40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  PSL, Page 22 of 52  Not logged in ELOG logo
ID Date Author Type Categoryup Subject
  1523   Thu Sep 18 13:57:00 2014 EvanNotesISSEOAM phenomenology

I've been unsure of how the EOAMs are affecting the state of the light impinging on the cavity.

So far we've been rotating the post-EOAM QWPs so as to maximize the strength of the amplitude modulation. I'm still not sure what this does. I'd like to instead fix the QWP at ±45° and then insert the EOAM, regardless of whether this introduces a DC power offset. At the very least this will give us a polarization state that we think we understand.

Attachment 1: eoam.pdf
eoam.pdf eoam.pdf
  1593   Sun Oct 18 20:15:55 2015 AntonioDailyProgressISSISS on the North path and new optical setup

Summary

========

 

The work done yesterday and today gave us a working ISS in the North path with a different optical setup.

———————————————————————————————————————————-

 

Yesterday I have made several attempts to make the ISS working again in the North path. I have failed until I have noticed

the following setup for the AEOM:

 

lambda/2 ———p————> AEOM —-—> lambda/4 ——> PBS —> lambda/4 ———s—>EOM…..

 

Because I was not in agreement and I have asked Evan and I have figured out that this setup was not what it was meant to be.

Today I have replaced the second lambda/4 with a lambda/2 which made the ISS North working. Now the setup is:

 

lambda/2 ———p————> AEOM —-—> lambda/4 ——> PBS —>lambda/2———s—>EOM

 

The spectrum shows the intensity noise measured at the photodiode in transmission of the North cavity. Not clear what is happening

with the dark noise.

 

Loop setup: PD North ---> SR560 --->AEOM

SR560 setup: Gain at 5e4, HP=30Hz; LP=1kHz;

 

From  Yesterday I have also measured:

 

1. TF from AEOM to PD North;

2. TF from PD North to PLL control signal (injecting noise on AEOM);

 

SOME of the THINGS that I think need TO BE DONE in a short term:

 

1. We should implement the second AEOM in the South path. My plan is to replace the EOM that currently is in the path with the

AEOM because the beam shape requirement are the same, so it will be faster, given that we will not use the PMC. 

 

2. We need to check the shape of the beams at the modulators (ALL) in order to figure out if the (A)EOM requirements are respected.

This could be important for beam deformations which affect the mode matching at the cavities.

 

3. Need of a working dataviewer/IRcamera and a beam profiler;

 

4. It is very important that we spend some time in organizing the lab. The amount of time spent for looking for things is becoming an

obstacle for a proper lab work.

 

5. We also need to consider about the height of the table. Aside note: After two days in the lab my back is very painful.

 

6. Implement two Faraday Isolators in order to use only one polarization; for the moment I am even tempted to use a 50/50 BS, j

ust for the moment.

 

Curiosity:

So far we have been locking the cavities on the resonance given by the S-polarized light.

 

Data

=====

controlfb2/data/2015101718_PLL_ISS/

 

  1604   Wed Nov 4 11:14:24 2015 AntonioDailyProgressISSISS on South path is "working"

Summary

========

The EAOM has been implemented again in the South path. I still see an intensity noise effect in transmission, but it is much less than what I have seen from the previous days.

However the loop is suppressing most of it (but I am not happy about this). The figure shows the intensity noise and its suppression (Vdc = ~80mV).

 

Setup

=====

The setup is the one that it is currently in use in the North path:

 

lambda/2 ———p————> AEOM —-—> lambda/4 ——> PBS —>lambda/2———s—>EOM

 

I have also tried a different setup with light entering in the EAOM at 45 degrees, but the loop does not show suppression of intensity noise. I do not explain why at moment.

 

Note: When the light entering the EAOM is p (the current setup) the light coming out of the modulator

is circular polarized. 15% of ‘p’ goes in ’s’. This is not happening in the north path where the light

remains mostly linear. I am not convinced that this EAOM is properly functioning.

 

 

Data

=====

controlfb2/home/data/20151104_ISS_South

 

 

Attachment 1: ISS_South_noise.pdf
ISS_South_noise.pdf
  1982   Tue Nov 14 01:31:41 2017 CraigDailyProgressISSLow Pass Dual Voltage Follower for locking the ISS

We need to lock our ISS to the PD output in real time without worrying about DC fluctuations in the PD response.

I made a dual voltage follower using an OP275 and some capacitors. 

The schematic is on the box in picture 2.

I checked both voltage follower input/output pairs with an SR785.  We see a nice low pass with cutoff frequency ~0.7 Hz.

I'll install this tomorrow.

Attachment 1: ISSBox_1.jpg
ISSBox_1.jpg
Attachment 2: ISSBox_2.jpg
ISSBox_2.jpg
Attachment 3: ISSBox_3.jpg
ISSBox_3.jpg
Attachment 4: ISSBox_4.jpg
ISSBox_4.jpg
  1985   Wed Nov 15 16:06:29 2017 PerrecaDailyProgressISSLow Pass Dual Voltage Follower for locking the ISS
Attachment 1: Untitled.jpg
Untitled.jpg
  2132   Tue Mar 13 15:32:49 2018 CraigDailyProgressISSTrans DC jumpiness

When the cavities relock themselves, our Trans DC values change drastically.


I just noticed this when the North cavity lost lock while I was messing around with some optics.  The autolockers worked their magic, but upon relocking the NCAV_TRANS_DC value went from ~3 V to ~4 V.  It's been as low as 0.9 Volts as well, that's why I changed the thresholds for awade's NCAV autolocker .ini file.
What the heck?  We know they are locking to the same fringe, at least for the Fabry-Perot cavity.  The PMC is locked to a different fringe though, maybe this increased it's power output?  But that wouldn't explain the South path jumps.
Unclear why this would happen.

First plot: Last 30 minutes.
Second plot: Last 12 hours.  EVEN CRAZIER

Attachment 1: Screen_Shot_2018-03-13_at_3.32.17_PM.png
Screen_Shot_2018-03-13_at_3.32.17_PM.png
Attachment 2: Screen_Shot_2018-03-13_at_3.43.39_PM.png
Screen_Shot_2018-03-13_at_3.43.39_PM.png
  2201   Mon Jun 11 15:03:15 2018 anchalDailyProgressISSLoop Gain Transfer Function analysis on LTspice

With the circuit of Johannes, I ran LT spice analysis with modeling cavity pole and AOM delay to get an estimate of how the loop gain would look like. Attached is a plot of the transfer function of loop gain and the circuit schematic used. Here I used this post of Johannes on elog to use DC Gain of AOM as 1.11 dB. But in case, this changes, I have a running code which will output the new unit gain frequencies and phase margins. I'll implement this into a board soon and move forward by optimizing the choice of elements with help from LISO.
I'm seeking input on anything which makes the frequency curve as shown here less than satisfactory.

