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ID Date Author Type Category Subject
15097   Fri Dec 13 12:28:43 2019 YehonathanUpdatePSLPMC cavity ringdown measurement

I grab the data we recorded yesterday from the scope and plot it in normalized units (remove noise level and divide by maximum). See attachment.

It can be seen that the measured ringdown time is ~ 17us while the shut-off time is ~12us.

I plan to model the PD+AOM as a lowpass filter with an RC time constant of 12us and undo its filtering action on the PMC trans ringdown measurement to get the actual ringdown time.

Is this acceptable?

Attachment 1: Ringdown_InitialProcess.pdf
15099   Tue Dec 17 00:23:28 2019 YehonathanUpdatePSLMapping the PSL electronics

I added to the PSL wiring list the ioo channels and the laser shutter (See attached pdf for an updated list).

The total channel numbers for now:

 ai 57 ao 13 bi 1 bo 36

I counted each mbbo as 1 bo but I am not sure that's correct.

Still need to allocate Acromags.

Attachment 1: PSL_Wirings_-_Sheet1_(2).pdf
15100   Tue Dec 17 18:05:06 2019 YehonathanUpdatePSLMapping the PSL electronics

Updated the channel list (Attached):

1. Removed the MC steering mirror PZT channels

3. Recounted the mbbos correctly

4. Allocated Acromags:

 Model Purpose No. Spare channels XT1221 ai 7 11 XT1541 ao + src bo 2 9 ao XT1121 src bo 2 4 XT1121 sink bo 1 4

I think we can start wiring.

Attachment 1: PSL_Wirings_-_Sheet1_(3).pdf
15103   Fri Dec 20 18:33:21 2019 YehonathanUpdatePSLMapping the PSL electronics

Final (hopefully) PSL channel list is attached with allocated Acromag channels. Wiring spreadsheet coming soon.

Current Acromag count:

 AI 8 AO 2 BIO 4 Number of channels 8*8+2*8+4*16=144 Number of wires 144*2=288

Attachment 1: PSL_Wirings_-_Channel_List.pdf
15104   Mon Dec 23 19:30:20 2019 YehonathanUpdatePSLMapping the PSL electronics

15105   Fri Dec 27 15:01:02 2019 YehonathanUpdatePSLPMC cavity ringdown measurement

I measured PMC ringdowns for several input powers. I change the input power by changing the DC voltage to the AOM.

First, I raise the DC voltage to the AOM from 0V and observe the signal on the picked off PD. I see that at around 0.6V the signal stops rising. The signal on the PD is around 4V at that point so it is not saturated.

Up until now, we provided 1.5V to the AOM, which means it was saturated.

I measured ringdowns at AOM voltages of 0.05, 0.1, 0.3, 0.5, 1 volt by shutting off the DC voltage to the AOM and measuring the signal at the PMC transmission PD and the picked off PD simultaneously for reference.

Attachment 1 shows the reference measurement for different AOM voltages. For low AOM DC voltages, the response of the AOM+PD is slower.

Attachment 2 shows the PMC transmission PD measurements which barely change as a function of AOM voltage but shows the same trend. I believe that if the AOM+PD response was much faster there would be no observable difference between those measurements.

Attachment 3 shows PMC transmissions and references for AOM voltages 0.05V and 1V. It seems like for low AOM voltages we are barely fast enough to measure the PMC ringdown.

I fitted the 0.3V ringdown and reference to a sum of two exponentials (Attachment 4).

The fitting function is explicitly a * nm.exp(-x/b) +c* nm.exp(-x/d) +e

For the PMC transmission I get:

a = 0.21
b = 3.64 (us)
c = 0.69,
d = 39.62 (us)
e = 2.0e-04

For the reference measurement:

a = 0.34
b = 4.97 (us)
c = 0.58
d= 31.22 (us)
e = 1.11e-03


I am still not able to do deconvolution of the ref from the measurement reliably. I think we should do a network analyzer measurement.

Shruti, the PD is again in your beam path.

Attachment 1: PDAOMResponse.pdf
Attachment 2: PMCTransmission.pdf
Attachment 3: RingdownsAndRefs.pdf
Attachment 4: TwoExponentialFitAOM0.3V.pdf
15106   Fri Dec 27 16:26:11 2019 YehonathanUpdatePSLPMC Linewidth measurement

I try to measure the linewidth of the PMC by ramping the PMC PZT.

I do it by connecting a triangular shape signal to FP Test 1 on the PMC servo front panel (I know, it is probably better to connect it to DC EXT. next time.) and turn the servo gain to a minimum.

Attachment 1 shows the PMC transmission PD as the PZT is swept with the EOM connected and when it is disconnected. It shows the PMC over more than 1 free spectral range.

For some reason, I cannot seem to be able to find the 35MHz sidebands which I want to use to calibrate the PZT scan. I made sure that the EOM is driven by a 35MHz signal using the scope. I also made sure that the PMC cannot to lock without the EOM connected.

I am probably doing something silly.

Attachment 1: PMCTransmissionSpectra.pdf
15109   Wed Jan 1 14:14:00 2020 YehonathanUpdatePSLPMC Linewidth measurement

Turns out the 35MHz sidebands are way too weak to resolve from the resonance when doing a PZT scan.

I connect the IFR2023B function generator on the PSL table to the EOM instead of the FSS box and set it to generate 150MHz at 13dbm.

To observe the resulting weak sideband I place a PDA55 at the peak-off path from the transmission of the PMC where there is much more light than the transmission of the PMC head mirror. Whoever is using this path there is a PD blocking it right now.

I do a PZT scan by connecting a triangular signal to the EXT DC on the PMC servo with and without the EOM (Attachment 1). A weak sideband can clearly be spotted now.

Using the above 150MHz sideband calibration I can find the roundtrip time to be 1.55ns.

I take a high-resolution scan of a resonance peak and fit it to a Lorentzian (Attachment 2) and find a roundtrip loss of 1.3%.

Using the above results the cavity decay time is 119ns.

We should investigate what's going on with the ringdown measurements.

Attachment 1: 150MHzSideBandCreation.pdf
Attachment 2: LinewidthMeasurment.pdf
15110   Wed Jan 1 16:04:37 2020 YehonathanUpdatePSLMapping the PSL electronics

Done.

Quote:

For the IMC servo board, it'd be easiest to copy the wiring scheme for the BIO bits as is configured for the CM board (i.e. copy the grouping of the BIO bits on the individual Acromag units). This will enable us to use the latch code with minimal modifications (it was a pain to debug this the first time around). I don't see any major constraint in the wiring assignment that'd make this difficult.

15115   Fri Jan 10 14:21:19 2020 YehonathanUpdatePSLc1psl reboot

PSL controls on the sitemap went blank. Rebooted c1psl. PSL screens seem normal again.

15119   Mon Jan 13 23:30:53 2020 YehonathanSummaryPSLChanges made since Gautam left

As per Gautam's request, I list the changes that were made since he left:

1. The AOM driver was connected to a signal generator.

2. The first order beam from the AOM was coupled into the PMC while the zero-order beam is blocked. We might want to keep this configuration if the pointing stability is adequate.

3. c1psl got Burt restored to Dec 1st.

4. Megatron got updated.

Currently, c1susaux seems unresponsive and needs to be rebooted.

15131   Fri Jan 17 21:56:22 2020 YehonathanUpdatePSLAOM first order beam alignment

Today I noticed that the beam reflected from the PMC into the RFPD has a ghost (attachment) due to reflection from the back of the high transmission beam splitter that stirs the beam into the RFPD.

