Jeff K. reports that the ETMX UIM driver has tripped. Cheryl reported this happening last Sunday: alog 20808

From plotting the L1 OSEM monitor signals it appears that it tripped on Aug 25 2015 03:08:25 UTC. (plot attached)

Daniel, Dan, Stefan

I used the 45MHz modulation depth reduction in alog 20777 to fit the amount of 45MHz sideband on the ASC-AS_C_SUM diode:

reduction   ASC-AS_C_SUM cts
 0dB           38430
-1dB           32630
-2dB           27460
-3dB           23680

This suggests that we have the equivalent of 8796cts of power that doesn’t respond to the 45MHz modulation index reduction, plus 29735cts of 45MHz sideband power (at 0dB reduction).
Thus 29735/38430 = 77% of the total light is 45MHz sideband, and 23% is something else (mostly carrier).

For the ASC_AS-C_SUM calibration I get:

4e-4          fraction of HAM6 light on AS_C (alog 17738, super-seeds 15431)
x 800V/W      PD gain (alog 15431 -> 200V/W, but in the digital system we do not divide by 4)
x 10^(36/20)  whitening gain
x 1638.4cts/V ADC gain
= 33080 cts/Watt_HAM6

I get under nominal conditions (23W, Gamma=0.3, 0dB reduction):
899 mW of 45MHz light (compare that to an expected 23W(INPUT)*(.3)^2/2(MOD)*0.88(IMC)*0.89(NOM IFO TRANSMISSION) = 811mW)
and
266 mW of other light (carrier junk?).

20mA of light on the OMC_DCPD transmission, corresponding to about 25mW of "good" carrier light - 10 times less than the junk.

Also, if I use the calibration of the ASC-AS_C-SUM diode, normalizing it by the 29735cts of 45MHz SB, I should get a calibrated (power) RIN sensor.
I can look at the driven oscillator amplitude noise transfer function to x-check this: I would expect the power RIN / amplitude RIN TF to be equal to sqrt(2).

(Note: Daniel's RIN sensor calibrated in Vrms/rtHz / Vrms - a sqrt(2) of my previous alogs, which all quote RIN as Vrms/rtHz / V_pk, being equivalent to a rad_rms/rtHz number. )

I indeed get 1.4. (plot 1).
Plot 2 shows the same transfer function but using only the seg1, with the IOP channel (H1:IOP-ASC0_MADC6_TP_CH11). Again, 1.4.

Now things hang together...

(Sheila Evan Daniel)

The ASC-AS_B_RF45 sensor is currently not used for the auto-alignment. To investigate, if centering on the 2Ω is different from DC, we temporarily cabled its LO up to 90MHz. To revert back, remove the output cable from the 9MHz (currently 90MHz) distribution amplifier in ISC R3 (slot 37) and hook it back to the 45MHz distribution amplifier in the same rack (slot 33).

This sensor had the analog whitening stage turned on and the digital anti-whitening stage turned off. Turned on the digital anit-whitening.

ssh, who and man commands all returned: 'Input/output error' but ps and grep commands worked
Firefox did not launch
gpg returned an error
I talked to Dave. He suggested I power cycle the computer and log in as myself instead of ops. I am going to use my own account for my shift.

Attached is a shot of the white board for tomorrow.  Let's green up the SDFs tonight as several restarts are in the offing.

J. Kissel, S. Dwyer, E. Hall

As I was about to characterizing the ETMY coil drivers (i.e. the UIM and PUM), I noticed that they were in their highest noise state. After conversations with Sheila and Evan, we (re)agreed that the PUMs should be run in their lowest noise state, which is with  LP ON and ACQ OFF, or State 3 from T1100507. As such, we've switched all QUADs to this state, and confirmed that ISC_LOCK guardian will ensure this to be true in the future (again). That guardian has been reloaded.

The reason they had been put back into high range (and taken out of the guardian) was that the range was needed to better damp the QUAD roll modes after they had been severely rung up in the Christmas Episode in early August. 

From a calibration stand point, this will affect the DARM calibration by a small amount, but I had not started characterizing the ETMY PUM drivers before I got started, and I'm now full aware of it, so it's affect will be fully understood and expected. As such, we're OK with this configuration change. Further, we'll all be happy with the little bit extra range we get from it (Evan will post an aLOG making a noise statement later)!

Calibration Measurements:

- Kiwamu, IFO down for calibrations, 9:05 - expected to be all day, continuing now

*** FYI, I move the IFO to Commissioning when this happened and should have been Calibrations - my bad.

Note; We are now in Calibration, so IFO has two states:

'"IFO is up'"  OR  "IFO is having calibration measurements run."

