[Paco, Yehonathan, Yuta]

Since we have installed BH44, we are seeing side lobes of 60 Hz + harmonics in AS55, REFL55, BH55, BH44, preventing us from locking FPMI BHD (40m/17405).

BH55 RF amp removed:
  - We have noticed that the side lobes are there in BH55 (but not in BH44) when LO-ITMX single bounce is fringing (ETMs and ITMY mis-aligned).
  - Changing whitening gains and turning on/off whitening/unwhitening filters didn't help.
  - When LO-ITMX single bounce is locked with BH55, the side lobe in BH55 reduces.
  - Dithering LO1 at 11 Hz created 180 +/- 11 Hz signal, which confirms that this side lobes are from the up conversion of optic motion.
  - We thought it could be from RF saturation, so we have put a 55-67 MHz bandbass filter (SBP-60+) in between BH55 RFPD and RF amp (ZFL-1000LN+; 40m/17195). Didn't help.
  - We then removed the RF amp. This largely reduced the side lobes (but still some at 180 Hz). We could lock LO-ITMX single bounce without the RF amp, so we decided to remove it for now.

Side lobes only when one of the arms is locked:
  - When ETMs are mis-aligned, MICH fringing and BHD fringing, there are 60 Hz + harmonics, but the side lobes are not there.
  - But with Xarm is locked (ETMY, ITMY mis-aligned) or Yarm is locked (ETMX, ITMX mis-aligned), the side lobes appear in AS55, REFL55, BH55, BH44.
  - Changing whitening gains and turning on/off whitening/unwhitening filters didn't help.
  - As the error signals are normalized by TRX and TRY, we turned on/off the power normalization, but didn't help.
  - Switching 60 Hz comb in BS, ITMX, ITMY, ETMX, ETMY suspension damping didn't help.

POY11 Investigations:
  - When ETMs are mis-alined, POX11 had relatively large 60 Hz + harmonics, but almost none in POY11 (unlike other RFPDs; see Attchment #1).
  - However, when ETMY is aligned and Yarm is loked with POY11, the side lobe grows in POY11.
  - Changing the feedback point from ETMY to ITMY or MC2 didn't help.
  - We have unplugged the IQ demod board for BH44 from the eurorack (without removing the cables) and removed the fuse for the power supply of the RF amp for 44 MHz generation (40m/17401), but these also didn't help.
  - We have also tried locking Yarm with REFL55(= ~2 x POY11), BH55(= ~10 x POY11), ALSY(= ~2000 x POY11), but the side lobes were always there.
  
Next:
  - Disconnect cables in BH44 to open possible ground loops made during BH44 installation (especially 44 MHz generation part??).
  - Check if the noise was there before BH44 installation using past data.

1) Turning the whitening filter before the ADC on/off didn't changed the relative height of 60 Hz peak compared with the noise floor. When the whitening filter was turned on, increase of the dark noise measured at C1:LSC-****_(I|Q)_IN1 was roughly consistent by eye with the whitening filter transfer function (gain of 1 at DC, ~15 Hz zero x2, ~150 Hz pole x2), which suggests the 60 Hz pickup is before the whitening filter.

2) Attached is the electronics diagram around BH44 and BH55.

Following was done to investigate 60 Hz noise issue, but no significant change in the FPMI noise observed.


REFL55 inspection:
  - Even before BH44 installation, we have been experiencing flaky REFL55 RF output. When some work was done at AP table or something, sometimes the amplitude of REFL55_I and REFL55_Q goes very low, and/or offset changes. This was usually fixed by touching the RF output of REFL55.
  - So, we took out REFL55 and opened the back lid to inspect. RF output seemed rigid and the SMA connector was properly grounded to the box; didn't find any issue (Attachment #1).
  - REFL55 was put back to its original position, and the cables were also put back.

BH44 Kapton tape:
  - I realized that other RFPDs have Kapton tape in between the RFPD golden box and the black mount, but not for BH44 we recently installed.
  - I have checked that the golden box of BH44 and the optical table is not grounded when RF output and the DB15 cable was disconnected, but is gounded when they are connected, just like BH55.
  - Anyway I removed BH44 and put a Kapton tape (Attachment #2), just in case, and BH44 was put back to its original position, and the cables were also put back.

FPMI noise spectra after the work:
  - Attachment #3,4,5 are noise spectra of FPMI BHD sensors when FPMI is RF locked with AS55_Q, REFL55_I, and REFL55_Q, and LO_PHASE is locked with BH55 with the following configurations.
  - Attachment #3: whitening/unwhitening filters for AS55, REFL55, POX11, POY11, BH55, BH44 turned on (nominal configuration after lock acquisition)
  - Attachment #4: whitening/unwhitening filters for AS55, REFL55, POX11, POY11, BH55, BH44 turned off. No significant change except for expected whitening filter transfer function.
  - Attachment #5: whitening/unwhitening filters for AS55, REFL55, POX11, POY11, BH55, BH44 turned on, 30 dB resonant gain at 60 Hz, Q=10 in CARM loop. Significant 60 Hz reduction everywhere. This was not observed when resonant gain at 60 Hz was put in DARM loop (only 60 Hz at AS55_Q was reduced). 60 Hz noise mainly coming from something in CARM loop?

Don't forget to:
  - Put a beam dump for BH44

[Paco, Anchal, Yuta]

Isolating BH44 setup from the rest didn't help reducing the 60 Hz noise.
Frequency noise from IMC also seems unchanged before and after BH44 installation.

Isolating BH44:
  - To see if BH44 setup installed is causing the 60 Hz issue, we compared the spectra of FPMI sensors with BH44 setup and with BH44 setup disconnected.
  - In the latter configuration, BH44 setup was isolated from the rest by disconnecting the SMA cables and the RFPD power cable, as shown in Attachment #1.
  - There was no significant difference in the spectra with BH44 and with BH44 isolated.
We have even put the old AS156 IQ demodulator board we have pulled out to insert BH44 IQ demodulator board back, but didn't change.
  - We have also disconnected the 22 MHz generation setup around 40m Frequency Generation Unit at 1X2 for switchable IMC/AS WFS, but it also didn't help.
  - Attachment #2 is the orignal spectra with both arms locked with POX and POY, feeding back to respective ETMs (MICH is not locked), and Attachment #3 is those with BH44 setup isolated, AS156 IQ demod back, and 1X2 22MHz generation isolated. Both look basically the same.
  - BH44 setup was reverted after the comparison.

IMC frequency noise:
  - As adding a resonant gain at 60 Hz helped reducing the 60 Hz noise (40m/17419), the noise might be from frequency noise. It also explains why it is not present in MICH when ETMs are mis-aligned, and only present when one of the arms is involved (40m/17413).
  - To see if the frequeny noise at 60 Hz increased after BH44 installation, I compared the spectrum of C1:IOO-MC_F_DQ on January 11 (same Wednesday) with that measured today at almost the same time.
  - Attachment #4 is the result. 60 Hz noise and its harmonics seems almost the same in MC_F. It is rather noisy today in other frequencies, but not at 60 Hz.

Next:
  - Read the book.

PMC aligned (Attachment #1).
Over the past month, PMC transmission is actually slowly growing from 0.68 to 0.70 (Attachment #2), since it suddenly dropped from 0.72 on Dec 27 (40m/17390).

So far different measurements are consistent with the hypothesis that the 60 Hz noise is from PSL frequency noise (40m/17423).
We have done several measurements in REFL55 and POX/POY to show this hypothesis, and all are consistent with the frequency noise hypothesis.
However, 60 Hz noise in the IMC error point seems too small to explain the 60 Hz noise in DARM.
 

[Koji, Paco, Yuta]

REFL55 attenuation experiment:
 - To check if the 60 Hz is in the light or not, we have compared the spectrum of REFL55_I_IN1 with different ND fiters in front of REFL55 RF PD.
 - Attachment #1 shows the result. Spectrum was taken when both arms are locked indivitually using POX and POY, feeding back to ETMs, MICH freely swinging. Red curve is nominal, blue is with OD0.5, and green is with OD1.
 - Attenuation in 60 Hz noise and side lobes are consistent with OD filter attenuation, which suggets that the noise is from the light.
 - Note that having side lobes is natural, as MICH is fringing (sorry for confusing plot). However, if the side lobes come from the RF saturation, we expect side lobes to decrease more than OD filter attenuation, but this was not the case.

Phase measurements between POX and POY:
 - When both arms are locked indivitually using POX and POY, feeding back to ETMs, transfer function from POX to POY had gain of ~1 and the phase of -10 deg (Attachment #2).
 - With PSL shutter is closed, transfer function from POX to POY had gain of ~0.1 and the phase of -100 deg, with lower coherence (Attachment #3).
 - These also support that 60 Hz noise in POX and POY when the arms are locked are from common origin, such as frequency noise.

[Michael, Paco, Yuta]

IMC error point measurement:
 - Attachment #4 shows the IMC Servo Board configuration we used for the all three measurements below.

For this measurement we took TP1A (from MC Servo board) and buffered it with a battery powered SR560 (DC coupled, low noise, gain x1) before connecting it to the single ended A1 channel on a SR785. The noise level was set to -42 dBVpk, and three different noise spectra were acquired:

• In Blue, the IMC is locked
• In Orange, IMC is unlocked by closing PSL Shutter (dark)
• In green, IMC is unlocked by closing PSL Shutter and the Servo board IN1 is disabled.

The estimated (in loop) line noise (60 Hz) levels are 70 uV/rtHz, which using the calibration 13 kHz/Vrms (from 40m/14691) amounts to 0.9 Hz/rtHz of (supressed) frequency noise at IMC Error point.

This number (0.9 Hz/rtHz) in terms of displacement corresponds to 1.28e-15 m/rtHz. The measured DARM noise (2e-10 m/rtHz @ 60 Hz from 40m/17414) is not accounted for by this amount.

Next:
  - Check the IMC error signal calibration
  - Measure the calibrated out-of-loop frequency noise using various signals (POX, POY, REFL55, AS55 with single arm, ALSBEAT, PMC_CTRL)

Timeline (as far as written in the elog):
 - Dec 20: FPMI BHD locked using BH55 (40m/17367).
 - Dec 21: FPMI RF locked, but not BHD, DARM noise 1e-11 m/rtHz @ 60 Hz (40m/17369).
 - Jan 10-11: AS WFS boards testing at 1X2 (40m/17391, 40m/17393).
 - Jan 11: FPMI BHD locked using BH55, DARM noise 2e-11 m/rtHz @ 60 Hz (40m/17392).
 - Jan 13 2pm: FPMI BHD locked using BH55, DARM noise 2e-11 m/rtHz @ 60 Hz (40m/17399).
  - After measuring the sensing matrix etc., LO_PHASE locking became unstable and FPMI BHD could not be recovered (I thought something similar to Dec 21 is happening).
 - Jan 13 6pm: FPMI BHD locked using BH55 recovered. DARM noise 2e-11 m/rtHz @ 60 Hz. Discovered that the 60 Hz noise is higher when LO_PHASE locking is unstable (40m/17400).
 - Jan 17: BH44 hardware/software installed. Found IQ demod board needs tuning (40m/17401).
 - Jan 18: Tuned IQ demod board for BH44 installed (40m/17402).
 - Jan 19: BH44 RF PD placed and connected to IQ demod board. FPMI RF locked, LO_PHASE locked with BH44, but found 60 Hz noise everywhere (40m/17405).
 - Jan 24: FPMI RF locked (with CARM locked with POX11+POY11 instead of REFL55_I). DARM noise 2e-10 m/rtHz @ 60 Hz (40m/17414).
 - Jan 24: AS WFS boards mounted in 1X2 (40m/17416).
 - Jan 25: Isolating BH44 setup didn't help (40m/17423).
 - Jan 26: Fixed tripping of -5V supply in 1X1 (40m/17425).
 - Jan 27: IMC error point measurements at 1X2 (this elog).

One of these V beam dumps was installed for BH44 RF PD.
The rest is now stored in the box in the shelf along Yarm, together with RF PD mounts.

[Paco, Yuta]

We estimated the frequency noise of IMC output beam at 60 Hz using different methods to see if they are consistent.
They are not inconsistent, but seems hard to explain by an easy single dominating noise source (multiple noise sources at similar noise level?).

IMC suspension damping:
 - We checked that 60 Hz comb filters are all on for all OSEM sensors of MC1, MC2, MC3 (Attachment #1), and they all have comb(60,30,-40,3), which is 60 Hz comb filter of Q=30, -40 dB, 3 harmonics.

Revisiting IMC error point calibrations:

 - We revisited this calibration in 40m/17431. First, 0.9 Hz/rtHz corresponds to 1.3e-13 m/rtHz, as L/nu = 40 m / 282 THz = 1.4e-13 m/Hz.
 - Also, we need to add a loop correction. MC servo board settings when we took this data was as follows:
   - +4 dB in IN1
   - 40 Hz pole, 4000 Hz zero filter was on
   - 0 boost
  assuming 1/f around UGF of 200 kHz (40m/17009), and 1/f^2 between 40-4000 Hz, openloop gain at 60 Hz will be (4e3/60)**2*(200e3/4e3)=2e5. So, the estimated frequency noise at the output of IMC in terms of arm length is 1.3e-13 m/rtHz * (1+G) = 2.6e-8 m/rtHz (or 1.8e-8 m RMS considering 0.5 Hz bandwith).
  - Noise measured with the same condition but PSL shutter closed was 7 uV/rtHz at 60 Hz (40m/17431). This correspond to 1.3e-14 m/rtHz (or 9.2e-15 m RMS), which is an estimated dark noise.