The two beams are focused into the RFPD.

In the past, the ghost beam was probably blocked by the BS mirror mount.

I put an iris to block the ghost beam.

Attachment 1: 20200117_174841.jpg
15132   Fri Jan 17 22:11:19 2020 YehonathanUpdatePSLRingdown measurements

I prepare for the ringdown measurement of the PMC according to Gautam's previous experiments.

1. I assembled the needed PDs and power supplies, lenses, beamsplitters and optomechanics needed for the measurement.

2. I surveyed the laser power with an Ophir power meter in the different parts of the experiment. All the measurements were done with the AOM driver excited with 1V DC.

For the PMC reflection, we chose to split off the beam that goes into the reflection camera. The power in that beam is ~ 0.11mW when the PMC is locked and 2.1mW otherwise.

For the PMC transmission, we chose to split the beam that is transmitted through the second steering mirror after the PMC. The power in that beam is 2mW.

For the peak off before the PMC, we chose to split the beam that goes into the fiber coupler. That path contains also the other AOM diffraction orders: 2.26mW in the 0th order beam, 6.5mW in the 1st order beam, 0.14mW in the 2nd order beam.

3. I placed a 10% beam splitter in the peak-off path such that 90% still goes into the fiber coupler (Attachment 1). I place a lens and PDA255 to measure the peak-off (Attachment 2).

It's getting late, I'll continue with the PD placements on Tuesday.

Attachment 1: 20200117_192455.jpg
Attachment 2: 20200117_192448.jpg
15154   Sat Jan 25 11:54:42 2020 YehonathanUpdatePSLRingdown measurements

Zero order beam PMC ringdown

On Wednesday I installed 3 PDs (see attached photos) measuring:

1. The input light to the PMC. Flip-mirror was installed (sorry Shruti) on the beam path to the fiber coupler.

2. Reflected light from the PMC.

3. PMC transmitted light.

I connected the three PDs to the oscilloscope and the AOM driver to a function generator. I drive the AOM with a square wave going from 1V to 0V.

I slowly increased the square wave frequency. The PMC servo doesn't seem to care. I reach 100KHz - it seems excessive but still works. In any case, I get the same results doing a single shut-down from a DC level.

I download the traces. I normalize the traces but I don't rescale them (Attachment 4) so that the small extinction can be investigated.

I notice now that the PDs show the same extinction. It probably means I should have taken dark currents data for the PDs.

Also, I forgot to take the reflected data when the PMC is out of resonance with the laser which could have helped us determine the PMC transmission.

Again, the shutdown is not as sharp as I want. There is a noticeable smoothening in the transition around t = 0 which makes the fit to an exponential difficult. I suspect that the function generator is the limiting device now. I hooked up the function generator to the oscilloscope which showed similar distortion (didn't save the trace)

I try to fit the transmission PD trace to a double exponential and to Zucker model (Attachment 5).

The two exponentials model, being much less restrictive, gives a better fit but the best fit gives two identical time constants of 92ns.

The Zucker model gives a time constant of 88ns. Both of these results are consistent with more or less with the linewidth measurement but this measurement is still ridden with systematics which hopefully will become minimized IMC ringdowns.

Attachment 1: Input_beam_path.jpg
Attachment 2: Reflected_Beam_Path.jpg
Attachment 3: Transmitted_Beam_Path.jpg
Attachment 4: PMCRingdownNormalizedRawdata.pdf
Attachment 5: TransPDFits.pdf
15170   Tue Jan 28 20:51:37 2020 YehonathanUpdateIOOIMC WFS servos stable again

I resume my IMC ringdown activities now that the IMC is aligned again.

To avoid any accidental misalignments Gautam turned off all the inputs to the WFS servo.

I set up a PD and a lens as in attachment 1 (following Gautam's setup).

I connect the REFL, TRANS and INPut PDs to the oscilloscope.

I connect a Siglent function generator to the AOM driver. I try to shut off the light to the IMC using 1V DC waveform and pressing the output button manually. However, it produced heavily distorted step function in the PMC trans PD.

I use a square wave with a frequency of 20mHz instead with an amplitude of 0.5V offset of 0.25V and dutycycle of 1% so there will be minimal wasted time in the off state. I get nice ringdowns (attachment 2) - forgot to take pictures. The autolocker slightly misaligns the M2 every time it is acting, so I manually align it everytime the IMC gets unlocked.

Data analysis will come later.

I remove the PD and lens and reenable the WFS servo inputs. The IMC locks easily. The WFS outputs are very different than 0 now though.

15175   Wed Jan 29 12:40:24 2020 YehonathanUpdateIOOIMC Ringdowns preliminary data analysis

I analyze the IMC ringdown data from last night.

Attachment 1 shows the normalized raw data. Oscillations come in much later than in Gautam's measurement. Probably because the IMC stays locked.

Attachment 2 shows fits of the transmitted PD to unconstrained double exponential and the Zucker model.

Zucker model gives time constant of 21.6us

Unconstrained exponentials give time constants of 23.99us and 46.7us which is nice because it converges close to the Zucker model.

Attachment 1: IMCRingdownNormalizedRawdata.pdf
Attachment 2: IMCTransPDFits.pdf
15183   Mon Feb 3 13:54:10 2020 YehonathanUpdateIOOIMC Ringdowns extended data analysis

I extended the ringdown data analysis to the reflected beam following Isogai et al.

The idea is that measuring the cavity's reflected light one can use known relationships to extract the transmission of the cavity mirrors and not only the finesse.

The finesse calculated from the transmission ringdown shown in the previous elog is 1520 according to the Zucker model, 1680 according to the first exponential and 1728 according to the second exponential.

Attachment 1 shows the measured reflected light during an IMC ringdown in and out of resonance and the values that are read off it to compute the transmission.

The equations for m1 and m3 are the same as in Isogai's paper because they describe a steady-state that doesn't care about the extinction ratio of the light.

The equation for m2, however, is modified due to the finite extinction present in our zeroth-order ringdown.

Modelling the IMC as a critically coupled 2 mirror cavity one can verify that:

$m_2=P_0KR\left[T-\alpha\left(1-R\right)\right]^2+\alpha^2 P_1$

Where $P_0$ is the coupled light power

$P_1$ is the power rejected from the cavity (higher-order modes, sidebands)

$K=\left(\mathcal{F} /\pi \right )^2$ is the cavity gain.

$R$ and $T$ are the power reflectivity and transmissivity per mirror, respectively.

$\alpha^2$ is the power attenuation factor. For perfect extinction, this is 0.

Solving the equations (m1 and m3 + modified m2), using Zucker model's finesse, gives the following information:

Loss per mirror = 84.99 ppm
Transmission per mirror = 1980.77 ppm
Coupling efficiency (to TEM00) = 97.94%
Attachment 1: IMCTransReflAnalysis_anotated.pdf
15186   Tue Feb 4 18:13:01 2020 YehonathanUpdatePSLBench testing of PSL ai channels

{Yehonathan, Jon, Jordan}

I tested the ai channels of the new PSL Acromag by looping an already-tested ao channel (C2:PSL-FSS-INOFFSET) back to the different ai channels.

I use Jon's IFOTest with /users/jon/ifotest/PSL.yaml.

I created a spreadsheet for the testing based on the current wiring spreadsheet. I added two columns for the high and low readings for each ai channel (attached pdf).

I marked in red the failed channels. Some of them are probably calibration issues, but the ones that show the same voltage for high and low are probably disconnected wires.

