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ID Datedown Author Type Category Subject
  17578   Tue May 2 17:33:53 2023 MayankSummaryLSCLocked PRMI in carrier for an hour with LO phase controlled using BH55

[Mayank, Radhika, Paco]

We locked PRMI for a solid hour devil and controlled LO phase angle using BH55_Q at higher power.

After Radhika aligned the IFO for us, and recovered the PRMI flashing (using REFLDC), we attempted a PRMI lock. After a few trials we succeeded.

Control parameters: see Attachment #1, basically REFL11_I to PRCL, and AS55_Q to MICH (error points) and actuation as previous locks with PRCL to PRMand MICH to 0.5 * BS - 0.33 * PRM.

The gains are slightly different, and in particular PRCL gain was increased from -0.07 to -0.09 after an OLTF estimated the UGF could be increased to > 120 Hz (Attachment #2 shows the measured OLTF) Do note we ended up disabling the FM1 on PRCL LSC filter bank (a boost) because we thought the loop was unstable when it got triggered ON. Finally, we took a quick noise spectrum of PRMI, and we have yet to calibrate it.

We also managed to reduce the AS_DC level from 0.4 to 0.1. We first tried to add an offset to MICH error point but the trick was to align the ITMX ITMY differential yaw.

Lock start Time: 1367107965 --> 1367111565


While PRMI was locked, we quickly locked homodyne angle using BH55_Q. For this the demod angle was optimized from -60 deg to 55.374 deg. The lock was acquired using FM5 and FM8 with a gain of -0.75. Attachment #3 shows the "calibrated" noise budget of the LO phase under this configuration. The main difference with respect to the previous  budget is in the "RIN" which we now realize is not relative... therefore the increase in this budget. We will revisit this calibration later.


- Next steps

  • Re-calibrate LO phase noise with high power
  • Investigate BH44 control
  • Calibrate PRMI noise for budget
  • Estimate LO phase sensitivities at MICH vs PRMI

 

  17577   Tue May 2 10:39:49 2023 JCConfigurationIMCBad Alignment

It took a while, but I was finally able to align IMC. It seems like WFS has been getting really whacky lately when we arent in the lab watching it angry. The picture attached has an arrow of where the beam spot was at this morning

  17575   Mon May 1 16:51:20 2023 PacoSummaryASCIFO alignment in bad shape

[Yuta, Mayank, JC, Paco]

We fixed the IFO nominal alignment.


  1. Yuta and Mayank had worked all morning and into the early afternoon to try and recover alignment. We noticed a few things seemed off:
    1. ASS loops still wouldn't work.
    2. ITMX oplev loops were weirdly unstable, but we suspected this had to do with the recent HeNe replacement saga.
      1. Paco revisited the setup, suspecting a lens near the QPD was wreaking havoc. This was not the case, but the setup now resembles the previous one. Furthermore, an iris was placed in the input ITMX OpLev path.
    3. Using AUX (green) beams as a reference didn't really work well.
  2. We decided to check the SUS rack electronics where some noise measurements were carried out last week.
  3. We found out that between the DW boards from ITMX and ITMY to the coil driver units for ITMX and ITMY there were two crossed wires at least (Ch4).
  4. Yuta and Paco reconnected all channels between the ITMX DW to ITMX Coil driver and ITMY DW to ITMY Coil driver units,
    1. All wires seemed to be crossed when going up the rack... suspicious...
  5. The first damping test failed, and we realized placing an offset in ITMY coils affected ITMX, so the DW board units were probably flipped because they were probably mislabeled!
  6. Yuta and JC swapped the cables again, and we ran a coil by coil test before damping. After this ITMs were successfully damped, so the labels were corrected in the AI + DW boards to prevent this confusion in the future.

  • IFO alignment was recovered by Yuta and Paco.
    • ASS now works again!
  • JC and Mayank aligned OpLevs
    • Loops were closed and remained stable in ITMs.

Attachment #1 shows the alignment state at the end of this work.

  17574   Mon May 1 14:45:48 2023 MayankSummaryLSCAttenuated BHD DC Beam

[Yuta, Mayank]

UPDATE: It turned out that the pair of 0.3 OD ND filters we used were not matched. So we replaced them with new 0.5 OD NENIR05A-C from thorlabs. Now both the photodiodes give similar count.

Counts Before OD After OD
C1:HPC-BHDC_A_OUT 114.5 counts 36.4 counts
C1:HPC-BHDC_B_OUT 111.5 counts 35.1 counts

 

 

The DC power incident on the PDs is 74 mW which may cause saturation. We attenuated the beam going to BHD_DC Photodiodes using ND filter of OD 0.3 which gives attenuation of 0.5. 

  17573   Mon May 1 08:57:45 2023 JCConfigurationIMCBad Alignment

I had to realign the IMC today. When I came in, it was very bad, not much flashing at all, I had to do it from scratch. CH01 Camera on MON7 in the control room is completely white. Did the camera go out over the weekend? I will come back to poke around later, I have headed over to WB for a moment and will be back soon. sitemapsi

  17572   Fri Apr 28 20:56:06 2023 KojiSummaryASCIFO alignment in bad shape

I suppose ASS Y arm is using PR2/3 to align the beam to the arm.
Can't we have ASS PRM bring the beams to the center (or some defined places) of the PRM and PR2 by moving the TTs?

 

  17571   Fri Apr 28 20:17:37 2023 yutaSummaryASCIFO alignment in bad shape

[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 crying

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)

  17570   Fri Apr 28 18:40:49 2023 YehonathanUpdateBHDUpdated noise budget with some input electronic noises

{Mayank, Yehonathan}

Yesterday, we measured AS55 and REFL11 dark noises at the IQ demod boards outputs (attachment 1) using SR560+SR785 setup.

We also measured the whitening board noise of REFL11 using an improvised adapter (picture will come later). The measurement result is shown in attachment 2. Didn't have time to measure the whitening noise for AS55

Also, after realizing the Finesse model doesn't account for the REFL port attenuation I measure how much DC power at the REFL11 PD to be 0.8mW by aligning PRM and misaligning the rest of the optics.

For some reason, the power before the attenuation is only ~ 360mW. The Finesse model predicts around 700mW. Where is the rest of the light going?

I added the PDs Dark noises (using the recently measured IQ demod gains) and shot noise to the PRMI carrier noise budget (attachment 3). ADC and whitening noises coming soon.

Measurements and PRMI noise budget notebooks were uploaded to the 40m git.

  17568   Wed Apr 26 18:41:56 2023 PacoUpdateOPLEV TablesITMX oplev laser died

[Paco, Koji, Mayank]

We replaced ITMX Oplev HeNe laser after last one died.