Measuring frequency noise using arms:
 - We then proceeded to measure frequency noise using arms locked with POX11 and POY11. Attachment #2 and #3 is calibrated XARM and YARM noise using the error signals and feedback signals. For both, it is 1e-10 m/rtHz at 60 Hz (or 4.3e-11 m RMS considering 0.187493 Hz bandwidth). And this is more than x10 higher than what we have measured in August 2022 (dotted lines).
 - MC_F calibrated using 1.4e-13 m/Hz reads 7.1e-9 m/rtHz at 60 Hz (or 3.1e-9 m RMS considering 0.187493 Hz bandwidth).
 - Noise measured at DARM in FPMI locked with RF (but CARM with POX11+POY11, as 60 Hz was too much to switch to REFL55_I) was 3e-10 m/rtHz at 60 Hz (or 1.8e-10 m RMS considering 0.374994 Hz bandwidth) (Attachment #5), which is roughly the same as past measurements (40m/17414).
 - To check if MC_F is calibrated correctly, we injected a line at 57 Hz with 3000 counts in amplitude into MC2. Using MC2 actuation efficiency -14.17e-9 /f^2 m/counts in arm length (40m/16978), this should give

14.17e-9/(60**2)*3000 = 1.2e-8 m -> 0.93e-8 m RMS

 in XARM length noise. RMS value of YARM calibrated spectra reads 1.1e-8 m (Attachment #4), which is consistent within ~20%, so MC_F calibration is OK. Note that MC_F at 60 Hz are at the same level in August 2022 (green curves).

Summary of frequency noise measurements at 60 Hz:
 - 1.8e-8 m RMS as measured at IMC error point TP1A
    This gives you total of IMC length noise, error point noise, PSL free run noise, feedback noise.
    Estimated dark noise at error point TP1A is 9.2e-15 m RMS, and is small.
    Calibration might be wrong, as this rely on IMC loop gain estimate and error signal calibration of 13kHz/V a while ago in 2018 (from 40m/14691, which is from 40m/13696), which might not be true for TP1A at 60 Hz (note that there is a 40 Hz/4000 Hz filter).
 - 3.1e-9 m RMS as measured at MC_F
    This gives you total of IMC length noise, error point noise, PSL free run noise, but the noise injected at feedback point before MC_F is suppressed by ~2e5.
    As estimated dark noise is much less, it is IMC length noise, PSL free run noise or noise injected after MC_F.
    Note that typical NPRO free run noise at 60 Hz is 1e4/60 Hz/rtHz * 1.4e-13 m/Hz = 2.3e-11 m/rtHz, and is small, but we might be having large NPRO noise.
 - 4.3e-11 m RMS as measured using XARM and YARM
     This gives you total of IMC length noise, error point noise, but PSL free run noise and feedback noise are suppresed by ~2e5.
     But this also includes noise injected in XARM and YARM loops.
     If this is mainly from PSL free run noise or feedback noise, we expect 3.1e-9 m RMS/2e5 = 1.6e-14 m RMS, so it doesn't explain 4.3e-11 m RMS.
     If this is mainly from IMC length noise, this should be equal to frequency noise measured at MC_F, but MC_F is higher by nearly two orders of magnitude.
     Noise in POX11 or POY11 are smaller by a factor of more than 100 when dark (see 40m/17431), so contribution from dark noise of POX11 and POY11 at 60 Hz to XARM/YARM noise is negligible.
     These mean that the noise might be from combination of IMC and PSL. (For example, if noise injected at error point is 9.2e-15 m RMS, IMC length noise is 4.3e-11 m RMS, PSL free run noise is 3.1e-9 m RMS, and noise injected at feedback point is 1.8e-8 m RMS, it explains all the measurements so far.)
 - 1.8e-10 m RMS as measured using FPMI DARM
     Frequency noise in DARM should be suppressed by common mode rejection, but it is actually x3 higher than what we see in XARM and YARM.
     There might be extra noise from FPMI loops (note that CARM is controlled by POX11+POY11 in this measurement).

Next:
  - Check IMC error point calibration (is 13 kHz/V correct?) by driving MC2 at around 60 Hz (but not at 60 Hz) by known amount
  - Measure frequency noise at IN1 of MC servo board to avoid 40 Hz/4000 Hz filter
  - Check what exactly are we measuring at MC_F. Are there possibility of additional noise for MC_F, which is not fed back to laser frequency?
  - Drive MC2 at around 60 Hz (but not at 60 Hz) to see if MC_F and X/YARM spectra matches
  - Estimate IMC length noise from MC OSEMs
  - Touch electronics around 1X2 to see if 60 Hz at IMC error point changes (monitor the live spectrum!)

[Anchal, Yuta]

We have measured OLTF of IMC loop, and revisited IMC error point calibration again.
Also, we have tried to break the ground loop between MC servo board and TTFSS, but didn't help.

IMC OLTF measurement:
 - IMC OLTF was measured using SR785 at TP1A and TP1B. MC servo board settings are the following.
   - +4 dB in IN1
   - 40 Hz pole, 4000 Hz zero filter was on
   - 0 boost
 - Eye-ball fit of OLTF gives zeros at [30e3,30e3] Hz, poles at [40,3e3,3e3] Hz (Attachment #1). 40 Hz pole is from 40:4000 Hz fiter in MC servo board and 4kHz zero is compensated by IMC cavity pole (~ 3.79 kHz). We are not sure where two 3k:30k are from.
 - Anyway, eye-ball fit gives OLTF gain of 1.7e5 at 60 Hz, which is accidentally roughly the same as previous estimate (40m/17446).

Revisiting IMC error point calibrations:
 - We realized that error signal calibration of 13kHz/V a while ago in 2018 (from 40m/14691, which is from 40m/13696) is a calibration for IN1.
 - So, 70 uV/rtHz at 60 Hz at TP1A corresponds to 70 uV/rtHz / 4dB / (4e3/60) * 13kHz/V = 0.009 Hz/rtHz, which corresponds to 1.2e-15 m/rtHz.
 - The estimated frequency noise at the output of IMC in terms of arm length is 1.2e-15 m/Hz * (1+G) = 2.0e-10 m/rtHz (or 1.4e-10 m RMS considering 0.5 Hz bandwith).
 - Noise measured with the same condition but PSL shutter closed was 7 uV/rtHz at 60 Hz (40m/17431). This correspond to 1.2e-16 m/rtHz (or 8.5e-17 m RMS), which is an estimated dark noise.

Summary of frequency noise measurements at 60 Hz:
 - 1.4e-10 m RMS (or 1.0e3 Hz RMS) as measured at TP1A (estimate of unsuppressed noise difference between IMC and PSL)
  - This being smaller than MC_F measurement is strange, as this should be an estimate of total unsuppressed noise (if 60 Hz noise is coherently cancelling each other, this can be explained).
 - 3.1e-9 m RMS (or 2.2e4 Hz RMS) as measured at MC_F
 - 4.3e-11 m RMS (or 3.1e2 Hz RMS)  as measured using XARM and YARM
 - 1.8e-10 m RMS as measured using FPMI DARM

Buffering MC servo board output to TTFSS:
 - We have inserted a battery-powered SR560 in between MC servo board output to TTFSS, trying to break the possible ground loop between 1X2 rack and PSL.
 - To do this, we had to lower IN1 gain to -6dB, to avoid saturation of SR560.
 - This didn't make any difference in MC_F or POY during YARM lock.

I just noticed that c1sus2 crashed again. Following 40m/17335, I fixed it by running

controls@c1sus2:~$ rtcds restart --all

"global diag reset" made all FE STATUS green.
Burt restored at 2023/Feb/8/19:19 for c1sus2 models.
Watchdogs reset for BHD optics and now all look fine.

[Anchal, Yuta]

Yesterday, we have measured the frequency noise of PSL with IMC locked/unlocked using ALS BEATX/Y to narrow down where the 60 Hz is coming from.
All the measurements so far is consistent with a hypothesis that 60 Hz noise injected after MC_F is picked-off (it could be from MC_F DAQ readout or something in the IMC loop).

Method:
 - Measured YARM noise spectra when YARM is locked with POY11 to measure the frequency noise with respect to YARM, and compared with MC_F
 - Measured ALS BEATX and BEATY spectra when PSL is free running and when IMC is locked. Here, when "PSL is free running" is done with PSL shutter closed, but all the cables remained the same and FSS loop was in "down" state. Shutters at both ends were closed, and PZT inputs to AUX lasers were terminated to avoid noise injection from PDH locking with dark noise (this was necessary to reduce noise in BEATY).

Result:
 - Attachment #1 is YARM noise calibrated into Hz, and Attachment #2 is BEATX and BEATY spectra with PSL free running (solid lines) and IMC locked (dotted lines). Below are summary of noise level at 60 Hz (RMS is calculated using a bandwidth of 0.187493 Hz)

YARM (PSL locked vs Yarm): 6.5e2 Hz/rtHz (2.8e2 Hz RMS)
MC_F (sum of noises in IMC loop): 4.9e4 Hz/rtHz (2.2e4 Hz RMS)
BEATX free (PSL free vs Xend free): 3.3e3 Hz/rtHz (1.4e3 Hz RMS)
BEATX locked (PSL locked vs Xend free): 8.8e2 Hz/rtHz (3.8e2 Hz RMS)
BEATY free (PSL free vs Yend free): 1.6e4 Hz/rtHz (6.9e3 Hz RMS)
BEATY locked (PSL locked vs Yend free): 1.5e4 Hz/rtHz (6.5e3 Hz RMS)

Discussion:
 - "BEATX locked" measurement suggests that PSL locked to IMC (and Xend free) has noise less than 3.8e2 Hz RMS. This is roughly consistent with YARM measurement of frequency noise, and suggests that Yarm is stable enough to measure the PSL locked frequency noise.
 - "BEATX free" measurement suggests that PSL free run (with cables connected) has noise of 1.4e3 Hz RMS (note that Xend free is less than 3.8e2 Hz RMS).
 - MC_F measurement is the sum of noises in IMC loop, including IMC length noise + noise injected at error point (3.8e2 Hz RMS), PSL free run noise (1.4e3 Hz RMS), noise injected at feedback. Therefore, this suggests that 2.2e4 Hz RMS we see in MC_F is from noise injected after MC_F pickoff point (or in the MC_F DAQ readout).
 - BEATY having large 60 Hz noise probably comes from noise in the beat measurement.

Next:
 - Use BEATX to monitor 60 Hz noise.
 - Try terminating PZT input to see if 60 Hz noise reduces. Try different gains at different point of MC servo board and TTFSS when IMC is unlocked to see where exactly 60 Hz noise is coming from.

[Anchal, Yuta]

Measurements yesterday (40m/17458) suggested that 60 Hz noise is injected after MC_F is picked-off.
So, we terminated PSL PZT input at several points to see where 60 Hz noise is injected.
It seems like the 60 Hz frequncy noise we see in MC_F is from TTFSS box, but the 60 Hz noise we see in YARM is not limited by this.

The 60 Hz noise we see in YARM is probably limited by IMC length noise.

Method:
 - We terminated PZT input to the PSL laser at various points one by one and monitored 60 Hz frequency noise using BEATX. PSL shutter was closed and IMC was not locked.

Result:
 - Below is the result at 60 Hz (RMS is calculated using a bandwidth of 0.187493 Hz)

Reference from 40m/17458, YARM (PSL locked vs Yarm): 6.5e2 Hz/rtHz (2.8e2 Hz RMS)
Reference from 40m/17458, MC_F (sum of noises in IMC loop): 4.9e4 Hz/rtHz (2.2e4 Hz RMS)
MC_F when PSL shutter is closed but MC servo board configuration at IMC locked state: 2.7e2 Hz/rtHz (1.2e2 Hz RMS) -- this gives IMC loop gain enhanced sensing noise

BEATX free (PSL free vs Xend free): 3.5e3 Hz/rtHz (1.5e3 Hz RMS) -- consistent with previous measurements
With PZT input to NPRO terminated (Attachment #1): 8.1e2 Hz/rtHz (3.5e2 Hz RMS)
Connected a terminated small box (we see in Attachment #1) before NPRO PZT: 6.3e2 Hz/rtHz (2.7e2 Hz RMS)
Connected input terminated Thorlabs PZT driver (MDT694): 5.9e2 Hz/rtHz (2.6e2 Hz RMS)
Connected input terminated summing amp (Attachment#2): 4.4e2 Hz/rtHz (1.9e2 Hz RMS)
Connected input terminated TTFSS (C1:PSL-FSS_MGAIN=-10dB, C1:PSL-FSS_FASTGAIN=-10dB): 3.9e3 Hz/rtHz (1.7e3 Hz RMS) -- consistent with "BEATX free (PSL free vs Xend free)" measurement
Connected input terminated TTFSS (C1:PSL-FSS_MGAIN=-10dB, C1:PSL-FSS_FASTGAIN=+10dB): 7.6e3 Hz/rtHz (3.3e3 Hz RMS)
Connected input terminated TTFSS (C1:PSL-FSS_MGAIN=+4dB, C1:PSL-FSS_FASTGAIN=+19dB): 2.9e4 Hz/rtHz (1.3e4 Hz RMS) -- Nominal gains when IMC is locked; consistent with "MC_F" measurement 40m/17458
Connected input terminated TTFSS (C1:PSL-FSS_MGAIN=+19dB, C1:PSL-FSS_FASTGAIN=+4dB): 1.1e4 Hz/rtHz (4.8e3 Hz RMS)

Discussion:
 - Connecting TTFSS increased 60 Hz frequency noise, which suggests that TTFSS is creating this 60 Hz frequency noise.
 - Setting TTFSS gains to nominal gains to IMC locked, 60 Hz frequency noise matched with frequency noise measurement using MC_F. This quantitatively supports that TTFSS is creating this 60 Hz frequency noise.
 - Increasing C1:PSL-FSS_MGAIN and reducing C1:PSL-FSS_FASTGAIN reduced 60 Hz frequency nosie. This means that some portion of 60 Hz noise is from between these two gains.
 - Note that having 60 Hz noise in TTFSS does not necessarily mean that our YARM noise is limited by this, because IMC loop suppresses the TTFSS noise. Assuming all 1.3e4 Hz RMS is all from TTFSS noise, it is suppressed to less than 1.3e4 Hz RMS/2e5 = 6.5e-2 Hz RMS (where 2e5 is IMC loop gain without super boosts, but it is actually higher with them) as frequency noise we see in YARM. YARM noise is measured to be 6.5e2 Hz/rtHz (2.8e2 Hz RMS), so it is not limited by TTFSS noise.
 - Also dark noise measured at MC_F (1.2e2 Hz RMS) tells you that the dark noise is not limiting the frequency noise we see in YARM.