I redid the test on the channel that seemed disconnected to confirm.

I created a yaml file with all the failed channels for retesting called /users/jon/ifotest/PSL_failed_channels.yaml.

Attachment 1: c1psl_wire_testing_-_By_Connector.pdf
15187   Wed Feb 5 08:57:11 2020 YehonathanUpdatePSLBench testing of PSL ai channels

I checked the failed channels against the EPICS database definitions and the yaml file inputted to IFOTest. The channels where the readings are something other than +10/0 V, but the high/low values do change, I think can be attributed to one of two things:

• An incorrect gain and/or offset conversion parameter in the yaml file
• The EPICS SMOO parameter (smoothing) is set to some long value

I fixed the channel gains/offsets in the master yaml file (PSL.yaml). I also disabled smoothing in the EPICS defintions of the new PSL channels for the purpose of testing. We can uncomment those lines after installing the new chassis if noise is a problem. Please go ahead and re-test the channels again.

 Quote: I marked in red the failed channels. Some of them are probably calibration issues, but the ones that show the same voltage for high and low are probably disconnected wires.
15189   Wed Feb 5 21:04:10 2020 YehonathanUpdatePSLBench testing of PSL ai channels

{Yehonathan, Jon}

We retested the failed ai channels. Most of them got fixed by applying the inverse calibration in the yaml file.

We still find some anomalous channels, mostly in the DB25 connector. Turns out, their limits were ill-defined in the EPICS database. Specifying the right limit fixed the issue.

We find one miswired channel (BNC4). We connected the BNC to the right channel on the Acromag unit which fixed the issue.

Overall all the ai channels were successfully bench-tested.

Quote:

I checked the failed channels against the EPICS database definitions and the yaml file inputted to IFOTest. The channels where the readings are something other than +10/0 V, but the high/low values do change, I think can be attributed to one of two things:

• An incorrect gain and/or offset conversion parameter in the yaml file
• The EPICS SMOO parameter (smoothing) is set to some long value

I fixed the channel gains/offsets in the master yaml file (PSL.yaml). I also disabled smoothing in the EPICS defintions of the new PSL channels for the purpose of testing. We can uncomment those lines after installing the new chassis if noise is a problem. Please go ahead and re-test the channels again.

 Quote: I marked in red the failed channels. Some of them are probably calibration issues, but the ones that show the same voltage for high and low are probably disconnected wires.
15190   Wed Feb 5 21:13:17 2020 YehonathanUpdateIOOIMC Ringdowns extended data analysis

I translate the results obtained in the previous elog to the IMC 3 mirror cavity. I assume the loss in each mirror in the IMC is equal and that M2 has a negligible transmission.

I find that to a very good approximation the loss per IMC mirror is 2/3 the loss per mirror in the 2 mirror cavity model. That is the loss per mirror in the IMC is 56 ppm. The transmission per mirror in the IMC is the same as in the 2 mirror model, which is 1980 ppm.

The total transmission is the same as in the 2 mirror model and is given by:

$\frac{P_0}{P_0+P1}KT^2\approx 90\%$

where $\frac{P_0}{P_0+P1}$ is the coupling efficiency to the TEM00 mode.

15198   Fri Feb 7 12:58:25 2020 YehonathanUpdateGeneralMetal PMC parts

I took the metal PMC box and examined its content and find the following items:

 Name Quantity Picture (Attachment #) Metal PMC body (PMC1) 1 1-3 Metal PMC body with two mounted 41 deg mirrors (PMC2) 1 4-6 "Baked PZT Caps" 3 7 PZT Caps 2 8 Flat mirror mounts 2 9 Bar clamps 4 10 Clamp studs 8 10 PZTs 4 11 ORings INF 12 Ball bearings INF 13 6.8 deg AoI curved mirrors (r=-1000mm) 6 14 41 deg AoI flat mirrors, R=99% @ 1064nm (1 Damaged) 11 15

There seem to be enough parts to build 2 PMCs + spares.

I find several problems in the metal PMCs:

PMC1 has a broken screw in one of its flat mirror mounts (Attachment 16). We need to get it out in the machine shop.

PMC2 one of the flat mirrors has a scratch on the AR coating and its ORing is failing (Attachment 17). Mirror and ORing need to be replaced.

I measure the physical dimensions of the PMC with the help of https://dcc.ligo.org/LIGO-E1400332. The roundtrip is found to be 24cm which gives an FSR of 1.25GHz.

I use Evan Hall's Python script for calculating the mode spectrum as a function of the cavity length of the metal PMC and overlay the RF sidebands (Green dashed lines) on it (Attachment 18) to check for any HOM coincidence. The width of the lines is the mode splitting due to the cavity astigmatism.

It seems like the only issue might come from a 10th order modes (green ribbon) which are hopefully small enough in reality.

Attachment 1: PMC1Side.jpg
Attachment 2: PMC1Front.jpg
Attachment 3: PMC1Back.jpg
Attachment 4: PMC2Side.jpg
Attachment 5: PMC2Back.jpg
Attachment 6: PMC2Front.jpg
Attachment 7: 20200207_123118.jpg
Attachment 8: 20200207_123055.jpg
Attachment 9: 20200207_122448.jpg
Attachment 10: 20200207_122400.jpg
Attachment 11: 20200207_122040.jpg
Attachment 12: 20200207_122227.jpg
Attachment 13: 20200207_122149.jpg
Attachment 14: 20200207_123328.jpg
Attachment 15: 20200207_123405_HDR.jpg
Attachment 16: PMC1Screw.jpg
Attachment 18: homVersusLength.pdf
15215   Sat Feb 15 12:56:24 2020 YehonathanUpdateIOOIMC Transfer function measurement

{Yehonathan, Meenakshi}

We measure the IMC transfer function using SR785.

We hook up the AOM driver to the SOURCE OUT, Input PD to CHANNEL ONE and the IMC transmission PD to CHANNEL TWO.

We use the frequency response measurement feature in the SR785. A swept sine from 100KHz to 100Hz is excited with an amplitude of 10mV.

Attachment 1 shows the data with a fit to a low pass filter frequency response.

IMC pole frequency is measured to be 3.795KHz, while the ringdowns predict a pole frequency 3.638KHz, a 4% difference.

The closeness of the results discourages me from calibrating the PDs' transfer functions.

I tend to believe the pole frequency measurement a bit more since it coincides with a linewidth measurement done awhile ago Gautam was telling me about.

Thoughts:

I think of trying to try another zero-order ringdown but with much smaller excitation than what used before (500mV) and than move on to the first-order beam.

Also, it seems like the reflection signal in zero-order ringdown (Attachment 2,  green trace) has only one time constant similar to the full extinction ringdown. The reason is that due to the fact the IMC is critically coupled there is no DC term in the electric field even when the extinction of light is partial. The intensity of light, therefore, has only one time constant.

Fitting this curve (Attachment 3) gives a time constant of 18us, a bit too small (gives a pole of 4.3KHz). I think a smaller extinction ringdown will give a cleaner result.

Attachment 1: IMCFrequencyResponse.pdf
Attachment 2: IMCRingdownNormalizedRawdata.pdf
Attachment 3: IMCREFLPDFits.pdf
15225   Wed Feb 26 17:17:17 2020 YehonathanUpdate Arms DC loss measurements

{Yehonathan, Gautam}

In order to measure the loss in the arm cavities in reflection, we use the DC method described in T1700117.