  • We noticed the ITMX HeNe laser died, so we couldn't have Oplev control. With Koji's help, we located a laser tube which had no labels and a sticker up front so we assumed this is new. We removed the faulty tube from the ITMX table and tested it using the display control unit (labeled 1). The laser head was 1103, and weirdly it turned on. We also located some control units in the Oplev cabinet which had been labeled "working with Display" from 2022.
  • After testing a few combinations we realized CARE NEEDS TO BE TAKEN TO NOTICE THE INTERLOCK SWITCH BEFORE TESTING ANY PAIR> it turned out our old controller was ok, but the interlock switch had fallen. We also noted the two spare units labeled "working with Display" were indeed operating correctly they just needed their interlock switches. Surprisingly the "new" laser head we planned to use as a spare is DEAD.
  • After assuming the old head was working and its controller just needed the interlock, we reinstalled it on the table. Unfortunately, after realigning the OPLEV beam we saw the SUM drop from 1500 counts (usually 15000) to 0. So the laser head was indeed faulty! + WE HAVE NO MORE 1103 SPARE HEADS!
  • We couldn't find another 1103 spare head, so we opted for the 1125 along with its corresponding controller. This worked fine, except the unit is thicker and the whole beam path changed by ~ 1 cm in height. Mayank and I restored the alignment and centered the ITMX oplev. A photo of the changes made to reach the final setup are in Attachments #1-2. Most notably we had to lower the big pedestals where the HeNe laser head is resting to accommodate this height difference.
  • Finally the laser beam diameter is different, so we removed the "collimating" lens immediately after the HeNe head. This had the effect of restoring the beam path, but we placed a shorter focal length lens between the last steering mirror and the QPD> this means the previous ITMX oplev calibration is now bogus.
  17567   Wed Apr 26 12:59:42 2023 YehonathanUpdateBHDUpdated noise budget with output electronics

I included the output electronic noises into the PRMI carrier noise budget (attachment 1).

The coil driver noise was calculated using the Johnson noises of the coil driver resistor:

PRM 430 ohm

BS 100 ohm

ITMX/Y 400 ohm

For the dewhitening noises I use the measurements from yesterday. As expected fro yesterday's measurements, the ITMX dewhitening noise is dominating. For the coil driver gain I use the recently measured actuation calibration (elog   17522 ) to extract it. I find that these gain values:

PRM 1.009

BS 1.333

ITMX/Y 0.24

For the DAC noise I assume 1uV/sqrtHz and use the simDW filters from the coil outputs MEDM screens as the DW filters TFs.

Next:

1. Break down input noises.

2. Measure how much light is reaching REFL11 to correct the sensing matrix and get the right shot noise.

  17566   Wed Apr 26 12:05:10 2023 RadhikaUpdateALSXEND green PDH controller

Tl;dr: Tried to replace of XEND green PDH servo controller with Moku template IIR filter, designed to match PDH servo frequency response. The green laser did not catch lock with this filter.

Attachment 1 plots the measured TF of the PDH servo controller, with boost on and the gain knob set to 7.22 (the current lock configurations). It also plots an 8th order Chebyshev type II low-pass filter, with cutoff frequency and scale chosen to best match the data. (8 was the highest order filter that could be represented by 4 second-order-sections, the maximum allowed by the Moku.) I wanted to test if the XAUX PDH lock could be maintained using this filter as the controller.

The phase of the Chebyshev II filter does not seem to be a good fit to the data, but I wanted to see how far we could get using a template filter already designed for discrete time, and with a magnitude frequency response that approximates the servo. This would bypass having to perform a bilinear transform from the s-domain to the z-domain, which can raise more complications.

The PDH error signal (mixer output) was split and sent to the Moku (input 1) and to the PDH servo input. Closing the loop with the Moku filter output, the green laser was not able to catch lock. Attachment 2 shows the Moku:Go Digital Filter Box configurations, as well as the traces comparing output of the filter and the output of the PDH servo. The red trace is the output of Moku filter, and the blue trace is the output of the PDH servo (input 2) with the loop open (nothing feeding back to laser PZT). The input gain of the filter module was chosen to match the amplitudes of the two control signals. Qualitatively, the filter output contains higher frequency components and preserves the odd polarity of the PDH error signal, compared to the servo output. 

I then tried to directly fit the PDH servo TF data. I fit the (analog) poles and zeros of the TF using vectfit. In theory, using a bilinear transform can convert the analog zpk TF to digital zpk, with some frequency pre-warping required. However, vectfit did not return a "normal" transfer function, defined as having at least as many poles as zeros. This caused the bilinear transform to fail.

Next, I will need to use a different fitting package (perhaps IIRrational) to obtain a nicer TF fit, in normal form. Then I can attemp the bilinear transform, confirm it preserves the desired frequency response, and test it out with the Moku:Go.

  17565   Wed Apr 26 11:27:49 2023 PacoSummaryBHDLO/MI(DARM) signal strength comparison between the configurations with finesse

I'm checking Koji + Yuta's not-so-naive calculations using finesse.

  Michelson PRMI carrier PRMI sideband PRFPMI
max(BH44) [W/m] 0.61 @ 90 deg 235.76 @ 90 deg    
max(BH55) [W/m] 4.55 @ 0 deg 1539.67 @ 0 deg    
max(BHD_DIFF) [W/m] 35550 10656140    

PRMI Carrier resonant:
- The HD phase signal @44 MHz is estimated to be 386.5 times stronger.
- The MICH signal @BHD_DIFF is estimated to be enhanced by a factor of 299.75.

PRMI Sideband resonant:
- The HD phase signal @44MHz is estimated to be () stronger.
- The MICH signal @BHD_DIFF is estimated to be suppressed by a factor of

PRFPMI: Now the carrier and the 11 and 55MHz sidebands are resonant.
- The HD phase signal @44MHz is estimated to be ().
- The MICH signal @BHD_DIFF is estimated to be the same level as the one with PRMI Carrier resonant.

  17564   Wed Apr 26 09:37:10 2023 PacoUpdateBHDIQ demod board gains for REFL11 and AS55

We measured the IQ demodulation board gains for REFL11 and AS55.

To do this, we replaced the PD input on the demod board with an RF signal at near the nominal frequencies of 11.066195 MHz and 55.330975 MHz using a Marconi 2024A identical to the one which sources the PM sidebands in our PSL. Even though we matched the modulation frequencies we found the two marconis were in practice offset by ~ 3 Hz. After tuning the frequency around a bit, we managed to get them to within 450 mHz.


REFL11

We started with REFL11 IQ demod board. After sourcing 11.066198 MHz into the PD input port, we took the I and Q outputs and looked at them using an osciloscope. We measured the Vpp levels on both as well as the Marconi output. The resulting levels were

  • Source = 44.4 mVpp, I = 8.8 mVpp and Q = 10.8 mVpp ==> Gains are therefore 0.19 and 0.24. The amplitude gain of this board is sqrt(0.19 ** 2 + 0.24 ** 2) = 0.153. This is in stark disagreement with the wiki. Has the wiki finally failed us?

AS55

We then moved on to AS55 IQ demod board. After sourcing 55.330975 MHz* into the PD input port, we took the I and Q outputs and looked at them using an osciloscope. We measured the Vpp levels on both as well as the Marconi output. The resulting levels were

  • Source = 16.8 mVpp, I = 50.8 mVpp and Q = 56.3 mVpp ==> Gains are therefore estimated to be 3.3 and 3.7. The amplitude gain of this board is sqrt(3.3**2 + 3.7**2) = 4.74. This is in slight contrast with the previously measured gain of 2.8, but we think a factor of 2 may have been misplaced in either calculation since one typically estimates AMP = 2 * sqrt(I**2 + Q**2).

* Note that in the second test, we didn't match up the frequency, which caused I and Q outputs to have significant gains (instead of just I).

