The power meter used in the measurements of elog entries 2822, 3698 and 3709 was the Ophir PD300-3W.  This power head has several damaged patches  and a slight movement of the laser spot changes the reading considerably.  To verify I checked the power out with another power meter (the Vector S310) and found that there is no significant variation of the power output with the temperature of the laser.  And the power at 2.1A of diode current is 2W with 10% fluctuation arising from slight repositioning of the laser head.  There are regions of the Ophir PD300 which show the laser power to be about 1.9W.

Steve measured an apparent power drop in the 2W NPRO output from 2.1W to 1.6W(elog entry no 3698) at 2.1A of diode current in the laser (elog entry:  2822).  It was later noticed that the laser temperature was set to about 45 degC while the initial calibration was done at 25 deg C.  

It was felt that the recent power drop may have something to do with the increase in the operating temperature of the laser from 25 to 45 deg C.  Therefore the laser was returned to 25 deg C and the power output was remeasured and found to be 2.1W as it was at the begining(elog entry:3709)

It was also noticed that returning the laser to 25 deg. C resulted in a loss of efficiency in coupling to the PMC.  We suspected that this might be due to multimode operating conditions in the laser at particular operating temperatures.  In order to see if this is indeed the case the laser power output was observed as a function of temperature.  We do notice a characteristic saw-tooth shape which might indicate multimode operation between 39 and 43 deg C.  It is best to verify this by observing the power fluctuations in the transmitted beam of the stabilised reference cavity.

The measurement was made by attenuating the roughly 2W laser beam by a stack of two Neutral Density filfers and then measuring the transmitted light with the PDA36A photodetector.  This was because both the power meters used in the past were found to have linear drifts in excess of 30% and fluctuations at the 10% level. 

From the plot, you observed the reduction of the output power only by 1% between 25deg to 45deg.
This does not agree with the reduction from 2.1W to 1.6W.
Is there any cause of this discrepancy?

[Koji, Kevin]

The profile of the Innolight 2W was previously measured by measuring the reflected beam from the front surface of a W2 window (see entry). To investigate thermal effects, Rana suggested also measuring the profile of the beam reflected from the back surface of the W2.

I used the same setup and methods as were used in the first measurement. The mirror was moved so that only the beam reflected from the back surface of the W2 was reflected from the mirror. This beam was reflected from both the front of the mirror and the back of the mirror. An extra beam dump was positioned to block the reflection from the back of the mirror.

This measurement was made with 2.004 A injection current and 25.04°C laser crystal temperature.

The data was fit to w = sqrt(w0^2+lambda^2*(x-x0)^2/(pi*w0)^2) with the following results

For the horizontal beam profile:

reduced chi^2 = 5.1

x0 = (-186 ± 6) mm


w0 = (125.8 ± 1.4) µm

For the vertical beam profile:

reduced chi^2 = 14.4

x0 = (-202 ± 11) mm


w0 = (132.5 ± 2.7) µm

In the following plots, the blue curve is the fit to the vertical beam radius, the purple curve is the fit to the horizontal beam radius, * denotes a data point from the vertical data, and + denotes a data point from the horizontal data.

The differences between the beam radii for the beam reflected from the front surface and the beam reflected from the back surface are

Δw0_horizontal = (12.8 ± 1.6) µm

Δw0_vertical = (8.5 ± 2.9) µm

So the two measurements are not consistent. This suggests that the passage through the W2 altered the profile of the beam.

The vertical beam profile of the Innolight 2W laser was measured at eight points along the axis of the laser.

These measurements were made with the laser crystal temperature at 25.04°C and the injection current at 2.091A. z is the distance from the razor blade to the flat black face of the front of the laser.

The voltage from a photodiode was measured for the razor at a number of heights. Except for the first two points, one scan was made with the razor moving down and a second scan was made with the razor moving up. This data was fit to

y = a*erf(sqrt(2)*(x-x₀)/w) + b with the following results:

The values for w and its uncertainty were estimated with a weighted average between the two scans for the last six points and all eight points were fit to

w = w₀*sqrt(1+(z-z₀)²/z_R²) with the following results:

chi^2/ndf = 17.88

w₀ = (0.07 ± 0.13) mm

z₀ = (-27 ± 121) mm

z_R = (65 ± 93) mm

It looks like all of the data points were made in the linear region so it is hard to estimate these parameters with reasonable uncertainty.

Ben, Steve, and Koji

Ben came to the 40m and hooked up a cable to the main interlock service.
We have tested the interlock and confirmed it's working.

[Now the laser is approved to be used by persons who signed in the SOP.]

The RC, PMC, and MZ were unlocked during the interlock maneuver.
Now they are relocked.

