In the last few days we always had a pitch motion very well visible in the AS port, when locked. It turns out that this is due to PRM: when locked, the PRM witness sensor see a 20-30 urad pitch motion at about 150 mHz.

We tried to switch off the top stage offloading, but this did not improve the situation. So we need to rework the M3 stage length to pitch decoupling. What we have right now dates back to 2014...

TITLE: 10/19 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Commissioning
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    Wind: 3mph Gusts, 2mph 5min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.22 μm/s
QUICK SUMMARY:

• Jenne noted the CDS issues this morning.  Have a couple of items RED on the CDS Overview:  ADC Error for H1IOPSUSAUXB12 & Configuration Change for H1PSLISS. 
• HAM5ISI has had bouts of 20-30Hz band noise on the nuc6 StripTool.

HAMs 2, 3, 4, 5 are tripped both HEPI and ISI.  I tried resetting HAMs 2 & 3, and they both re-tripped.

At first glance, it looks like maybe there was a timing glitch, a la alog 43806. 

Danny,  Sheila

• DSOFT P
  • Earlier this evening Hang moved PR3 pitch from -116.8 to -112.7 and the PRG improved from 46 to 47.  We then lost lock because of the ~0.5Hz DSOFT instability.  
  • Danny and I tried engaging the oplev damping to help with the ~0.5 Hz instability, then attempted to move DSOFT P, but lost lock due to the same instability.
  • Perhaps manually walking SRM to keep the DARM cavity pole high would help avoid the instabilty
  • We saw high coherence between DARM and DSOFT P (because the bandwidth of DSOFT P is increased to try to address the DSOFT instability).  We copied the cut off from CSOFT P to DSOFT, and it works fine reducing the noise from 15-20 Hz.  (see attached spectra)
  •  
• Our spectrum is dominated by ASC noise below 50 Hz, and there is high coherence with LSC from 45-100 Hz.  We ran A2L, and also tried running the A2L script that Gabriele writes about here with the 30 Hz notches on.  We used default settings and got an error:
  • >>> Starting line in H1:SUS-ETMX_L2_DRIVEALIGN_Y2L_EXC (freq = 30.000000 Hz, ampl = 1000.000000)
        Measuring...
        Stopping line in H1:SUS-ETMX_L2_DRIVEALIGN_Y2L_EXC (freq = 30.000000 Hz, ampl = 1000.000000)
        Measured coherence = nan, transfer function abs = nan phase = nan deg
    >>> Results <<<
        Ratio Y2Y/Y2L: nan + 1j * nan
        Coherences: Y2Y = 0.999951, Y2L = nan
        Imaginary / Real part of ratio = nan
        Current Y2L value = 2.946300
        New     Y2L value = nan
    >>> Saving A2L gains to /opt/rtcds/userapps/release/isc/common/scripts/decoup/rec_LHO//20181018/data_ETMX_YAWa2l_decoup_235653.txt
     
• We added the low pass in DARM (FM9 in DARM1) to the guardian, we have still been loosing lock about once an hour.
• We saw improvements in the range but don't know why.  (see attached spectra)
• To save some time with lock acquisition we damped the ETMY bounce mode, +60 degrees gain -1 filter on and a gain of 1 in the gain setting.  This damped it well a few times.  We put this damping in the guardian.  

S. Dwyer, J. Kissel

The third attachment shows one of the fast glitches that has been causing our large drops in range.  This glitch in particular nearly saturated the ESD DAC, and we think that some of our sudden locklosses could be caused by these glitches when they are slightly larger.  

Since the frequency of this glitch is above 1 kHz, we decided to try to roll of the DARM loop a little faster, to make it more similar to LLO's.  We copied the soft elliptic low-pass from LLO's violin notch filter.

The following filter has been installed into FM9 of the DARM1 bank (replacing an old, unused RG3 filter)

Name: LLO_LP

Design String: zpk([200-900i; 200+900i; 2000], [250-500i; 250+500i; 500+700i; 500-700i], 1, "n").

(see attached BODE plot of the new filter.)

With this new filter, the new DARM OLG phase margin was reduced from ~42ish to 35ish (see attached OLG).

we lost lock right as we were measuring the changed open loop gain transfer function, so it's yet unclear if this improves anything.

The size of TEM01 compared to TEM00 is much worse than before. 01 mode used to be just 30% of 00 mode back in September 5th. Now it's 70%. 

Note that no alignment in air could've caused this. We suspect that the fiber is slowly degrading and slowly spitting out higher order modes.

Here's data from today (top) comparing to data taken on Sep 5 (bottom). Both cavity scan was without the 20dB attenuator on at 80MHz (hence the clearly visible sideband peaks).

The end.

TITLE: 10/18 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Commissioning
INCOMING OPERATOR: None
SHIFT SUMMARY:

Commissioning work continues.  EX BRS is dead (until Krishna visits us on Tues).  
LOG:  See Attached

Jim W mentioned there has been an intermittant ~20 Hz noise source observed by the HAM5 GS13s (he mentioned it being seen on the SRM OSEMs as well).  Attachment #1 shows channels for Y & RX BLRMS for 10-30Hz where there are times when the noise appears.  