  17563   Tue Apr 25 21:21:03 2023 YehonathanUpdateBHDDewhitening noises

{Mayank, Paco, Yehonathan}

Dewhitening noise curves were taken using SR785+SR560 for the PRMI noise budget. One representative channel was measured at each board, suspensions were tripped before work was done. The input pins to the dewhitening boards were shorted using an exposed ribbon cable.

At each board, the measurement was taken with and without dewhitening filter on. The toggling of the dewhitening filter was done by turning on and off the SimDW filters at the coil filter screen of each suspension.

Attachment 1 summarizes the results.

ITMX dewhitening noise is much higher than the rest.

ITMY measurement turned out to be bogus since we mostly measured dark noise. The reason we made the gain so low in that measurement is that it was saturating the SR560 whenever we used gain>1.

  17562   Tue Apr 25 17:06:17 2023 AnchalUpdateALSDFD demod normalized by amplitude

I modified the analysis to correct for any affects due to Anti-Aliasing or Anti-Imaging filters, and I also found a insignificant error on how I was undoing the suppression due to MICH loop in the MICH data. I also propagated the calibration in MICH method better. Attached are the updated results. The upward swing is still present.

Also, last night, Koji and I looked into any frequency dependent deviation in sensing arm length between POY11 and BEATY_PHASE (using DFD+Phase tracker) This was done by locked the YARM to the main laser and locking YAUX to the YARM, sending excitationa at C1:SUS-ETMY_POSCAL_EXC and taking transfer function between C1:LSC-YARM_IN1 and C1:ALS-BEAT_Y_FINE_PHASE_OUT. This transfer function was flat upto about 600 Hz and the deviation from there to 2000 Hz was expected based on limited bandwidth of the phase tracker. I don't have the plot to attach, someone should redo this quick measurement to save the data.
Interestingly, the same measurement when done with  C1:LSC-DARM_IN1 in FPMI configuration did not show a flat response. This is can mean that the DARM strain relationship with the beatnote frequency deviation is not a simple constant factor and/or depends on DARM or CARM OLTFs. I leave my remarks on this project here for the baton to be picked up by others in future. I unfortunately only have this much time to contribute to FPMI calibration.

  17561   Tue Apr 25 15:51:21 2023 JcUpdateIMCIMC has been tripping

It has happened multiple times today that IMC has tripped on its own. Yehonathan and I have had to come back to manually lock IMC multiple times.


Wed Apr 26 10:24:07 2023 [EDIT]

[Paco] I aligned the MC by hand, let it run locked for 30 minutes without angular controls, and then switched on the WFS loops yesterday at ~ 6 PM. IMC has been locked ever since.

  17560   Mon Apr 24 19:11:20 2023 KojiSummaryBHDLO/MI(DARM) signal strength comparison between the configurations

Yuta and I had a discussion last week about the signal strength between the configurations. Here are some naive calculations.
=== Please check the result with a more precise simulation ===


Michelson: Homodyne (HD) phase signal @44MHz is obtained from the combination of LO11xAS55 and LO CAxAS44. SBs at AS rely on the Schnupp asymmetry, the signal is weaker than the one with a single bounce beam from an ITM.

PRMI Carrier resonant:
- Despite the non-resonant condition of the sidebands, the HD phase signal @44MHz is expected to be significantly stronger (~x300) compared with the MI due to the resonance of the carrier and the 44MHz sidebands (the 2nd-order SBs of 11 and 55) in the PRC. Thus, the LO CAxAS44 term dominates the signal.
- The MICH signal @55MHz is enhanced by the resonant carrier by a factor of ~5.5, in spite of the non-resonant 55MHz SBs.
- The MICH signal @BHD is enhanced by the resonant carrier by a factor of ~300. This is the comparable phase sensitivity to PRFPMI case.

PRMI Sideband resonant:
- Despite the non-resonant condition of the carrier, the HD phase signal @44MHz is expected to be even stronger (~x400) compared with the MI due to the resonance of the 11MHz and 55MHz sidebands in the PRC. Thus, the LO11xAS55 term dominates the signal.
- The level of the MICH signal @55MHz is expected to be comparable to the one with PRMI carrier resonant as the resonant condition for the CA and 55MHz SBs are interchanged.
- The MICH signal @BHD is expected to be negligibly small due to non-resonance of the carrier.

PRFPMI: Now the carrier and the 11 and 55MHz sidebands are resonant.
- The HD phase signal @44MHz is expected to be the same level as the SB resonant PRMI, and the LO11xAS55 term dominates the signal.
- The level of the MICH sensitivity @AS 55MHz shows x300 of the MICH signal of the MI and x50 of the MICH with PRMI.
- The MICH signal @BHD is going to be the same level as the one with PRMI Carrier resonant.
-
The DARM signal shows up at the dark port signal enhanced by x300 from the MICH level due to the finesse of the arms.



Simple assumptions
1) PRM has a transmission of TPRM = 0.05
2) PRG is limited by the transmission of PR2 (TPR2=0.02 per bounce).
    If the IFO is lossless, PRG is 25 (i.e. theoretical maximum). In reality, the IFO loss is 2~3% -> PRG is ~15.
    The asymmetry of 30mm has a negligible effect.
3) For the anti-resonant fields, APRG is ~TPRM/4 = 0.0125
4) Arm finesse is 450. Therefore the phase enhancement factor N is ~300.
5) Modulation depth is ~0.1. J0=1, J1=0.05, J2=0.00125
6) Sideband leakage by the asymmetry is ɑ=l_asym wm / c = 0.008 for 11MHz and 5ɑ for 55MHz.


Single Bounce

The numbers are power transmission to each port
   Carrier              11MHz                    55MHz
LO
TPRM TPR2 = 1.0e-3   J1^2 TPRM TPR2 = 2.5e-6  J1^2 TPRM TPR2 = 2.5e-6
AS TPRM/4    = 1.3e-2   J1^2 TPRM/4    = 3.1e-5  J1^2 TPRM/4    = 3.1e-5

LO phase @44MHz: LO 11 x AS 55 = Sqrt(2.5e-6 * 3.1e-5) = 8.8e-6


Michelson

   Carrier               11MHz                     55MHz                      44MHz
LO
TPRM TPR2 = 1.0e-3    J1^2 TPRM TPR2 = 2.5e-6   J1^2 TPRM TPR2   = 2.5e-6
AS TPRM ε^2  = 0.05 ε^2  ɑ^2 J1^2 TPRM  = 8.0e-9   25 ɑ^2 J1^2 TPRM = 2.0e-7  16 ɑ^2 J1^4 TPRM = 3.2e-10

LO phase @44MHz: LO 11 x AS 55 = Sqrt(2.5e-6 * 2.0e-7)  = 7.1e-7
                 LO CA x AS 44 = Sqrt(1.0e-3 * 3.2e-10) = 5.7e-7

AS MICH  @55MHz: AS CA x AS 55 = Sqrt(0.05 * 2.0e-7) ε  = 1.0e-4 ε
AS MICH  @BHD:  LO CA x AS CA = Sqrt(1.0e-3 * 0.05) ε  = 7.1e-3 ε


PRMI (Carrier Resonant)