Attachment 1: ISSLoopGainAnalysis.pdf
ISSLoopGainAnalysis.pdf
Attachment 2: ISSLoopGainTFwithAOMDCG1.11.pdf
ISSLoopGainTFwithAOMDCG1.11.pdf
  2202   Wed Jun 13 18:04:32 2018 anchalDailyProgressISSLoop Gain Transfer Function analysis on LTspice

I implemented the feedback part of this circuit and measured the transfer function on SR785. Attached is the measured transfer function. It is close to the one given by LTspice except that there is a nearly flat top between ~100Hz to ~1.3kHz while analytically this was supposed to be a smooth peak.
I checked with attenuating the input signal to make sure the flat top is not due to saturation, it is in fact two peaks close together. By changing a capacitor C10 (see the last post for the circuit)., we can move these peaks closer or further. However, making them move closer decreases the overall gain of the point, so I stuck to 4.7uF value.
I'll now test this circuit with a low pass filter modeling the cavity and some delay for modeling the AOM and see if the loop gain is as expected.

Quote:

With the circuit of Johannes, I ran LT spice analysis with modeling cavity pole and AOM delay to get an estimate of how the loop gain would look like. Attached is a plot of the transfer function of loop gain and the circuit schematic used. Here I used this post of Johannes on elog to use DC Gain of AOM as 1.11 dB. But in case, this changes, I have a running code which will output the new unit gain frequencies and phase margins. I'll implement this into a board soon and move forward by optimizing the choice of elements with help from LISO.
I'm seeking input on anything which makes the frequency curve as shown here less than satisfactory.

 

Attachment 1: ISSMeasuredTF06-13-2018.pdf
ISSMeasuredTF06-13-2018.pdf
Attachment 2: ISSLTSpiceTF.pdf
ISSLTSpiceTF.pdf
  2205   Mon Jun 18 14:42:45 2018 anchalPhotosISSBreadboard circuit testing

Attached is the image of circuit implemented on breadboard with modelled AOM and cavity as phase shifter and low pass filter respectively.
In the image, all red/orange wires are at +15V, all white/grey wires are GND, all green wires are at -15V, all yellow wires are carrying signal and one violet wire is the voltage offset set to 0V right now. All the opamps are OP27G except the adder and an inverter which are OP27E. The circuit corresponds to the attached LTspice circuit.

Attachment 1: Breadboard_Circuit_Labeled.jpg
Breadboard_Circuit_Labeled.jpg
Attachment 2: ISSAOMCavity.pdf
ISSAOMCavity.pdf
  2206   Wed Jun 20 17:54:45 2018 anchalDailyProgressISSLISO Analysis of Feedback Part of the circuit

OUr measurements of the actual circuit showed noise level in the order of several uV/sqrt(Hz). I did the noise analysis on LISO and the results indicate that the second stage amplifier's input current noise is causing most of the noise till around 30 Hz and then its input voltage noise dominates till around 200 kHz. I would work more on identifying ways to reduce the noise, would do the simulation for the loop gain transfer function and would do the stability analysis as well.

Attachment 1: ISSCircuitSchematic.jpg
ISSCircuitSchematic.jpg
Attachment 2: ISSLisoNoiseAnalysis.pdf
ISSLisoNoiseAnalysis.pdf ISSLisoNoiseAnalysis.pdf ISSLisoNoiseAnalysis.pdf
Attachment 3: ISS.fil
r R14 510 IN n1
c C7 1u n1 n2
c C4 470p n1 n4
r R15 560k n2 n4
r R16 560k n3 gnd
c C6 1u n3 gnd
op ISS2 op27 n3 n2 n4

r R18 1k n4 n5
c C8 4.7n n5 n7
... 20 more lines ...
  2207   Thu Jun 21 11:43:53 2018 anchalDailyProgressISSLISO Analysis of complete circuit

I did TF, input impedance, opamp stability and noise analyses of the complete circuit with feedback part, modeled AOM (by phase shifter) and modeled Cavity (by LPF+NOT). Attached are the results. In the process, I completed wrapping some more LISO functions in python. We can do calculate input referred noise, input impedance, opamp stability and plot only dominant noise sources. The circuit schematic is attached and for now uses OP27. Next steps are to figure out what adjustments (components and values) can lower the noise. Opamps are in the stable region only.

Attachment 1: ISSAOMCavity.pdf
ISSAOMCavity.pdf
Attachment 2: ISSAOMCavityNoiseAnalysis.pdf
ISSAOMCavityNoiseAnalysis.pdf ISSAOMCavityNoiseAnalysis.pdf ISSAOMCavityNoiseAnalysis.pdf ISSAOMCavityNoiseAnalysis.pdf ISSAOMCavityNoiseAnalysis.pdf
Attachment 3: ISSAOMCavity.fil
r R14 510 OUT n1
c C7 1u n1 n2
c C4 470p n1 n4
r R15 560k n2 n4
r R16 560k n3 gnd
c C6 1u n3 gnd
op ISS2 op27 n3 n2 n4

r R18 1k n4 n5
c C8 4.7n n5 n7
... 41 more lines ...
  2213   Mon Jul 23 18:07:14 2018 anchalDailyProgressISSIntroduced zero to cancel cavity pole. Mostly final circuit.

After discussion with Johannes, I added a zero near the cavity pole to neutralize its effect at higher frequencies. I also replaced the passive high frequency boost with an active one in stage 3. Attached is the new circuit schematic (Mostly final one as it looks good). Also attached are open loop transfer function from LTSpice.
Next steps are to do noise analysis and individual opamp stability analysis in LISO one last time.

Attachment 1: CRYO_ISS2LoopGainTF.pdf
CRYO_ISS2LoopGainTF.pdf
Attachment 2: Cryo_ISS2_AOMCavity_Schematic.pdf
Cryo_ISS2_AOMCavity_Schematic.pdf
Attachment 3: Cryo_ISS2_AOMCavity_LTSpiceAnalysis.zip
  2214   Tue Jul 24 11:04:37 2018 johannesDailyProgressISSIntroduced zero to cancel cavity pole. Mostly final circuit.

By making stage 3 active you may be adding a lot of OpAmp noise, since you're amplifying it by a factor of 100 at low frequencies. It sits behind the first two gain stages so it might not matter for the input referred noise? But I don't think it's good practice. What was wrong with having that stage passive? A gain stage like this, which doesn't provide gains higher than 1 and actually attenuates over a broad range is usually better kept passive because of amplifier noise.

Did you check the circuit for stability? The AD829 in stage 3 is driving a pretty low resistance as load. Not sure if LTSpice can identify such problems.

  2215   Tue Jul 24 13:47:48 2018 anchalDailyProgressISSIntroduced zero to cancel cavity pole. Mostly final circuit.

Here is LISO analysis on the version 2 of this circuit. I'll take Johannes' advice and remove the active filter on stage 3 and move the addition to stage 4 in the next version.

The first file is the transfer function and the input impedance of just the feedback circuit (the 5 stages).

The second file is open loop transfer function of feedback circuit with modeled AOM and Cavity, the input referred noise and the opamps'stability in the closed loop.