Touching various parts around TTFSS:
 - We moved on to touch various parts around TTFSS to see if 60 Hz noise reduces in MC_F. We removed unused cables around TTFSS interface, touched power cables into TTFSS (both at TTFSS interface in the rack and TTFSS box on PSL table), BNC cables into TTFSS, disconnected slow controls, tried to avoid grounding of cables going into EOM (there is a small box that sums FSS feedback signal and 33.5 MHz; Attachment #3), but 60 Hz noise we see in MC_F didn't change significantly.

Next:
 - Check grounding situation around TTFSS box.
 - Check IMC length noise and error point noise by monitoring BEATX.
 - Check coil drivers for MC1, MC2, MC3 by disconnecting drivers while IMC is locked.
 - Try feeding back IMC servo also to MC2 with 60 Hz resonant gain to cancel 60 Hz noise


Note added at 23:50 to clarify:
nIMC : IMC length noise in frequency
nPSL: PSL free run noise in frequency
ne: sensing noise in frequency
nf: feedback noise in frequency
G: IMC loop gain (estimated to be 2e5 at 60 Hz without boosts)

MC_F = G/(1+G) * (nIMC + nPSL + ne + nf) + [noises in MC_F DAQ]
 = 2.2e4 Hz RMS
 MC_F when dark, MC servo nominal gain = G * ne
 = 1.2e2 Hz RMS
PSL frequency noise after IMC lock = G/(1+G) * (nIMC + ne) + 1/(1+G) * (nPSL + nf)
YARM = [PSL frequency noise after IMC lock] + [noises from YARM loop]
 = 2.8e2 Hz RMS
BEATX when PSL is free run, TTFSS low gain connected = nPSL + [noises from Xend AUX and BEATX sensing]
 = 1.7e3 Hz RMS
BEATX when PSL is free run, TTFSS nominal gain connected = nPSL + nf + [noises from Xend AUX and BEATX sensing]
 = 2.9e4 Hz RMS
BEATX when IMC is locked = [PSL frequency noise after IMC lock] + [noises from Xend AUX and BEATX sensing]
 = 3.8e2 Hz RMS
 
So, our estimate is
ne ~ 1.2e2/G Hz RMS (small)
nPSL ~ 1.7e3 Hz RMS
nf ~ 2e4 Hz RMS (this dominates MC_F, but already suppressed enough in [PSL frequency noise after IMC lock])
[PSL frequency after IMC lock] ~ 3e2 Hz RMS (this dominates YARM and BEATX when IMC is locked)
nIMC ~ 3e2 Hz RMS (this dominates [PSL frequency noise after IMC lock])

[JC, Yuta]

We have found that MC1 coils are causing 60 Hz noise.
Tripping watchdogs for MC1 coils reduced 60 Hz noise seen in YARM by a factor of 100.

Method:
 - Locked YARM with POY11 and measured YARM sensitivity to use it for 60 Hz frequency noise monitor0.187493**0.5
 - Tripped MC1, MC2, MC3 coil output watchdogs to see if they are causing this 60 Hz frequency noise. IMC WFS were turned off.

Result:
 - Attachment #1 is YARM sensitivity and MC_F in Hz with MC1,2,3 untripped (dotted) and MC1 tripped (solid).

YARM (PSL locked vs Yarm), MC1,2,3 untripped: 6.0e2 Hz/rtHz (2.6e2 Hz RMS)
MC_F (sum of noises in IMC loop), MC1,2,3 untripped: 4.8e4 Hz/rtHz (2.1e4 Hz RMS)
YARM (PSL locked vs Yarm), MC1 tripped: 6.6e0 Hz/rtHz (2.9e0 Hz RMS) -- reduced by a factor of 100
MC_F (sum of noises in IMC loop), MC1 tripped: 4.7e4 Hz/rtHz (2.0e4 Hz RMS)

 - We have also tried tripping MC2 and MC3 coils, but they didn't make much difference.
 - Untripping only one of MC1 face coils created 60 Hz frequency noise, so all the face coils seem to have the same level of 60 Hz noise.

Next:
 - Inspect around MC1 coil driver

Below are summary of electronics around MC1 and cable disconnection tests.
These suggest that the 60 Hz noise is probably from somewhere between DAC and the coil driver.
For now, we can work on IFO with SimDW off.

MC1 local damping electronics diagram:
Vacuum Flange
|| DB25 cable x2
Satellite Amp Chassis (LIGO-S2100029, LIGO-D1002818)
|| DB9 split cable
Suspension PD Whitening and Interface Board (LIGO-D000210)
||| 4pin LEMO x3
Anti-aliasing filter
|
ADC
|
CDS
 (SimDW is zpk([35.3553+i*35.3553;35.3553-i*35.3553;250],[4.94975+i*4.94975;4.94975-i*4.94975;2500],1,"n") gain(1.020); InvDW is the inverse)
|
DAC
|
SOS Dewhitening and Anti-Image Filter (LIGO-D000316) Shared with MC3
 (has 2ea. 800 Hz LPF & 5th order, 1 dB ripple, 50 dB atten, 28Hz elliptic LPF that can be turned on or bypassed)
||||| SMA-LEMO cable x5
 ("test in" are used; inputs can be disconnected with watchdogs)
SOS Coil Driver Module (LIGO-D010001, LIGO-D1700218)
 (HV offsets from Acromag are added at the output (independent from watchdogs))
|| DB9 split cable
Satellite Amp Chassis

Disconnecting cables:
 - Disconnecting cables between Satellite Amp Chassis and Suspension PD Whitening and Interface Board didn't help reducing 60 Hz noise.
 - Disconnecting LEMO cables between Suspension PD Whitening and Interface Board and Anti-aliasing filter didn't help reducing 60 Hz noise.
 - Turning off C1:SUS-MC1_SUSPOS/PIT/YAW/SIDE outputs didn't help reducing 60 Hz noise.
 - Turning off SimDW reduced 60 Hz noise.
 - Turning off watchdogs reduced 60 Hz noise.

Dewhitening filters:
 - When 60 Hz frequency noise was high, SimDW was on, but InvDW was off, which is in a weired state.
 - Now, all the MC suspensions have SimDW turned off and InvDW turned on (which supposed to turn on analog dewhitening filter, which is probably 28 Hz ELP which has a notch at 60 Hz)
 - Probably, when realtime model modifications for BH44 was made on Jan 17, coil dewhitening filter situation was not burt restored correctly, and we started to notice 60 Hz noise (which was already there but didn't notice because of dewhitening).
 - See 40m/17431 for the timeline, possibly related elogs 40m/17359, 40m/17361 about MC1 dewhitening switching on Dec 14-16.

Next:
 - Check if analong dewhitening filter actually has 28 Hz ELP by measuring transfer functions
 - Design SimDW and InvDW to correctly take into account of real dewhitening filters

FPMI BHD with LO phase locked using BH55 is recovered after 60 Hz frequency noise saga.
Attachment #1 shows the calibrated FPMI spectrum with RF(AS55_Q) readout and BHD, compared with those taken on January 13 (40m/17400, before BH44 installation).
There is unknown excess noise at round 30-40 Hz. This is not from MC2 DAC noise, as turning on/off dewhitening filters didn't make a difference.
Attachment #2 shows the samething but zoomed at 60 Hz. 60 Hz noise is actually reduced by an order of magnitude compared with what we had before BH44 installation.
Note that RF amp for BH55 which was there on January 13 was removed now (40m/17413).
LO_PHASE is locked with BH55_Q, under whitening gain of 45 dB, whitening filter on, C1:LSC-BH55_PHASE_R=-110 deg, C1:HPC-LO_PHASE_GAIN=-10, FM5 and FM8. This gives UGF of ~20 Hz (we used to be able to get ~100 Hz, but not possible now).

Locking LO_PHASE with BH44 is not stable now, probably due to small optical gain. We might have to install RF amp for BH44.

Next:
 - Check the beam alignment to BH44 RF PD
 - Install RF amp for BH44
 - Re-install RF amp for BH55

Since we need more signal for both BH55 and BH44 to compare LO phase locking scheme, BH55 and BH44 RF outputs are now amplified with ZFL-1000LN+ and ZFL-500HLN+ respectively (see Attachment #1).
The amplifiers each draw ~0.1 A current of 15V DC power supply, and Sorensen power supply now reads 6.9 A (see Attachment #2).
With ITMX single bounce and LO beam fringing, BH55_Q (45 dB whitening gain, C1:LSC-BH55_PHASE_R=-110 deg) gives ~500 counts in amplitude, and BH44_Q (24 dB whitening gain, C1:LSC-BH44_PHASE_R=4.387 deg) gives ~100 counts in amplitude (and they are orthogonal) (see Attachment #3).

Ideally, BH55 and BH44 should give orthogonal signals to lock LO phase (40m/17302).
This was checked with various interferometer configurations.
BH55 and BH44 are indeed orthogonal in ITM single bounce and MICH, but was not measurable in FPMI.
Maybe we should investigate BH44 in MICH BHD configuration first to see why BH44 is very noisy in FPMI.

Method:
 - X-Y plotted BH55_Q and BH44_Q and fitted with an ellipse to derive amplitude of each signal and phase difference between them.
 - Amplitude and phase differences are calculated using the following equations, where (ap, bp) are the semi-major and semi-minor axes, respectively, and phi is the rotation of the semi-major axis from the x-axis. (Thanks to Tomohiro for checking the calculations!)

 xAmp = np.sqrt((ap * np.cos(phi))**2 + (bp * np.sin(phi))**2)
 yAmp = np.sqrt((ap * np.sin(phi))**2 + (bp * np.cos(phi))**2)
 phaseDiff = np.arctan(bp/ap*np.tan(phi)) + np.arctan(bp/ap/np.tan(phi))

Jupyter notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/BHD/MeasurePhaseDiff.ipynb

 - This was done un following 4 configurations.
  - ITMX single bounce vs LO
  - ITMY single bounce vs LO
  - AS beam in MICH locked with AS55_Q vs LO
  - AS beam in FPMI locked with REFL55/AS455 vs LO
 - For each configuration, RF demodulation phases were tuned to minimize I.
 - Statistical error was estimated by calculating the standard deviation of 3 measurements.

 - Also, FPMI BHD sensing matrix was measured when FPMI is locked with REFL55/AS55, and LO_PHASE is locked with BH55_Q or BH44_Q.

Jupyter notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/SensingMatrix/ReadSensMat.ipynb

Result of BH55/BH44 orthogonality check:
 - ITMX single bounce vs LO
            Demod phase         Amplitude       Phase Diff
    BH55_Q  -94.4 +/- 0.2 deg   600.4 +/- 0.6   
    BH44_Q  -9.0 +/- 0.2 deg    124.3 +/- 0.2   -86.7 +/- 0.1 deg
 - ITMY single bounce vs LO
            Demod phase         Amplitude       Phase Diff
    BH55_Q  -92.9 +/- 0.3 deg   588.0 +/- 0.3   
    BH44_Q  -8.9 +/- 0.3 deg    123.0 +/- 0.1   -87.2 +/- 0.1 deg
 - AS beam in MICH locked with AS55_Q vs LO
            Demod phase         Amplitude       Phase Diff
    BH55_Q  -68.7 +/- 0.8 deg   44 +/- 1   
    BH44_Q  -28.5 +/- 1.7 deg   10.3 +/- 0.1   -84 +/- 2 deg
 - AS beam in FPMI locked with REFL55/AS455 vs LO
            Demod phase         Amplitude       Phase Diff
    BH55_Q  35 +/- 3 deg        257 +/- 4   
    BH44_Q  -16 +/- 3 deg       44 +/- 1        -77 +/- 3 deg
 - Attachmented pdf contain example X-Y plots from each configuration. For ITM single bounce and MICH, BH55 and BH44 seems to be orthogonal, but for FPMI, ellipse fit does not go well.
 - Difference in the BH55 demodulation phase for ITMX single bounce and ITMY single bounce (1.5 +/- 0.4 deg) agrees with past measurement and agree marginally with Schnupp asymmetry (40m/17274).
 - Maybe we can derive some length differences using these demodulation phases.

Result of FPMI sensing matrix measurements:
 - Below is the sensing matrix when FPMI is locked with REFL55/AS55, and LO_PHASE is locked with BH55_Q. BH44 is noisier than BH55, and the response to LO1 is consistent with zero. This is also consistent with BH44 being orthogonal to BH55, but the error bar is too large to say.

Sensing matrix with the following demodulation phases (counts/m)
{'AS55': -168.5, 'REFL55': 92.32, 'BH55': -110.0, 'BH44': -8.93097234187195}
Sensors       DARM @307.88 Hz           CARM @309.21 Hz           MICH @311.1 Hz           LO1 @315.17 Hz           
AS55_I       (-2.49+/-8.35)e+10 [90]    (+2.36+/-0.85)e+11 [0]    (-0.64+/-3.99)e+10 [0]    (+0.57+/-4.07)e+09 [0]    
AS55_Q       (-3.50+/-0.08)e+11 [90]    (+0.09+/-1.20)e+11 [0]    (-0.79+/-8.66)e+09 [0]    (-0.70+/-5.96)e+08 [0]    
REFL55_I       (+0.72+/-8.09)e+11 [90]    (-1.42+/-2.75)e+12 [0]    (+0.00+/-1.37)e+11 [0]    (-0.38+/-2.78)e+09 [0]    
REFL55_Q       (+0.19+/-1.93)e+11 [90]    (-2.14+/-6.92)e+11 [0]    (+0.00+/-3.16)e+10 [0]    (+0.17+/-1.19)e+09 [0]    
BH55_I       (-1.41+/-0.55)e+11 [90]    (+1.46+/-2.28)e+11 [0]    (-1.60+/-3.72)e+10 [0]    (-0.07+/-3.05)e+09 [0]    
BH55_Q       (+2.05+/-3.10)e+10 [90]    (-1.72+/-4.86)e+10 [0]    (-0.31+/-2.19)e+10 [0]    (-3.06+/-0.87)e+09 [0]    
BH44_I       (-0.41+/-2.03)e+11 [90]    (+0.10+/-2.39)e+11 [0]    (+0.06+/-1.31)e+11 [0]    (-0.01+/-2.71)e+10 [0]    
BH44_Q       (+0.14+/-3.23)e+12 [90]    (+0.02+/-3.67)e+12 [0]    (+0.07+/-2.03)e+12 [0]    (-0.02+/-4.22)e+11 [0]    
BHDC_DIFF       (+8.49+/-0.47)e+11 [90]    (-0.06+/-2.93)e+11 [0]    (-0.16+/-1.01)e+10 [0]    (-0.27+/-2.04)e+09 [0]    
BHDC_SUM       (-2.30+/-0.11)e+11 [90]    (+0.68+/-7.92)e+10 [0]    (-0.44+/-3.33)e+09 [0]    (-0.63+/-5.63)e+08 [0]    

 - Below is the sensing matrix when FPMI is locked with REFL55/AS55, and LO_PHASE is locked with BH44_Q. BH44 response to LO1 is again consistent with zero. Locking LO_PHASE with BH44 is not robust. Also, BHDC_DIFF response to DARM is less, compared with LO_PHASE locked with BH55_Q. This means that BH55 is somehow better than BH44 in our FPMI BHD, which contradicts with simulations (with no contrast defect and DARM offset).