   Carrier              11MHz                     55MHz                      44MHz
LO PRG TPR2 = 0.3       J1^2 APRG TPR2 = 2.5e-7   J1^2 APRG TPR2   = 2.5e-7  J1^4 PRG TPR2 = 1.9e-6
AS PRG ε^2  = 15 ε^2    ɑ^2 J1^2 APRG  = 8.0e-10  25 ɑ^2 J1^2 APRG = 2.0e-8  16 ɑ^2 J1^4 PRG = 9.6e-8


LO phase @44MHz: LO 11 x AS 55 = Sqrt(2.5e-7 * 2.0e-8)  = 7.1e-8
                 LO CA x AS 44 = Sqrt(0.3 * 9.6e-8)     = 1.7e-4
AS MICH  @55MHz: AS CA x AS 55 = Sqrt(15 * 2.0e-8) ε    = 5.5e-4 ε

AS MICH  @BHD:  LO CA x AS CA = Sqrt(0.3 * 15) ε       = 2.1 ε
 


PRMI (Sideband Resonant)

   Carrier               11MHz                     55MHz                      44MHz
LO APRG TPR2 = 1e-4      J1^2 PRG TPR2 = 7.5e-4    J1^2 PRG TPR2   = 7.5e-4  J1^4 APRG TPR2 = 6.3e-10
AS APRG ε^2  = 5e-3 ε^2  ɑ^2 J1^2 PRG  = 2.4e-6    25 ɑ^2 J1^2 PRG = 6.0e-5  16 ɑ^2 J1^4 APRG = 3.2e-11


LO phase @44MHz: LO 11 x AS 55 = Sqrt(7.5e-4 * 6.0e-5)  = 2.1e-4
                 LO CA x AS 44 = Sqrt(1e-4 * 3.2e-11)   = 5.7e-8
AS MICH  @55MHz: AS CA x AS 55 = Sqrt(5e-3 * 6.0e-5) ε  = 5.5e-4 ε

AS MICH  @BHD:  LO CA x AS CA = Sqrt(1e-4 * 5e-3) ε    = 7.1e-4 ε


PRFPMI

   Carrier             11MHz                     55MHz                      44MHz
LO PRG TPR2 = 0.3      J1^2 PRG TPR2 = 7.5e-4    J1^2 PRG TPR2   = 7.5e-4   J1^4 APRG TPR2 = 6.3e-10
AS PRG ε^2  = 15 ε^2   ɑ^2 J1^2 PRG  = 2.4e-6    25 ɑ^2 J1^2 PRG = 6.0e-5   16 ɑ^2 J1^4 APRG = 3.2e-11


LO phase @44MHz: LO 11 x AS 55 = Sqrt(7.5e-4 * 6.0e-5)  = 2.1e-4
                 LO CA x AS 44 = Sqrt(0.3 * 3.2e-11)    = 3.1e-6
AS MICH  @55MHz: AS CA x AS 55 = Sqrt(15 * 6.0e-5) ε    = 3.0e-2
ε  ==> DARM@55MHz 9.0 ε
AS MICH  @BHD:  LO CA x AS CA = Sqrt(0.3 * 15) ε       = 2.1 ε     ==> DARM@BHD   6.3e2 ε


  17559   Mon Apr 24 18:33:22 2023 AlexUpdateIMCBeam offset movement for MC1,2,3 in PIT and YAW from dither results

Mayank and I worked on finalizing the plots for the beam offset from the dithering test done in 17552. Plotted in attachment 1 are the beamspot demodulated signals from MC_F_DQ which are averaged over 1 second each (blue) for YAW and PIT in MC1,2,3. The yellow line over each plot shows the 3 Hz lowpassed signal of the beamspot movement.

Additionally, we have seen no direct correlation to the WFS1 or 2 sensors due to the MC movements. This may be because the WFS display a complete signal that includes all changes in the cavity length due to the shaking of the mirrors. Thus, the signal (shown in red) of the WFS sensors will show a combined average of movement from all 3 dither lines.

  17558   Mon Apr 24 10:53:39 2023 AlexUpdateGeneralSummary Pages Fixed

This morning I found a helpful post in the git.ligo pages that referred to the issue that was stopping the summary pages from being submitted to the codor. In the last 3 weeks the accounting_tag ligo.dev.o3 was retired, and thus the accounting tag "ligo.dev.o3.detchar.daily.summary" which is found in both /condor/gw_daily_summary.sub and /condor/gw_daily_summary_rerun.sub was preventing the summary pages from bieng submitted.

The post referred to a running list in the nodus that points to all active accounting tags: etc/condor/accounting/valid_tags this showed that "ligo.dev.o4.detchar.daily.summary" and "ligo.dev.o5.detchar.daily.summary" were currently active tags. I then tested the files using this tag (o4) with success in starting the pages up again. I have now committed the change to the git. 

The prior 3 days of summary pages were also regenerated: 

relocate to /bin

run ./gw_daily_summary_40m --day YYYYMMDD

once finished run ./pushnodus YYYYMMDD

      (must do independently for each day)

  17557   Fri Apr 21 19:07:07 2023 ranaConfigurationIOOback on RL

this afternoon I did some swapping around of linear and RL for IMC WFS.

In the end, I left in in the 'both' state:

  • The WFS1,2,MC_TRANS PIT loops are all on but with -40, -40, -20 dB of nominal gain
  • the RL is on for PIT

this is so that we have good DC control with integrators and good HF performance too.

  17556   Fri Apr 21 14:31:26 2023 AnchalUpdateALSDFD demod normalized by amplitude

Last night I took ITMY calibration data using MICH with AS55_Q. Adding that to the same plot. The error bars are probably underestimate with the MICH calibration method due to systematics not taken into account. For this measurement, MICH was locked with low UGF of 20 Hz to avoid all lines in MICH loop. Notches at the line frequencies were also put in. MICH OLTF was measured and any possible suppression of lines has been compensated for (very small). Note that error bars are present for DFD method too, but they are too small in this scale.

MICH calibration did not independently verify the higher actuation strength found by DFD methods at higher frequencies. For an ideal pendulum, the calibration constants should ahve been freqeuncy independent. It does see higher calibration constant values at 500 Hz and 1.4 kHz lines, but with a lot of noise. See attachment 2 for the calibration in real time, but this plot is bit messy. For the three lower frequency lines, DFD+Phase tracker and DFD with offline analysis match in their estimates , there is a significant mismatch at 500 kHz line and we do not have data for doing this for 1.4 kHz line.

  17555   Thu Apr 20 23:51:14 2023 AnchalUpdateALSDFD demod normalized by amplitude

I did offline analysis with the available data. We were only saving signals at 2048 Hz rate, so analysis can not be done on 1.4 kHz line. See attached plot for the difference in the two analysis.

We are aiming to prepare a realtime system deployable calibration method, that's why we were using phase tracker. Note that the calibration results with phase tracker have been compensated for any lack of gain due to phase tracke limited bandwidth, open loop gain of aux loop or remaining suppression from YARM loop despite the notches.

About the moku, we think that something is wrong in connection of moku output to ADC. We see the same cal line heights in the moku app in ipad but after going through ADC, we see about 10 times less line heights and 10 time sles noise floor too. But when we stick a marconi split between DFD and moku, we see the same results, so we are not sure what is wrong with it but it is not trustworthy. Maybe the order of magnitude noise reduciton is because of this factor of 10 that happens when it reads beatnote. To be solved in future, we will carry on with DFD for now.