Attachment 1: Cryo_ISS2_LISO_Analysis.pdf
Cryo_ISS2_LISO_Analysis.pdf Cryo_ISS2_LISO_Analysis.pdf
Attachment 2: CRYO_ISS2AOMCavityLisoAnalysis.pdf
CRYO_ISS2AOMCavityLisoAnalysis.pdf CRYO_ISS2AOMCavityLisoAnalysis.pdf CRYO_ISS2AOMCavityLisoAnalysis.pdf
  2216   Tue Jul 24 14:28:08 2018 johannesDailyProgressISSIntroduced zero to cancel cavity pole. Mostly final circuit.

Modified the design to make stage three passive again and moved stage 5 (addition of offset) to stage 4. PFA the circuit schematic.

Also attached are LISO analysis of the circuit.

The first file is the transfer function of the feedback circuit alone with its input impedance.

The second file is the open loop transfer function of the feedback circuit with AOM and cavity, the input referred noise and the opamps' stability in closed loop operation.

P.S. The unstable region shown in figure one of the second file is calculated as the region where |KP + 1|<1 as per the phase of calculated KP, where KP is the open loop gain function.

Quote:

By making stage 3 active you may be adding a lot of OpAmp noise, since you're amplifying it by a factor of 100 at low frequencies. It sits behind the first two gain stages so it might not matter for the input referred noise? But I don't think it's good practice. What was wrong with having that stage passive? A gain stage like this, which doesn't provide gains higher than 1 and actually attenuates over a broad range is usually better kept passive because of amplifier noise.

Did you check the circuit for stability? The AD829 in stage 3 is driving a pretty low resistance as load. Not sure if LTSpice can identify such problems.

 

Attachment 1: Cryo_ISS3_AOMCavity_Schematic.pdf
Cryo_ISS3_AOMCavity_Schematic.pdf
Attachment 2: Cryo_ISS3_LISO_Analysis.pdf
Cryo_ISS3_LISO_Analysis.pdf Cryo_ISS3_LISO_Analysis.pdf
Attachment 3: CRYO_ISS3AOMCavityLisoAnalysis.pdf
CRYO_ISS3AOMCavityLisoAnalysis.pdf CRYO_ISS3AOMCavityLisoAnalysis.pdf CRYO_ISS3AOMCavityLisoAnalysis.pdf
  2217   Thu Jul 26 18:30:51 2018 anchalDailyProgressISSNoise analysis of soldered circuit

I soldered the servo circuit on a prototype board. The transfer function of the soldered board is matching very well with the analytical calculation. We found a few more corrections required in the circuit relating to the voltage offset compensation resistors. Then I did a complete noise analysis of the circuit using SR785. Attached are the results. First I measured the transfer function of each individual stage by sourcing the input of the circuit and taking the ratio of the output to the input of each stage separately. Then, I used 2 different methods to calculate input referred noise at different stages of the circuit (which are soldered together).
Method 1: I connected a 50 Ohm terminator at the input of the stage and measured output noise of the stage. Then I divided it by the transfer function of the stage.
Method 2: I only measured output noise at the output of each stage. And calculated the input referred noise by dividing the output noise by transfer function and subtracting the excess noise from the previous stage at its input.
In the process, I have written a module which can be used by others too to fit transfer function data and calculate input referred noise in general using SR785. I would put this code on github soon.
It seems that as the LISO analysis shows, most of the noise below 20-30 Hz is due to the amplification of input current noise of the first stage amplifier. Next steps are to figure out a better opamp if any to reduce noise in this region. We are well below the shot noise for 2mW 1550 nm laser above 30 Hz.

Attachment 1: ISS_Noise_Analysis_Method1.pdf
ISS_Noise_Analysis_Method1.pdf ISS_Noise_Analysis_Method1.pdf ISS_Noise_Analysis_Method1.pdf ISS_Noise_Analysis_Method1.pdf ISS_Noise_Analysis_Method1.pdf ISS_Noise_Analysis_Method1.pdf ISS_Noise_Analysis_Method1.pdf ISS_Noise_Analysis_Method1.pdf
Attachment 2: ISS_Noise_Analysis_Method2.pdf
ISS_Noise_Analysis_Method2.pdf ISS_Noise_Analysis_Method2.pdf ISS_Noise_Analysis_Method2.pdf ISS_Noise_Analysis_Method2.pdf ISS_Noise_Analysis_Method2.pdf ISS_Noise_Analysis_Method2.pdf ISS_Noise_Analysis_Method2.pdf ISS_Noise_Analysis_Method2.pdf
  2218   Fri Jul 27 12:29:43 2018 ranaDailyProgressISSNoise analysis of soldered circuit

for any circuit where power noise is measured, the units should be input referred current noise, not voltage noise. So you have to include a mode of the photodetector circuit.

  2219   Mon Jul 30 13:28:37 2018 anchalDailyProgressISSNoise analysis of soldered circuit

Just replotting the measured noise with LISO prediction for comparison.

Attachment 1: ISS_Noise_Analysis_Meas_vs_LISO.pdf
ISS_Noise_Analysis_Meas_vs_LISO.pdf
  2220   Mon Jul 30 16:54:50 2018 anchalDailyProgressISSUnderstanding the ISS box we found

I was given an ISS box which was made in 2013. It is numbered D1300694-v1 and the schematics are present in DCC. I tried to go through the schematic to get an understanding of it and mark the differences of the real circuit on the schematic. PFA a commented schematic which marks the measured component values and shows what is not present on this circuit.

Breif Description of this circuit and what it intended to do:
The circuit is DC coupled and the PD signal first goes through an instrumentation amplifier with about 1.33 gain. Then a 5V reference is subtracted from this signal (so the servo do DC stabalization to keep PD signal at 5V).
Then the signal goes through 3 stages of filtering and amplification.
Stage 1: (Always On) Is a simple gain of 6.36
Stage 2: Is a 554 Hz Zero and 10kHz pole with DC gain of 18 (Called Boost 1)
Stage 3: Is a 0 Hz Pole and 4.57MHz zero with the open loop gain of AD829 at DC. (Called Boost 2)
The Boost 1 and 2 are supposed to start only when rms value of PD signal is below a certain threshold. Currently, this functionality is not working due to a problem in RMS-to-DC converter as specified in elog 40m/9332.

I will see if I can find a way to hack this circuit to do what we want to do without making any irreversible changes.

Attachment 1: D1300694-v1_Commented_AG.pdf
D1300694-v1_Commented_AG.pdf D1300694-v1_Commented_AG.pdf D1300694-v1_Commented_AG.pdf D1300694-v1_Commented_AG.pdf D1300694-v1_Commented_AG.pdf D1300694-v1_Commented_AG.pdf
  2221   Mon Jul 30 18:58:27 2018 anchalDailyProgressISSMinor version improvement in design.

It seems difficult to implement our AC coupled circuit in D1300694_v1 board which is DC coupled.