The 2 W Innolight shutter is closed and enclosure door removed. Beam path blocked. Do not change this condition.

The PSL output beam guide was upgraded from 2" to 8" OD . It is green ready. Shutter is open.

The second set of Guralp channels is now plugged into the PEM ADCU, into channels which are confirmed to be working.  (Method: 1Vpp sine wave into channel, check with DataViewer).

Direction, Channel Name, .ini chnum, BNC plug # on ADCU

Vertical: C1:PEM-SEIS_GUR_VERT, 15023, #24

N/S (should be Y when the seismometer is put in place): C1:PEM-TEMP_2, 15001, #2

E/W (should be X when the seismometer is put in place): C1:PEM-TEMP_3, 15002, #3

There is IFO work going on, so I don't want to rename the channels / restart fb40m until a little later, so I'll just use the old TEMP channel names for now. 

There is something totally wrong with the E/W channel.  I can look at all 3 channels on a 'scope (while it's on battery, so the op-amps in the breakout box aren't grounded), and VERT and NS look fine, and when I jump around ("seismic testing"), they show spikes.  But the EW channel's signal on the 'scope is way smaller, and it doesn't show anything when I jump. 

I might use the handheld Guralp tester breakout box to check the seismometer.  Also, a suspicion I have is that whoever put the box back in on Friday night after our final noise measurements left the inputs shorted for this one channel.  It's the 3rd channel in the set, so it would be most likely to be stuck shorted...  Investigations will ensue.

 All the channels are now good, and all the names are back to making sense. 

The problem with EW2 was in fact that the alligator clip used to short the inputs during the noise test Friday night was left in the box.  Not great, but now it's taken care of, and we have recorded data of the noise of the breakout box, so we can include that in our plots to see if we're at the limit of how good we can do at subtracting noise.

The channels are now named thusly:

C1:PEM-SEIS_GUR_VERT  (BNC input #24, .ini channel #15023)

C1:PEM-SEIS_GUR_EW     (BNC input #3, .ini channel #15002)

C1:PEM-SEIS_GUR_NS      (BNC input #2, .ini channel #15001)

C1:PEM-SEIS_MC1_X         (BNC input #11, .ini channel #15010)

C1:PEM-SEIS_MC1_Y        (BNC input #12, .ini channel #15011)

C1:PEM-SEIS_MC1_Z       (BNC input #10, .ini channel #15009)

C1:PEM-SEIS_MC2_Y (Ranger, which for the Huddle Test is oriented VERTICALLY)   (BNC input #4, .ini channel #15003)

Now we wait.....and tomorrow extract the noise of each of the seismometers from this!

The 2nd trial of the Y arm ALS noise budgeting :

(Removal of broad band noise)

I will add the dark noise of the broad-band beat-note PD  and the MFD read out noise on the budget.

[Tega, JC]

We received the remaining 3 front-ends from LHO today. They each have a timing card and an OSS host adapter card installed. We also receive 3 dolphin DX cards. As with the previous packages from LLO, each box contains a rack mounting kit for the supermicro machine.

[JC, Tega]

We got the 3 front-ends from LLO today. The contents of each box are:

1. FE machine
2. OSS adapter card for connecting to I/O chassis
3. PCI riser cards (x2)
4. Timing Card and cable
5. Power cables, mounting brackets and accompanying screws

 Three good days of IOO pointing: Friday, Sat and Sun    What was changed?  May be the clamping on Friday?

IOO vertical changes recovering as tempeture. IP is clipping at plastic enclosure of ETMY

NOTE: ANTS at the PSL optical table.  I will mop with chemicals tomorrow if we see more.

I have added a .1", 45deg chamfer to the bottom of the adapter ring. This was added for a new placement of the eq stops, since the barrel screws are hard to access/adjust.

This also required a modification to the eq stop bracket, D960008-v2, with 1/4-20 screws angled at 45 deg to line up with the chamfer.

The issue I am running into is there needs to be a screw on the backside of the ring as well, otherwise the ring would fall backwards into the OSEMs in the event of an earthquake. The only two points of contact are these front two angled screws, a third is needed on the opposite side of the CoM for stability. This would require another bracket mounted at the back of the SOS tower, but there is very little open real estate because of the OSEMs.

Instead of this whole chamfer route, is it possible/easier to just swap the screws for the barrel eq stops? Instead of a socket head cap screw, a SS thumb screw such as this, will provide more torque when turning, and remove the need to use a hex wrench to turn.