Sensing matrix with the following demodulation phases (counts/m)
{'AS55': -168.5, 'REFL55': 92.32, 'BH55': -110.0, 'BH44': -8.93097234187195}
Sensors       DARM @307.88 Hz           CARM @309.21 Hz           MICH @311.1 Hz           LO1 @315.17 Hz           
AS55_I       (-7.56+/-4.89)e+10 [90]    (+1.61+/-1.05)e+11 [0]    (+0.51+/-2.48)e+10 [0]    (+0.88+/-8.02)e+08 [0]    
AS55_Q       (-3.62+/-0.05)e+11 [90]    (+0.02+/-1.23)e+11 [0]    (+0.67+/-3.73)e+09 [0]    (+0.02+/-1.28)e+08 [0]    
REFL55_I       (+1.09+/-8.12)e+11 [90]    (-1.47+/-2.82)e+12 [0]    (+0.01+/-1.34)e+11 [0]    (+2.20+/-5.29)e+08 [0]    
REFL55_Q       (+0.22+/-1.93)e+11 [90]    (-1.83+/-7.23)e+11 [0]    (+0.02+/-3.18)e+10 [0]    (+0.56+/-1.17)e+08 [0]    
BH55_I       (-1.21+/-0.08)e+12 [90]    (+0.17+/-4.31)e+11 [0]    (-1.24+/-3.02)e+10 [0]    (-0.30+/-3.55)e+09 [0]    
BH55_Q       (-3.83+/-0.30)e+11 [90]    (-0.12+/-1.42)e+11 [0]    (-0.61+/-1.96)e+10 [0]    (-0.21+/-1.49)e+09 [0]    
BH44_I       (-0.22+/-2.01)e+11 [90]    (-0.07+/-2.30)e+11 [0]    (-0.02+/-1.27)e+11 [0]    (+0.08+/-2.62)e+10 [0]    
BH44_Q       (-0.77+/-8.27)e+11 [90]    (-0.13+/-9.51)e+11 [0]    (-0.04+/-5.23)e+11 [0]    (+0.02+/-1.08)e+11 [0]    
BHDC_DIFF       (+1.94+/-0.81)e+11 [90]    (-0.58+/-1.84)e+11 [0]    (+0.18+/-3.53)e+10 [0]    (-0.49+/-3.84)e+09 [0]    
BHDC_SUM       (-2.22+/-0.12)e+11 [90]    (+0.66+/-7.70)e+10 [0]    (-1.04+/-3.97)e+09 [0]    (+0.31+/-6.10)e+08 [0]

Other notes:
 - TRX and TRY are noisier at ~28 Hz when locked with REFL55/AS55 than when locked with POX/POY. DARM signal seems to be contaminated with broad 28 Hz noise. Needs investigation of the cause.
 - BS oplev loops seem to be close to unstable. When FPMI is unlocked, BS is kicked significantly.

Next:
 - Repeat measurement in 40m/17351 with BH44.
 - Compare LO phase noise in MICH configuration when LO_PHASE is locked with BH44 and BH55.
 - Investigate 28 Hz noise in FPMI
 - Tune BS local damping loops

FPMI BHD sensing matrix was measured by an updated method with updated RF demodulation phases for REFL55 and AS55.
Now audio demodulation phase for CARM components is 90 deg to make the sign correct.
Also, oscillators are turned on one by one to reduce contamination between DoFs (especially between MICH and CARM).
These helped a lot in reducing errors.

Sensing matrix with FPMI locked in RF, LO_PHASE locked with BH55_Q using LO1

Sensing matrix with the following demodulation phases (counts/m)
{'AS55': -177.9, 'REFL55': 77.06, 'BH55': -110.0, 'BH44': -8.9}
Sensors       DARM @307.88 Hz           CARM @309.21 Hz           MICH @311.1 Hz           LO1 @315.17 Hz           
AS55_I       (+3.25+/-0.67)e+11 [90]    (-8.63+/-0.41)e+11 [90]    (-1.02+/-1.49)e+09 [0]    (+0.44+/-1.39)e+07 [0]    
AS55_Q       (-6.04+/-0.05)e+11 [90]    (+0.92+/-3.10)e+10 [90]    (+9.10+/-6.78)e+08 [0]    (+0.12+/-2.08)e+07 [0]    
REFL55_I       (+1.18+/-0.03)e+11 [90]    (+2.78+/-0.12)e+12 [90]    (-0.35+/-2.34)e+09 [0]    (-0.94+/-2.38)e+07 [0]    
REFL55_Q       (+5.85+/-0.43)e+09 [90]    (-2.34+/-0.13)e+10 [90]    (+2.39+/-0.38)e+08 [0]    (+3.56+/-7.44)e+06 [0]    
BH55_I       (-3.51+/-3.45)e+10 [90]    (-6.65+/-0.82)e+10 [90]    (-4.91+/-3.03)e+08 [0]    (-1.82+/-0.09)e+09 [0]    
BH55_Q       (+7.86+/-0.29)e+11 [90]    (+2.99+/-0.42)e+11 [90]    (-2.87+/-7.76)e+08 [0]    (+2.81+/-0.15)e+09 [0]    
BH44_I       (-0.34+/-1.99)e+12 [90]    (+0.02+/-1.49)e+12 [90]    (-0.42+/-8.53)e+10 [0]    (-0.01+/-3.08)e+10 [0]    
BH44_Q       (-0.60+/-3.95)e+13 [90]    (-0.01+/-3.00)e+13 [90]    (+0.00+/-1.68)e+12 [0]    (-0.15+/-5.77)e+11 [0]    
BHDC_DIFF       (-9.18+/-0.29)e+11 [90]    (-4.11+/-4.66)e+10 [90]    (+1.46+/-0.10)e+09 [0]    (-1.70+/-0.41)e+08 [0]    
BHDC_SUM       (+2.97+/-0.21)e+11 [90]    (+0.44+/-1.57)e+10 [90]    (-1.01+/-0.06)e+09 [0]    (+2.68+/-0.84)e+07 [0]

 - AS55_Q now has 70% more gain to DARM for some reason (see 40m/17478). Whitening gain haven't changed from 24 dB.
 - There's still some room to tune AS55 RF demodulation phase to maximize DARM response.
 - CARM to REFL55_Q is 100 times smaller than that to REFL55_I; this is good.
 - There's still some room to tune BH55 RF demodulation phase to maximize LO1 response.
 - BH44 doesn't have much response to LO1, probably because LO_PHASE is locked with orthogonal BH55.

Sensing matrix with FPMI locked in RF, LO_PHASE locked with BH44_Q using LO1

 Sensing matrix with the following demodulation phases (counts/m)
{'AS55': -177.9, 'REFL55': 77.06, 'BH55': -110.0, 'BH44': -8.9}
Sensors       DARM @307.88 Hz           CARM @309.21 Hz           MICH @311.1 Hz           LO1 @315.17 Hz           
AS55_I       (+3.94+/-0.52)e+11 [90]    (-1.00+/-0.05)e+12 [90]    (-1.61+/-1.17)e+09 [0]    (+0.45+/-1.52)e+07 [0]    
AS55_Q       (-5.52+/-0.24)e+11 [90]    (+1.19+/-2.99)e+10 [90]    (+1.10+/-0.43)e+09 [0]    (-1.06+/-2.30)e+07 [0]    
REFL55_I       (+8.97+/-0.49)e+10 [90]    (+2.71+/-0.11)e+12 [90]    (-0.38+/-2.28)e+09 [0]    (-0.97+/-2.10)e+07 [0]    
REFL55_Q       (+6.30+/-0.65)e+09 [90]    (-2.01+/-0.12)e+10 [90]    (+2.26+/-0.69)e+08 [0]    (-2.61+/-6.97)e+06 [0]    
BH55_I       (+4.46+/-0.52)e+11 [90]    (-1.52+/-0.27)e+11 [90]    (-1.82+/-0.56)e+09 [0]    (+0.68+/-1.24)e+08 [0]    
BH55_Q       (+9.59+/-0.44)e+11 [90]    (+2.79+/-0.52)e+11 [90]    (+2.75+/-2.49)e+08 [0]    (+2.45+/-1.06)e+08 [0]    
BH44_I       (-0.40+/-2.42)e+12 [90]    (-0.03+/-1.88)e+12 [90]    (-0.03+/-1.13)e+11 [0]    (+0.12+/-4.18)e+10 [0]    
BH44_Q       (-0.19+/-1.09)e+13 [90]    (+0.70+/-7.91)e+12 [90]    (-0.09+/-4.65)e+11 [0]    (+0.11+/-1.34)e+11 [0]    
BHDC_DIFF       (+3.90+/-0.46)e+11 [90]    (+1.06+/-0.18)e+11 [90]    (-4.62+/-1.89)e+08 [0]    (+3.60+/-0.40)e+08 [0]    
BHDC_SUM       (+1.96+/-0.18)e+11 [90]    (-1.08+/-1.29)e+10 [90]    (-8.93+/-1.41)e+08 [0]    (-8.67+/-0.81)e+07 [0]

 - BHDC_DIFF sensitivity to DARM is less than that with LO_PHASE locked with BH55.
 - BH44 sensing matrix has too much error. Requires more averaging time and oscillator amplitude.

Jupyter notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/SensingMatrix/ReadSensMat.ipynb

Next:
 - Tune AS55, BH55, BH44 RF demodulation phases
 - Try measuring sensing matrix for BH44 with more averaging time, oscillator amplitude, and PD whitening gain
 - Repeat measurement in 40m/17351 with BH44 under MICH configuration.
 - Compare LO phase noise in MICH configuration when LO_PHASE is locked with BH44 and BH55.
 - Make a noise budget in MICH BHD.
 - Investigate 28 Hz noise in FPMI
 - Tune BS local damping loops

[Anchal, Yuta]

We have measured LO phase noise in ITMX single bounce, simple MICH and FPMI configurations with LO phase locked with BH55 or BH44.
We found that BH55 and BH44 have almost exactly same noise in ITMX single bounce, but BH44 is noisier than BH55 in MICH and FPMI configurations.
In any case, LO phase can be locked within 0.1 rad RMS, so optical gain fluctuations in BHD_DIFF should be fine for BHD locking.

Method:
 - We have locked ITMX single bounce vs LO, AS beam under MICH locked with AS55_Q vs LO, and AS beam under FPMI locked with REFL55 & AS55 vs LO, using BH55_Q or BH44_Q
 - In each IFO configuration, we have minimized I phase to set RF demodulation phases for BH55 and BH44.
 - In each IFO configuration, optical gain of BH55_Q and BH44_Q was measured by elliptic fit of X-Y plot for BH55_Q vs BHDC_A or BH44_Q vs BH55_Q.
 - For each LO_PHASE lock, feedback gain was adjusted to set the UGF to around 50 Hz, and actuator used was LO1.
 - LO_PHASE_IN1 was calibrated using the measured optical gain, and LO_PHASE_OUT was calibrated using LO1 actuator gain of 26.34e-9 /f^2 m/counts measured in 40m/17285.
 - To convert meters in radians, 2*pi/lambda is used (which means dark fringe to dark fringe is pi).
 - Below summarizes the result of RF demodulation phases and optical gains (whitening gains were 45 dB for BH55 and 39 dB for BH44). RF demod phases aligns well with previous measurement, but optical gain for BH44 seems higher by an order of magnitude compared with 40m/17478 (whitening gain changed??). Optical gain for BH55_Q is consistent with previous measurement in 40m/17506 (note the demodulation phase change).

LO_PHASE lock in ITMX single bounce
        Demod phase  Optical gain     filter gain
BH55_Q  -99.8 deg    7.6e9 counts/m   -0.3
BH44_Q  -6.5 deg     1.3e10 counts/m  -0.15

LO_PHASE lock in MICH
        Demod phase  Optical gain     filter gain
BH55_Q  -67.7 deg    6.1e8 counts/m   -3.9
BH44_Q  -31.9 deg    8.5e8 counts/m   -3.1

LO_PHASE lock in FPMI
        Demod phase  Optical gain     filter gain
BH55_Q  35.7 deg     3.4e9 counts/m   -0.65
BH44_Q  -9.3 deg     4.3e10 4.3e9 counts/m  -0.84  (Typo fixed on Apr 18, 2023 by YM)

Result:
 - Attached are calibrated LO phase noise spectrum in different IFO configurations.
 - In ITMX single bounce, LO phase noise estimated using BH55 and BH44 are almost equivalent, and LO phase noise in-loop is ~0.04 rad RMS.
 - In MICH, LO phase noise estimated using BH44 is noisier than BH44 at around 20-60 Hz for some reason. LO phase noise in-loop is ~0.04 rad RMS for both cases.
 - In FPMI, LO phase noise estimated using BH44 is noisier than BH44 above ~20 Hz for some reason. LO phase noise in-loop is ~0.03 rad RMS for both cases. Dark noise is not limiting the measurement at least below 1 kHz.