Quote:

how about the other idea of downloading the I & Q channels and doing the analysis offline? I'm curious if its better or worse.How could the Moku possibly be better?

Another idea is to use the frequency divider and then directly digitize. I believe someone tried that a few years ago, but not sure how good it was.

 

 

  17554   Thu Apr 20 12:00:34 2023 ranaUpdateALSDFD demod normalized by amplitude

how about the other idea of downloading the I & Q channels and doing the analysis offline? I'm curious if its better or worse. How could the Moku possibly be better?

Another idea is to use the frequency divider and then directly digitize. I believe someone tried that a few years ago, but not sure how good it was.

 

  17553   Wed Apr 19 22:46:17 2023 PacoUpdateALSDFD demod normalized by amplitude

[Anchal, Paco]

We updated the LSC model to use the amplitude as a normalization (analogous to what happens in OpLevs). For reference Attachment #1 shows the previous model detail, and Attachment #2 shows the updated one. We then built, restarted and ran the model to realize the phase tracker gain can now be set once and for all assuming we still have a simple integrator and 2 kHz of phase tracker bandwidth. Doing this results in the ALS residual noise shown in Attachment #3. Compared against the reference spectra, the improvement is modest but not as great as what the moku had.

We ran ITMY actuation calibration using this infrastructure; to do this we lock arm cavities to PSL, lock AUX lasers to arm cavities, turn on our five lines and read back the demodulated signals from the beatnote as it goes through DFD + phase tracker. The results are summarized in Attachment #4. This time we correctly accounted for all known sources of statistical and systematic uncertainties (including a recently  measurement of the AUX loop gain),

  17552   Wed Apr 19 17:32:11 2023 AlexUpdateIMCBeam offset calculation for MC1,2,3 from dither results

Today, we ran dither lines on the MC1,2,3 mirrors in YAW from 136598007 to 1365981967 and similarly on PIT from 1365982917 to 1365984618.

The following frequencies and amplitudes were recorded for each dither line:

optic freq amp YAW amp PIT
MC1 21.21 3000 6000
MC2 26.62 6000 9000
MC3 23.10 3000 6000

 

The urad conversions used to calculate theta DC and AC can be found at 17481

 

The dither lines were then demodulated in python and the steps shown in 17516 were followed to calculate the beam offset that each dither line represented in pitch and yaw. 

The following results were found:

Optic Delta Y (mm)
MC1 YAW 1.42
MC2 YAW 1.6
MC3 YAW 1.78
MC1 PIT 2.72
MC2 PIT 2.33
MC3 PIT 2.83

 

Attatched bellow is the power spectrums for both yaw and pitch.

  17551   Wed Apr 19 17:02:48 2023 YehonathanSummarySUSCoil dewhitening check for BS and ITMX

[Yehonathan, Paco]

Repeated the coil dewhitening check for BS. Attachment #1 show results. Note however the DW filter shape for BS is more complicated:

zpk([86.7884+i*86.5657, 86.7884-i*86.5657,57.338+i*66.4261, 57.338-i*66.4261,68.83, 546.83],[10.4774+i*10.8736, 10.4774-i*10.8736,10.7093+i*10.5571, 10.7093-i*10.5571,8.67, 3235.8], 1.0252))

Note that YAW data here is actually PIT data and PIT data is plotted twice, as we messed up with data saving...crying

 


Repeated also for ITMX. See Attachment #2.

zpk([82.211+i*77.2492;82.211-i*77.2492;62.4258+i*68.3807;62.4258-i*68.3807;113.86;549.5],[10.7026+i*10.6661;10.7026-i*10.6661;10.3176+i*10.6734;10.3176-i*10.6734;13.99;3226.8],1.026)


 

  17550   Wed Apr 19 15:12:01 2023 yutaSummarySUSCoil dewhitening check for PRM

[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?

  17549   Wed Apr 19 11:35:20 2023 YehonathanUpdateBHDPRMI estimated noise budget

First, simple stuff. We estimate the noise budget with total input and output noises. Later, we will break it down (ADC, DAC, whitening, dewhitening noises etc.):

We take the dark noise of AS55, REFL11 and make sure that the whitening and "unwhitening" software filters are on (attachment 1)

To convert cts to Watts we use the values from previous MICH noise budgeting for AS55:

PD_responsivity = 1e3*0.8 #V/W
ADC_TF = 3276.8 #cts/V
demod_gain = 2 #6.77 #According to https://wiki-40m.ligo.caltech.edu/Electronics/LSC_demoddulators
whitening_gain = 10**(24/20) #24 dB

We are not sure why the demod gain was chosen to be 2 and not 6.77 as in the Wiki, maybe it was chosen to match the measurements back then. The demod gain for AS55 was actually measured to be 2.4 in elog 16961.

For now, for lack of time, we use the PD responsivity and demod gain of REFL11 from the wiki:

PD_responsivity = 4.08e3*0.8 #V/W
ADC_TF = 3276.8 #cts/V
demod_gain = 4.74 #According to https://wiki-40m.ligo.caltech.edu/Electronics/LSC_demoddulators
whitening_gain = 10**(18/20) #18 dB

Using the Finesse model for PRMI (should push to git) we calculate the sensing matrix (attachment 3). We turn off the HOMs as it gives us strange results for now.

We take the output noise that was measured at the output of the BS coil driver measured in elog 16960.

Attachment 2 shows the estimated PRMI noise budget. Notice that the dark noise contribution is an order of magnitude better than MICH (elog 16984) due to PRG.

  17548   Wed Apr 19 09:52:50 2023 RadhikaUpdateNeuralNetRayleigh spectrograms

Attached are the Rayleigh spectrograms of the error/control signal channels associated with the NN nonlinear control of IMC (pitch). The 4-hour data stretch starts at 3:45pm PDT on 4/18. The spectrograms were generated with (stride=5, fftlength=2, overlap=1). PNG images are attached for reference; the generated pdf files were too large to include here or send over email.

The Rayleigh statistic measures nongaussianity of the data.

  17547   Tue Apr 18 19:29:43 2023 yutaUpdateBHDLO phase noise measurements in ITMX single bounce, MICH and FPMI

[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.

  17546   Tue Apr 18 17:37:58 2023 ranaSummaryASCRL controller left for overnight

Anchal and I turned on another RL policy (ninedwarfs) with Chris's help.

It looks to be performing great, with good low frequency suppression and low noise injection at higher frequencies.

Going to leave it on overnight. It seems to respond well to lockloss of IMC, me whacking the MC2 chamber, walking near the MC2 chamber, kicking the optics by step in actuators, and turning off the sensors for a few seconds. Pretty robust!

 

  17545   Fri Apr 14 07:31:28 2023 JCUpdateGeneralAccelerometer for Tours

I was able to get this accelerometer going for the next Lab tours. I want to get this guy up on a big screen to give people a nice "wow". I found this accelerometer on the Y end cabinet and there is 1 more available if anyone needs it at 40m. It is a Brüel & Kjær 8318. It contains a PZT so there is no need to input a signal. The accelerometer seemed to only put out roughly 2 mV max, so i had to amplify with an SR560 to get a good looking signal. 