Meanwhile, I was looking into improving noise performance of present design ISS3, and it seems we can get some improvement directly by including a buffer at the input (to have good input impedance) and reduce resistance values in stage 1 to lower the impact of the current noise of first stage amplifier. This design ISS3_1 and its LISO analysis are attached.

Attachment 1: Cryo_ISS3_1schematic.pdf
Cryo_ISS3_1schematic.pdf
Attachment 2: Cryo_ISS3_1_LISO_Analysis.pdf
Cryo_ISS3_1_LISO_Analysis.pdf
  2222   Wed Aug 1 11:16:22 2018 anchalDailyProgressISSFinal Design for ISS Servo v3.2

I checked with some replacements of opamp at stage 1 to reduce the noise due to current noise. It seems AD743 is the best balanced opamp for this location. Attached is the circuit schematic of this final version v3.2 , with LISO analysis and also the analysis done to reach to this opamp.

Attachment 1: Cryo_ISS3_2schematic.pdf
Cryo_ISS3_2schematic.pdf
Attachment 2: Cryo_ISS3_2_LISO_Analysis.pdf
Cryo_ISS3_2_LISO_Analysis.pdf Cryo_ISS3_2_LISO_Analysis.pdf
Attachment 3: Cryo_ISS3_1_ISS1_Optimization.pdf
Cryo_ISS3_1_ISS1_Optimization.pdf Cryo_ISS3_1_ISS1_Optimization.pdf
  2223   Wed Aug 1 17:31:19 2018 awadeDailyProgressISSFinal Design for ISS Servo v3.2

AD743 is discontinued.  We have a few in stock, and there are still a few SOIC-16 version that you can buy. 

But better to design with a op amp that is replaceable into the future.

Quote:

I checked with some replacements of opamp at stage 1 to reduce the noise due to current noise. It seems AD743 is the best balanced opamp for this location. Attached is the circuit schematic of this final version v3.2 , with LISO analysis and also the analysis done to reach to this opamp.

 

  2224   Sat Aug 4 21:37:55 2018 johannesDailyProgressISSFinal Design for ISS Servo v3.2

These are some "low-noise" FET input OpAmps which are all still alive:

  • MAX4475
  • AD8655
  • LT1792

not exact substitutes for AD743 but lower noise of all alternatives that I've come across so far.

 

Quote:

AD743 is discontinued.  We have a few in stock, and there are still a few SOIC-16 version that you can buy. 

But better to design with a op amp that is replaceable into the future.

Quote:

I checked with some replacements of opamp at stage 1 to reduce the noise due to current noise. It seems AD743 is the best balanced opamp for this location. Attached is the circuit schematic of this final version v3.2 , with LISO analysis and also the analysis done to reach to this opamp.

 

 

  2225   Mon Aug 6 15:02:57 2018 anchalDailyProgressISSFinal Design for ISS Servo v3.2

Yes I realized this later. AD743, unfortunately, was the best choice for us. Its replacement ADA4627 from Analog Devices is worse than OPA827 which is the next best choice according to the LISO simulation. So we'll go ahead with OPA827 in the Stage 1. I'll put the final schematic with board design soon.

Quote:

AD743 is discontinued.  We have a few in stock, and there are still a few SOIC-16 version that you can buy. 

But better to design with a op amp that is replaceable into the future.

Quote:

I checked with some replacements of opamp at stage 1 to reduce the noise due to current noise. It seems AD743 is the best balanced opamp for this location. Attached is the circuit schematic of this final version v3.2 , with LISO analysis and also the analysis done to reach to this opamp.

 

 

  2227   Mon Aug 13 17:41:39 2018 anchalSummaryISSDCC link of finished design

The board design is finished and all the files have been uploaded on dcc (LIGO-D1800214-v1). PCB Layout, circuit schematic, Gerber files, LISO analysis, front panel and full BOM are attached. There are two copies of ISS circuits on the single board and they will be mounted on rack with a 2U front panel.

Notes:
1) The Noise performance analysis is present in the LISO_and_LTSpice_Files folder.
2) The present values in stage 4 of the circuit has cavity pole neutralization for a pole frequency of ~40kHz. To make this different, change the capacitor C22 and C53 accordingly.
3) The resistors R9 and R14 in Stage 0 can be populated to give an overall gain to the circuit.

  2538   Fri Feb 14 17:40:27 2020 anchalDailyProgressISSInstalled ISS on both paths using SR560s

I've installed ISS on both paths using 3 SR560s each. Preliminary feedback is setup to get a stable loop. More optimization with TF analysis can be done further.


Path changes:

  • I replaced the unmarked waveplate in the north path right after the EOAM at (112, 39) with a zeroth-order quarter waveplate.
  • I adjusted these quarter waveplates at (112, 39) and (90, 24) to the half transmission through the PBS when EOAM inputs are shorted.
  • I followed the notes in Antonio's post (See CTN:1593 and CTN:1604).

ISS:

  • ISS is formed with three SR560s in series.
  • First SR560 is AC coupled, has a 2nd order zero at 1 Hz and gain of 100 at Low noise Mode.
  • The second SR560 is DC coupled and has a pole at 1 kHz (North) and 3 kHz (South) with gain 1 and High Dynamic Reserve setting.
  • The third SR560 is also DC coupled and has a pole at 300 kHz with gain 1 and High Dynamic Reserve setting.

Measurement:

  • I took the measurement of the spectrum from the output of transmission photodiodes.
  • I used the calibrated coupling factor I measured earlier to convert the measured voltage to watts of power right after the cavities. (See CTN:2528).
  • Measurement configuration files is attached.
  • We see about a factor of 10 improvement in the intensity noise between 100Hz to 1 kHz.
  • Note that the bad spikes notes in the beatnote spectrum at 480 Hz and around 900 Hz are present in the north transmission spectrum as well.
  • Effect on the beatnote noise would be evident after tonight's measurement at 3 am. In my preliminary measurements, I see some reduction in noise below 200 Hz but nothing much.

Data

Attachment 2: ISS_Effect.pdf
ISS_Effect.pdf
  2539   Sat Feb 15 18:57:43 2020 ranaDailyProgressISSInstalled ISS on both paths using SR560s

you don't need 6(!!) SR560s - just 1 for each loop:

  • AC coupled,
  • 1st order high pass at 300 Hz,
  • 1st order low pass at 300 Hz
  • Aim for a UGF of ~10 kHz

Then use multi-res spectra and check out the out-of-loop noise (with loop on/off). The in-the-loop noise is always an underestimate.

  2542   Thu Feb 20 17:42:23 2020 ranaDailyProgressISSInstalled New ISS on both paths using SR560s

I've installed new ISS consisting of one SR560 per path.