Jupyter notebook: /opt/rtcds/caltech/c1/Git/40m/measurements/BHD/BH55_BH44_Comparison.ipynb

Next:
 - Lock MICH BHD with BH55 and BH44, and compare LO phase noise contributions to MICH sensitivity
 - Investigate why BH44 is noisier than BH55 in MICH and FPMI (offsets? contrast defect? mode-matching?)
 - Reduce 60 Hz + harmonics in BH55 and BH44

[Paco, Yuta]

MICH was locked with balanced homodyne readout with LO phase locked using BH55_Q and BH44_Q.
It turned out that BH44_Q gives better LO phase in MICH configuration (in FPMI, BH55_Q is better; see 40m/17506).
LO phase noise seems to contribute to MICH sensitivity in 30-200 Hz region in BH55 case, and 30-100 Hz in BH44 case (this was not the case in FPMI BHD, see 40m/17392).
The mechanism for this coupling needs investigation.

MICH BHD sensing matrix:
 - MICH BHD sensing matrix was measured when MICH is locked with AS55_Q and LO_PHASE is locked with BH55_Q or BH44_Q.
 - MICH UGF was at around 50 Hz, and LO_PHASE UGF was at around 10 Hz.
 - BHDC_DIFF had better sensitivity to MICH when LO_PHASE was locked with BH44_Q.
 - BH44 component was not measured well.

MICH sensing matrix with MICH locked with AS55_Q and LO_PHASE locked with BH55_Q

Sensing matrix with the following demodulation phases (counts/m)
{'AS55': 2.1, 'REFL55': 76.01784975834194, 'BH55': -63.16236453101908, 'BH44': -39.01036239539396}
Sensors       MICH @311.1 Hz           LO1 @315.17 Hz           
AS55_I       (+0.40+/-6.23)e+07 [0]    (-0.83+/-3.01)e+07 [0]    
AS55_Q       (+1.38+/-0.26)e+09 [0]    (+0.76+/-6.58)e+07 [0]   
BH55_I       (-3.22+/-0.37)e+09 [0]    (-0.81+/-8.42)e+07 [0]    
BH55_Q       (+4.03+/-0.52)e+09 [0]    (-4.01+/-1.05)e+08 [0]    
BH44_I       (-0.06+/-4.22)e+10 [0]    (+0.29+/-4.63)e+10 [0]    
BH44_Q       (-0.03+/-3.21)e+11 [0]    (+0.21+/-3.12)e+11 [0]    
BHDC_DIFF       (-1.07+/-0.39)e+09 [0]    (-3.35+/-7.47)e+07 [0]    
BHDC_SUM       (+2.07+/-0.57)e+08 [0]    (+0.32+/-1.65)e+07 [0]

MICH sensing matrix with MICH locked with AS55_Q and LO_PHASE locked with BH44_Q

Sensing matrix with the following demodulation phases (counts/m)
{'AS55': 2.1, 'REFL55': 76.01784975834194, 'BH55': -63.16236453101908, 'BH44': -39.01036239539396}
Sensors       MICH @311.1 Hz           LO1 @315.17 Hz           
AS55_I       (+0.22+/-5.36)e+07 [0]    (+0.91+/-3.10)e+07 [0]    
AS55_Q       (+1.43+/-0.08)e+09 [0]    (-0.78+/-7.45)e+07 [0]   
BH55_I       (+4.92+/-5.18)e+08 [0]    (-5.20+/-7.93)e+07 [0]    
BH55_Q       (-1.45+/-0.75)e+09 [0]    (+1.76+/-0.59)e+08 [0]    
BH44_I       (+0.01+/-1.14)e+11 [0]    (+0.02+/-1.08)e+11 [0]    
BH44_Q       (+0.03+/-1.95)e+11 [0]    (+0.07+/-1.98)e+11 [0]    
BHDC_DIFF       (+3.05+/-0.17)e+09 [0]    (+1.70+/-2.51)e+07 [0]    
BHDC_SUM       (-2.33+/-0.23)e+08 [0]    (+0.19+/-1.53)e+07 [0]

  - Jupyter notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/SensingMatrix/ReadSensMat.ipynb

MICH BHD locking:
 - MICH lock with AS55_Q was handed over to BHD_DIFF using following ratio:
C1:LSC-PD_DOF_MTRX_3_4 = 1 (AS55_Q to MICH_A)
C1:LSC-PD_DOF_MTRX_4_34 = -1.34 (BHDC_DIFF to MICH_B, when BH55_Q is used)
C1:LSC-PD_DOF_MTRX_4_34 = 0.47 (BHDC_DIFF to MICH_B, when BH44_Q is used)

MICH BHD noise budget:
 - FM2 of C1:CAL-MICH_CINV was updated to 1/1.4e9 = 7.14e-10 to use measured optical gain.
 - Dark noise was measured at C1:CAL-MICH_W_OUT with PSL shutter closed, PD DOF matrix at various settings for various readout scheme.
 - Attachment #1 shows MICH sensitivity with MICH locked using AS55_Q (green), BHD_DIFF under BH55_Q (blue), BHD_DIFF under BH44_Q (red). BH44 case gives the least noise due to larger optical gain. However, there are excess noise at around 100 Hz, when MICH is locked with BHD_DIFF. The excess noise (bump at around 50 Hz) was similar to what we saw in LO phase noise estimate (40m/17511).
 - At low frequencies below ~30 Hz, the MICH sensitivity is probably limited by seismic noise, as it alignes with FPMI DARM sensitivity (orange curve; measured in 40m/17468).
 - Attachemnt #2 and #3 show estimate of LO phase noise contribution to MICH sensitivity in BH55 case and BH44 case. The coupling was estimated by measuring a transfer fuction from BH55_Q/BH44_Q to MICH_W_OUT. As there was significant coherence in 30-200 Hz region in BH55 case, and 30-100 Hz in BH44 case, transfer function value in that regions was used to estimate the coupling.
 - The coupling was estimated to be the following

 2e-10 m/count for BH55_Q to MICH_W_OUT (0.035 m/m using BH55_Q calibration factor to LO1 motion of 1.76e8 counts/m)
 2e-11 m/count for BH44_Q to MICH_W_OUT

 - Diaggui file: /opt/rtcds/caltech/c1/Git/40m/measurements/LSC/MICH/MICH_Sensitivity_Live.xml

Next:
  - Calibrate BH44_Q to LO1 motion
  - Measure transfer function from LO1 motion to BHD_DIFF under BH44 and BH55
  - Find out the cause of 50 Hz bump in LO phase noise
  - Compare LO phase noise coupling with simulations

[Paco, Yuta]

We locked PRMI in sideband using REFL55_I and REFL55_Q.
Lock is not quite stable probably due to alignment fluctuations, and power recylicing gain is breathing.

PRMI preparations:
 - We aligned PRM using PRY (PRM-ITMY) cavity. Aligning PRM to oplev QPD center or last PRM alignment values in May 2022 (! see 40m/16875) didn't work, but we were in the middle of these two, both in pitch and yaw.
 - After this, we centered PRM oplev, aligned REFL camera, POP RFPD (which provides POP22, POP110, and POPDC), and REFL11.

PRY/PRX locking:
 - PRY/X was locked using REFL55_I or REFL11_I. Locking configuration which gives UGF of ~100 Hz was as follows

REFL55_I (24 dB whitening gain, 76.02 deg demod angle) C1:LSC-PRCL_GAIN=-0.03
REFL11_I (18 dB whitening gain, 32.55 deg demod angle) C1:LSC-PRCL_GAIN=-0.8
FM4,5 used for acquisition, FM1,2,6,9 turned on triggered.

 - Attachment #1 is the measured OLTF when PRY was locked.
 - When PRY is flashing, ASDC_OUT, POPDC_OUT, POP22_I, POP11_Q flashes upto 0.33, 1000, 30, 80, respectively.

PRMI locking:
 - PRMI was locked using REFL55_I for PRCL and REFL55_Q for MICH using the following configurations to give UGF of ~100 Hz for both DoF.

PRCL
  REFL55_I (24 dB whitening gain, 76.02 deg demod angle) C1:LSC-PRCL_GAIN=-0.03
  FM4,5 for acquisition, FM1,2 turned on triggered using POPDC.
  Actuating on 1 * PRM

MICH
  REFL55_Q (24 dB whitening gain, 76.02 deg demod angle) C1:LSC-MICH_GAIN=+0.9
  FM4,5 for acquisition, FM1,2 turned on triggered using POPDC.
  Actuating on 0.5 * BS - 0.275 * PRM

 - REFL55 demodulation phase was the same as FPMI and PRY. We checked this is roughly enough by measuring the sensing matrix to minimize PRCL component in Q.
 - MICH actuation of PRM/BS ratio was roughly tuned by minimizing the sensing of MICH component in REFL55_I.
 - PRCL and MICH gain was estimated by measuring the amplitude of error signals in PRY or PRM-misalgined MICH, and comparing that in PRMI.
 - Attachment #2 shows the screenshot of the configuration.
 - Attachment #3 and #4 are measured OLTF for PRCL and MICH.
 - Attachment #5 shows the time series data when PRMI is locked.

Next:
 - Tune PRM local damping
 - Tune REFL55 demodulation phase better by measuring the sensing matrix
 - Measure PRM actuation efficiency to check what is the right BS/PRM balancing
 - Estimate power recycling gain and compare with expectations
 - Lock PRMI using REFL11, AS55
 - PRMI BHD

PRM actuator was calibrated using PRY by comparing the actuation ratio between ITMY.
It was measured to be

PRM : -20.10e-9 /f^2 m/counts

This is consistent with what we have measured in 2013! (40m/8255)

Method:
 - Locked PRY using REFL55_I using the configuration described in 40m/17521 (UGF of ~100 Hz)
 - Measured transfer function from C1:LSC-(ITMY|PRM)_EXC to C1:LSC-PRCL_IN1
 - Took the ratio between ITMY actuation and PRM actuation to calculate PRM actuation, as ITMY actuation is known to be 4.90e-9 /f^2 m/counts (40m/17285).

Result:
 - Attachment #1 is the measured TF, and Attachment #2 is the actuator ratio PRM/ITMY.
 - The ratio was -4.10 on average in 70-150 Hz region, and PRM actuation was estimated to be 4.90e-9 * -4.10 /f^2 m/counts.

MICH actuator for PRMI lock:
 - When BS moves in POS by 1, BS-ITMX length stays the same, but BS-ITMY length changes by sqrt(2), so MICH changes by sqrt(2) and PRCL changes by -sqrt(2)/2.
 - So PRM needs to be used to compensate for this, and the ratio will be BS + k * PRM, where

 k = 26.54e-9/sqrt(2) / -20.10e-9 * sqrt(2)/2 = -0.66

 - So, good MICH actuator will be 0.5 * BS - 0.33 * PRM, which is not quite consistent with the rough number we had yesterday (-0.275; 40m/17521), but agrees with the Gautam number (-0.34; 40m/15996).
 - PRMI sensing matrix for REFL55 needs to be checked again.

Summary of actuation calibration so far:
 They are all actuator efficiency from C1:LSC-{$OPTIC}_EXC

BS   : 26.54e-9 /f^2 m/counts in MICH (40m/17285)
ITMX :  4.93e-9 /f^2 m/counts (40m/17285)
ITMY :  4.90e-9 /f^2 m/counts (40m/17285)
LO1  : 26.34e-9 /f^2 m/counts (40m/17285)
LO2  :  9.81e-9 /f^2 m/counts (40m/17285)
AS1  : 23.35e-9 /f^2 m/counts (40m/17285)
AS4  : 24.07e-9 /f^2 m/counts (40m/17285)
ETMX : 10.91e-9 /f^2 m/counts (40m/16977, 40m/17014)
ETMY : 10.91e-9 /f^2 m/counts (40m/16977)
MC2 : -14.17e-9 /f^2 m/counts in arm length (40m/16978)
MC2 :   5.06e-9 /f^2 m/counts in IMC length (40m/16978)
MC2 :  1.06e+05 /f^2 Hz/counts in IR laser frequency (40m/16978)
PRM : -20.10e-9 /f^2 m/counts (40m/17522)

PRMI sensing matrix was measured under PRMI locked with REFL55_I and Q.
MICH actuator is 0.5*ITMX-0.5*ITMY (to have more pure MICH, according to 40m/15996) and PRCL actuator is PRM.
RF demod phases seem to be good within a degree or so to minimize PRCL component in Q.

Sensing matrix with the following demodulation phases (counts/m)
{'AS55': 2.1, 'REFL55': 76.02, 'REFL11': 32.63833493469488}
Sensors       MICH @311.1 Hz           PRCL @313.31 Hz           
AS55_I       (+0.31+/-1.48)e+09 [90]    (+6.56+/-2.23)e+10 [0]    
AS55_Q       (-3.49+/-0.87)e+08 [90]    (+4.62+/-1.80)e+09 [0]    
REFL55_I       (-1.52+/-5.61)e+09 [90]    (+3.21+/-1.36)e+11 [0]    
REFL55_Q       (+8.77+/-0.46)e+09 [90]    (+5.01+/-3.63)e+09 [0]    
REFL11_I       (-0.23+/-1.92)e+08 [90]    (+1.13+/-0.47)e+10 [0]    
REFL11_Q       (+0.39+/-2.14)e+07 [90]    (-4.00+/-9.79)e+07 [0]    

Phase for AS55 to minimize PRCL in Q is 6.14+/-2.08 deg (4.04+/-2.08 deg from current value)
Phase for REFL55 to minimize PRCL in Q is 76.91+/-0.75 deg (0.89+/-0.75 deg from current value)
Phase for REFL11 to minimize PRCL in Q is 32.44+/-0.50 deg (-0.20+/-0.50 deg from current value)

Next:
 - Lock PRMI in carrier
 - PRG is not so stable; Measure g-factor of PRC using Kakeru-Gupta method (40m/8235)

that is really a lot of high precision for the REFL_11 demod phase...

for this kind of measurement, I wish we had a python code that would plot this measurment relative to our Finesse/PyKat model so we know if this table is like "Oh, nothing to see here." or "Wow! that's a Nobel prize worthy measurement !!"