Today's parasitic IFO/site activities:

- JeffB to EY, dust monitor investigation, 9:07 - done

- Hugh to EX and EY, HEPI, 9:07 - done

- JeffK, ETMY, measuring coil drivers, 9:15

- Sudarshan, PEM channel check in LVEA, 9:20 - done

- TJ EX BRS reset - 9:54 - done

- Kyle, near EY (Y28) to gather stuff - done

- Dave, EX, drawing updates - 12:10 - done

- Kyle, near EY (Y28) to gather stuff, 12:54 - done

- more visits to end stations while there was the opportunity, but no changes, just monitoring or restoring equipment.

Currently no outstanding IFO issues.

Calibration measurements continue.

Stefan, Elli

On Saturday Stefan measured the AS36 signals with dither lines from the BS and SRM (alog 20777):

Lines:
H1:SUS-SRM_M3_ISCINF_P_EXC 7.0Hz, 300cts
H1:SUS-SRM_M3_ISCINF_Y_EXC 7.5Hz, 900cts
H1:SUS-BS_M3_ISCINF_P_EXC  8.0Hz, 100cts
H1:SUS-BS_M3_ISCINF_Y_EXC  8.5Hz,  30cts

Here are some plots of the AS36 signals demodulated against these line frequencies.  These signals  show how the sensitivy of the AS_36 WFS to the BS and SRM, which changes during the heat-up stage of the whole interferometer, and during 45MHz modulation depth reduction.  Attached are plots of the original and demodulated signals vs time.  Two vertical red lines are plotted; the first corresponds with when the IFO reaches full power, the second is when the 45MHz modulation depth reduction begins.  At the end of the time series the traces go crazy-  this is where Stefan reports lock was lost due to SRC1 yaw run away.

The following WFS channels are fed back to the optics at this point:
AS_B_RF36_I_PIT      >>   SRC1 PIT      (seen in demodulation of 7.0Hz line. Right two plots, red trace)
AS_B_RF36_I_YAW   >>   SRC1 YAW    (7.5 Hz line.  Right two plots, blue trace)
AS_A_RF36_I_PIT      >>   MICH PIT       (8 Hz line. Left two plots, red trace)
AS_B_RF36_Q_YAW  >>  MICH YAW    (8.5Hz line.  Right two plots, brown trace)

The SRC1 PIT signal doesn't change much, which is good.  SRC1 YAW has a 180deg ohase change during the heat-up stage.  Lines 1813 and 1815 of the guardian indicate a sign change in the ASC input matrix, maybe this corresponds to this phase change (?).  MICH PIT signal looks pretty good, getting close to 180deg phase at the end of the modulation depth reduction.  MICH YAW drifts downwards in phase, it looks like it hit -180deg just at the point we lost lock.

Following up to the problem (insufficient whitening) reported in  alog 20700,  new dewhitening filters  are implemented in the following DEALTAL_CTRL channels:

H1:CAL-CS_DARM_DELTAL_CTRL_M0/L1/L2/L3_WHITEN:  Original -- (zpk([1, 1, 1], [500,500,500],1,"n")

Changed to  (zpk([0.1,0.1,0.1,0.1], [100,100,100,100],1,"n")

H1:CAL-CS_DARM_DELTAL_CTRL_SUM_WHITEN: Original --(zpk([1, 1, 1,1,1], [100,100,500,500,500],1,"n")

Changed to  (zpk([0.1,0.1,0.1,0.1], [100,100,100,100],1,"n")

The first attached plot shows DARM CTRL signal with original filter in dotted  lines and the new filter  in solid lines.

The second plot shows the effect of different filter combinations on DARM_CTRL signal. This measurement gave us an intuition on what filter to use eventually.

- Duty Cycle: 54%

- range: 75 - 85 Mpc

- PRM M3 LL coil driver caused noise in 10-60 Hz range on Friday, may have been responsible for some loud glitches

- Also on Friday there were some strange lines in the strain spectrogram at around 10Hz

- loud glitches that cause brief, large drop in range that we saw in ER7 continue; the rate is improved

- link to full DQ shift

Sheila, Evan

We looked again at the situation with the 45 MHz REFL WFSs, which are used as sensors for the PR3 ASC loop. In the end, we didn't implement any changes to the sensors or the associated loops.