ISS SR560 Details:

Path Input Coupling Invert High Pass Roll off (dB/octave) High Pass Corner (Hz) Low Pass Roll off (dB/octave) Low Pass Corner (Hz) Gain Mode Gain Output Impedance (Ohms)
North AC No 6 300 6 300 Low Noise 5x103 600
South AC Yes 6 300 6 300 Low Noise 1x104 600

Measurements:

  • I took transfer function by exciting at port B and using mode A-B on the SR560.
  • The transfer function was measured as Actuation Signal (output of SR560) over Error Signal (input to SR560).
  • This transfer function should be equal to open-loop gain over the SR560 transfer function.
  • So, I took another measurement of the transfer function of SR560 itself not connected to the loop.
  • This gave me total open-loop transfer function.
  • I used \frac{\pi}{2V_{\pi}} as the transfer function of EOAM in units of relative intensity change per V (1/V).
  • I used the coupling factor (See CTN:2528) and DC power level of the laser after transmission to get the detector transfer function in units of V.
  • Using the above, I calculated the plant transfer function for each path and then used that to calculate the closed-loop transfer function.
  • To compare, I also calculated noise suppression before and after switching on ISS.
  • These two separate methods match very well. At 300 Hz, intensity noise is suppressed by 40 dB.
  • There is no other witness detector after transmission to use as an out-of-loop photodiode, neither is there any space to put a new one.
  • There is oscillation happening at UGF  fo around 40 kHz in both paths. I can work on it if this looks like a problem in the final beatnote or if it seems to saturate FSS loops. Currently, I saw nothing alarming.

Data

Attachment 1: ISS_New_Analysis.pdf
ISS_New_Analysis.pdf ISS_New_Analysis.pdf ISS_New_Analysis.pdf
  2544   Sun Feb 23 18:19:32 2020 ranaDailyProgressISSInstalled New ISS on both paths using SR560s
  1. too much gain peakin!
    1. 0 dB - thats no fun
    2. 20 dB - too much cowbell !!
    3. 10 dB - ahhhh, that's nice....
  2. in-loop performance is "fake news": u need to have an unbiased reporter
  2545   Fri Feb 28 14:00:11 2020 anchalDailyProgressISSInstalled New ISS on both paths using SR560s - PROBLEM

I'm currently struggling with a problem in North ISS which I think needs to be documented here. Here's the synopsis:


The problem:

  • After running for the weekend with high gains and gain peaking at ~45 kHz, I found this week that the North ISS was overloading.
  • The power level reaching the cavities change over the course of the day by +- 20-30% usually (still a mystery to me), so I assumed this could just be because of increased laser power saturating the SR560.
  • But what I have found is that except for some random instances, I can't keep the gain high enough in this ISS path.
  • At the start, I thought this problem is at least reset-able by unlocking the North FSS and locking the cavity back. But later, I've found that it is not working either now.
  • The defining feature is, as I slowly increase the gain (giving ample time for the loop to settle), at the first point where I see any sign of overload, it happens at a rate of ~300 mHz, that's once every 3  seconds!
  • I checked at the photodiode output at this gain setting and I see the loop gets unstable and for about half a second every 3 seconds or so.
  • On increasing the gain further, this overload just becomes a constant condition.
  • My first guess is that somehow the lower unity gain frequency is becoming unstable. But the mystery is:
    • Why did this not happen before?
    • Why is this not seen in the South Path at all? It is healthy as ever.
    • What really changed during the weekend?
    • And why once in a while, it was actually working?
  • The only difference in the SR560 settings for the two loops is that the South path has 'invert' ON while North path does not. At first, I was perplexed by this too. South needed 'invert' to be stable and the North did not. Maybe this is the reason?
  • I have ruled out any failure in SR560 by switching it with another one and seeing the exact same phenomenon.
  • Remaining suspects are a damaged BNC cable/connector, damaged photodiode or EOAM (I wish not). However, some bad control loop configuration is my primary suspect.

I would like it if anyone has any comments on any of the points above or suggestions to tackle this problem. I can make some measurements and post them on requests.

  2546   Sun Mar 1 16:34:31 2020 ranaDailyProgressISSInstalled New ISS on both paths using SR560s - PROBLEM

do some step response and swept sine and post plots

  2547   Mon Mar 2 16:48:12 2020 anchalDailyProgressISSFollow-up, porbalem stopped happening, OLTF plot.

The issue isn't visible right now. I'm not sure what changed but with a similar power level, I'm able to increase the gain on North ISS to much higher than before. Currently, I'm taking RIN measurements (still using in-loop detector) to update the noise budget plot which is taking some time as I'm trying to measure the uncertainty in the measurement as well. So, the step response plot would come later.


OLTF

  • Open-loop transfer function of the North ISS loop was measured by exciting at port B in SR560 and using mode A-B.
  • Measurement was taken as Input A / Output which is equivalent to open loop gain divided by the transfer function of SR560.
  • I measured the transfer function of SR560 separately and hence obtained the OLTF.
  • The first measurement is actually product of Actuator TF, Plant and Detector and I have plotted it as well.
  • This plot shows that a pole of 20 kHz is coming through the plant. It can't be detector or actuator as they have very high bandwidths.
  • At the lower end, we couldn't reach to the point where AC coupling sets in. SR560 manual (at page 12) says it is 30 mHz.
  • Lower UGF is roughly 5 Hz, which the gain margin from lower ugf must be more than 20 dB.
  • Since the power level of laser changes somehow  over day, keeping this OLTF is not really fixed and moves up and down. Hopefully, in the present setting, it doesn't hit oscillations.

 


Witness detector?

The beatnote detector SN101's DC output has electronically railed. This might be due to a disconnection inside which may or may not be intentional. I don't think I should meddle around with that detector so close to the result. I will instead replace the other 1611 detector in the blocked port of beam splitter (11,19) with a thorlabs PDA10CS and use that for RIN measurement. But since, the loops were in modd of being stable today, I decided to go ahead and take the measurement with current settings. This will also work as in-loop measurement for comparison later.


Data

Attachment 1: NISS_OLTF.pdf
NISS_OLTF.pdf NISS_OLTF.pdf
  2549   Tue Mar 3 11:49:16 2020 anchalDailyProgressISSTransmitted Laser Relative Intensity Noise

Attached are the latest transmitted RIN measurements.


Measurement:

  • These are taken with in-loop photodiodes of ISS and hence are mostly Fake News. I'll do an out-of-loop measurement as well.
  • The measurement is done by running SR785 repeatedly with no averaging and saving all the curves. 238 measurements were taken this way.
  • The median, lower bound (15.865% percentile (lower 1-sigma for Normal Distribution)) and upper bound (84.135% percentile (upper 1-sigma for Normal Distribution)) are calculated.

Data

Attachment 1: CTN_Trans_RIN_measurement.pdf
CTN_Trans_RIN_measurement.pdf
  2551   Sat Mar 7 09:50:31 2020 anchalDailyProgressISSTransmitted Laser Relative Intensity Noise - Out of loop

Attached are the latest transmitted RIN measurements.