There was a problem with running the webview report generator in matlab on Mafalada.  It complained of not having a spare report generator license to use, even though the report generator was working before and after on other machines such as Rosalba.  So I moved the old 32 bit matlab directory from /cvs/cds/caltech/apps/Linux/matlab to /cvs/cds/caltech/apps/Linux/matlab_old.  I installed the latest R2010b matlab from IMSS in /cvs/cds/caltech/apps/Linux/matlab and this seems to have made the cron job work on Mafalda now.

The 33MHz mod depth is now controlled by the OMC (C1:OMC-SPARE_DAC_CH_15).  The setting to give us the same modulation depth as before is 14000 (in the offset field).

I have been able to recover the ability to sit at zero CARM offset while the PRMI is locked on RELF33 and CARM/DARM are on ALS, effectively indefinitely. However, I feel like the transmon QPDs are not behaving ideally, because the reported arm powers freqently go negative as the interferometer is "buzzing" through resonance, so I'm not sure how useful they'll be as normalizing signals for REFL11. I tried tweaking the DARM offset to help the buildup, since ALS is only roughly centered on zero for both CARM and DARM, but didn't have much luck.

Example:

Turning off the whitening on the QPD segments seems to make everything saturate, so some thinking with daytime brain is in order.

How I got there:

It turns out triggering is more important than the phase margin story I had been telling myself. Also, I lost a lot of time to needing demod angle change in REFL33. Maybe I somehow caused this when I was all up on the LSC rack today?

We have previously put TRX and TRY triggering elements into the PRCL and MICH rows, to guard against temporary POP22 dips, because if arm powers are greater than 1, power recylcing is happening, so we should keep the loops engaged. However, since TRX and TRY are going negative when we buzz back and forth through the resonsnace, the trigger row sums to a negative value, and the PRMI loops give up. 

Instead, we can used the fortuitously unwhitened POPDC, which can serve the same function, and does not have the tendancy to go negative. Once I enabled this, I was able to just sit there as the IFO angrily buzzed at me. 

Here are my PRMI settings

REFL33 - Rotation 140.2 Degrees, -89.794 measured diff

PRCL = 1 x REFL33 I; G = -0.03; Acquire FMs 4,5; Trigger FMs 2, 9; Limit: 15k ; Acutate 1 x PRM

MICH = 1 x REFL33 Q, G= 3.0, Acquire FMs 4,5,8; Trigger FM 2, 3; Limit: 30k; Actuate -0.2625 x PRM + 0.5 x BS

Triggers = 1 x POP22 I + 0.1 * POPDC, 50 up 5 down

Just for kicks, here's a video of the buzzing as experienced in the control room

Given the checkout of the aLIGO BBPDs happening (aLOG link), wherein the PDs were acting funny, and Koji has made some measurements determining that intermodulation/nonlinearity of circuitry can corrupt 3F signals, I've made a similar measurement of the RF spectra of REFL165 when we're locked on DRMI using 1F signals. Maybe this could give us insight to our bad luck using REFL165...

In essence, I plugged the RF output of the PD into an AG4395, through a 10dB attenuator and downloaded the spectrum. I also did REFL33 as a possible comparison and because why not. The attached plots have the 10dB accounted for; the text files do not. 

REFL165 (Exposed PCB BBPD):

(What is all that crap between 8 and 9 fmod?)

REFL33 (Gold Box resonant RFPD):

If you look at the intermodulation at 14 (4+10) and 16 (6+10), 15 (5+10) would make any problem, thanks to the notch at 1f and 5f.

BUT, this absolute level of 165MHz is too tiny for the demodulator. From the level of the demodulated signal, I can say REFL165 has
too little SNR. We want to amplify it before the demodulator.

Can you measure this again with a directional coupler instead of the direct measurement with an attenuator?
The downstream has bunch of non-50Ohm components and may cause unknown effect on the tiny 165MHz signal.
We want to measure the spectrum as close situation as possible to the nominal configuration.

90MHz crap is the amplifier noise due to bad power bypassing or bad circuit shielding.

I have no comment on REFL33 as it has completely different amplification stages.

Now that I have followed the chain, the PD signal is indeed being amplified at the LSC rack. It goes into a ZFL-1000LN+ amplifier (~23dB gain at 165MHz and 15V supply), followed by a SHP-100 high pass filter, and then enters the RF IN of the demod board. 

I repeated the measurement in two spots.

First, I took a spectrum of the RF MON of the REFL165 demod board during DRMI lock; this was input-referred by adding 20dBm. 

Second, I inserted a ZFDC-10-5 coupler between the high pass and the RF input of the demod board. This was input-referred by adding 10dBm. 

My calibration isn't perfect; the peaks above the high pass corner seem to be different by a consistent amount, but within a few dBm. 