RXA: link to Manual

  17544   Thu Apr 13 17:58:16 2023 PacoUpdateALSMoku Phasemeter calibration and ALS noise

Ditto of 40m/17543 but for XBEAT >> Calibrated to 0.3061 +/- 0.0001


An interesting thing to look at is the ALS out of loop spectra using our Moku DPLL. Attachment #1 shows the calibrated noise spectra in Hz/rtHz of both XBEAT and YBEAT as taken by the Moku phasemeter when the ARM cavities are locked to PSL using POX/POY. A great improvement is noted at lower frequencies (almost an order of magnitude for Y, over an order of magnitude for X) and some residual seismic noise (between ARMs and IMC) is noticeable! At higher frequencies, the suppressed laser frequency noises are close to their former references.

However this is only great news for our ALS calibration scheme, as the DPLL range is limited and may not be useful for the usual CARM offset reduction using ALS.

The rms fluctutations for the ALS beatnotes using the Moku Phasemeter have dropped below the 100 Hz floor! We now have 50-55 Hz (before we had 200 to 300 Hz)


Took some ITM/ETM single arm calibration data using Moku Phasemeter ALS>

  • ITM gpstimes = [1365471104 to 1365471582]
  • ETM gpstimes = [1365472286 to 1365473448]

I then took some ITM actuation calibration data using the Michelson fringe. For this I lock MICH and turn on all five lines using AS55_Q >

  • ITMX gpstimes = [1365474355 to 1365474788]
  • ITMY gpstimes = [1365474816 to 1365475268]
  • Free swing = [1365475309 to 1365475535] (to get the fringe amplitude)

The ETM actuation calibration at these frequencies can be transferred using the POX/POY error signals and the ITM calibration from the gpstimes above. This should allow us a back to back cross-calibration comparison for arm cavities. Full analysis to follow this entry.


Finally, please take note of the area around the LSC rack! The temporary Moku phase meter calibration and setup referenced above are still a bit in the way. See Attachment #2

  17543   Thu Apr 13 11:38:50 2023 AnchalUpdateALSMoku Phasemeter calibration

I calibrated the moku phasemeter setup for reading beatnote fluctuations today. The calibration is referred to the DFD output (not including the phase tracker) channels by using the measurement made by gautam in 40m/14981.

Measurement setup

  • Set marconi to 40 MHz carrier, FM1 sine deviation of amplitude 2000 kHz (we expect maximum beatnote fluctuation of ~1.8 kHz for 50 pm length modulation in the arm length) at 145 Hz.
  • The output of amrconi is splitted, one half going to DFD for BEATY, one half going to Moku Phasemeter input 1.
  • Moku phase meter is set with following settings:
    • Input1:
      • Frequency : Auto
      • Bandwidth: 1 MHz
      • Coupling: AC
      • Impedance: 50 Ohms
      • Range: 400 mVpp
    • Output1:
      • Signal Freq offset
      • Scaling: 1 mV/Hz
      • Invert: Off
      • Offset: 0
      • Range: 10 Vpp
  • Measurement taken from 1365442502 to 1365444003

Analysis

  • Read channels C1:ALS-BEATY_FINE_I_OUT C1:ALS-BEATY_FINE_Q_OUT C1:ALS-BEATY_MOKU_PHASE_IN1 for 500s.
  • Used np.arctan2(Q, I) to read DFD phase output. Multiplied it by 1e6/70.973 to convert it into Hz using DFd calibration by Gautam in 40m/14981. This measurement brings in 340 ppm of uncertainty in the measurement.
  • Demodulated the phase at 145 Hz to get the signal sent by Marconi. Blue trace in the attachment is this signal.
  • Demodulated Moku phase output at 145 Hz and calculated the calibration constant required to match the ampltiude with 400second averaged DFD output.
    Calibration constant came out to be: 0.2953 +/- 0.0001
  • Multiplied the calibration constant to moku phase output. This is the orange curve in the attachment.
  • With this method, we get 0.035% uncertainty on phase calibration from Moku.
  • We can now use moku phasemeter for calibration measurements as the pahse tracker gain is not high enough for calibration lines above 200 Hz.

 

 

  17542   Wed Apr 12 21:32:22 2023 yutaSummaryLSCPRMI BHD power measurements

[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.

  17541   Wed Apr 12 16:11:41 2023 RadhikaSummaryLSCPRMI sensing matrix and RF demodulation phase tuning

[Yuta, Radhika]

We copied the coil balancing procedure found in /scripts/SUS/coilStrengthBalancing/AS1/CoilStrengthBalancing.ipynb to a new PRM directory. After modifying channel names for PRM, we followed the coil balancing procedure:

1. Locked PRY. This was chosen since full PRCL lock was not maintainable for the duration of measurement.

2. Injected 13 Hz line into the butterfly mode and looked for a peak in the LSC PRCL control signal (C1:LSC-PRCL_OUT_DQ). It appeared like the existing coil gains for PRM are already tuned to minimize the but-pos coupling.

3. Injected 13 Hz line into the POS mode and looked for a peak in the PRM oplev pitch and yaw signals (C1:SUS-PRM_OL_PIT_IN1_DQ / C1:SUS-PRM_OL_YAW_IN1_DQ). Like above, the existing coil gains seemed to be tuned to minimize the pos-angle coupling.

The attached spectrum was taken when POS was excited at 13 Hz using LOCKIN1. As expected the PRCL control signal sees the actuation, but we do not see a 13 Hz peak in the oplev pitch/yaw signals.

  17540   Tue Apr 11 19:46:45 2023 RadhikaUpdateALSX end green now indefinitely locking

I measured the OLTF of the XAUX-PDH loop [Attachment 1] now that the green laser is stably locking. I injected an excitation (100mVpp) at the error point of the loop using a Moku:Go. The excitation was summed with the PDH error signal (alpha) using an SR560, and the summed signal (beta) was sent to the PDH servo. (The Moku excitation was buffered with another SR560.) The transfer function beta/alpha was measured on the Moku. 

The loop has a UGF of 26.3 kHz, and a phase margin of ~25º (using 1/1-OLG convention).

Next steps:

- Replace PDH servo demod + controller with Moku:Go lock-in amplifier (ensure loop shape is maintained)

- Deploy digital filters to further increase loop bandwidth/phase margin

 

  17539   Fri Apr 7 16:28:34 2023 RadhikaSummaryLSCPRMI sensing matrix and RF demodulation phase tuning

[Paco, Radhika]

To determine the PRM angle-to-length coupling for PRCL, we want to inject pitch/yaw lines into PRM and find the corresponding peaks in the PRCL closed-loop control signal (below loop UGF). Below is a summary of PRMI locking efforts.

Locking PRMI carrier

- Locked arm cavities, ran YARM, XARM ASS to get PR2/PR3 alignment

- Locked MICH to dark fringe

- Aligned PRM by maximizing drop in REFLDC (reaches 2 when well aligned)

         *This was the hurdle when attempting to lock PRMI last week*

- Locked PRMI carrier using configurations in PRMI-AS55_REFL11.yml. There is now a "Lock PRMI (carr) using AS55/REFL11" action on the LSC screen that runs operateLSC.py with the aforementioned yaml file.

- Final DoF gains used: MICH --> 0.8; PRCL --> -0.07. At times BS was being kicked too hard, so we reduced the MICH gain from 1.2.