Measurement:

  • I setup a Thorlabs PDA10CS photodiode at the dumped end of beatnote (15, 13).
  • Then, I took out-of-loop RIN measurement of transmitted light by blocking either the North or the South path falling on the beatnote beamsplitter (11, 19).
  • I found out that, when the cavity transmission photodiodes are connected to Acromag input, the acromag input injects some noise into the ISS.
  • On disconnecting the acromags, I was able to increase gains in ISS loops to 20000.
  • A major issue was to measure DC power together with the spectrum to calculate the RIN. I first connected the measured photodetector to Acromag Cavity Transmission Channels (which are empty now) and measured the ratio of DC level with the cavity reflection photodiode.
  • Later, using the cavity reflected dc level and this ratio, I was able to estimate the dc level of the spectrum I'm measuring. This way, I ran RIN measurements sequentially for North and South transmitted light.
  • The measurement is done by running SR785 repeatedly with no averaging and saving all the curves. 500measurements were attempted, few of them had file transfer errors and were ignored.
  • The median, lower bound (15.865% percentile (lower 1-sigma for Normal Distribution)) and upper bound (84.135% percentile (upper 1-sigma for Normal Distribution)) are calculated.

Inference:

  • Higher gain improved the noise a little bit more upto 30 kHz.
  • Notice that there are 60 Hz harmonics (both odd and even) in the South RIN, while they are not present in the North RIN.

Data

 

Attachment 1: CTN_Trans_RIN_measurement.pdf
CTN_Trans_RIN_measurement.pdf
  2552   Wed Mar 11 12:45:15 2020 ranaDailyProgressISSTransmitted Laser Relative Intensity Noise - Out of loop

weird - why is the Gain different for in loop and out of loop ?

  2553   Wed Mar 11 13:16:09 2020 anchalDailyProgressISSTransmitted Laser Relative Intensity Noise - Out of loop

These measurements take a long time as I take a median over 500 single measurement instances. I was able to increase gain later after having taken in-loop noise measurement, so I didn't repeat it. But what I can do is a take a quick in-loop measurement today with simple averaging and no error bars and post it here for comparison. If we are really interested, I can run overnight measurement for in-loop at this gain as well.

Quote:

weird - why is the Gain different for in loop and out of loop ?

 

  2555   Wed Mar 11 16:43:55 2020 anchalDailyProgressISSComparison between Out of loop vs In loop RIN

I took spectrum of Out-of-loop (OOL) photodiode and In-loop (IL) photodiodes with transmitted light from the cavities when ISS is on in both paths at gain value of 2x10000.


Measurement:

  • In-loop photodiodes of ISS have been disconnected from Acromag cards as this was injecting noise into the loops.
  • So, without witnessing the DC level, we can increase the ISS loops' gain to 2x1000 with HF and LF both set at 300 Hz with 6 dB/octave roll off.
  • A major problem in this measurement is the slow drift of DC power level during the time of measurement.
  • I was measuring DC value of photodiode averaged over 10 s with an oscilloscope just before the measurement was taken.
  • In fact, one can see that between two measurements of the different spans, the DC value has changed enough to show mismatch in South In-Loop RIN.
  • The out-of-loop photodiode was measured with sequentially blocking either the north laser or the south laser.
  • The same issue with knowing the exact DC level persists here as well.

Inference:

  • As expected the out-of-loop noise is higher than the in-loop noise, but I did not expect a factor of ~5 difference.
  • However, this method of measuring RIN isn't very faithful.
  • Overall for the experiment, it is clear that increasing the gain of ISS further did not lower the beatnote spectrum much.
  • This suggests that we have damped down photothermal noise in the experiment below other fundamental noise sources.
  • My future efforts would be focused solely to get rid of the peaks in the range of 200 Hz to 1 kHz.
  • I see that the sharp peak at 480 Hz has changed into a tri-peak around the same frequency without any changes in the experiment other than ISS.
  • This atleast indicates that this peak was not undefeatable, and so must be the remaining ones.

Data

Attachment 1: CTN_Trans_RIN_OOLvsIL.pdf
CTN_Trans_RIN_OOLvsIL.pdf
  2559   Thu Mar 12 19:11:00 2020 shrutiDailyProgressISSRemoved half-wave plate in north path

[Anchal, Shruti]

We realized that the half-wave plates before the EOAMs probably had no real function in the setup and therefore we proceeded to remove the one from the north path at (39,121) aka row 39, column 121 of the Optical layout.

After this was done, we had to re-adjust the quarter wave-plate (39,112) after the EOAM (39,115) to make sure that the EOAM was still functioning about the 50% transmission point. The beam going into the PMC was also re-aligned by adjusting the two mirrors at (32,92) and (37,92). Finally, the mirror at (43,88) was adjusted to align the beam reflecting from the PMC into the photo-diode.

We were able to re-lock the north PMC and north cavity after increasing the power in that path by adjusting some waveplates.

As may be expected, the sign of the ISS feedback had to be inverted. The ISS actuates on the EOAM; removing the half-wave plate would have switched the circularity of the polarization of the beam entering the PBS at (39,110), so the sign of the voltage that would have previously caused the transmission to increase would now cause it to decrease and vice versa.

  2560   Mon Mar 16 16:16:17 2020 anchalDailyProgressISSAdded true OOL transmission PD for South Path

Today, I added a new out-of-loop transmission PD (Thorlabs PDA10CS) for the south path. This will be helpful in future measurements of RIN coupling to beatnote noise. This PD is added at (1, 40) using the dumped light. The optical layout would be updated in a few days. I've confirmed that this photodiode is reading the same RIN as read earlier in CTN:2555. I've also connected Acromag channel for South Transmission DC to this photodiode, so the transmitted power channels and the mode matching percentage channel of South Cavity are meaningful again.

 

  2561   Tue Mar 17 18:03:22 2020 anchalDailyProgressISSAdded true OOL transmission PD for North Path

Today, I added a new out-of-loop transmission PD (Thorlabs PDA10CS) for the north path. This will be helpful in future measurements of RIN coupling to beatnote noise. This PD is added at (8, 42) using the dumped light. The optical layout would be updated in a few days. I've also connected Acromag channel for North Transmission DC to this photodiode, so the transmitted power channels and the mode matching percentage channel of North Cavity are meaningful again.

ISS Gain for the Northside has been increased to 2x10000 since half of the light is now being used by the OOL PD.

Attachment 1: IMG_20200317_180420.jpg
IMG_20200317_180420.jpg
  2608   Thu Feb 11 18:01:39 2021 AnchalDailyProgressInstrumentCharacterizationSR560 Intermodulation Test

I added script SRIMD.py in 40m/labutils/netgpibdata which allows one to measure second order intermodulation product while sweeping modulation strength, modulation frequency or the intermodulation frequency. I used this to measure the non-linearity of SR560 in DC coupling mode with gain of 1 (so just a buffer).