Thus, it looks like the demod board is getting a little under -40dBm of 165MHz signal at its input. 

Where is the PD out spectrum measured with the coupler???

 The "coupled" port of the coupler went to the AG4395 input, the output of the Highpass is connected to the "IN", and the "OUT" goes to the demod board. 

That's not what I'm asking.

Also additional cables are left connected to the signal path. I removed it.

After some enlightening conversation with Koji, we figured that the RF amplifier in the REFL165 chain is probably being saturated (the amp's 1dB compression is at +3dBm, has 23dB gain, and there are multiple lines above -20dBm coming out of the PD). I took a few more spectrum measurements to quantify the consequences, as well as a test with the highpass connected directly to the PD output, that should reduce the power into the amplifier. However, I am leaving everything hooked back up in its original state (and have removed all couplers and analyzers...)

I also took some DRMI sensing measurements. In the simple Michelson configuration, I took TFs of each ITMs motion to AS55Q to make sure the drives were well balanced. They were. Then, in the DRMI, I took swept sine TFs of PRCL, SRCL and differential ITM MICH motion to the Is and Qs of AS55 and all of the REFLs. I constrained the sweeps to 300Hz->2kHz; the loops have some amount of coupling so I wanted to stay out of their bandwidth. I also took a TF of the pure BS motion and BS-PRM MICH to the PDs. From these and future measurements, I hope to pursue better estimates of the sensing matrix elements of the DRMI DoFs, and perhaps the coefficients for compensating both SRCL and PRCL out of BS motion. 

I'm leaving analysis and interpretation for the daytime, and handing the IFO back to Diego...

The measurements I took yesterday bear this out. However, even putting the high-pass directly on the PD output doesn't reduce the signal enough to avoid saturating the amplifier.

We need to think of the right way to get the 165MHz signal at large enough, but undistorted, amplitude to the demod board. 

 The current signal chain looks like:

I previously made measurements at (3). Let's ignore that. 

Last night, I took measurements with a directional coupler at points (1) and (2), to see the signal levels before and after the amplifier. I divided the spectrum at (2) by the nominal gain of the amplifier, 23.5dB; thus if everything was linear, the spectra would be very similar. This is not the case, and it is evident why. There are multiple signals stronger than -20dBm, and the amplifier has a 1dB compression point of +3dBm, so any one of these lines at 4x, 6x and 10x fMod is enough to saturate. 

I also made a measurement at point 4 in the following arrangement, in an attempt to reduce the signal amplitude incident on the amplifier.  

 Though the signals below 100MHz are attenuated as expected, the signal at 110MHz is still too large for the amplifier. 

Minicircuits' SHP-150 only has 13dB suppression at 110MHz, which would not be enough either. SHP-175 has 31dB suppression at 110MHz and 0.82dB at 160MHz, maybe this is what we want.

I have found an SHP-150, but no SHP-175's (also, several 200's, and a couple of 500's).

Why do you say the SHP-150 isn't enough?  The blue peak at 10*fmod in your plot looks like it's at -12 dBm.  -13 dB on top of that will leave that peak at -25 dBm.  That should be enough to keep us from saturation, right?  It's not a lot of headroom, but we can give it a twirl until a 175-er comes in.  

Koji also suggests putting in a 110 MHz notch, combined with either an SHP-150 or SHP-175, although we'll have to measure the combined TF to make sure the notch doesn't spoil the high pass's response too much.

 I think 'saturation' here is a misleading term to think about. In the RF amplifiers, there is always saturation. What we're trying to minimize is the amount of distorted waveforms appearing at 3f and 15f from the other large peaks. Usually for saturation we are worried about how much the big peak is getting distorted; not the case for us.

 Jenne and I measured the situation using a SHP-150 directly attached to the REFL165 RF output, and at first glance, the magnitude of the 165MHz signal seems to not be distorted by the amplifier. 

We will soon investigate whether 165 signal quality has indeed improved. 

I was able to lock the DRMI on 3f signals this evening, although the loops are not stable, and I can hear oscillations in the speakers.  I think the big key to making this work was the placement of the SHP-150 high pass filter at the REFL165 PD, and also the installation of Koji's 110 MHz notch filter just before the amplifier, which is before the demod board for REFL165.  These were done to prevent RF signal distortion.

DRMI 3f:   With DRMI locked on 1f (MICH gain = 1, PRCL gain = -0.05, SRCL gain = 2, MICH = 1*REFL55Q, PRCL = 0.1*REFL11I, SRCL = 1*REFL165I), I excited lines, and found the signs and values for 3f matrix elements.  I was using the same gains, but MICH = 0.5*REFL165Q, PRCL = 0.8*REFL33I and SRCL = -0.2*REFL165I.  Part of the problem is likely that I need to include off-diagonal elements in the input matrix to remove PRCL from the SRCL error signal. 