It was not trivial to find free channels on the LSC rack. The least intrusive way we found was to disconnect the ALS signals DSUB9 (Attachment 1) and connect a DSUB breakout board instead (Attachment 2).

The names of the channels are ALS_BEATY_FINE_I_IN1_DQ for AS reflection and ALS_BEATY_FINE_Q_IN1_DQ for MC transmission. Actually, the script that downloads the data uses these channels exactly...

We misalign the Y arm (both ITM ad ETM) and start a 30 rep measurement of the X arm loss cavity using /scripts/lossmap_scripts/armLoss/measureArmLoss.py and download the data using dlData.py.

We analyze the data. Raw data is shown in attachment 3. There is some drift in the measurement, probably due to drift of the spot on the mirror. We take the data starting from t=400s when the data seems stable (green vertical line). Attachment 5 shows the histogram of the measurement

X Arm cavity RT loss calculated to be 69.4ppm.

We repeat the same procedure for the Y Arm cavity the day after. Raw data is shown in attachment 5, the histogram in attachment 6.

Y Arm cavity RT loss calculated to be 44.8ppm. The previous measurement of Y Arm was ~ 100ppm...

Loss map measurement is in order.

Attachment 1: 20200226_171155.jpg
Attachment 2: 20200226_171539.jpg
Attachment 3: XArmLossMeasurement_RawData.pdf
Attachment 4: XArmLossMeasurement_Hist.pdf
Attachment 5: YArmLossMeasurement_RawData.pdf
Attachment 6: YArmLossMeasurement_Hist.pdf
15243   Tue Mar 3 17:59:33 2020 YehonathanUpdateElectronicsPSL Shutter and PMC TRANSPD working

I used existing BNC cables running from the PSL table to the PSL rack and reassigned them to the PSL Shutter and PMC transmission PD channels.

The PSL shutter turned out to be a sinking channel. Jordan reconnected the PSL shutter wires to a sinking BIO Acromag. Channel list is updated.

Both channels have been tested to be working as expected.

• the PSL shutter channels were previously hosted on c1aux.
• I didn't comment out the original database entries on c1aux because we changed the prefix for all these channels - i.e. C1:AUX-PSL_Shutter --> C1:PSL-PSL_Shutter.
• Modified the LSC offset script to close/open the PSL shutter by writing to the correct channel now.
• there is some EPICS logic that checks the main volume pressure and prevents the opening of the PSL shutter if the main volume pressure is between 0.003 torr and 500 torr. I preserved this capability (so there are some associated soft channels in the database as well).

P.S - there is a problem we noticed - if the modbus process is started with the local subnet not having a fixed IP address, then all the EPICS channels will not be responsive. The way to fix this is to run the following sequence of commands:

sudo systemctl stop modbusIOC.service
sudo ifdown enp4s0
sudo ifup enp4s1
sudo ssytemctl start modbusIOC.service
15246   Wed Mar 4 11:10:47 2020 YehonathanUpdateComputersAllegra revival

Allegra had no network cable and no mouse. We found Allegra'snetwork cable (black) and connected it.

I found a dirty old school mouse and connected it.

I wiped Allegra and now I'm currently installing debian 10 on allegra following Jon's elog.

04/01 update: I forgot to mention that I tried installing cds software by following Jamie's instruction: I added the line in /etc/apt/sources.list.d/lscsoft.list: "deb http://software.ligo.org/lscsoft/debian/ stretch contrib". But this the only thing I managed to do. The next command in the instructions failed.

15255   Thu Mar 5 15:03:48 2020 YehonathanUpdateElectronicsPSL Shutter and PMC TRANSPD working

[Jon, Yehonathan]

Summary

With the Acromag chassis now permanently installed, we tested the C1PSL channels going over the channel list one by one, excluding the IMC channels which Gautam is taking responsibility for (the servo board itself is also in question).

The strategy is to check the response of input channels to specific output channels for expected behaviour whenever is possible.

We marked on the channel list spreadsheet the status of the channels that were tested.

In more detail

FSS

 Channels under test What was done C1:PSL-FSS_SW1 Switched C1:PSL-FSS_SW1 and observed the IMC unlock C1:PSL-FSS_SW2, C1:PSL-FSS_MIXERM Connected a signal to Test2 on FSS box and observed a proportional change on C1:PSL-FSS_MIXERM C1:PSL-FSS_INOFFSET Disconnected feedback by switching C1:PSL-FSS_SW1. Tweaked C1:PSL-FSS_INOFFSET and observed a proportional response in C1:PSL-FSS_MIXERM C1:PSL-FSS_MGAIN, C1:PSL-FSS_PCDRIVE Disconnected feedback, turned on some offset using C1:PSL-FSS_INOFFSET. Tweaked C1:PSL-FSS_MGAIN and observed a response in C1:PSL-FSS_PCDRIVE C1:PSL-FSS_SLOWDC, C1:PSL-FSS_SLOWM Disconnected feedback. Tweaked C1:PSL-FSS_SLOWDC and obsereved a proportional response in C1:PSL-FSS_SLOWM C1:PSL-FSS_FASTGAIN, C1:PSL-FSS_FAST Disconnected feedback, turned on some offset using C1:PSL-FSS_INOFFSET. Tweaked C1:PSL-FSS_FASTGAIN and obsereved a response in  C1:PSL-FSS_FAST

Frequency Ref

 Channels under test What was done C1:PSL-PMC_PHCON Observed the PMC unlocks when a big change in C1: PSL-PMC_PHCON is made C1:PSL-PMC_RFADJ, C1:PSL-PMC_MODET Tweaked C1:PSL-PMC_RFADJ and obsereved a proportional response in C1:PSL-PMC_MODET C1:PSL-PMC_PHFLIP Observed the PMC unlock when C1:PSL-PMC_PHFLIP is switched

PMC Servo Card

 Channels under test What was done C1:PSL-PMC_SW1, C1:PSL-PMC_PMCERR, C1:PSL-PMC_INOFFSET, C1:PSL-PMC_PZT Unlocked the PMC by switching C1:PSL-PMC_SW1. Tweaked C1:PSL-PMC_INOFFSET and observed a proportional change in C1:PSL-PMC_PMCERR and C1:PSL-PMC_PZT C1:PSL-PMC_BLANK Observed the PMC unlock with when C1:PSL-PMC_BLANK is switched C1:PSL-PMC_GAIN Unlocked the PMC by switching C1:PSL-PMC_SW1. Turned on some offset using  C1:PSL-PMC_INOFFSET. Tweaked C1:PSL-PMC_GAIN and observed response in C1:PSL-PMC_PZT C1:PSL-PMC_SW2 Unlocked the PMC by switching C1:PSL-PMC_SW1. Connected a signal to TP2 on the PMC card and observed a proportional change in C1:PSL-PMC_PZT. C1:PSL-PMC_RAMP Unlocked the PMC by switching C1:PSL-PMC_SW1. Tweaked C1:PSL-PMC_RAMP and observed a change in C1:PSL-PMC_PZT. C1:PSL-PMC_RFPDDC Observed a high value 0.5V when PMC is unlocked and a low value 0.03V when it is locked

WFSs

 Channels under test What was done C1:IOO-WFS*_SEG*_ATTEN We misaligned MC1 to get a measurable signal in WFS channels. NDScoped the corresponding C1:IOO-WFS*_SEG*_I&Q channels and observed a change in those channels in response to switching the attenuation on and off. C1:IOO-WFS*_LO_LOCK_MON Disconnected the LO cable from the WFS boards and observed C1:IOO-WFS*_LO_LOCK_MON go to zero. C1:IOO-WFS*_SEG*_I&Q Connected a short SMA cable to the 29.5MHz frequency distribution board. Attenuated the signal by 20db and connected it to the different SEG channels one at a time and observed a response in C1:IOO-WFS*_SEG*_I&Q channels. C1:IOO-WFS*_SEG*_DC We shined a laser pointer to the different quadrants and observed saturation in the corresponding C1:IOO-WFS*_SEG*_DC with no cross talks.