IP2 Characterization

  • Generally the second order intercept product increases in strength proportional to the strength of modulation frequency with some power between 1 and 2.
  • The modulation frequency strength where the intermodulation product is as strong as the original modulation frequency signal is known as intercept point 2 or IP2.
  • For SR560 characterization, I sent modulation signal at 50 kHz and set intermodulation frequency to 96 Hz.
  • The script sends two tones at 50 kHz and 50khz -96 Hz at increasing amplitudes and measured the FFT bin around 96  Hz with dinwidth set by user. I used 32 Hz bin width.
  • In attachment 1, you could see that beyond 0.1 V amplitude of modulation signal, the intermodulation product rises above the instrument noise floor.
  • But it weirdly dips near 0.8 V value, which I'm not sure why?
  • Maybe the modulation signal itself is too fast at this amplitude and causes some slew rate limitation at the input stage of SR560, reducing the non-linear effect downstream.
  • Usually one sees a straight curve otherwise and use that to calculate the IP2 which I have not done here.

IMD2TF Characterization

  • First of all, this is a made up name as I couldn't think of what else to call it.
  • Here, we keep the amplitude constant to some known value for which intermodulation signal is observable above the noise floor.
  • Then we sweep the modulation frequency and intermodulation frequency both, to get a 2-dimensional "transfer function" of signal/noise from higher frequencies to lower frequencies.
  • Here I kept the source amplitude to 0.4V and swept the modulation frequency from 10kHz to 100kHz and swept the intermodulation frequency from 96 Hz to 1408 Hz, with integration bandwidth set to 32 Hz.
  • I'm not completely sure how to utilize this information right now, but it gives us an idea of how much noise from a higher frequency band can jump to a lower frequency band due to the 2nd order intermodulation effect.

 


Edit Wed Feb 17 15:34:40 2021:

Adding self-measurement of SR785 for self-induced intermodulation in Attachment 3 and Attachment 4. From these measurements at least, it doesn't seem like SR785 overloaded the intermodulation presented by SR560 anywhere.

Attachment 1: IP2SR560_11-02-2021_175029.pdf
IP2SR560_11-02-2021_175029.pdf
Attachment 2: IMD2TFSR560s_11-02-2021_180005.pdf
IMD2TFSR560s_11-02-2021_180005.pdf
Attachment 3: SR785_SelfIP2_12-02-2021_145140.pdf
SR785_SelfIP2_12-02-2021_145140.pdf
Attachment 4: SR785_SelfIMD2TF_12-02-2021_145733.pdf
SR785_SelfIMD2TF_12-02-2021_145733.pdf
Attachment 5: SR560.zip
  1654   Wed Jun 29 15:57:13 2016 awadeSummaryInventoryList of current available lenses in PSL and 40m labs

As we are doing mode matching I compiled a list of presently available lenses to save time looking or ordering. See below.

A dynamically updated version is here: https://docs.google.com/spreadsheets/d/1x4-VQ85Wl7kGUH-V7HffCr6B7wIcD1y3VxXO4j6H5T0/edit?usp=sharing (this may not be a stable link far into the future)

At the time of posting the list is as follows:

Code Vendor Type ROC1 ROC2 n f location note
KBC040 Newport Bi-Concave       -75.00 40m  
KBC043 Newport Bi-Concave       -50.00 40m  
KBC046 Newport Bi-Concave       -25.00 40m  
KBX043 Newport Bi-Convex       19.00 40m  
KBX046 Newport Bi-Convex       25.40 40m  
KBX064 Newport Bi-Convex       100.00 40m  
KBX064.AR.33 Newport Bi-Convex       100.00 40m  
KBX088 Newport Bi-Convex       1000.00 40m  
KPC028 Newport Plano-Concave       -200.00 40m  
KPC031 Newport Plano-Concave       -150.00 40m  
KPC034 Newport Plano-Concave       -100.00 40m  
KPC037 Newport Plano-Concave       -75.00 40m  
KPC043 Newport Plano-Concave       -25.00 40m  
KPX076 Newport Plano-Convex       25.00 40m  
KPX079AR.18 PCX Lens, BK7 Newport Plano-Convex       38.10 40m  
KPX115AR.33 PCX BK7 Newport Plano-Convex       400.00 40m  
LA1172-C Thorlabs Plano-Convex       400.00 40m Thorlabs pre-mounted
LA1464-C Thorlabs Plano-Convex       1000.00 40m Thorlabs pre-mounted
LA1484-C Thorlabs Plano-Convex       300.00 40m Thorlabs pre-mounted
LA1509-C Thorlabs Plano-Convex       100.00 40m Thorlabs pre-mounted
LA1908-C Thorlabs Plano-Convex       500.00 40m Thorlabs pre-mounted
LA1951-C Thorlabs Plano-Convex       25.40 40m Thorlabs pre-mounted
LA1978-C Thorlabs Plano-Convex       750.00 40m Thorlabs pre-mounted
LB1056-C Thorlabs Bi-Convex       250.00 40m Thorlabs pre-mounted
LB1391-C Thorlabs Bi-Convex       400.00 40m Thorlabs pre-mounted
LB1409-C Thorlabs Bi-Convex       1000.00 40m Thorlabs pre-mounted
LB1471-C Thorlabs Bi-Convex       50.00 40m Thorlabs pre-mounted
LB1475-C Thorlabs Bi-Convex       750.00 40m Thorlabs pre-mounted
LB1761-C Thorlabs Bi-Convex       25.40 40m Thorlabs pre-mounted
LB1779-C Thorlabs Bi-Convex       300.00 40m Thorlabs pre-mounted
LB1869-C Thorlabs Bi-Convex       500.00 40m Thorlabs pre-mounted
LB1901-C Thorlabs Bi-Convex       75.00 40m Thorlabs pre-mounted
LB1904-C Thorlabs Bi-Convex       125.00 40m Thorlabs pre-mounted
LC1715-C Thorlabs Plano-Concave       -50.00 40m Thorlabs pre-mounted
LC2297-C Thorlabs Plano-Concave       -25.00 40m Thorlabs pre-mounted
LC2679-C Thorlabs Plano-Concave       -30.00 40m Thorlabs pre-mounted
LD1170-C Thorlabs Bi-Concave       -75.00 40m Thorlabs pre-mounted
LD1464-C Thorlabs Bi-Concave       -50.00 40m Thorlabs pre-mounted
LD2297-C Thorlabs Bi-Concave       -25.00 40m Thorlabs pre-mounted
PLCX-25.4-103-UV-1064 CVI Plano-Convex 1.00E+99 103 1.44963 229.08 PSL  
PLCX-25.4-103.0-UV-1064 CVI Plano-Convex 1.00E+99 103 1.44963 229.08 40m  
PLCX-25.4-1030.2-UV-1064 CVI Plano-Convex 1.00E+99 1030.2 1.44963 2291.22 40m  
PLCX-25.4-12.9-C-1064 CVI Plano-Convex 1.00E+99 12.9 1.5066 25.46 40m  
PLCX-25.4-13.1-UV-1064 CVI Plano-Convex 1.00E+99 13.1 1.44963 29.14 40m (Chipped)
PLCX-25.4-154.5-UV-1064 CVI Plano-Convex 1.00E+99 154.5 1.44963 343.62 PSL  
PLCX-25.4-1545.0-C-633-1064 CVI Plano-Convex 1.00E+99 1545 1.5066 3049.74 40m  
PLCX-25.4-180.3-UV-1064 CVI Plano-Convex 1.00E+99 180.3 1.44963 401.00 PSL  
PLCX-25.4-180.3-UV-1064 CVI Plano-Convex 1.00E+99 180.3 1.44963 401.00 PSL  
PLCX-25.4-20.6-UV-1064 CVI Plano-Convex 1.00E+99 20.6 1.44963 45.82 PSL  
PLCX-25.4-257.5-UV-1064 CVI Plano-Convex 1.00E+99 257.5 1.44963 572.69 PSL  
PLCX-25.4-257.5-UV-1064 CVI Plano-Convex 1.00E+99 257.5 1.44963 572.69 PSL  
PLCX-25.4-257.5-UV-1064 CVI Plano-Convex 1.00E+99 257.5 1.44963 572.69 PSL  
PLCX-25.4-2575-C-1064 CVI Plano-Convex 1.00E+99 2575 1.5066 5082.91 40m  
PLCX-25.4-309.1-UV-1064 CVI Plano-Convex 1.00E+99 309.1 1.44963 687.45 PSL  
PLCX-25.4-309.1-UV-1064 CVI Plano-Convex 1.00E+99 309.1 1.44963 687.45 PSL  
PLCX-25.4-309.1-UV-1064 CVI Plano-Convex 1.00E+99 309.1 1.44963 687.45 PSL  
PLCX-25.4-357.5-UV-1064 CVI Plano-Convex 1.00E+99 357.5 1.44963 795.10 PSL  
PLCX-25.4-38.6-UV-1064 CVI Plano-Convex 1.00E+99 38.6 1.44963 85.85 PSL  
PLCX-25.4-46.4-UV-1064 CVI Plano-Convex 1.00E+99 46.4 1.44963 103.20 PSL  
PLCX-25.4-46.4-UV-1064 CVI Plano-Convex 1.00E+99 46.4 1.44963 103.20 PSL  
PLCX-25.4-51.5-UV-1064 CVI Plano-Convex 1.00E+99 51.5 1.44963 114.54 PSL  
PLCX-25.4-515.1-UV-1064 CVI Plano-Convex 1.00E+99 515.1 1.44963 1145.61 PSL  
PLCX-25.4-64.4-UV-1064 CVI Plano-Convex 1.00E+99 64.4 1.44963 143.23 PSL  
PLCX-25.4-77.3-UV-1064 CVI Plano-Convex 1.00E+99 77.3 1.44963 171.92 40m  
PLCX-25.4-77.3-UV-1064 CVI Plano-Convex 1.00E+99 77.3 1.44963 171.92 40m  
PLCX-25.4-772.6-UV-1064 CVI Plano-Convex 1.00E+99 772.6 1.44963 1718.30 40m  
SPX028AR.1 PLXLens, UV Newport Plano-Convex       200.00 40m  
Unspecified Unspecified Unspecified       100.00 40m  
  1698   Thu Aug 4 13:33:39 2016 awadeNotesInventoryBorrowed SRS DB64 delayer box from Crackle Lab