With the DRMI locked on 1f, I took a sensing matrix measurement.  I don't think we believe the W/ct of the photodiode calibration (we need to redo this), but otherwise the sensing matrix measurement should be accurate.  Since the calibration of the PDs isn't for sure, the relative magnitude for signals between PDs shouldn't be taken as gospel, but within a single PD they should be fine for comparison. 

As a side note, we weren't sure about the MICH -> ITMs balancing, so we checked during a MICH-only, and with the locking apparatus we are unable to measure a difference between 1's for both ITMs in the output matrix, and 1 for ITMX and 0.99 for ITMY.  So, we can't measure 1% misbalances in the actuator, but we think we're at least pretty close to driving pure MICH. 

We kind of expect that SRCL should only be present in the 55 and 165 PDs, although we see it strongly in all of the REFL PDs.  Also, PRCL and SRCL are not both lined up in the I-phase.  So, I invite other people to check what they think the sensing matrix looks like. 

• The excitation lines (and matching notches) were on from 12:14am (
• Nov 11 2014 08:14:00 UTC / GPS 1099728856) to 12:20am (
•  
• Nov 11 2014 08:20:00 UTC / GPS 
• 1099729216) for 360sec. 
• MICH was driven with 800 counts at 675.13 Hz, with +1*ITMY, -1*ITMX. 
• PRCL was driven with 1000 counts at 621.13 Hz with the PRM. 
• SRCL was driven with 800 counts at 585.13 Hz using the SRM. 

All 3 degrees of freedom have notches at all 3 of those frequencies in the FM10 of the filter banks (and they were all turned on).  During this time, DRMI was locked with 1f signals. 

DRMI sensing matrix:

Earlier in the evening, I also took a PRMI sensing matrix, with the PRMI locked on REFL33 I&Q.  Watch out for the different placement of the plots - I couldn't measure AS55 in the DRMI case, since cdsutils.avg freaked out if I asked for more than 14 numbers (#PDs * #dofs) at a time.

Rana, Koji and I were staring at the DRMI sensing matrix for a little while, and we aren't sure why PRCL and SRCL aren't co-aligned, and why they aren't orthogonal to MICH.  Do we think it's possible to do something to digitally realign them?  Will the solution that we choose be valid for many CARM offsets, or do we have to change things every few steps (which we don't want to do)? 

Things to work on:

* Reanalyze DRMI sensing matrix data from 12:14-12:20am. 

* Make a simulated scan of higher order mode resonances in the arm cavities.  Is it possible that on one or both sides of the CARM resonance we are getting HOM resonances of the sidebands? 

* Figure out how to make DRMI 3f loops stable.

* Try CARM offset reduction with DRMI, and / or PRMI on REFL 165.

Sensing matrix calculation using DTT + Matlab

Note: If the signal phase is, for example,  '47 deg', the phase rotation angle is -47deg in order to bring this signal to 'I' phase.

Note2: As I didn't have the DQ channels for the actuation, only the relative signs between the PDs are used to produce the radar chart.
This means that it may contain 180deg uncertainty for a particular actuator. But this does not change the independence (or degeneracy) of the signals.


=== Sensing Matrix Report ===
Test time: 2014-11-11 08:14:00
Starting GPS Time: 1099728855.0
 

== PRCL ==
Actuation frequency: 621.13 Hz
Suspension (PRM) response at the act. freq.: 5.0803e-14/f^2 m/cnt
Actuation amplitude: 20.3948 cnt/rtHz
Actuation displacement: 1.0361e-12 m/rtHz
 
C1:LSC-AS55_I_ERR_DQ 4.20e+10
C1:LSC-AS55_Q_ERR_DQ -1.91e+11
==> AS55: 1.95e+11 [m/cnt] -24.58 [deg]
C1:LSC-REFL11_I_ERR_DQ 3.17e+12
C1:LSC-REFL11_Q_ERR_DQ -8.04e+10
==> REFL11: 3.17e+12 [m/cnt] -18.20 [deg]
C1:LSC-REFL33_I_ERR_DQ 4.15e+11
C1:LSC-REFL33_Q_ERR_DQ 4.28e+10
==> REFL33: 4.17e+11 [m/cnt] -137.11 [deg]
C1:LSC-REFL55_I_ERR_DQ 1.90e+10
C1:LSC-REFL55_Q_ERR_DQ -9.91e+09
==> REFL55: 2.14e+10 [m/cnt] -58.58 [deg]
C1:LSC-REFL165_I_ERR_DQ -1.16e+11
C1:LSC-REFL165_Q_ERR_DQ -3.14e+10
==> REFL165: 1.20e+11 [m/cnt] 45.20 [deg]
 