Attachment #2 is a screenshot of nuc6 with the new temporary StripTool for HAM5 ISI.  If the channels here stray from 0, then there could be an issue with the SRM/HAM5ISI.

Daisy chain OMC DCPD signals going to split whitening chassis in ISC-R5 U18 through squeezer OMC/homodyne chassis in ISC-R5 U16 (requires DB25 jumper cable).

For the DCPD whitening chassis this should make no difference, and only look like a slightly longer cable. The squeezer OMC DCPD chassis routes all signals straight through, picks off the DCPD signal and extracts the 3.125MHz LO locking signal.

It should now be possible to engage the ISS second loop by requesting the state ISS_ON of the IMC guardian. This state engages an AC coupled ISS loop.

The you can request the state ISS_DC_COUPLED. This state for now just switches off the digital AC coupling. It used to have the engagement of two boosts: for now I left them out, since we need to be at high power to ensure that the ISS second loop has enough gain to be stable with the boosts.

I tested the switching on and off at 2 W. The third plot shows both the first loop (PDA and PDB) and second loop (INNER and OUTER) signals in the three different configurations: ISS 2nd loop off, ISS 2nd loop AC coupled, ISS 2nd loop DC coupled (no boosts)

To be tested at high power (including the boosts)

Some details

• The AC coupling integrator was in a wrong configuration, basically completely off. The right configuration is shown in the first attachment
• Adjusted the diffracted power reference servo offset (second figure)
• Adjusted the reference servo filter banks and gain so that the two servos are working: one is active when the ISS second loop of off and should maintain the board output close to zero; the other is active when the ISS second loop is on, and keeps the refracted power close to the set offset (which is  H1:PSL-ISS_SECONDLOOP_REFERENCE_DIFFRACTION_CAL_OFFSET)

Empirically CM gain and 100Hz noise are correlated (alog 44585) but the sense among us is that it's not residual frequency noise (at least via linear coupling), as no coherence was observed between DARM and signals like CM board output and POP9I etc.

To eliminate the possibility that 100Hz noise is the linear coupling of gain-limited residual frequency noise, we need to show the following.

1. At least one of the relevant signals are not limited by the ADC noise and out of loop electronics noise.
2. At least one of those signals that satisfy 1. above have no out-of-loop down-conversion to 100Hz, masking the true frequency noise in the readback (e.g. large high frequency out-of-band noise makes the amplifiers hit the slew rate limit or something). This is very, very unlikely, though.

This alog shows that the first point is true.

In the attached, left middle shows LSC-REFL_SERVO_CTRL_OUT_DQ when there was no light on REFL_A (green), and in low noise state before CM gain setting was made incorrect on Sunday (red) and with an incorrect CM setting (blue).

Both red and blue are more than an order of magnitude larger in-lock than the green trace, so apparently it's not limited by the ADC and read out electronics noise.

In the middle right is the CAL-DELTAL_EXTERNAL_DQ (without necessary calibration TF applied), just look at red/blue difference, blue is about a factor of 2 larger than red at 80Hz. If this is a linear frequency noise coupling it should be obvious in the coherence (left bottom) but there's really nothing to talk about while there's a clear difference in coherence at higher frequency.

In conclusion, the point 1. listed above is correct, yet there's no coherence for broadband 100Hz-ish noise, and therefore it's unlikely that this is linear frequency noise coupling.

Without addressing the point 2 (as it sounds unlikely), the next thing is to see if this is nonlinear coupling of the frequency noise. Injections would be useful, looking at demod signal of REFL_A_RF9_I would be useful, and changing CM gain somewhere in the chain would be useful.

Due to fire department work on site.

Bypass will expire:
Thu Oct 18 13:10:42 PDT 2018
For channel(s):
    H0:FMC-CS_FIRE_PUMP_1
    H0:FMC-CS_FIRE_PUMP_2

Today I requested twice the state CHECK_MICH_FRINGES, and then requested PRMI_LOCKED. The guardian went straight to the end of PRMI_LOCKED, reporting the state to be concluded, even if PRMI was NOT locked.

It might be useful to summarize the TCS changes made from Monday to today:

10-15-2017

ITMX RH @ 0 W

ITMY RH @ 1.04 W 

Please see first figure for relevant time series of a 20 W lock stretch

10-17-2017 

ITMX RH @ 0 W

ITMY RH @ 1.74 W 

Please see second figure for relevant time series of a 20 W lock stretch

OSA scans

The following two tables list the carrier and sideband power when at 20W: 

The new TCS settings seems to have improved the balance between the 9 MHz sidebands, and RF18 when at 20 watts. 

TCS to do list: 

• Improve the noise on ITMX HWS (in progress)
• Common lens adjustments 

The 60Hz line is *very* bad today.  I don't think we noticed it yesterday since we weren't really going to Nom Low Noise, since we were doing TCS tuning instead.  But, it's incredibly clear that something happened between Monday and today that has made the 60Hz line very bad.  If DetChar wanted to have a look at what witnesses see this, that would be helpful. 

I don't think that anything happened with the ETMX ESD power supply yesterday.  (It was going to be swapped out, but JeffK asked around, and it doesn't sound like we got that far before the end of maintenance yesterday).