night's and today's trouble with Mode26 were partially a result of not knowing this crossover was happening. 

Both modes are differential drumhead. Crossover happens a few hours in from cold lock: ETMY Mode26 (tallest peak shown below) begins around 15007.6 Hz and slowly drifts upward with heating over about 5 hours. ETMX Mode18 begins at a lower frequency 15007.5 Hz, drifts upwards in frequency more rapidly, and crosses over Mode26 to a higher frequency until you see it poke out at a higher frequency. Drift is shown sequentially below (in order of REF#) in a bit less than 1 hour snapshots over the 5 hours. 

This cold-start 5 hour lock was followed by two rapid relocks of 3 and 4 hours respectively, allowing for a general trend of what a 12 hourish lock would look like since optics had little time to cool down. Attached are snapshots over the following two locks; combine with that above to get a good stop motion of the drift. Note that warm locks most likely won't see crossover. 

Note the static peak ~ 15007.8 Hz. Its lack of drift with temperature suggest not a body mode, though its similar apparent width and overlap with the later stages of Mode18 helped me miss that crossover was happening. Crossover was also probably missed due to cold locks being more rare and the gain of Mode18 seemingly low during the times it's frequency is below Mode26.

Also attached is plot of frequency shift with time (not yet fit). 

Damping: I've set up sequential guardian controlled band passes for Mode26 (and witnessed successful switching via guardian tonight); these should cover locks at least 12 hours long and each BP has at most +/- 24 deg phase. Mode18 is currently bandpassed for frequencies above Mode26; we'll have to think about and play with the PLL handling crossing modes a bit. Leaving this for now with the hopes that we relock over night in some reasonable time period and don't have a stone cold lock. 

Summary:  I have moved the POP_A and SOFT offsets to find better recycling gain (31.2ish rather than the 29.5 we had been getting).  I was hoping that this would help eliminate the peaks in the 200-900 Hz region, and I think it did a bit, although not as much as I'd hoped.  It did help the high frequency noise "tail" though.

History:  Some time ago, Sheila and I moved the POP_A offsets to improve the recycling gain from 25ish, and that worked very well and has been very consistent.  At the time, we stopped where we did because the POP_X centering PZT was hitting its rail, not because we thought we had found the best possible location.  Then, we elected to move on to trying to get to low noise rather than continuing to chase alignment offsets.  Now that we're at low noise though, I wanted to see if continuing to move the QPD offsets would help get rid of some of this jitter / frequency noise coupling. 

What I did:

• Moved POP_A offsets to maximize recycling gain.  Watched to ensure POP_X PZT wasn't railing.  Moved SRM alignment sliders to keep POP90 low.
• Upon relock, let the DRMI ASC move the IFO (including SRM) closer to the place that was good for the new POP_A offsets (i.e., just leave the offsets in permanently).  This was good, and meant that SRM didn't need to be moved by hand later.  I think it does make the CHARD engaging do a little more work, although that can be ameliorated by resetting all of our initial alignment setpoints.
• Upon relock, also noticed that when the SOFT loops came on, we went through a max for the power recycling gain then came down a bit, all before powering up.  This indicated that I needed to move some SOFT offsets.
• Moved the SOFT offsets, while moving SRM to keep POP90 low.
• Went back to re-try POP_A offsets, ended up adjusting pitch a little more.
• Ran A2L for the test masses.

In the end, the power recycling gain is about 31.2, whereas it used to be about 29.5 in NomLowNoise before this work.  Also, as Jeff points out in alog 30481, it looks like this did good things for the DARM cavity pole and the optical gain. 

At about 06:49:15 UTC, I had just about the lowest value for the broad peak at about 440 Hz.  Going back to the offsets I had at the time did not reproduce that low of a peak though and the recycling gain wasn't at its maximum, so I ended up sticking with the offsets that maximized the power recycling gain.  I may go back and look at the alignment of all the optics at that time to see if there was anything drastically different. 

I also turned back on Gabriele's Jitter feedforward with the same gain of -1, and it still seems to be doing quite well.  I haven't looked at the coherence, so I don't know if this is quite as good as when he and I were tuning it earlier today, but it still made a significant improvement in the 80 Hz - 250+ Hz region.  I have this feedforward turning off in the Down state of the ISC_LOCK guardian, but it must still be turned on by hand.  Once we're satisfied that it does good consistently, we can add it to NoiseTunings.

For now, I'm leaving the POP_A offsets in place, but the SOFT offsets will be turned off upon lockloss.  I want to make sure that including them during the acquisition sequence isn't harmful to lock acquisition before accepting them permanently.  I'm hoping though that they're fine, so that the ASC will handle all the SRM moving and we don't have to do anything by hand.  To be checked tomorrow.