We were motivated by the following:

1. The current demod phases for these WFSs simply do not make sense; we expect that they should be similar (since the analog delays should be fairly well matched), but instead they are scattered by 100+ degrees.
2. The cHard and PR3 loops are strongly cross-coupled. We would like to be able to turn up the gain of cHard without impressing extra motion from other optics into DARM. [20523, 20497]
3. Any perturbation in the PR3 seems to couple into the SRC loops. We already know that the SRM loop is quite delicate, and we would like to get rid of this coupling if possible.

We tried the following:

• We changed the demod phases of the 45 MHz REFL WFSs, and then closed the PR3 loops.
  • We chose phases so that cHard pitch appears entirely in the Q phase (thereby leaving I dominated mostly by PR3 motion, hopefully). This was done previously, but loop retuning was not investigated in detail. Also, the phases of A3, A4, B3, and B4 seem to need an extra 180° phase shift in order to produce correctly phased signals (see screenshot).
  • We then found that only REFL45B gave a sensible error signal in response to PR3 motion (both pitch and yaw), so we closed the loops around B only. Additionally, the required digital gain went from 2 ct/ct (with the old phasing) to 40 ct/ct, perhaps indicating that the "old" PR3 configuration is actually dominated by cHard motion.
• This seemed to produce a constellation of bad things:
  • The sideband buildups (POP18 and AS90) were slightly suboptimal (i.e., fuzzy and not maximized).
  • The soft loops reduced the recycling gain (to 36 W/W or so) when they came on.
  • Switching the SRM yaw loop input matrix elements at 3 W seemed to make POP90 worse.
• We tried using new trans QPD offsets for the soft loops, but this led to the familiar angular instability when going to 20+ W.
• We also tried to find a new SRM yaw matrix element, but this didn't work either.
• We also turned off the dc oplev coupling on SR3, since we didn't want the optic position to be dragged away by the ground.
• In the end, we simply reverted all the changes we made.

After that, we couldn't get to full power because of an oscillation that showed up in dHard pitch when going to 20+ W. (We've seen this before, and it seems to be distinct from the angular instability mentioned above.) To get around this, we had to slightly beef up the resonant gain that gets turned on in dHard pitch when the power is increased.

Also, there were some small maintenance tasks that we did:

• Improved the filter hygiene of the DC centering loops (there were some integrators that didn't have ac gain of 1, some low-pass filters that didn't have dc gain of 1, some filters with ambiguous names, etc.)
• Added an optional ISC_LOCK guardian state called REDUCE_MODULATION_DEPTH, which implements the 3 dB modulation depth reduction that Stefan and I have carried out before.

Jim, Evan

We have grown tired of the glitching in the PRM M3 LL OSEM, so here is a script that ramps it off in full lock. It gets rid of the glitching and allows us to recover 60ish Mpc range.

Also included is a screenshot of the usual Euler/OSEM matrix for PRM.

This entry is meant to survey the sensing noises of the OMC DCPDs before the EOM driver swap. However, other than the 45 MHz RFAM coupling, we have no reason to expect the couplings to change dramatically after the swap.

The DCPD sum and null data (and ISS intensity noise data) were collected from an undisturbed lock stretch on 2015-07-31.

Noise terms as follows:

• Shot noise
  • For 20.0 mA dc on the DCPD sum, we expect a shot noise of 8.0×10⁻⁸ mA/Hz^1/2.
• Dark noise
  • Dan and I measured this a few months ago. In full lock we use one stage of whitening, which amounts to a dark noise of 1.5×10⁻⁸ mA/Hz^1/2 or so above 100 Hz. We have at times experimented with two stages of whitening, but it requires some vigilance regarding the violin modes.
• Intensity noise
  • Coupling was measured à la Kiwamu by leaving the outer loop off and driving the inner-loop excitation point. For the noise estimation, I used the outer loop out-of-loop sensor. Since Sudarshan et al. previously found that this is artificially high, this estimation is an upper limit (though probably no more than a factor of 3, given Sudarshan's plot).
• Frequency noise [CARM sensing noise only]
  • Previously (i.e., when we locked CARM using the in-air REFL sensor), I estimated the coupling by looking at the TF in-vac REFL to DARM, and for the frequency noise estimation I used the noise of in-vac REFL as an upper limit for the frequency noise. Since we now lock with in-vac REFL, which has more light on it than in-air REFL does, I do not expect that the noise of in-air REFL is a particularly useful upper limit for the frequency noise.
  • Therefore, I have tried to instead estimate the sensing noise in CARM (from in-vac REFL, the summing-node board, the common-mode board, and PDH shot noise) in V/Hz^1/2 and propagate it (using the Izumi/Sigg expression) into a frequency noise in Hz/Hz^1/2. For the CARM optical TF I use 12.7 W/Hz at dc, with a pole at 0.48 Hz.
  • Then I have injected noise into CARM and looked at the TF from the residual of the excitation into DARM. This is the coupling TF needed to propagate the estimated sensing noise to DARM, assuming the CARM gain is high (this isn't quite true at high frequencies; the ugf is 17 kHz or so, and the gain does not exceed 20 dB until 3 kHz).
  • Since this includes sensing noise only (and not, for example, FSS noise), I have labeled it as a lower limit. In fact, the coherence between REFL 9Q and the DCPD sum is about 0.04 around 7 kHz, perhaps suggesting a frequency noise contribution of 2×10⁻⁸ mA/Hz^1/2 or so. More investigation required.
• Oscillator phase noise [not included here]
  • Stefan and I measured the coupling of the 9 MHz RF source into DARM, and using the expected performance of the OCXO estimated the noise in DARM should be 2.8×10⁻¹⁰ mA/Hz^1/2 at 1 kHz. This is quite low (and not shown on the plot).
  • This number should be replaced with Alexa's and Daniel's measurements of the phase noise. An even more satisfying number could be made by trying to measure the 9 MHz and 45 MHz phase noises in situ, closer to the EOM (e.g., at the output of the distribution system on the ISC rack).
• Oscillator amplitude noise [45 MHz only]
  • In this case we know that the 45 MHz RFAM is the dominant contributor (other than shot noise) to the DARM noise above a few hundred hertz. Here I use Stefan's estimate of the RFAM-induced photocurrent (1.8×10⁻⁸ mA/Hz^1/2), which (as he notes) is not enough to explain the excess between sum and null.
  • However, based on tonight's measurements using the new EOM driver readback, it seems that 45 MHz RFAM is enough to explain the excess. Perhaps Stefan's measurement is an underestimate, since it was done at the output of the distribution system and did not include the final rf amplifier before the EOM.
  • As for 9 MHz RFAM, Stefan and I made an estimate of the coupling from the 9 MHz source into DARM. Based on the specified performance of the OCXO, the expected noise in DARM is quite small. However, it would be better to look somewhere further downstream, as Stefan did (although I think he said the measurement was not that clean). This noise is not estimated in the plot.

The downward slope in the null at high frequencies is almost certainly some imperfect inversion of the AA filter, the uncompensated premap poles, or the downsampling filter.

We observed broadband coherence of OMC_DC_SUM with ASC_AS_C_LF_SUM and ASC_A_RF36_PIT. We made some numbers and plots, using the 64kHz version of the channels.

First the measurements we made on OCXO oscillator:
- ASC_AS_C sees a RIN of about 5e-7/rtHz above 100Hz (either from H1:ASC-AS_C_SUM_OUT_DQ or from H1:IOP-ASC0_MADC6_TP_CH11). The same is true for its segment 1.
- The calculated shot noise RIN at 20mA (quantum efficiency 0.87) detected is 4.0e-9/rtHz.
- The 4.0e-9/rtHz agrees with DCPD_NULL_OUT_DQ's prediction (8.0e-8 mA/rtHz/20mA).
- DCPD_SUM_OUT_DQ sees a slightly elevated RIN of 4.6e-9/rtHz (9.2e-8 mA/rtHz/20mA).

- The RIN in DCPDA (H1:IOP-LSC0_MADC0_TP_CH12, corrected for the whitening) is about 5.9e-8 mA/rtHz, or RIN = 5.9e-9/rtHz at 20mA/2diodes (~15pm DARM offset)...
- ...or about 3.3e-8 mA/rtHz or 1.2e-8/rtHz at 5.7mA/2diodes (~8pm DARM offset).

- ASC-AS_C_SEG1 (H1:IOP-ASC0_MADC6_TP_CH11) and OMC-DCPD_A (H1:IOP-LSC0_MADC0_TP_CH12) shows a coherence of 0.053 at 20mA, suggesting a white noise floor a factor of 0.23 below shot noise.
- At 5.7mA the same coherence is about 0.13, i.e. the white noise floor is a factor of 0.39 below shot noise.
- These two measurements are in plot 1.