 
== MICH ==
Actuation frequency: 675.13 Hz
Suspension (ITMX) response at the act. freq.: 1.0312e-14/f^2 m/cnt
Suspension (ITMY) response at the act. freq.: 1.0224e-14/f^2 m/cnt
Actuation amplitude: 974.2957 cnt/rtHz
Actuation displacement (ITMX+ITMY): 2.0007e-11 m/rtHz
 
C1:LSC-AS55_I_ERR_DQ 2.55e+12
C1:LSC-AS55_Q_ERR_DQ 4.51e+12
==> AS55: 5.18e+12 [m/cnt] 113.51 [deg]
C1:LSC-REFL11_I_ERR_DQ -4.84e+10
C1:LSC-REFL11_Q_ERR_DQ -4.07e+09
==> REFL11: 4.85e+10 [m/cnt] 168.06 [deg]
C1:LSC-REFL33_I_ERR_DQ 2.06e+10
C1:LSC-REFL33_Q_ERR_DQ -9.39e+09
==> REFL33: 2.26e+10 [m/cnt] -167.51 [deg]
C1:LSC-REFL55_I_ERR_DQ 2.52e+09
C1:LSC-REFL55_Q_ERR_DQ -1.02e+10
==> REFL55: 1.05e+10 [m/cnt] -107.09 [deg]
C1:LSC-REFL165_I_ERR_DQ -1.79e+10
C1:LSC-REFL165_Q_ERR_DQ -5.50e+10
==> REFL165: 5.79e+10 [m/cnt] 102.02 [deg]


== SRCL ==
Actuation frequency: 585.13 Hz
Suspension (SRM) response at the act. freq.: 5.5494e-14/f^2 m/cnt
Actuation amplitude: 1176.3066 cnt/rtHz
Actuation displacement: 6.5278e-11 m/rtHz
 
C1:LSC-AS55_I_ERR_DQ -9.90e+10
C1:LSC-AS55_Q_ERR_DQ -1.18e+11
==> AS55: 1.54e+11 [m/cnt] -76.89 [deg]
C1:LSC-REFL11_I_ERR_DQ 2.96e+08
C1:LSC-REFL11_Q_ERR_DQ 4.78e+08
==> REFL11: 5.62e+08 [m/cnt] 41.42 [deg]
C1:LSC-REFL33_I_ERR_DQ -2.93e+09
C1:LSC-REFL33_Q_ERR_DQ 1.23e+10
==> REFL33: 1.27e+10 [m/cnt] -39.63 [deg]
C1:LSC-REFL55_I_ERR_DQ 3.71e+09
C1:LSC-REFL55_Q_ERR_DQ 2.78e+09
==> REFL55: 4.63e+09 [m/cnt] 5.86 [deg]
C1:LSC-REFL165_I_ERR_DQ -1.80e+10
C1:LSC-REFL165_Q_ERR_DQ 2.68e+10
==> REFL165: 3.23e+10 [m/cnt] -26.02 [deg]
 

Demodulation phases of the day

    'C1:LSC-AS55_PHASE_R = -53'
    'C1:LSC-REFL11_PHASE_R = 16.75'
    'C1:LSC-REFL33_PHASE_R = 143'
    'C1:LSC-REFL55_PHASE_R = 31'
    'C1:LSC-REFL165_PHASE_R = 150'


Koji pointed out something to me that I think he had told me ages ago, and Rana alluded to last night:  Since I'm not tuning my "demod phase" for the sensing matrix lockins, unless I happened to get very lucky, I was throwing away most of the signal.  Lame.  

So, now the magnitude is sqrt(real^2 + imag^2), where real and imag here are the I and Q outputs of the lockin demodulator, after the 0.1Hz lowpass.  (I put in the low pass into all of the Q filter banks).  To keep the signs consistent, I did do a rough tuning of those angles, so that I can use the sign of the real part as the sign of my signal.  When I was PRMI locked, I set the phase for all things acutated by MICH to be 79deg, all things actuated by PRCL to be 20 deg, and when DRMI locked set all things SRCL to be 50deg. 

After doing this, the phases of my sensing matrix output matches Koji's careful analyses.  I don't know where the W/ct numbers I was using came from (I don't think I made them up out of the blue, but I didn't document where they're from, so I need to remeasure them).  Anyhow, for now I have 1's in the calibration screen for the W/ct calibration for all PDs, so my sensing matrices are coming out in cts/m, which is the same unit that Koji's analysis is in. (Plot for comparing to Koji is at end of entry).