MC Servo

 Channels under test What was done C1:IOO-MC_SW1, C1:IOO-MC_OPTIONA, C1:IOO-MC_POL, C1:IOO-MC_OPTIONB,C1:IOO-MC_FASTSW These switches unlocked the IMC when flipped. C1:IOO-MC_SW2, C1:IOO-MC_SUM_MON, C1:IOO-MC_SLOW_MON, C1:IOO-MC_FAST_MON A sine wave signal was injected in IN2 on the servo board. C1:IOO-MC_SW2 was switched on and the value of C1:IOO-MC_SUM_MON, C1:IOO-MC_SLOW_MON and C1:IOO-MC_FAST_MON changed accordingly. C1:IOO-MC_SW3 Connected a scope to OUT2 on the servo board. Switched C1:IOO-MC_SW3 on and observed a signal on the scope. C1:IOO-MC_EXCA_EN Unlocked the IMC by switching C1:IOO-MC_SW1 off. Connected a signal to EXC A and a scope to TP2A on the servo board and observed the signal on the scope when C1:IOO-MC_EXCA_EN was switched on. C1:IOO-MC_EXCB_EN Unlocked the IMC by switching C1:IOO-MC_SW1 off. Connected a signal to EXC B and a scope to TP2B on the servo board and observed the signal on the scope when C1:IOO-MC_EXCB_EN was switched on. C1:IOO-MC_REFL_OFFSET Unlocked the IMC by switching off. Tweaked C1:IOO-MC_REFL_OFFSET and observed a proportional change in C1:IOO-MC_SUM_MON. C1:IOO-MC_LATCH_EN Tweaked the VCO gain slider and observed the latch switch off and on. C1:IOO-MC_LIMIT Unlocked the IMC by switching C1:IOO-MC_SW1 off. Connected a sine wave signal to EXC B and enabled C1:IOO-MC_EXCB_EN. Ramped up the VCO gain. Raised the sine wave amplitude until C1:IOO-MC_LIMIT turned on. C1:IOO-MC_LIMITER We ramped the VCO such that C1:IOO-MC_LIMIT was switched on. We switched C1:IOO-MC_LIMITER on and observed C1:PSL-FSS_MIXERM high value go down.

NPRO Diagnostics

 Channels under test What was done C1:PSL-NPRO_* The signals were compared to previous values for consistency. Then they were unplugged from the Acromag chassis to confirm their values went to 0 and returned to the same values after being reconnected.
15264   Tue Mar 10 19:59:09 2020 YehonathanUpdateLoss MeasurementArm transfer function measurement

I want to measure the transfer function of the arm cavities to extract the pole frequencies and get more insight into what is going on with the DC loss measurements.

The idea is to modulate the light using the PSL AOM. Measure the light transmitted from the arm cavities and use the light transferred from the IMC as a reference.

I tried to start measuring the X arm but the transmission PD is connected to the QPD whitening filter board with a 4 pin Lemo for which I couldn't find an adapter.

• I switch to the Y arm where the transmission PD - Thorlabs PDA520 (250KHz Bandwidth) - is BNC all the way.
• I lay an 82ft BNC cable from the Y Arm 1Y4 to 1Y1 where the BNC from the IMC Trans PD and an SR785 are found.
• I lock the Arm cavities.
• I connect the AOM cable to the source, the TRY PD (Teed off from the QPD whitening filter) to CH1 and IMC_TRANS to CH2 and measure the transfer function using a swept sine with an offset of 300mV and amplitude of 100mV.
• I fit it to a low pass filter function - see attachment 1 - but it seems like the fit rails off at 10KHz.

Could this be because of the PDA520 limited BWs? I tried playing with the PD gain/bandwidth switch but it seems like it was already set to high bandwidth/low gain.

In any case, the extracted pole frequency ~ 2.9kHz implies a finesse > 600 (assuming FSR = 3.9MHz) which is way above the maximal finesse (~ 450) for the arm cavities.

I disconnected the source from the AOM. But left the other two BNCs connected to the SR785. Also, TRY PD is still teed off. Long BNC cable is still on the ground.

Attachment 1: YArmFrequencyResponse.pdf
15270   Thu Mar 12 11:10:49 2020 YehonathanUpdateGeneralPMC got unlcoked

Came this morning to find the PMC was unlocked since 6AM. Laser is still on, but PMC REFL PD DC shows dead white constant 0V on PMC screen. All the controls on the PMC screen show constant 0V actually except for the PMC_ERR_OUTPUT which is a fast channel.

I restarted the IOC but it didn't help.

I am now rebooting c1psl... That seemed to help. PMC screen seem to be working again. I am able to lock the PMC now.

IMC was locking easily once some switches on the MC servo screen were put to normal states.

TTs were grossly misaligned. Onces they where aligned, arm cavities were locking easily. Dither align for the X arm is very slow though...

15277   Mon Mar 16 15:23:03 2020 YehonathanUpdateLoss MeasurementArm transfer function measurement

I measured the cross-calibration of the two PDs on the PSL table.

I used the existing flip mounted BS that routes the beam into a PDA255, the same as in the IMC transmission.

I placed a PDA520, the same as the one measuring TRY_OUT on the ETMY table,  on the transmission of the BS (Attachment 1).

I used the SR785 to measure the frequency response of PDA520 with reference to PDA255 (Attachment 2). Indeed, calibration is quite significant.

I calibrated the Y arm frequency response measurement.

However, the data seem to fit well to 1/sqrt(f^2+fp^2) - electric field response - but not to 1/(f^2+fp^2) - intensity response. (Attachment 3).

Also, the extracted fp is 3.8KHz (Finesse ~ 500) in the good fit -> too small.

When I did this measurement for the IMC in the past I fitted the response to 1/sqrt(f^2+fp^2) by mistake but I didn't notice it because I got a pole frequency that was consistent with ringdown measurements.

I also cross calibrated the PDs participating in the IMC measurement but found that the calibration amounted for distortions no bigger than 1db.

Attachment 1: Cross_calibration_setup.jpg
Attachment 2: PDA520overPDA255_Response.pdf
Attachment 3: YArmFrequencyResponse.pdf
15285   Thu Mar 26 22:31:34 2020 YehonathanUpdateCDSC1AUXEY wiring + channel list

I have made a wiring + channel list that need to be included in the new C!AUXEY Acromag.

It was mostly copied from C1AUXEX

I ignored the IPANG channels since it is going to be removed from the table.

15307   Sat Apr 18 14:57:44 2020 YehonathanUpdateLoss MeasurementArm transfer function measurement

Ok, now I understand my foolishness. It should definitely be 1/sqrt(f^2+fp^2) .