Lock stability

During PRMI lock, REFLDC was noisy with ~1 Hz fluctuations. We got PRMI to stay locked for a couple minutes at a time. Additionally it couldn't lock the AS port to dark fringe, and it stayed bright while tweaking the BS alignment.

We took spectra of ASDC during a lock stretch to quantify the DC power fluctuations at the AS port [Attachment 1]. The red trace is ASDC with PRMI locked. REF0 (black) is ASDC with MICH locked; REF1/REF2 (blue/green) are ASDC with single-bounce PRCL locked (either ITMX or ITMY misaligned). Note that the PRMI spectrum might need to be normalized by the PRCL gain / PRM transmission: ~ 10/0.057 = 175. The factor difference in ASDC fluctuations between MICH and PRMI for a single test point is ~144 --> with PRMI normalized, the ASDC fluctionations are comparable with MICH.

  17538   Thu Apr 6 21:09:12 2023 KojiSummaryNeuralNetTesting neural network controller during day time

I'm going to get into the PSL enclosure. Also turn on the HEPA for a while during the intrusion.
Work done.

Start of the work:
(cds) ~>gpstime 
PDT: 2023-04-06 21:09:36.670623 PDT
UTC: 2023-04-07 04:09:36.670623 UTC
GPS: 1364875794.670623

End of the work:
(cds) ~>gpstime 
PDT: 2023-04-06 21:19:37.331716 PDT
UTC: 2023-04-07 04:19:37.331716 UTC
GPS: 1364876395.331716

  17537   Thu Apr 6 11:49:45 2023 AnchalSummaryNeuralNetTesting neural network controller during day time

I've turned on NN controller for MC WFS PIT loops. One can disable this controller and go back to linear controller by sitemap>IOO>C1IOO_WFS_MASTER>Actions!>Stop Shimmer . One can start the controller again sitemap>IOO>C1IOO_WFS_MASTER>Actions!>Run Shimmer .

  17536   Wed Apr 5 16:44:31 2023 RadhikaSummaryLSCPRMI sensing matrix and RF demodulation phase tuning

[Paco, Radhika]

We calibrated the PRM oplev.

1. Disabled PRM damping and oplev loops
2. Injected excitation (f = 10 Hz; amplitude = 300 counts) to C1:SUS-PRM_ASCPIT_EXC
3. Measured spectra of C1:SUS-PRM_OL_PIT_IN1
     - 10 Hz spectral peak reached level of 1/rtHz (spectral counts)
4. Repeated steps 2-3 in yaw (excitation in C1:SUS-PRM_ASCYAW_EXC; spectra of C1:SUS-PRM_OL_YAW_IN1)
     - 10 Hz spectral peak also reached level of 1/rtHz (spectral counts)
4. Used PRM POS actuation calibration (-2.01e-8 m/counts/f^2) to estimate angular (PIT, YAW) actuation calibration
     - geometric calculation of angular displacement per count, given spatial displacement per count
     - PIT/YAW actuation calibration: 0.791 µrad/count/f^2
5. Estimated lever arm length of 1.5m (distance from PRM to QPD)
6. Calculated angular excitation amplitude: (300 actuation counts) x 0.791 µrad/count/f^2 = 237 µrad/f^2
7. Calculated calibration for oplev PIT/YAW spectra: spectral counts to radians
    - 1 count(m) = 1.5m * 237 µrad/f^2= 356 m*µrad/f^2.
---> For 10 Hz excitation, spectrum calibration = 3.56 µrad/count.

We took calibrated spectra of oplev PIT and YAW (Attachment 1) with the oplev loops open and closed. We see noise suppression up until a few Hz, as expected. The high-frequency floor appears to be at 1e-9 rad/rtHz with this calibration.

Next steps: improving PRMI angular control

 

  17535   Tue Apr 4 11:10:19 2023 AnchalSummaryNeuralNetTesting neural network controller during day time

I ran two recently trained neural network controllers today between 10 am and Noon. Each test comprised of four segments:

  • All loops open
  • Linear loop closed
  • Neural Network working alone
  • Neural Network + Linear Loop

The latest controller unfortunately failed in both cases, working alone and working together with linear loop.

The second latest controller functioned well, keeping the arm locked throughout.

  17534   Tue Apr 4 11:03:35 2023 JCSummaryElectronicsSR560: reworking
<p>I purchased some more of these from DigiKey. These parts are currently in the EE shop. These are replacements for the NDP5565 part of the SR560.</p>
  17533   Mon Apr 3 12:01:59 2023 RadhikaSummaryLSCPRMI sensing matrix and RF demodulation phase tuning

[Paco, Radhika]

We locked PRMI in carrier.

We refereced the old IFOconfigure script (/opt/rtcds/caltech/c1/burt/c1ifoconfigure/C1configurePRM_Carr.sh) to manually configure the LSC screen for PRMI. The final MICH/PRCL gain values used to achieve lock were flipped in sign:

(.snap file ---> final value)

MICH gain: -1.2 ----> 1.2
PRCL gain: 0.021 ---> -0.07

The FM trigger levels (enable/disable) for PRCL and MICH were set to (150/50). The following filter modules were engaged:

MICH: 2, 3, 6, 8
PRCL: 1, 2, 6, 9

During PRMI lock, the POPDC level reached 13130 counts, or 6.8 mW (using calibration of 1.931e6 counts/W). The POPDC counts level was ~1330 with only MICH locked, meaning the PRC gain was ~10. Attachment 1 is an image of REFL, AS, and POP monitors during lock.

Lock was maintained for close to a minute, allowing us to estimate the UGF at around 100 Hz. We used the AA_PRCL_UGF_meas.xml template to measure the loop transfer function. The GPS time (start, end) for a lock stretch with boost on is (1680547905, 1680547933 1364583160, 1364583442).

Next steps

1. Achieve better angular alignment to keep MICH locked to dark fringe - ASS? Seismic FF?

  17532   Thu Mar 30 16:45:09 2023 PacoSummaryLSCPRMI gain estimates and expected flashing at BHD and POP ports

Here are our best estimates for the optic transmission (power) coefficients.

PRM PR2 PR3 BS ITMX ITMY LO1 LO2 SRM SR2 AS1 AS2 AS3 AS4 BHD-BS
0.05637 0.022 0.00005 0.5 0.01384 0.01384 0 0 0.09903 0.00005 0 0.1 0 0 0.5

Assuming our input power to the IFO is 0.95 Watts, and the IMC transmission is 90%, about 855 mW should be incident on the PRM. Furthermore, following our recent estimates we can estimate our PRMI gain to be ~ 13.4.

  • Using these numbers we expect a single pass AS power of 517.8 uW and LO power of 530.1 uW when the PRM is misaligned and MICH is free swinging, consistent with recent estimates. When the PRM is aligned we would then expect the max PRMI BHD single port flash to be 7.6 mW.
  • Similarly, using these numbers we expect a single pass POPDC power of 1.01 mW, which then is expected to flash at a ~ 13.5 mW level when the PRM is aligned. The POP beam is split between the position sensor, our broadband POP22 and POP110 RFPD, and a CCD camera to monitor the POP beam.