[Paco, Yuta]

We measured the power around BHD PDs to see if the numbers make sense.
Measured values are 10-20% less than expected values, which sounds good.
BHD DC PDs require slight reduction of gains to avoid saturation.

What we measured and result:
 - We measured the power with a Newport power meter (Model 840) for BHD A and B right after the viewport (A path and B path), in front of BHDC A and B, and in front of BH44 and BH55.
 - Note that BH44 is a pick-off from A path and BH55 is a pick-off from B path (see Attachment #1). A path also has a pick-off to BHD camera. So the measured numbers roughly sum up.
 - Measurement was done with LO beam only (misaligned AS4) and PRM misaligned, and PRMI carrier locked (forgot to misalign AS beam, but the most of the power is from LO beam).
 - Results are the following.

        LO beam only        PRMI carrier locked
        (PRM misalgined)    
A path  450 +/- 10 uW       110 +/- 10  mW
B path  360 +/- 10 uW       91 +/- 5 mW
BHDC A  330 +/- 10 uW       74 +/- 1 mW
BHDC B  320 +/- 10 uW       74 +/- 4 mW
BH44    100 +/- 3 uW        27 +/- 2 mW
BH55    3 +/- 1 uW          10 +/- 2 mW

                    LO beam only        PRMI carrier locked
                    (PRM misalgined)
C1:HPC-BHDC_A_OUT16 104                 saturated at ~22000
C1:HPC-BHDC_B_OUT16 103                 saturated at ~22000

Consistency check with previous measurement:
 - Power with LO beam only was measured in July 2022 (elog 40m/17046).
 - Compared with values in July 2022, it is now 10-20% less. This could be explainable by PMC transmission power drop on Dec 27, 2022 by ~10% (elog 40m/17390).

Expected values:
 - Expected values using PSL output of 890 mW (measured in elog 40m/17390) and calculated PRG of 13.4 (elog 40m/17532) are the following (see, also elog 40m/17040). Note that BHD BS has the transmission of 44% and the reflectivity is 56%.

A path, LO beam only
 890 mW * 0.9 (IMC transmission?) * 5.637%(PRM) * 2.2%(PR2) * 56%(BHDBS) = 560 uW
B path, LO beam only
 890 mW * 0.9 (IMC transmission?) * 5.637%(PRM) * 2.2%(PR2) * 44%(BHDBS) = 440 uW
A path, PRMI carrier locked
 890 mW * 0.9 (IMC transmission?) * 13.4(PRG) * 2.2%(PR2) * 56%(BHDBS) = 130 mW
B path, PRMI carrier locked
 890 mW * 0.9 (IMC transmission?) * 13.4(PRG) * 2.2%(PR2) * 44%(BHDBS) = 100 mW

  - Measured values are 10-20% less than expected values.

BHDC PD saturation:
 - Expected counts for C1:HPC-BHDC_A_OUT16 when PRMI carrier locked using LO beam only numbers are

 104 / 5.637% * 13.4 = ~25000

 - So, we are barely saturating.

Next:
 - Measure PRG using POPDC.
 - Reduce transimpedance gain of BHDC A and B by small amount to avoid saturation.

[Anchal, Yuta]

We have repeated LO phase noise measurement done in elog 40m/17511.
Method we took was the same, but this time, we used (1+G)*[C1:HPC-LO_PHASE_IN1]/[optical gain] to estimate the free-running noise, instead of using [C1:HPC-LO_PHASE_OUT] multiplied by LO1 actuator gain.
We confirmed that both method agrees down to ~ 10 Hz (at lower frequencies, OLTF measurement is not robust; we used interpolated measured OLTF (Attachment #1) for compensation).
Below is the summary of optical gains etc measured today.
Filter gains were adjusted to have UGF of 50 Hz for all.

LO_PHASE lock in ITMX single bounce
        Demod phase  Optical gain     filter gain
BH55_Q  -102.7 deg    6.9e9 counts/m  -0.34
BH44_Q  -5.7 deg     1.3e10 counts/m  -0.17

LO_PHASE lock in MICH
        Demod phase  Optical gain     filter gain
BH55_Q  -72.6 deg    8.7e8 counts/m   -4.4
BH44_Q  -27.6 deg    8.8e8 counts/m   -2.2

LO_PHASE lock in FPMI
        Demod phase  Optical gain     filter gain
BH55_Q  24.2 deg     3.7e9 counts/m   -0.67
BH44_Q  2 deg        5.3e8 counts/m   -4.4  (An order of magnitude smaller than elog 40m/17511)

The values are consistent with elog 40m/17511, except for BH44 in FPMI.
It took sometime to robustly rock LO_PHASE with BH44_Q in FPMI today.
After some alignment, offset tuning and demod phase tuning, it finally worked.
Demod phase of BH44 was tuned to have more DC signal when LO_PHASE was locked with BH55_Q, considering that BH55 and BH44 are orthogonal.
It actually created BH44_I having more amplitude (some noise?) than BH44_Q, but BH44_Q was more coherent to LO_PHASE fringe in BH55_Q.
It might be related to why we are not dark noise limited for BH44_Q, while BH55_Q is dark noise limited in FPMI, and why we cannot lock FPMI BHD with BH44.

[Mayank, Paco, Yohanathan, Yuta]

We checked if coil dewhitening switch is working by measuring transfer function from coil outputs to oplev pitch and yaw.

Method:
 - Turned off oplev damping loops (this actually changed the result, this means that oplev loops have quite high UGFs)
 - Measured transfer functions from C1:SUS-PRM_(UL,UR,LR,LL)COIL_EXC to C1:SUS-PRM_OL_(PIT|YAW)_OUT, with SimDW and InvDW filters on/off.
 - Injected excitations are about 30000 at 100 Hz and 3000 at 10 Hz.
 - When SimDW and InvDW filters are on, analog dewhitening filter should be off, so it should give suspension mechanical response and other filter shapes in coil driver.
 - When SimDW and InvDW filters are off, analog dewhitening filter should be on, so it should give the same transfer function with analong dewhitening filter.
 - Taking the ratio between two should give analog dewhitening filter shape, which is zero at [70.7+i*70.7,70.7-i*70.7] Hz and pole at [10.61+i*10.61,10.61-i*10.61] Hz, from SimDW filter.

Notebook: /opt/rtcds/caltech/c1/Git/40m/measurements/SUS/PRM/CoilDewhitening/PRMCoilDewhiteningCheck_COIL2OL.ipynb

Result:
 - Attachment #1 shows the result for each coil. 4th panel is the ratio, which should match with analog dewhitening filter shape.
 - The result looks consistent with our expected analog dewhitening filter shape.

Next:
 - Repeat this measurement for other suspensions.
 - PRM suspension response have residual frequency dependence from 1/f^2. What is this?

[Mayank, Paco, Yuta]

IFO alignment is not good.
It seems like the input pointing drifted a lot during PRMI and noise measurements, and beam spot on both ITMY and ITMX are not good.
They are so off from the center (by about a beam size mainly in yaw) that ASS cannot handle.
Current situation is as attached (compare with good alignment in March 23 40m/17521).
Yarm ASS is not working, Xarm ASS is not working, POP is clipped, AS is clipped

Message: Always check the alignment from TTs using BHDC_A/B, and always check the arm alignment, even if you are only doing PRMI. (Follow the steps in 40m/17277)

[Paco, Yuta]

Measured power recycling gain at POP is 10(2), consistent with our expectation.

We measured power at POP with ITMY single bounce and estimated power recycling gain in PRMI.
As POP RFPD (Thorlabs PDA10CF; used for POPDC, POP22, POP110) was saturating, we attenuated the input power by OD2.5 ND filter.
Power recycling gain was estimated to be 10(2), roughly consistent with our expectation of 13.2 (40m/17532).

What we did:
 - Realigned POP path in ITMX table after aligning the IFO. It turned out that when POP power measurements were done in 40m/17532, POP was not well aligned.
 - We measured the power with ITMY single bounce at POP right after the viewport and in front of POP RFPD.
 - We also measured counts in C1:LSC-POPDC_OUT under ITMY single bounce, PRMI carrier locked, and MICH locked with PRM misaligned, with different ND filters.

Results:

 - Estimated power recycling gain is 1600(300) / (9.0(6) / 5.637%) = 10(2) .

Expected values:
 - Expected power using PSL output of 890 mW (measured in elog 40m/17390) under ITMY single bounce at POP is the following, and is consistent with the measurement.
[a] 890 mW * 0.9 (IMC transmission?) * 5.637%(PRM) * (1-2.2%)(PR2) * 50%(BS) * (1-1.384%)(ITMY) * 50%(BS) * 2.2%(PR2) = 0.240 mW

 - Calibration for C1:LSC-POPDC_OUT into power at POP RFPD is
[b] 437 counts / 0.108 mW = 4.0e3 counts/W.

 - Thorlabs PDA10CF has a transimpedance gain of 1e4 V/A and output range of 0-5 V. So, the saturation happens at 5 V / (1e4 V/A * 0.8 A/W) = 0.625 mW. We ended up attenuating POP RFPD with OD2.5 to make it not saturating (0.4 mW on the PD with PRMI carrier lock).

[Paco, Yuta]

RF FPMI is recovered after c1sus DAC-0 card replacement

Summary:
 - We wanted to check if FPMI locks after DAC-0 card relacement (40m/17620).
 - 60 Hz noise similar to what we saw in February prevented us from locking FPMI stably, but fixed it by turning off FM9 of coil output filters in MC1 and MC3 (40m/17462).
 - There are slight changes in locking gains, but it now locks reliably.

FPMI locking:
 - MICH: 1 for REFL55_Q, MICH_GAIN=18 (used to be 11) gives UGF of 45 Hz
 - DARM: 1 for AS55_Q, DARM_GAIN=0.044 (used to be 0.04) gives UGF of 134 Hz
 - CARM: 0.567 (used to be 0.496) for REFL55_I, CARM_GAIN=0.011 gives UGF of 224 Hz
 - Attachment #1 shows all the OLTFs.

60 Hz noise:
 - FPMI locking was not stable, and we moved back to YARM locking to see if 60 Hz noise is higher or not.
 - Attachment #2 shows 60 Hz noise measured with MC_F and YARM. The noise was actually similar to what we saw in 40m/17461, so we checked MC1 and MC3 dewhitening
 - FM9 of coil output filters was turned on for some reason (probably because of burts we were doing when fixing c1sus). MC1 and MC3 FM9 ELP28 filters should be off.
 - This made FPMI locking stable and 60 Hz noise lower by more than an order of magnitude (Attachment #3).

[Mayank, Yuta]

We noticed that c1sus2 crashed again on June 8, 2023 17:25 UTC (Yarm has been locked since 1:49:24 UTC, with a short interruption 10:31:51-10:32:29 UTC due to IMC unlock; Attachment #1 and #2).
Following 40m/17335, we fixed it by running

controls@c1sus2:~$ rtcds restart --all

"global diag reset" made all FE STATUS green.
Burt restored at 2023/Jun/8/09:19 for c1sus2 models, and BHD optics are now damping OK.
MC suspensions, BS, PRM, SRM, ITMX, ITMY were also affected (BS, PRM, SRM watchdogs even tripped), and c1x02 showed DAC error (Attachment #3).
Following 40m/17606, we also had to run

./opt/rtcds/caltech/c1/Git/40m/scripts/cds/restartAllModels.sh

Now all look fine.

[Paco, Mayank, Yuta]
CARM Common Mode Board works for YARM locking

For using it for FPMI and PRFPMI, we tested the CARM Common Mode Board by implementing the high bandwidth YARM lock in a way similar to what Paco did in 2021 (40m/16248).
(YARM locking work was done yesterday and modeling was done today,)

What we did:
  - Connected POY11_I MON to IN1 of CARM Common Mode Board. (POY11_I MON is basically similar to POY11_I_ERR as C1:LSC-POY11_PHASE_R=-9.033 deg is almost zero).
  - Locked YARM at UGF of around 200 Hz using POY11_I_ERR.
  - Turned on CARM Common Mode Board with C1:LSC-CM_REFL1_GAIN=+25 dB, C1:IOO-MC_AO_GAIN=-2dB, C1:LSC-CM_REFL_OFFSET=2.972 V to remove the offset. (BOOST OFF, SUPER BOOST 0, POLARITY PLUS, OPTIONs Disabled). Increasing the gains unlocked the lock (+30 dB, +4dB is probably the maximum we could get).
  - Measured OLTF of CARM loop at TP1A and TP2A of CARM Common Mode Board using Moku Pro.
  - Modeled YARM loop by fitting the measured OLTF data (G_YARM; plotted in blue curve in Attachment #1).
  - Modeled IMC loop by fitting the measured OLTF data (G_IMC; plotted in green curve in Attachment #1; OLTF data is from 40m/17009).
  - Measured CARM Common Mode Board transfer function from IN1 to AO output. This was basically flat upto 1 MHz in 0dB setting for all (Attachment #2).
  - Using CARM OLTF can be calculated as

G_CARM = G_IMC / O_IMC * O_YARM * C_YARM * F_CMB / (1+G_YARM) = r * G_IMC * C_YARM * F_CMB / (1+G_YARM)

  where C_YARM is YARM cavity pole (~4 kHz), O_IMC and O_YARM are IMC REFL and POY11_I optical gains. r is some gain used to fit the data. F_CMB is a CARM Common Mode Board transfer function, which is basically flat.
 - OLTF of CARM loop measured at CARM Common Mode Board can be calculated as

G_meas = G_CARM / (1 + G_IMC)

Result:
 - Attachment #1 gives modeled G_meas (brown line) and measured G_meas (pink dots). r was tuned to match the overall gain. The measurement and the model matches well.
 - G_CARM (purple line) also looks stable.