 Quote: However, the data seem to fit well to 1/sqrt(f^2+fp^2) - electric field response - but not to 1/(f^2+fp^2) - intensity response. (Attachment 3).
15323   Sat May 9 17:01:08 2020 YehonathanUpdateLoss Measurement40m Phase maps loss estimation
I took the phase maps of the 40m X arm mirrors and calculated what is the loss of a gaussian beam due to a single bounce. I did it by simply calculating 1 - (overlap integral)^2 where the overlap is between an input Gaussian mode (calculated from the parameters of the cavity. Waist ~ 3.1mm) and the reflected beam (Gaussian imprinted with the phase map). The phase maps were prepared using PyKat surfacemap class to remove a flat surface, spherical surface, centering, etc. (Attachments 3, 4)

I calculated the loss map (Attachments 1,2: ~ 4X4 mm for ITM, 3X3mm for ETM) by shifting the beam around the phase map. It can be seen that there is a great variation in the loss: some areas are < 10 ppm some are > 80 ppm.

For the ITM (where the beam waist is) the average loss is ~ 23ppm and for the ETM its ~ 61ppm due to the enlarged beam. The ETM case is less physical because it takes a pure gaussian as an input where in reality the beam first interacts with the ITM.

I plan to do some first-order perturbation theory to include the cavity effects. I expect that the losses will be slightly lower due to HOMs not being completely lost, but who knows.

Attachment 1: ITMX_Loss_Map.pdf
Attachment 2: ETMX_Loss_Map.pdf
Attachment 3: ITMX_Phase_Map_(nm).pdf
Attachment 4: ETMX_Phase_Map_(nm).pdf
15329   Wed May 13 15:13:11 2020 YehonathanUpdateLoss Measurement40m Phase maps loss estimation

Koji pointed out during the group meeting that I should compensate for local tilt when I move the beam around the mirror for calculating the loss map.

So I did.

Also, I made a mistake earlier by calculating the loss map for a much bigger (X7) area than what I thought.

Both these mistakes made it seem like the loss is very inhomogeneous across the mirror.

Attachment 1 and 2 show the corrected loss maps for ITMX and ETMX respectively.

The loss now seems much more reasonable and homogeneous and the average total arm loss sums up to ~ 22ppm which is consistent with the after-cleaning arm loss measurements.

Attachment 1: ITMX_Loss_Map.pdf
Attachment 2: ETMX_Loss_Map.pdf
15332   Thu May 14 12:21:56 2020 YehonathanUpdateLoss Measurement40m Phase maps loss estimation

I finished calculating the X Arm loss using first-order perturbation theory. I will post the details of the calculation later.

I calculated loss maps of ITM and ETM (attachments 1,2 respectively). It's a little different than previous calculation because now both mirrors are considered and total cavity loss is calculated. The map is calculated by fixing one mirror and shifting the other one around.

The losin total is pretty much the same as calculated before using a different method. At the center of the mirror, the loss is 21.8ppm which is very close to the value that was calculated.

Next thing is to try SIS.

Attachment 1: ITMX_Loss_Map_Perturbation_Theory.pdf
Attachment 2: ETMX_Loss_Map_Perturbation_Theory(1).pdf
15333   Thu May 14 19:00:43 2020 YehonathanUpdateLoss Measurement40m Phase maps loss estimation

Perturbation theory:

The cavity modes $\left|q\rangle_{mn}$ , where q is the complex beam parameter and m,n is the mode index, are the eigenmodes of the cavity propagator. That is:

$\hat{R}_{ITM}\hat{K}_L\hat{R}_{ETM}\hat{K}_L\left|q\rangle_{mn}=e^{i\phi_g}\left|q\rangle_{mn}$,

where $\hat{R}$ is the mirror reflection matrix. At the 40m, ITM is flat, so $\hat{R}_{ITM}=\mathbb{I}$. ETM is curved, so $\hat{R}_{ETM}=e^{-i\frac{kr^2}{2R}}$, where R is the ETM's radius of curvature.

$\phi_g$ is the Gouy phase.

$\hat{K}_L=\frac{ik}{2\pi L}e^{\frac{ik}{2L}\left|\vec{r}-\vec{r}'\right|^2}$is the free-space field propagator. When acting on a state it propagates the field a distance L.

The phase maps perturb the reflection matrices slightly so:

$\hat{R}_{ITM}\rightarrow e^{ikh_1\left(x,y \right )}\approx 1+ikh_1\left(x,y \right )$

$\hat{R}_{ETM}\rightarrow e^{ikh_2\left(x,y \right )}e^{-i\frac{kr^2}{2R}}\approx\left[1+ikh_2\left(x,y \right )\right]e^{-i\frac{kr^2}{2R}}$,

Where h_12 are the height profiles of the ITM and ETM respectively. The new propagator is

$H = H_0+V$, where $H_0$ is the unperturbed propagator and

$V=ikh_1\left(x,y \right )H_0+ik\hat{K}_Lh_2\left(x,y \right )e^{-i\frac{kr^2}{2R}}\hat{K}_L$

To find the perturbed ground state mode we use first-order perturbation theory. The new ground state is then

$|\psi\rangle=\textsl{N}\left[ |q\rangle_{00}+\sum_{m\geq 1,n\geq1}^{}\frac{{}_{mn}\langle q|V|q\rangle_{00}}{1-e^{i\left(m+n \right )\phi_g}}|q\rangle_{mn}\right]$

Where N is the normalization factor. The (0,1) and (1,0) modes are omitted because they can be zeroed by tilting the mirrors. Gouy phase of TEM00 mode is taken to be 0.

Some simplification can be made here:

${}_{mn}\langle q|V|q\rangle_{00}={}_{mn}\langle q|ikh_1\left(x,y \right )|q\rangle_{00}+{}_{mn}\langle q|\hat{K}_Likh_2\left(x,y \right )e^{-i\frac{kr^2}{2R}}\hat{K}_L|q\rangle_{00}$

${}_{mn}\langle q|\hat{K}_Likh_2\left(x,y \right )e^{-i\frac{kr^2}{2R}}\hat{K}_L|q\rangle_{00}={}_{mn}\langle q-L|ikh_2\left(x,y \right )e^{-i\frac{kr^2}{2R}}|q+L\rangle_{00}={}_{mn}\langle q+L|ikh_2\left(x,y \right )|q+L\rangle_{00}$

The last step is possible since the beam parameter q matches the cavity.

The loss of the TEM00 mode is then:

$L=1-\left|{}_{00}\langle q|\psi\rangle\right|^2$

15338   Tue May 19 15:39:04 2020 YehonathanUpdateLoss Measurement40m Phase maps loss estimation

Phase maps perturb the spatial mode of the steady-state of the cavity, but how is this different than mode-mismatch? The loss that I calculated is an overall loss, not roundtrip loss.

The only way I can think this can become serious loss is when the HOMs themselves have very high roundtrip loss. Attached is the modal power fraction that I calculated.

Attachment 1: Mode_power_fraction1.pdf
15429   Wed Jun 24 22:47:21 2020 YehonathanUpdateWikiUpdated phase maps webpage
I uploaded the new phase maps measurements made by GariLynn to nodus and updated the optics phase maps page.
I also added MetroPro and Matlab analysis for these phase maps.
15507   Thu Aug 6 00:34:38 2020 YehonathanUpdateBHDMonte Carlo Simulations

I've pushed an MCMC simulation to the A+ BHD repo (filename MCMC_TFs.ipynb). The idea is to show how random offsets around ideal IFO change the noise couplings of different DOFs to readout.

At each step of the simulation:

1. Random offsets for the different DOFs are generated from a normal distribution. The RMSs are taken from experimental data and some guesses and can be changed later. The laser frequency is tuned to match the CARM offset.