While reducing the CARM offset, I left the sensing matrix lines on, and watched how they evolved.  The phases don't seem to change all that much, but the magnitudes start to decrease as I increase the arm power.

For this screenshot, the left plot is the phases of the sensing matrix elements (all the REFL signals, MICH and PRCL), and the right plot is the magnitudes of those same elements.  Also plotted is the TRX power, as a proxy for CARM offset.  The y-scale for the TRX trace is 0-15.  The y-scale for all the phases is -360 to +360.  The y-scale of the magnitude traces are each one decade, on a log scale.

Bonus plot, same situation, but the next lock held for 20 minutes at arm powers of 8.  We don't know why we lost lock (none of the loops were oscillating, that I could see in the lockloss plot).

Here are some individual sensing matrix plots, for a single lock stretch, at various times.  One thing that you can see in the striptool screenshots that I don't know yet how to deal with for the radar plots is the error bars when the phase flips around by 360 degrees.  Anyhow, the errors in the phases certainly aren't as big as the error boxes make them look.

PRMI just locked, CARM offset about 3nm, CARM and DARM on ALS comm and diff, arm powers below 1:

PRMI still on REFL33 I&Q, CARM and DARM both on DC transmissions, arm powers about 4:

CARM offset reduced further, arm powers about 6:

CARM offset reduced even more, arm powers about 7:

For this plot for comparing with Koji's analysis, I had not yet put 1's in the calibration screen, so this is still in "W"/m, where "W" is meant to indicate that I don't really know the calibration at all.  What is good to see though is that the angles agree very well with Koji's analysis, even though he was analyzing data from yesterday, and this data was taken today.  This sensing matrix is DRMI-only (no arms), 1f locking.

Bonus plot, PRMI-only sensing matrix, with PRMI held using REFL 33 I&Q:

I have reconfigured the refl beam path on the AP table to include REFL33 and REFL165. Would be done if we hadn't prepared P BSs instead of S, which required some serious digging to find two others. And if someone hadn't stolen our two 3m SMA cables that Keiko and I made on our previous visit and I had left with the 3f PDs. I don't expect them to reappear but if they do, it would be grand.

Note: Refl beam from ifo looks a bit high, ~1cm on the lens 20'' from output port. Not sure what that means about ifo alignment change, I've left it as is. When we know we have a good alignment, we should be able to easily realign the beam path if necessary. If it remains the same, we might want to change the lens height.

Done:

1) REFL11 and REFL55 are now hooked up and aligned in a low power beam. (I set the power as low as I could by eye to not risk burning the PDs during alignment)

2) The required BSs and REFL33 and REFL165 are in place, powered.

3) I have set them in a configuration such that the beam is the same distance from the main beam, to adjust beam size easily for all 4.

4) Camera has been moved from main beam to behind a steering mirror, ND filters removed, centered on camera.

To Do:

1) Find one more longish SMA cable.

2) Align beam on REFL33 and REFL165.

3) Check beam size carefully. (I get a plateau on the scope, and I can "hide" the beam on the PD, but it could be better. The path has become longer by ~5-8inches.)

4) Adjust power.

5) Redo layout diagram, post in wiki.

So, I really should have done this as soon as Manasa measured the arm lengths... I've updated my MIST model with the real arm lengths, but still am using assumed identical losses of 75ppm on each mirror. (I've tried measuring the arm losses for real, but got numbers in the hundreds of ppms, so I need to reexamine things...) 

Here's a simulation of the fields in a perfectly locked PRC when CARM is swept (Normalized to input power = 1). 

More importantly, here's the latest simulation of MICH vs. PRCL demodulation angle separation in the 3F signals. It seems that we may be getting burned by using REFL33 for the PRC lock. REFL165, on the other hand looks much more robust. We should try this out. 

(Some of my previous simulations incorrectly implemented MICH excitations; I only moved the ITMS, not the ETMS along with them, so some other stuff slipped in... )

 Here's the angles of MICH and PRCL from the my earlier plot by themselves; this shows that the individual demod angles in REFL165 aren't changing much either. 

 To check the demodulation boards for REFL33 and REFL165, a long cable from ETMY (SUS-ETMY-SDCOIL-EXT monitor) is pulled to the rack on Y side.

(1) A filter just after the RF input and (2) transfer function from the RF input to the demodulated signal will be checked for the two 3f demod boards to confirm that they are appropriate for 33 and 165 MHz.