POPDC calibration

I misaligned the PRM and ITMX to get a single ITMY bounce configuration. From the numbers above, I should expect a single ITMY bounce POPDC power of 255 uW. Instead, I measure a total of 173.5 uW = 78 uW (POP QPD) + 91 uW (POP RFPD) + 4.5 uW (POP camera) which is 50% less than expected frown.  The C1:LSC-POPDC_OUT level for this measurement was 335 counts, giving a rough empirical calibration of 1.931e6 counts / W. When the PRM is aligned and the MICH is free swinging, the POPDC flashes reach levels in excess of 14,500 counts implying 7.51 mW PRMI POPDC power. When PRM is misaligned the POP MICH flashes reach 1360 counts, implying 703 uW (which falls short by ~ 50% from our expectation).

There is probably an unaccounted BS in the ITMX table that may explain our observed difference. Nevertheless, our POPDC calibration should be good from here on.

  17531   Thu Mar 30 09:51:41 2023 PacoUpdateALSXALS / YALS power normalized and noise spectra

After the XAUX - XARM lock was recovered the C1:ALS-TRX_GAIN was set from 0.002 to 0.0006 to normalize the green transmission to 1 when the cavity is aligned. This situation was verified with YAUX as well. The green transmissions are now normalized to 1 when both arm cavities are aligned.


After this I took a reference ALS noise spectra (Attachment #1). The XALS rms noise is ~ 100 Hz (which is great compared to previous reference of > 250 Hz), while the YALS is slightly worse at high frequency but the rms is comparable to previous references (~ 250 Hz). This is somewhat encouraging for our future PRFPMI lock acquistions.

  17530   Wed Mar 29 19:19:41 2023 KojiUpdateALSX end green now indefinitely locking

Stable lock of the X End green laser was recovered.

- The biggest issue was that the laser PZT input had been terminated with a 50ohm at the laser head. (See Attachment 1: The terminator has already been removed in the photo.) Since the PZT output of the servo box (output impedance 10Ohm) goes through 680Ohm at the summing node for the modulation, the PZT output was attenuated by a factor of 15. This made the required servo gain for locking more than the box could deliver. More importantly, the PZT range (in terms of the laser frequency) was also limited. Momentary locks were still possible with the reduced range and gain. However, the actuation signal hit the rail within a few seconds because of the pendulum motion.

Once the terminator was removed from the head, the Xarm was locked with the green laser like a charm.

- On the way to the resolution, I had to go through the full scrutinization of the loop components one by one. Here is the record of the findings:

  • Inspected the green Refl PD (Thorlabs PFA36A). The gain setting of the PD was 40 dB, and the unlocked output voltage was 10.8 V. This is not only very close to saturation, but also the bandwidth drops below the modulation frequency (150 kHz according to Thorlabs' manual). The gain was changed to 20dB. This made the unlocked PD output to be 1.08V and the BW was expected to be 1MHz.
     
  • Checked the LO setting. The box has a label saying "LO 7dBm". The function generator setting of "0.66 Vrms" resulted in 7.0dBm at the mixer LO input. So this number is used. Exactly the same amount goes to the PZT summing node.
     
  • Checked the mod freq. The PDH error signal amplitude was maximized at 278.5kHz (mixer output observed with 50Ohm: 46.0mV), however, the signal looked distorted from the text-book shape of the PDF error. This means that the demod phase was not optimized.
    The mod freq of 287.5kHz made the PDH error signal look better while the response was weaker (mixer out: 31.2mV). It turned out that the cavity locking didn't like these mod freq between 280kHz~290kHz. The momentary lock stretches showed a lot of quasi-sinusoidal fluctuation ~600Hz in the error and transmission signals. Instead, the modulation of 210.5kHz was used. This made the error signal during lock stretches clean and tight. 
     
  • Box inspection: Checked the signal ratio between the error in and the error mon. The monitor gain seemed x20~x21. The PZT output and the PZT mon had identical gains. The transfer function of the box was measured with the gain knob changed from 0.00 to 7.00 where the transfer function started to get distorted with the given input. The gain was increased by 5dB/turn (i.e., 1 turn increases the gain by 5dB). ? It does not match with the info on the schematic and the datasheet? Anyways, the gain knob is working fine.
     
  • To resurrect the SLOW THERMAL servo, the monitor channels were connected to the DAQ interface. The existing slow channel servo/setting worked fine, wh
     
  • Usual caution: a slight touch to the satellite amp caused the UR OSEM PD completely black out. It means that just your presence at the X end can make some changes to the suspension.
     
  17529   Wed Mar 29 17:00:23 2023 AnchalUpdateIOOMC Length feedback is present but not visible in MEDM

I confirmed that MC Length feedback path to MC2 position is present and has been turned off in recent history. Feedback filter module can be seen in sitemap>IOO>Lock MC>MC2_LSC where the bottom fitler module is for feeding back MC Length to MC2. See attached screenshot.

This feedback signal goes and gets added to MC2 suspension longitudnal signal through ALTPOS path which is nominally not shown in any of the suspension screens (including the old ones). Note that this path is different than the LSC path that comes into each suspension screen.

Today, I tried a quick turning ON of this apth without playing around with any of the filters to see if the feedback helps. On first glance, it does not seem to help. Probably the gain values and filter modules need ot be adjusted. See attachment 2.

I'm turning this off again and in future someone should take a look at this loop.

  17528   Wed Mar 29 16:36:04 2023 PacoSummaryBHD"On why BH55 senses the LO phase, a finesse adventure of loss and residual DARM offsets"

I repeated the calculations but with FPMI (last case was all MICH). The qualitative behavior is the same, the BH55 sensing is mostly affected by residual darm offset. If the darm offset is of a couple of nm, the single RF sideband may sense the LO phase at as much as > 20 deg away from the nominal phase angle. This is not too different from the MICH case; so maybe I overlooked something about how I define FPMI in the calculation.

Attachments #1-3 show the plots of the BH55 (single RF sideband) and BH44 (double RF sideband) sensitivity to LO phase fluctuations around various nominal LO phase angles. Attachment #1 looks at the effect of differential loss, Attachment #2 looks at the effect of differential dc reflectivity (of the ITMs), and Attachment #3 looks at the effect of residual darm offsets. Dashed lines show the orthogonal quadrature (I) of the demodulated RF signals (always minimized).

  17527   Wed Mar 29 15:59:01 2023 AnchalUpdateIOOc1ioo model updated to add sensing to optic angle matrices

I've updated c1ioo model with adding WFS sensor to optic angle matrix and output filter module option. The output filter modules are named like EST_MC1_PIT to signify that that these are "estimated" angles of the optic. We can change this naming convention if we don't like it. I've also started DQ on the outputs of these filter moduels at 512 Hz sampling rate.

No medm screens have been made for these changes yet. One can still access them through:

For SENS_TO_OPT_P Matrix

medm -x /cvs/cds/rtcds/caltech/c1/medm/c1ioo/C1IOO_SENS_TO_OPT_P.adl

For SENS_TO_OPT_Y Matrix

medm -x /cvs/cds/rtcds/caltech/c1/medm/c1ioo/C1IOO_SENS_TO_OPT_Y.adl

For filter modules:

medm -x /cvs/cds/rtcds/caltech/c1/medm/c1ioo/C1IOO_EST_MC1_PIT.adl
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