These are the current RMS detunings I use:

 DOF RMS Taken from DARM 10fm PHYSICAL REVIEW D 93, 112004 (2016), Table 2 CARM 1fm PHYSICAL REVIEW D 93, 112004 (2016), Table 2 MICH 3pm PHYSICAL REVIEW D 93, 112004 (2016), Table 2 PRCL 1pm PHYSICAL REVIEW D 93, 112004 (2016), Table 2 SRCL 10pm PHYSICAL REVIEW D 93, 112004 (2016), Table 2 OMCL 0.1pm Guess OMC Breadboard angle 1\mu rad Guess Differential arm loss 15ppm Guess BHD BS imbalance 10% Guess OMC finesse imbalance 5ppm Guess

2. A transfer function is computed for the noisy DOFs.

3. Projected noise is calculated.

These are the noise level for the DOFs:

 DOF Noise Taken from MICH 2e-16 m PHYSICAL REVIEW D 93, 112004 (2016), Fig 9 PRCL 0.5e-17 m PHYSICAL REVIEW D 93, 112004 (2016), Fig 9 SRCL 5e-16 PHYSICAL REVIEW D 93, 112004 (2016), Fig 9 OMCL 2.5e-17*(100/f)^(1/2) LIGO-G1800149 OMC Breadboard angle 1nrad Guess RIN 2e-9 Optics Letters Vol. 34, Issue 19, pp. 2912-2914 (2009)

The attachments show the projected noise levels for the noisy DOFs. Each curve is a different instance of random offsets. The ideal case - "zero offsets" is also shown.

OMC Comm and OMC diff refer to the common and differential length change of the OMCs.

Attachment 1: MICH_Aplus_MCMC.pdf
Attachment 2: PRCL_Aplus_MCMC.pdf
Attachment 3: SRCL_Aplus_MCMC.pdf
Attachment 4: OMC_Comm_Aplus_MCMC.pdf
Attachment 5: OMC_Diff_Aplus_MCMC.pdf
Attachment 6: OMC_Angle_Yaw_Aplus_MCMC.pdf
Attachment 7: OMC_Angle_Pitch_Aplus_MCMC.pdf
Attachment 8: L0_RIN_Aplus_MCMC.pdf
15512   Mon Aug 10 07:13:00 2020 YehonathanUpdateBHDMonte Carlo Simulations

I fixed some stuff in the MCMC simulation:

1. Results are now plotted as shades from minimum to maximum. I tried making the shade the STD around a mean but it doesn't look good on a log scale when the STD is bigger than the mean.

2. Added comparison with aLigo. The OMCL diff and comm motions in A+ are both compared to the single OMCL DOF of aLigo.

3. I fixed a serious error in the code that produced incorrect results.

4. Imbalances in the IFO such as differential arm loss are generated randomly at the beginning and stay fixed for the rest of the simulation instead of being treated as an offset.

5. The simulation now runs with maxtem=2. That is, TEM modes up to 2nd order are considered.

The results are attached.

Attachment 1: MICH_AplusMCMC.pdf
Attachment 2: PRCL_AplusMCMC.pdf
Attachment 3: SRCL_AplusMCMC.pdf
Attachment 4: OMC_Comm_AplusMCMC.pdf
Attachment 5: OMC_Diff_AplusMCMC.pdf
Attachment 6: OMC_Angle_Yaw_AplusMCMC.pdf
Attachment 7: OMC_Angle_Pitch_AplusMCMC.pdf
Attachment 8: L0_RIN_AplusMCMC.pdf
15539   Tue Aug 25 05:51:29 2020 YehonathanUpdateBHDMonte Carlo Simulations

I re-plotted the MCMC results as semi-transparent lines so that probable lines stick out.

This also reveals what is behind the extreme sparsity in the aLIGO simulation results (In the previous post).

There seem to be some bi-stability/phase transition/whatever in the aLIGO simulation. The aLIGO transfer functions are very sensitive to one or more of the DOFs. Not sure which yet.

Attachment 1: MICH_AplusMCMC.pdf
Attachment 2: PRCL_AplusMCMC.pdf
Attachment 3: SRCL_AplusMCMC(1).pdf
Attachment 4: OMC_Diff_AplusMCMC.pdf
Attachment 5: OMC_Comm_AplusMCMC.pdf
Attachment 6: OMC_Angle_Yaw_AplusMCMC.pdf
Attachment 7: OMC_Angle_Pitch_AplusMCMC.pdf
Attachment 8: Main_Laser_RIN_AplusMCMC.pdf
15569   Mon Sep 14 07:50:01 2020 YehonathanUpdateBHDMonte Carlo Simulations

Turns out what was causing the instability in the aLIGO plots were the lock commands which I forgot to remove before running the simulation. Removing these also made the simulation much faster.

Other than that I improved other stuff in the simulations:

• The LO phase in the aPlus simulation is now optimized for the lowest noise at 100Hz.
• Added RF PDs diagnostics (see attachments 8 for aPlus and 9 for aLIGO). The thresholds (red dashed lines in attachments 8,9) for cutting marginal simulations are set such that roughly 30% of the simulations are discarded.
• Removed DHARD because it jacks up the RF PD readings in aPlus for some reason.
• Fixed the sign of laser frequency shift in response to CARM offset.

Still need to do:

• Incorporate Jon’s noise curves.
• Add phase noise for LO beam.
• Include feedback loops using Pytickle.

Feel free to add to the todo list.

Attachment 1: MICH_AplusMCMC.pdf
Attachment 2: PRCL_AplusMCMC.pdf
Attachment 3: SRCL_AplusMCMC(1).pdf
Attachment 4: OMC_Comm_AplusMCMC.pdf
Attachment 5: OMC_Diff_AplusMCMC.pdf
Attachment 6: OMC_Angle_Yaw_AplusMCMC.pdf
Attachment 7: OMC_Angle_Pitch_AplusMCMC.pdf
Attachment 8: Main_Laser_RIN_AplusMCMC.pdf
Attachment 9: aPlus_RF_Diagnostics.pdf
Attachment 10: aLIGO_RF_Diagnostics.pdf
15631   Fri Oct 16 09:16:37 2020 YehonathanUpdateBHDMonte Carlo Simulations

Pushed another update to MCMC simulation. This includes:

• Added new imbalances: ITM transmission, ITM & ETM RoCs.
• Added new static offsets: DHARD, DSOFT, CHARD, CSOFT. All pitch. The RMS is calculated from the data Jon fetched with /input_noises/input_noises.ipynb.
• SRCL noise ASD and RMS are now taken from data in /input_noises.
• RF PD diagnostics were redone: Instead of post-discarding marginal simulations, simulations are now discarded when one or more of the RF PDs demodulated signal does not cross zero when the associated DOFs are scanned by 1um in the offset state.

The DOFs<->RFPD associations I use are:

 DARM AS_f2_I CARM REFL_f1_I MICH POP_f2_Q PRCL POP_f1_I SRCL REFL_f2_I

However, one thing that bothers me is that for some reason ~ 15 out of 160 aLigo simulations are discarded while none for A+. It can also be seen that the A+ simulations are more spread-out which might be related.

The new simulation results are attached.