Next:
  - Try high bandwidth CARM loop in FPMI

IFO alignment is in a strange state.
BHD is not fringing, and misalignment script is not working properly

IFO alignment status
 - YARM ASS is working
 - XARM ASS is not working (because of ETMX coil driver upgrade)
 - Attached is the current alignment when YARM and XARM are both aligned, AS4 misaligned. Powers at photo diodes are as follows.

>cdsutils avg -s 10 C1:PSL-PMC_PMCTRANSPD C1:IOO-MC_TRANS_SUMFILT_OUT C1:LSC-TRY_OUT_DQ C1:HPC-BHDC_A_OUT C1:HPC-BHDC_B_OUT C1:LSC-TRX_OUT_DQ
C1:PSL-PMC_PMCTRANSPD 0.688543850183487 0.0010497113504850193
C1:IOO-MC_TRANS_SUMFILT_OUT 13378.8802734375 58.42096336275247
C1:LSC-TRY_OUT_DQ 1.0218201756477356 0.006230110889854089
C1:HPC-BHDC_A_OUT 34.033762741088864 0.1877582940472513
C1:HPC-BHDC_B_OUT 33.95858993530273 0.1951729492341625
C1:LSC-TRX_OUT_DQ 0.9446217834949493 0.01777568349190775

 - After this, we usually misalign ETMY, ETMX, ITMY to have LO-ITMX fringe in BHD DCPDs (elog #17277), but it seems like it is hard to see the fringe by aligning AS beam with SR2 and AS4 we usually use.
 - Also, misalign/restore script we use are not working properly. Alignment changes a lot when restored after misalignment.
 - We also found that "gain_offset" of gain(0.48) for ETMY coil outputs was turned off.  This changed the alignment offsets to get the correct alignment. This probably also affected LSC.

Next:
 - Recommission XARM ASS with updated ETMX coil driver
 - Check the "gain_offset" filter for ETMY and update relevant gains
 - Check the misalignment script.
 - Align LO-AS fringe

"gain_offset" for ETMY coil outputs has been turned on

As mentioned in elog #17671, the "gain_offset" of gain(0.48) for ETMY coil outputs had been turned off for some reason.
I have turned on all of the "gain_offset" for ETMY coils and have changed the alignment offsets for ETMY to compensate the effect of "gain_offset": 

P: 2703 -> 5631
Y: -2296 -> -4783

After the operation above, I confirmed that the Y arm is flashing and the OPLEV laser is hitting on the QPD.

• ETMX damping loops are not good. ETMX is moving by ~10 urad (if oplev is correctly calibrated), and beam spot moves by ~0.5 beam spot on ETMX when Xarm is locked. TRX fluctuates by ~10%. Simply tuning gains did not solve.
• ETMX does not come back after putting some offset to misalign and remove the offset to align. Hysterisis makes me hysteric.
• Xend acromag is removed, and we cannot access Xend shutter and ETMX slow channels.
• XARM ASS is not working.
• Yend laser is not working.

PRMI carrier on 1f now locks for ~1min but not more. Below is the configuration.
The configuration is the same as basically the same as 40m/17578, except for PRCL gain. Maybe the RF demodulation phases changed?

MICH
  - AS55_Q (24 dB whitening gain, C1:LSC-AS55_PHASE_R=2.1 deg)
  - C1:LSC-MICH_GAIN = 0.4 gives UGF of around 30 Hz
  - -0.33*PRM+0.5*BS
PRCL
  - REFL11_I (18 dB whitening gain,C1:LSC-REFL11_PHASE_R = 32.6 deg)
  - C1:LSC-PRCL_GAIN = -0.005 gives UGF of around 150 Hz
  - PRM

Lock stretches:
  - 1373325207-1373325231 (with MICH @ 211.1 Hz and PRCL 311.31 Hz lines on)
  - 1373328637-1373328718 (without lines)

Next:
 - Check PRM actuation
 - Measure beam spot positions on PRM, PR2, PR3 and BS (with PRX or PRY configurations to make it easier)
 - Investigate why PRG fluctuates so much
 - Sensing matrix measurement (need longer lock stretch)
 - Try PRMI 3f for PRFPMI

I did the same test we did in 40m/17616 to see if DACs are working fine for ITMX and ITMY.
I used awggui to excite all the coil outputs of the optic with 0.1 Hz with an amplitude of 3000 counts, and checked VMons.
Found that ITMX, ITMY, PRM and BS face coil DAC outputs cannot drive positive voltages. In contrast, SRM is fine (see attached).
This is consistent with what we have found in June (40m/17616).
We need to investigate what is causing this DAC failure...

I just wanted to take the same time series data I took back in 2012 (40m/6874).
ALS noise look much better than 2012, but MICH contrast during both arms hold on IR resonance with ALS looks pretty bad compared with 2012, which indicate unbalance of the arms.

[JC, Yuta]

PMC was unlocked from last night, so we aligned PMC
c1sus2 crashed again during the PMC alignment, so we ran

./opt/rtcds/caltech/c1/Git/40m/scripts/cds/restartAllModels.sh

We burt restored to 2023/Aug/14/16:19 by

./opt/rtcds/caltech/c1/Git/40m/scripts/cds/burtRestoreAndResetSUS.sh /opt/rtcds/caltech/c1/burt/autoburt/snapshots/2023/Aug/14/16:19

[JC, Yuta]

Transitioning from 1f to 3f in both PRMI carrier and sideband is now smooth once you have PRMI nicely aligned (key is to tweak TT1 and TT2).
We measured the sensing matrix for PRMI carrier/sideband locks and measured MICH and PRCL sensitivity with different locking configurations.
PRCL sensitivity does not change between different sensors, but MICH sensitivity gets worse with REFL33_Q.

PRMI sensing matrix during 1f carrier lock:
(whitening gains: AS55 24 dB, REFL55 24 dB, REFL11 15 dB, REFL33 30 dB, REFL165 24 dB)

Sensing matrix with the following demodulation phases (counts/m)
{'AS55': 2.1, 'REFL55': 76.02, 'REFL11': 32.638, 'REFL33': -19.275, 'REFL165': 108.88}
Sensors       MICH @211.1 Hz           PRCL @313.31 Hz           
AS55_I       (+1.77+/-0.44)e+09 [90]    (+3.31+/-0.93)e+09 [0]    
AS55_Q       (+1.45+/-0.10)e+10 [90]    (-0.90+/-1.15)e+09 [0]    
REFL55_I       (-0.06+/-2.51)e+12 [90]    (+1.17+/-0.18)e+13 [0]    
REFL55_Q       (+0.32+/-6.10)e+11 [90]    (-4.99+/-0.38)e+12 [0]    
REFL11_I       (-1.28+/-0.93)e+10 [90]    (+1.16+/-0.07)e+12 [0]    
REFL11_Q       (-0.07+/-1.76)e+09 [90]    (+3.47+/-0.25)e+10 [0]    
REFL33_I       (-3.00+/-1.02)e+09 [90]    (+1.65+/-0.10)e+11 [0]    
REFL33_Q       (+2.06+/-0.64)e+09 [90]    (-8.01+/-0.55)e+09 [0]    
REFL165_I       (-4.16+/-0.51)e+09 [90]    (+8.11+/-0.52)e+10 [0]    
REFL165_Q       (-2.85+/-0.21)e+09 [90]    (-5.59+/-0.56)e+09 [0]    

Ratio AS55_Q/REFL33_Q for MICH was 1.45e10/2.06e9 = 7.0 (it was 3.9 in 40m/17755)
Ratio REFL11_I/REFL33_I for PRCL was 1.16e12/1.65e11 = 7.0 (it was 6.7 in 40m/17755)

PRMI sensing matrix during 3f sideband lock:
(whitening gains: AS55 24 dB, REFL55 24 dB, REFL11 15 dB, REFL33 30 dB, REFL165 24 dB)

Sensing matrix with the following demodulation phases (counts/m)
{'AS55': 2.1, 'REFL55': 76.02, 'REFL11': 32.638, 'REFL33': -19.275, 'REFL165': 108.88}
Sensors       MICH @211.1 Hz           PRCL @313.31 Hz           
AS55_I       (-1.09+/-1.48)e+09 [90]    (-5.73+/-3.01)e+09 [0]    
AS55_Q       (+1.59+/-0.13)e+10 [90]    (-5.50+/-3.46)e+09 [0]    
REFL55_I       (+1.42+/-0.16)e+12 [90]    (-3.70+/-0.17)e+13 [0]    
REFL55_Q       (-1.39+/-0.09)e+12 [90]    (-2.39+/-0.12)e+13 [0]    
REFL11_I       (+1.34+/-0.36)e+10 [90]    (-1.23+/-0.06)e+12 [0]    
REFL11_Q       (+9.64+/-0.78)e+09 [90]    (+1.77+/-0.10)e+11 [0]    
REFL33_I       (+2.89+/-0.54)e+09 [90]    (-1.85+/-0.09)e+11 [0]    
REFL33_Q       (-2.10+/-0.19)e+09 [90]    (+1.77+/-0.10)e+10 [0]    
REFL165_I       (+2.50+/-0.37)e+09 [90]    (-8.24+/-0.38)e+10 [0]    
REFL165_Q       (+3.73+/-0.25)e+09 [90]    (+2.15+/-0.11)e+10 [0]    

Signs flip from carrier lock for REFL33_I and Q, and REFL11_I, but not for AS55_Q.

Jupyter notebook: /Git/40m/scripts/CAL/SensingMatrix/ReadSensMat.ipynb

Locking configurations:
PRMI 1f carrier
 - MICH: 1*AS55_Q
 - PRCL: 1*REFL11_Q

PRMI 1f sideband
 - MICH: 1*AS55_Q
 - PRCL: -1*REFL11_Q

PRMI 3f carrier
 - MICH: 7*REFL33_Q
 - PRCL: 7*REFL33_Q

RPMI 3f sideband
 - MICH: -7*REFL33_Q
 - PRCL: -7*REFL33_Q

Common
 - Trigger on POPDC for carrier, POP110_I for sideband (we can also use POP110_I for both by flipping the sign)
 - C1:LSC-MICH_GAIN = 0.4
 - C1:LSC-PRCL_GAIN = -0.0054
 - No power normalization
 - MICH actuator is 0.5*BS-0.307*PRM
 - PRCL actuator is 1*PRM

PRCL and MICH sensitivity curves:
 See Attachment #1.
 Calibration factors used are as follows.
 C1:CAL-MICH_CINV FM3 is "PRMI_AS55Q" 1/1.45e10=6.9e-11 (from sensing matrix above)
 C1:CAL-MICH_A FM2 is 50.88e-09 (40m/17752)
 C1:CAL-PRCL_CINV FM3 is "PRMI_REFL11I" 1/1.16e12=8.6e-13 (from sensing matrix above)
 C1:CAL-PRCL_A FM2 is 41.40e-09 (40m/17752)

/Git/40m/measurements/LSC/MICH/MICH_Sensitivity_PRMI.xml
/Git/40m/measurements/LSC/PRMI/PRCL_Sensitivity_PRMI.xml

Sensing matrix comparison with past measurements:
 - It is pretty hard to read Gautam's radar plots, but REFL33 and REFL165 both had optical gain of ~10^7 V/m for PRCL and ~10^5 V/m for MICH in PRMI with no arms in 2021 (40m/15883)
 - From his thesis (see Figure 3.21), REFL33 and REFL165 had whitenings gain of 30 dB and 24 dB, respectivly, which are the same as the current gains.
 - Using ADC conversion of 2^16 counts/20 V, ~10^7 V/m for PRCL and ~10^5 V/m for MICH is ~3e11 counts/m for PRCL and ~3e9 counts/m for MICH. This is roughly consistent with the measurement above.
 - This means that REFL33 and REFL165 are probably working as they were in 2021.

Next:
 - Restore PRMI ASS. Alignment takes too much time. (AS WFS?)
 - Further tune REFL33 demodulation phase
 - Tweak suspension damping of ETMX (it is also contributing to ALS out-of-loop noise 40m/17773; coil balancing not enough? 40m/17771; oplev servo tweak necessary?)
 - Investigate ALS out-of-loop noise around 100 Hz (both ALSY 40m/17766 and ALSX 40m/17773)
 - Try PRMI 1f to 3f transition during both arms holded with ALS

[Paco, Yuta]

 We checked whitening and dewhitening situations in all the suspensions, and fixed them for ETMY.

ETMY trans QPD and ETMX trans QPD whitening:
  These QPDs have analog whitening filter of two 40:4s (LIGO-D1400415 and LIGO-D1400414). So, two of 4:40 in FM1 and FM2 of C1:SUS-ETM(Y|X)_QPDx should be always on. FM2s were off, so we turned ON today (see Attachment #1).

Fixing ETMY coil dewhitening BIO switch:
  Binary switching for ETMY coil dewhitening was not working because DB37 cable from Contec 32 BO card was not connected to the Binary Output Interface Chassis (LIGO-D1002593).
  After connecting the DB37 cable with a gender changer (we need a F to F cable), some of the switching worked but not in the correct order. Using a BD37 breakout board, we noticed that the binary switching is doing the switch in the mixed order of coil dewhitening and OSEM whitening. We modified the c1scy model so that the coil dewhitening switches Run/Acq LEDs correctly (Attachment #2 was before, and modified to Attachment #3). OSEM whitening binary switches are now terminated in c1scy model, because OSEM analog whitenings are always on (LIGO-D2100144).
  We also modified c1scx model to match with c1scy, although we don't have the acromag for Xend yet.
  Attachment #4 is the BIO status when ETMX and ETMY are in run mode (coil dewhitening on). ETM(Y|X)_BO_0_0 is for coil dewhitening, and BO_0_1 is for trans QPDs.
  Attachment #5 is the photo of LEDs correctly lit when ETMY is in run mode, after all these modifications.

Summary of Coil Driver situation for all optics:
  See, also, LIGO-D1100687

  By the way, for OSEMs, analog 30:3 whitening are always ON, no matter what the BIO situations are (LIGO-D2100144). So FM1 of C1:SUS-xxxx_xxSEN should be always ON.
  Also, since the recent coil driver upgrade, the order of coil outputs in SUS_SINGLE_COIL is UL/LL/UR/LR/SD, and the signs of C1:SUS-xxxx_xxCOIL_GAIN are +--++ (or flipped one). Note that it used to be +-+-+, as the order was UL/UR/LR/LL/SD (40m/16898).