There is a LP filter just after the RF input of an demodulation board (its schematic can be found as D990511-00-C on DCC). I have checked if the 3f freq, 33MHz, can pass  this filter. The filter TF from the RF input to RF monitor (the filter is between the input and monitor) on REFL33 demo-board was measured as shown in Fig. 1. At 33MHz, the magnitude is still flat and OK, but the phase is quite steep. I am going to consider if it is ok for the PDH method or not.

 Fig. 1 Transfer function from the RF input to RF monitor on the REFL33 demodulation board. At 33MHz, a very steep phase is applied on the input signal.

The phase delay due to the RF input filter on the demodulation board will not bother the resulting PDH signals.

I quickly calculated the below question (see the blue sentence in the quote below). I applied an arbitrary phase delay (theta) due to the filter I measured, on the detected RF signal by the photo detector. Then the filtered RF signal is multiplied by cos(omega_m) then filter the higher (2 omega_m) freqency as the usual mixing operation for the PDH signal. As a result, the I signal is delayed by cos(theta) and the Q signal is delayed by sin(theta). Therefore the resulting signals and its orthogonalitity is kept ok. From the sideband point of view, theta is applied on both upper and lower and seems to make the unbalance, however, as it is like a fixed phase offset on both SBs at the modulation frequency, the resulting signals is just multiplied by cos or sin theta for I and Q, respectively. It won't make any strange effect (it is difficult to explain by sentence not using equations!).

Filters at the RF inputs of REFL33 and REFL165 demodulation boards were measured again. The filters will be totally fine for 33MHz and 165MHz.

Last time I forgot to calibrate the cable lengths, therefore the phase delay of the measurement included the cable lengths. This time the measurements were done for REFL33 and REFL165 demod board with calibration. As the cable lengths were calibrated, the shown plots (Fig.1 and Fig.2) do not include the phase delay dues to measurement cables. Please note that the x-axis is in linear. The phase delays of both boards seems to be not too steep (it will not affect anyway, as Kiwamu pointed out in his comment on the previous post). You can see that the two filters do not filter 33MHz and 165MHz component out.

Fig.1 A response of a filter which is placed just after the RF input of the demodulation board for REFL33. X-axis is shown in linear (~50MHz).

Fig.2 A response of a filter which is placed just after the RF input of the demodulation board for REFL165.

I also quickly checked the orthogonality of the demodulation board for REFL33 and REFL165 using function generators and oscilloscope. I checked the frequencies at 1,10,100,1K,10KHz of the demodulated signals. They are fine and ready for 3f signal extraction.

Wait. I am checking the whitening filters of the 33 and 165 demodulation boards.

Also, LSC-REFL33-I-IN1(IN2, OUT) and LSC-REFL165-Q-IN1(IN2,OUT) channels may not be working??

LSC-REFL33-I-IN1(IN2, OUT) and LSC-REFL165-Q-IN1(IN2,OUT) channels are back!

We disconnected and connected again the AA filters then the channels are fixed. Apparently the AA filters just before the digital world were somhow charged and not working... Thank you Kiwamu!

Whitening filters for the REFL33 & 165 demodulated channels were measured and confirmed that they are working. They can be turned on and off by un-white filter switches on the MEDM screen because they are properly linked. The measured filter responses are showen below. (Sorry, apparentyl the thumbnails are not shown here. Please click the attachments.) 

Attachments: (top) Whitening filter for REFL33 demodulation board. (bottom) Whitening filter response for REFL 165 demodulation board.

Keiko, Jamie , Kiwamu

The I and Q orthogonalities of REFL33 and 165 demodulation board were measured by "orthogonality.py"  Python package scipy were addied on Pianosa to run this code. Please note that "orthogonality.py" can be run only on Pianosa.  

The results were:

REFL165

ABS = 1.070274, PHASE = -81.802479 [deg]

if you wanna change epics values according to this result, just copy and execute the following commands

ezcawrite C1:LSC-REFL165_Q_GAIN 0.934340 && ezcawrite C1:LSC-REFL165_PHASE_D -81.802479

- - - - - - - - - - - - - - - - - -

REFL33

ABS = 1.016008 , PHASE = -89.618724 [deg]

if you wanna change epics values according to this result, just copy and execute the following commands

ezcawrite C1:LSC-REFL33_Q_GAIN 0.984244 && ezcawrite C1:LSC-REFL33_PHASE_D -89.618724

Fig.1 and 2  are the resulting plots for 33 and 165 MHz demod baoards, respectively.You should look at the 3Hz in x axis, as the demodulated signal frequency was set as 3 Hz.

Fig. 1 REFL33 I and Q orthogonality at 3 Hz.

Fig. 2 REFL165 I and Q orthogonality at 3 Hz.