- Taking the last two statements together, we predict a coherent noise of
  - 5.9e-8 mA/rtHz *0.23 = 1.4e-8 mA/rtHz at 20mA/2diodes (~15pm DARM offset)  (RIN of coherent noise = 1.4e-9/rtHz) - The pure shot noise part is thus 5.7e-8 mA/rtHz
  - 3.3e-8 mA/rtHz *0.39 = 1.3e-8 mA/rtHz at 5.7mA/2diodes (~8pm DARM offset)  (RIN of coherent noise = 4.5e-9/rtHz) - The pure shot noise part is thus 3.0e-8 mA/rtHz.

- AS_C calibration:
 - 200V/W (see alog 15431)
 - quantum efficiency 0.8 (see alog 15431)
 - 0.25% of the HAM 6 light (see alog 15431)
 - We have 39200cts in the AS_C_SUM. Thus we have
   - 39200cts / (1638.4cts/V) * 10^(-36/40) (whitening) / (200V/W) = 1.89mW and AS_C. (shot noi
   - 1.89mW/0.025 = 76mW entering HAM6. I.e. we have slightly more sideband power than carrier power (Carrier: 27mW in OMC transmission).
   - Shot noise level on AS_C_SUM is at 2.0e-8 mA/rtHz, corresponding to a RIN of 1.6e-8/rtHz. I.e. the coherent noise seen at 5e-7/rtHz is high above the shot noise. Dark noise TBD.
   - The light entering HAM 6 has a white noise of 5e-7/rtHz*76mW = 3.8e-5 mW/rtHz 
    

Bottom line:
 -We have ~1.4e-8mA/rtHz, or 1.9e-8mW/rtHz of coherent white noise on each DCPD.
 -It corresponds to 3.8e-5mW/rtHz before the OMC, i.e. the the OMC seems to attenuate this component by 2000.
 -This noise stays at the same level (in mW/rtHz) for different DCPD offsets.


Next, we switched back to the IFR for testing. plot 2 shows the same coherences (all at 5.7mA / 8pm DARM offset), but on the IFR. Interestingly now AS_C and AS_A_RF36 start seeing different noise below 2kHz. We convinced our selfs that the higher excess noise seen in AS_A_RF36 is indeed oscillator phase noise from the IFR - so that is clearly out of the picture once of the OCXO. (Evan will shortly log the oscillator phase noise predictions.)


64k Channel list:
H1:IOP-LSC0_MADC0_TP_CH12:     OMC-DCPD_A  (used in plot)
H1:IOP-LSC0_MADC0_TP_CH13:     OMC-DCPD_B
H1:IOP-LSC0_MADC1_TP_CH20:     REFLAIR_A_RF9_Q
H1:IOP-LSC0_MADC1_TP_CH21:     REFLAIR_A_RF9_I
H1:IOP-LSC0_MADC1_TP_CH22:     REFLAIR_A_RF45_Q
H1:IOP-LSC0_MADC1_TP_CH23:     REFLAIR_A_RF45_I
H1:IOP-LSC0_MADC1_TP_CH28:     REFL_A_RF9_Q
H1:IOP-LSC0_MADC1_TP_CH29:     REFL_A_RF9_I
H1:IOP-LSC0_MADC1_TP_CH30:     REFL_A_RF45_Q
H1:IOP-LSC0_MADC1_TP_CH31:     REFL_A_RF45_I


H1:IOP-ASC0_MADC4_TP_CH8:      ASC-AS_A_RF36_I1
H1:IOP-ASC0_MADC4_TP_CH9:      ASC-AS_A_RF36_Q1
H1:IOP-ASC0_MADC4_TP_CH10:     ASC-AS_A_RF36_I2
H1:IOP-ASC0_MADC4_TP_CH11:     ASC-AS_A_RF36_Q2
H1:IOP-ASC0_MADC4_TP_CH12:     ASC-AS_A_RF36_I3
H1:IOP-ASC0_MADC4_TP_CH13:     ASC-AS_A_RF36_Q3   (used in plot)
H1:IOP-ASC0_MADC4_TP_CH14:     ASC-AS_A_RF36_I4
H1:IOP-ASC0_MADC4_TP_CH15:     ASC-AS_A_RF36_Q4

H1:IOP-ASC0_MADC6_TP_CH11:     ASC-AS_C_SEG1  (used in plot)
H1:IOP-ASC0_MADC6_TP_CH10:     ASC-AS_C_SEG2
H1:IOP-ASC0_MADC6_TP_CH9:      ASC-AS_C_SEG3
H1:IOP-ASC0_MADC6_TP_CH8:      ASC-AS_C_SEG4