Attachment 1: MICH_AplusMCMC.pdf
Attachment 2: PRCL_AplusMCMC.pdf
Attachment 3: SRCL_AplusMCMC.pdf
Attachment 4: OMC_Comm_AplusMCMC.pdf
Attachment 5: OMC_Diff_AplusMCMC.pdf
Attachment 6: OMC_Angle_Yaw_AplusMCMC.pdf
Attachment 7: OMC_Angle_Pitch_AplusMCMC.pdf
Attachment 8: Main_Laser_RIN_AplusMCMC.pdf
15637   Thu Oct 22 11:48:08 2020 YehonathanUpdateBHDMonte Carlo Simulations

I found this H1 alog  entry by Izumi confirming that the calibrated channels CAL-CS_* need the same dewhitening filter.

This encouraged me to download the PRCL and MICH data and using Jon's example notebook. I incorporated these noise spectra into the MCMC simulation. The most recent results are attached.

I am still missing:

• Laser frequency noise
• Laser RIN
• Estimation of the LO phase noise
• Estimation of the BHD breadboard angular noise

Also, now the MCMC repeats a simulation if it doesn't pass the RF PDs test so the number of valid simulations stays the same. I'm still not sure about why the A+ simulations are much more robust to these tests than aLigo simulations.

Attachment 1: MICH_AplusMCMC.pdf
Attachment 2: PRCL_AplusMCMC.pdf
Attachment 3: SRCL_AplusMCMC.pdf
Attachment 4: OMC_Comm_AplusMCMC.pdf
Attachment 5: OMC_Diff_AplusMCMC.pdf
Attachment 6: OMC_Angle_Yaw_AplusMCMC.pdf
Attachment 7: OMC_Angle_Pitch_AplusMCMC.pdf
Attachment 8: Main_Laser_RIN_AplusMCMC.pdf
15727   Thu Dec 10 14:48:00 2020 YehonathanUpdateBHDMonte Carlo Simulations

I have rebuilt the MCMC simulation in an OOP fashion and incorporated Lance/Pytickle functionality into it. The usage of the MCMC now is much less messy, hopefully.

I made an example that calculates the closed-loop noise-coupling from SRCL sensing and displacement to DARM in A+. I used the control filters that Kevin defined in his controls example.

The resulting noise budget is in attachment 1. The code is in the 40m/bhd git.

I also investigated why aLIGO simulations behave so different than the A+ simulation (See few previous elogs in this thread). That is why aLIGO results are much less variable, and the simulations in aLIGO barely pass the validity checks, while A+ simulations almost always pass.

The way I check for the validity of a kat model is by scanning all the DOFs and checking that the corresponding sensing RFPDs demodulated signals cross zero. Attachment 2 shows these scanning for 3 such RFPDS for 3 cases:

A+ model with maxtem = 2

ALigo model with maxtem = 2

ALigo model with maxtem = 'off'

It seems like the scanning curves for A+ and ALigo with no HOMs are well behaved and look like normal PDH signals, while the ALigo with maxtem = 2 curves look funky. I believe that the aLIGO+HOMS curves indicate that the IFO is not really in a good locking point. All the IFO lockings were done by using the locking methods straight out of the PyKat package.

Attachment 1: MCMCLance_NoiseBudget_Example.pdf
Attachment 2: IFO_Check.pdf
15734   Mon Dec 14 11:09:28 2020 YehonathanUpdateBHDMonte Carlo loop coupling Simulations

I spent a few hours monkeying around with the control filters. They are totally made up and also it's my first time trying to design control filters.

The OLTFs of the different length controls are shown in attachment 1.

The open-loop couplings of the DOFS to DARM are shown in attachment 2.

Note that in Lance/Pytickle the convention is that CLTFs are 1/(1 - G). Where G is the OLTF.

 Quote: Cool. Can you give us Bode plots of the open loop gain for each of the 5 length control loops?

Attachment 1: MCMC_LANCE_OLTFs.pdf
Attachment 2: MCMC_LANCE_OLCoupling2DARM.pdf
15758   Mon Jan 11 16:11:51 2021 YehonathanUpdateBHDMonte Carlo loop coupling Simulations

I dived into the alog to make the OLTFs in the MC_controls example more realistic. I was mainly inspired by these entries:

https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=18742

https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=20466

and Evan's and Dennis's Theses.

Attachment 1 shows the new OLTFs. I tried to make them go like 1/f around the UGF and fall as quickly as possible at higher frequencies. I didn't do more advanced stability checks.

I also noticed that imbalances and detunings in the MC simulation can change the plants significantly. Especially DARM, CARM, and sometimes PRCL. I added the option to fix some OLTFs throughout the simulation. At every iteration, the simulation computes the required control filter to fix the selected OLTFs such that it will match the OLTFs in the undetuned and balanced IFO.

Attachment 1: MC_LANCE_OLTFs.pdf
15796   Thu Feb 4 15:14:55 2021 YehonathanUpdateBHDSOS assembly

I gathered all the components I could find from the SOS towers and the cleanroom and put it all on the table next to the flow bench (See attachment).

I combed through the cleanroom cabinet for SOS parts but didn't find all the parts listed in the procurement spreadsheet. I did find some extra items that were not listed.

This table compares the quantities in the spreadsheet to the quantities collected on the table. Green rows are items I found more than in the procurement spreedsheet while red rows are items I found less.

 ITEM DCC # Qty required Qty in procurement spreadsheet How much I found SENSOR/ACTUATOR PLATE D960002 14 21 21 SUSPENSION BLOCK D960003 7 9 9 TOWER BASE D960004 7 10 11 RIGHT SIDE PLATE D960005 7 12 13 LEFT SIDE PLATE D960006 7 12 13 UPPER MIRROR CLAMP D960007 7 8 7+1 teflon LOWER CLAMP D960008-1 7 8 8 LOWER CLAMP, OPPOSITE D960008-2 7 8 8 WIRE CLAMP 1205308-1 10 17 9 CLAMP, SUSPENSION BLOCK D960134 14 19 21 STIFFENER PLATE D960009 7 9 9 DUMBBELL STANDOFF D970075 50 10 7 SAFETY STOP, LONG D970313 14 2 10 OSEM assy D960011 35 2 13 wire wound osem housings (gold) WIRE STANDOFF D970187 20 7 0 GUIDE ROD D970188 10 9 0 MAGNET D960501 50 54 51 rusted + 37 slightly rusted. Didn't put on table SAFETY STOP, SMALL D970312 28 0 4 SAFETY STOP D970311 28 0 16+9 stained w/o spring SS Spring Plunger 8498A999 35 4 27
Attachment 1: 20210204_144007.jpg
15808   Tue Feb 16 13:13:39 2021 YehonathanUpdateBHDSOS assembly

Gautam pointed out that there are extra Sm-Co magnets stored in the clean optics cabinet.

I took the magnet box out and put it on the rolling table next to south flow bench. The box contains 3 envelopes with magnets.

They are labelled as following:

FLUX 94 - 50 parts

FLUX 93 - 10 parts

FLUX 95 - 40 parts

(What is FLUX??)

The box also contains some procurement documents.

The clean and bake dcc says :

1. Ultrasonic clean in methanol for 10 minutes

2. Bake in vacuum at 177 C° for 96 hours

Should we go ahead with the C&B?

15811   Tue Feb 16 22:59:36 2021 YehonathanUpdateBHDSOS assembly

Done.

Also, the magnets are nickel-plated. I guess that doesn't matter for the baking (Curie temp of 355 °C)?

 Quote: The curie temp of SmCo seems about x2 (in K) of the one for NdFeB. i.e. 600K vs 1000K. So I believe 177degC = 450K is not an issue. Just make sure the curie temp, referring the specific property for the magnets from this company. (You already know the company from the procurement doc). It'd be great if you upload the doc on the 40m wiki.

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