Borrowed SRS DB64 delayer box from Crackle Lab.  

Has a set of binary switches in increments of 0.5,1,2,4,8,16,32 ns.  This should be useful in varifying if we have the optimal phase delay for the error signal.  Distance from cavities to PDs has changed but the cabling is the same.  We might as well know that we are opimised rather than trust that it is just OK.

  2037   Wed Jan 10 11:31:03 2018 awadeSummaryLab InfrastructureLasers cycled on and off

I had a guy come and fix the lighting in the lab.  I tried to replace the tubes yesterday and found that the ballast had died for one row of lights.

A facilities guy came this morning and replaced the ballast on the outer row on the north side of the lab.  I turned the lasers off from 10 am till 11:30 am Wed Jan 10 to make  it easier for him.  The lasers are now back on and cavities are locked. I didn't relock the PLL. 

  2042   Thu Jan 11 13:31:36 2018 awadeMiscLab InfrastructureAnts nesting in PSL lab

There are a large number of ants making a trail from the ATF lab to the PSL lab.  They seem to be heading into a hole next to the lab door.  I just saw a queen ant poke its head out of the hole.  

Ants in the ATF lab are taking their ussual route along the AC conduit.  There are Terro baits laid ever 3-4 meters and they have almost emptied every one. The trails continue to the mechanical plant room accross the hall (room 259ME)

Laying down Terro ant poison now. Will buy more.

Thu Jan 11 13:33:04 2018

Attachment 1: 20180111_antnestforming.jpg
20180111_antnestforming.jpg
  2079   Thu Feb 8 12:42:49 2018 awadeDailyProgressLab InfrastructureUltrasonic bath broken

I turned on the ultrasonic bath this morning.  It looks like one of the front panel buttons for incrementing values of temperature and time is latched in the on state.  The interface now just sits there cycling 0-99 through set time with all other buttons disabled.  

I tried massaging the button to see if I could break the short but it appears to be stuck.  Don't think the bath will be serviceable anymore so we're down an ultrasonic bath.

  2088   Mon Feb 12 20:03:53 2018 awade, CraigMiscLab InfrastructureFlipped circuit breaker at around 8 pm

Flipped circuit breaker at around 8 pm.

I looks like we've overloaded the UPS group one circuit.  I was operating a heat gun off some of the table power and flipped the circuit breaker.  

Unfortunately the lasers were running off this circuit. The whole point of the UPS was to avoid the hard shutdowns. We switching the lasers to group 2 on the UPS so that this doesn't happen again.

  15   Wed Nov 18 20:52:39 2009 FrankLaserLaserlaser error

this morning the laser was off with the error "HT error". As the chiller was off too i think that means high temperature error, right?
So i checked everything and started the laser again. So far everything is fine and working. Any idea?

  48   Thu Feb 4 20:13:53 2010 FrankLaserLaseroutput coupler to acav changed

exchanged the old mirror (T330-HR, T331-AR) by a simple Y1-1025-45P to get more power.

measured laser power : 7.17W
downstream of the new output coupler : 134.6mW

added waveplates & pbs to make the power adjustable. current power through the EOM is 8mW which gives about 4.33V on the RF-PD (Thorlabs PDA10CS, 0dB-setting, 17MHz)

  56   Sun Feb 7 18:29:06 2010 FrankLaserLasernew channels + changes

added the following channels:

C3:PSL-RCAV_DIFFPWR : diffracted power (single pass) measured behind curved mirror
C3:PSL-126MOPA_PWRMON : laser output power monitor measured after PC

 

changes:

C3:PSL-RCAV_QPDSUM changed back to QPD sum signal

 

all signals available in both framebuilders

ELOG V3.1.3-