Offsets that I like in the end are:

• POP_A_P: 0.52
• POP_A_Y: 0.44
• DSOFT_P: 0.00
• DSOFT_Y: 0.04
• CSOFT_P: 0.06
• CSOFT_Y: -0.04

Ideas: 

• A2L for recycling cavity optics
• Re-look for SRM ASC error signal - maybe there's a bit more hope if the overall IFO alignment is better?

Sheila, Jenne, Kiwamu

Attached is a spectra of IMC-F in different configurations.  (MC locked at different powers, DC readout, low noise)  From 100 Hz to about 1 kHZ, the spectrum of IMC F doesn't change much at all in all of these different configurations. So the IMC control signal is not dominated by REFL9 sensing noise in full lock, and probably represents the real frequency noise at the input to the IMC.  

We can do a better job later, but if we assume this is really frequency noise we can roughly calibrate this into Watts on REFL 9I:

At 1kHz:  0.1Hz/rt Hz Frquency noise arriving at IMC (which is roughly consistent with measurements in P1100192, Fig 8) Suppresion of IMC loop: 1/200 (alog 22188) Supression of CARM loop (alog 22188, our ugf is now more like 8kHz) roughly a factor of 1/30.  We can scale the DC optical gain of 0.017W/Hz used in 22188 by sqrt(2) to account for the factor of 2 increase in input power and the 6dB modulation index decrease since then.  Taking into account the coupled cavity pole at 0.5 Hz give another factor of 1/2000:

0.1Hz/rtHz(1/200 Hz/Hz IMC supression )(1/30 Hz/Hz CARM suppression) (0.024*0.5/1000)W/Hz  = 2e-10 Watts/rt Hz signal on REFL 9I or 1.7e-5 Hz/rt Hz of residual frequency noise expected.  

We can repeat this at 400 Hz:

0.03Hz/rtHz(1/600 Hz/Hz IMC supression )(1/300 Hz/Hz CARM suppression) (0.024*0.5/400)W/Hz  = 5e-12 Watts/rt Hz signal on REFL 9I or 1.7e-12 Hz/rt Hz of residual frequency noise expected.  

Comparing this to Evan's in loop measurement of the CARM noise using REFL control, (here) it is close at 1 kHz but not at 400 Hz.  You can also compare it to the transfer functions from REFL 9I to DARM posted here, and see that at 1 kHz the expected frequency noise is of the order of 5e-20 m/rt Hz at 1 kHz.  

The main message: It is probably worth making a projection for frequency noise in DARM using IMC-F to estimate the frequency noise after the ref cav, because a very rough estimate says it could be within a factor of 2 of DARM at 1kHz. 

J. Kissel, D. Tuyenbayev,

We turned on two calibration lines using ETMY coil drivers on stages L1 and L2. The SNRs of these lines are roughtly 1/3 of the regular calibration lines (regular cal. lines have SNR of ~100 with 10s FFT).

                              _FREQ (Hz)  _CLKGAIN (ct)
H1:SUS-ETMY_L1_CAL_LINE          33.7             60.0     O2-scheme synched oscillator for kappa_U
H1:SUS-ETMY_L2_CAL_LINE          34.7             27.0     O2-scheme synched oscillator for kappa_P

These lines will be used to better quantify calibration of the PUM and UIM actuators.

A related report: LHO alog 29291.

Evan, Daniel

17:12:30 UTC Oct 7 2016:

• RF modulation off for 9 and 45 MHz
• 45 dB whitening gain compensated by a filter gain of 0.0056
• 1 stage of whitening, compensated
• V/ct filter engaged, referred to TNC ouptut of 2-chn demod board
• Dark

17:16:30 UTC Oct 7 2016:

• same input configuration
• 29 mA of photocurrent

17:18:30 UTC Oct 7 2016:

• turn DC centering of REFL WFS on

17:24:30 UTC Oct 7 2016:

• turn DC centering off again
• 14.8 mA of photocurrent

17:32:00 UTC Oct 7 2016:

• 9 MHz modulation on
• 14.8 mA of photocurrent
• DC values: 9I = 3.7 mV; 9Q = 9.5mV

17:34:30 UTC Oct 7 2016:

• 9 MHz modulation on
• 29 mA of photocurrent
• DC values: 9I = +7.2 mV; 9Q = +18.1mV

18:06:30 UTC Oct 7 2016:

• 9 MHz and 45 MHz modulation on
• 29 mA of photocurrent
• DC values: 45I = –14.3 mV; 45Q = +62 mV