Next:
  - Check sign convensions on all the suspensions
  - Check 60 Hz noise related dewhitening situation in MC suspensions (40m/17466)
  - For LO1, LO2, AS1, AS4, PR2, PR3, SR2, make them "lower half shorted" so that analog dewhitening will be turned off similarly to other vertex suspensions.

[Paco, Yuta]

We checked the polarity of suspension damping loops if they follow the conventions we agreed in 40m/16898.
Suspensions are nicely homogenized nicely , with some exceptions (see Attachment #1).

• ​PRM SDSEN_GAIN is 0.2, but it should be 1.
• LO1, LO2, AS1, AS SDCOIL_GAIN is +/-13, but it should be +/- 1. (Unless there are reasons for these 13)
• Let's make coil dewhitening to be off (in Acq mode) for all by default to homogenize (40m/17875). MC1 and MC3 might require 28Hz ELP for 60Hz noise.
• INMAT should be normalized nicely so that SUSPOS/SIDE_IN will be um and SUSPIT/YAW_IN will be urad. (Are cnts2um in *SEN filters correct?)
• Gain offsets in *COIL filters (e.g. V2A, x0.414) can be adjusted later to have the same actuation efficiencies between suspensions.

Note that *COIL_GAIN are now +--++ or flipped one in the order of UL/LL/UR/LR/SD.

Next:
  - Address the points raised above
  - Make a script to show current EPICs values for all suspensions to check the damping configurations.

To further homogenize the suspensions, we did the following changes.

 - Turned on DECIMATION in PR2 URCOIL
 - Changed +/- 13 in SDCOIL_GAIN of SR2,LO1,LO2,AS1,AS4 to +/-1 and increased SUSSIDE_GAIN accordingly
 - PRM SDSEN_GAIN was changed from +0.2 to +1 (see 40m/17877)
 - Moved FM6 "gain_offset" of gain(0.48) to FM1 in ETMY *COIL to align with other suspensions. Also added x0.48 to SDCOIL as well, and adjusted SUSSIDE_GAIN accordingly.
 - "Half shorted" binary inputs to coil drivers for PR2,PR3,SR2,LO1,LO2,AS1,AS4 so that they are always in "Acq" mode. FM9 SimDW filters were turned on accordingly.

Before work today:

2023-09-28 17:10:19 UTC (GPS: 1379956237)
channel\optic   MC1     MC2     MC3     BS      ITMX    ITMY    PRM     SRM     ETMX    ETMY    PR2     PR3     SR2     LO1     LO2     AS1     AS4     
ULSEN_GAIN        +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
LLSEN_GAIN        +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
URSEN_GAIN        +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
LRSEN_GAIN        +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
SDSEN_GAIN        +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +0.20   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
ULSEN_SWSTAT      37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923 
LLSEN_SWSTAT      37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923 
URSEN_SWSTAT      37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923 
LRSEN_SWSTAT      37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923 
SDSEN_SWSTAT      37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923 
SUSPOS_GAIN     +120.00 +150.00 +100.00 +100.00 +150.00  +50.00  +28.00  +25.00 +150.00  +41.00   +8.00  +10.00  +27.00  +10.00  +10.00  +14.00  +15.00 
SUSPIT_GAIN      +60.00  +10.00  +24.00  +10.00  +14.00   +7.00   +5.00   +1.20  +15.00   +6.00   +2.00   +5.00   +6.00   +4.00   +3.00   +2.50   +3.10 
SUSYAW_GAIN      +60.00  +10.00   +8.00   +3.00  +10.00   +8.00   +4.00   +1.50  +10.00   +6.00   +2.00   +5.00   +6.00   +3.00   +3.00   +3.00   +3.00 
SUSSIDE_GAIN    +100.00 +150.00 +125.00  +10.00  +60.00  +50.00  +50.00   +7.50 +150.00 +300.00  +11.54  +20.00  +10.77   +3.08   +3.85   +6.54   +3.15 
OL_PIT_GAIN       +1.00   +1.00   +1.00   -0.05   +5.00   +3.50   +6.00  +12.68   +1.00   -1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
OL_YAW_GAIN       +1.00   +1.00   +1.00   +0.10   +5.00   -4.00   -8.00  -15.85   +1.00   -1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
ULCOIL_GAIN       +1.01   +1.07   +0.94   +1.06   -1.10   +1.06   +0.97   +1.09   -1.01   -1.00   -1.00   -1.00   -1.00   -0.94   -1.05   -0.94   -0.98 
LLCOIL_GAIN       -0.95   -0.98   -0.94   -0.98   +0.90   -1.01   -1.04   -1.00   +0.97   +0.81   +1.00   +1.00   +1.00   +0.98   +0.63   +0.99   +0.97 
URCOIL_GAIN       -0.98   -0.98   -1.04   -1.04   +0.93   -0.99   -1.04   -0.92   +1.03   +0.74   +1.00   +1.00   +1.00   +1.00   +1.34   +1.04   +0.98 
LRCOIL_GAIN       +1.06   +0.97   +1.08   +0.92   -1.07   +0.94   +0.90   +0.99   -0.99   -1.05   -1.00   -1.00   -1.00   -1.07   -0.98   -1.03   -1.07 
SDCOIL_GAIN       +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   -1.00   -1.00   -1.00   -1.00  -13.00  -13.00  -13.00  +13.00  -13.00 
ULCOIL_SWSTAT     37889   38657   37889   38657   38657   38657   38657   38657   55041   38688   38400   38400   38400   38400   38400   38400   38400 
LLCOIL_SWSTAT     37889   38657   37889   38657   38657   38657   38657   38657   38657   38688   38400   38400   38400   38400   38400   38400   38400 
URCOIL_SWSTAT     37889   38657   37889   38657   38657   38657   38657   38657   38657   38688    5632   38400   38400   38400   38400   38400   38400 
LRCOIL_SWSTAT     37889   38657   37889   38657   38657   38657   38657   38657   38657   38688   38400   38400   38400   38400   38400   38400   38400 
SDCOIL_SWSTAT     37889   38657   37889   38145   38145   38145   38145   38145   38657   38656   38144   38144   38144   38144   38144   38144   38144 

After work today:

2023-09-28 18:26:55 UTC (GPS: 1379960833)
channel\optic   MC1     MC2     MC3     BS      ITMX    ITMY    PRM     SRM     ETMX    ETMY    PR2     PR3     SR2     LO1     LO2     AS1     AS4     
ULSEN_GAIN        +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
LLSEN_GAIN        +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
URSEN_GAIN        +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
LRSEN_GAIN        +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
SDSEN_GAIN        +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00 
**SEN_SWSTAT      37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923   37923 
(...snip...) 
SUSSIDE_GAIN    +100.00 +150.00 +125.00  +10.00  +60.00  +50.00  +50.00   +7.50 +150.00 +625.00  +11.54  +20.00 +140.00  +40.00  +50.00  +85.00  +40.00 
(...snip...)
SDCOIL_GAIN       +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   +1.00   -1.00   -1.00   -1.00   -1.00   -1.00   -1.00   -1.00   +1.00   -1.00 
ULCOIL_SWSTAT     37889   38657   37889   38657   38657   38657   38657   38657   55041   38657   38656   38656   38656   38656   38656   38656   38656 
LLCOIL_SWSTAT     37889   38657   37889   38657   38657   38657   38657   38657   38657   38657   38656   38656   38656   38656   38656   38656   38656 
URCOIL_SWSTAT     37889   38657   37889   38657   38657   38657   38657   38657   38657   38657   38656   38656   38656   38656   38656   38656   38656 
LRCOIL_SWSTAT     37889   38657   37889   38657   38657   38657   38657   38657   38657   38657   38656   38656   38656   38656   38656   38656   38656 
SDCOIL_SWSTAT     37889   38657   37889   38145   38145   38145   38145   38145   38657   38657   38144   38144   38144   38144   38144   38144   38144 

ULCOIL_STAT of ETMY being 55041 is OK. 38657+2**14 = 55041.
Script to produce these tables live in /opt/rtcds/caltech/c1/Git/40m/scripts/SUS/suspension_epics_check.py

Current coil dewhitening filter situations:

Next:
 - Investigate 60 Hz noise in laser frequency and check 28 Hz ELP situation for MC1,MC2,MC3
 - Fix ETMX acromag

[Yuki, Gautam]

Attachments #1 is the current setup of AUX Y Green locking and it has to be improved because:

• current efficiency of mode matching is about 50%
• current setup doesn't separate the degrees of freedom of TEM01 with PZT mirrors (the difference of gouy phase between PZT mirrors should be around 90 deg) 
• we want to remotely control PZT mirrors for alignment
  (Attachments #2 and #3)

About the above two: 

One of the example for improvement is just adding a new lens (f=10cm) soon after the doubling crystal. That will make mode matching better (100%) and also make separation better (85 deg) (Attachments #4 and #5). I'm checking whether we have the lens and there is space to set it. And I will measure current power of transmitted main laser in order to confirm the improvement of alignment.

About the last:

I am considering what component is needed. 

Reference:

• current setup of Y: elog:40m/11897

[ Yuki, Koji, Gautam ]

An alignment of AUX Y end green beam was bad. With Koji and Gautam's advice, it was recovered on Friday. The maximum value of TRY was about 0.5.

[ Yuki, Gautam ]

The setup I designed before has abrupt gouy phase shift between two steering mirrors which makes alignment much sensitive. So I designed a new one (Attached #1, #2 and #3). It improves the slope of gouy phase and the difference between steering mirrors is about 100 deg. To install this, we need new lenses: f=100mm, f=200mm, f=-250mm which have 532nm coating. If this setup is OK, I will order them.

There may be a problem: One lens should be put soon after dichroic mirror, but there is little room for fix it. (Attached #4, It will be put where the pedestal is.)  Tomorrow we will check this problem again.

And another problem; one steering mirror on the corner of the box is not easy to access. (Attached #5) I have to design a new seup with considering this problem.

[ Yuki, Steve ]

With Steve's help, we checked a new lens can be set soon after dichroic mirror.

[ Yuki, Gautam ]

We want to remotely control steeing PZT mirrors so its driver is needed. We already have a PZT driver board (D980323-C) and the output voltage is expected to be verified to be in the range 0-100 V DC for input voltages in the range -10 to 10 V DC.
Then I checked to make sure ir perform as we expected. The input signal was supplied using voltage calibrator and the output was monitored using a multimeter. 
But it didn't perform well. Some tuning of voltage bias seemed to be needed. I will calculate its transfer function by simulation and check the performance again tommorow. And I found one solder was off so it needs fixing.  

Reference:
diagram --> elog 8932
 

Plan of Action:

• Check PZT driver performs as we expected
• Also check cable, high voltage, PZT mirrors, anti-imaging board
• Obtain calibration factor of PZT mirrors using QPD
• Measure some status value before changing setup (such as tranmitted power of green laser)
• Revise setup after a new lens arrives
• Align the setup and check mode-matching
• Measure status value again and confirm it improves
• (write programming code of making alignment control automatically)

[ Yuki, Gautam ]

I fixed the input terminal that had been off, and made sure PZT driver board performs as we expect. 

At first I ran a simulation of the PZT driver circuit using LTspice (Attached #1 and #2). It shows that when the bias is 30V the driver performs well only with high input volatage (bigger than 3V). Then I measured the performance as following way:

1. Applied +-15V to the board with an expansion card and 31.8V to the high voltage port which is the maximum voltage of PS280 DC power supplier C10013.
2. Terminated input and connectd input bias to GND, then set offset to -10.4V. This value is refered as elog:40m/8832.
3. Injected DC signal into input port using a function generator.
4. Measured voltage at the OUT port and MON port.

The result of this is attached #3 and #4. It is consistent with simulated one. All ports performed well.

• V(M1_PIT_OUT) = -4.86 *Vin +49.3 [V]
• V(M1_YAW_OUT) = -4.86 *Vin +49.2 [V]
• V(M2_PIT_OUT) = -4.85 *Vin +49.4 [V]
• V(M2_YAW_OUT) = -4.86 *Vin +49.1 [V]
• V(M1_PIT_MON) = -0.333 *Vin +3.40 [V]
• V(M1_YAW_MON) = -0.333 *Vin +3.40 [V]
• V(M2_PIT_MON) = -0.333 *Vin +3.40 [V]
• V(M2_YAW_MON) = -0.333 *Vin +3.40 [V]

The high voltage points (100V DC) remain to be tested.

[ Yuki, Gautam, Steve ]

Results:
I calibrated a QPD (D1600079, V1009) and made sure it performes well. The calibration constants are as follows:

X-Axis: 584 mV/mm
Y-Axis: 588 mV/mm

Details:
The calibration of QPD is needed to calibrate steeing PZT mirrors. It was measured by moving QPD on a translation stage. The QPD was connected to its amplifier (D1700110-v1) and +-18V was supplied from DC power supplier. The amplifier has three output ports; Pitch, Yaw, and Sum. I did the calibration as follows:

• Center beam spot on QPD using steering mirror, which was confirmed by monitored Pitch and Yaw signals that were around zero.  
• Kept Y-axis micrometer fixed, moved X-axis micrometer and measured the outputs. 
• Repeated the procedure for the Y-axis. 

The results are attached. The main signal was fitted with error function and I drawed a slope at zero crossing point, which is calibration factor. I determined the linear range of the QPD to be when the output was in range -50V to 50V, then corresponding displacement range is about 0.2 mm width. Using this result, the PZT mirrors will be calibrated in linear range of the QPD tomorrow. 

Comments:

• Some X-Y coupling existed. When one axis micrometer was moved, a little signal of the other direction was also generated.
• As Gautam proposed in the previous study, there is some hysteresis. That process would bring some errors to this result.
• A scale of micrometer is expressed in INCH!
• The micrometer I used was made to have 1/2 inch range, but it didn't work well and the range of X-axis was much narrower. 

Reference:
previous experiment by Gautam for X-arm: elog:40m/8873, elog:40m/8884