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ID Date Authorup Type Category Subject
  9323   Thu Oct 31 20:05:48 2013 RANAUpdateIOOMode Cleaner Tune-UP

Quote:

Steve, can you please put 2 mounted  razor dumps near the WFS for this purpose??    

            Tuesday: Razor dumps are waiting for you.

 I couldn't find any dumps near the WFS. Koji looked. I looked twice. Maybe they are spooky and absorbing all of the light?

The MC alignment was bad and the WFS were making it drift. Koji aligned the beam into the PMC. I then restored the MC suspensions to where they were 8 days ago (back when the transmission and reflection were good). With the WFS OFF, this gave us a MC trans ~ 16000. With WFS ON it goes to 17500 which is about as good as its been over the last 80 days.

I centered the beam on the WFS with the MC unlocked and also centered the beam on the whole WFS path (it was near clipping between WFS 1 & 2). Also for some reason that beamsplitter which steers the beam onto WFS1 is a R=33% (!? why is this not a R=50% ??).

Steve, please swap this out to a BS1-1064-50-1025-45S if we have one sitting around. If not, we want to add this to the CVI purchase list, but not buy until we get a bigger list together.

I also centered this newly aligned beam into the IMC onto the PSL QPDs. We should now use these as a pointing reference for the beam into the IMC.

While doing this I noticed that the beam was almost clipping on the Uniblitz shutter used to block the PSL beam. That shutter is mounted too short and was also not centered horizontally. I removed it for now so that Steve can find a more adjustable mount for it and put it back into play. The beam going into the IMC is BIG, so you have to very careful when centering the shutter. Might be that we cannot leave it at 45 deg and still get a big enough aperture.

Note #3 for Steve: please also replace the mount for last steering mirror into the IMC with a Polanski or a Superman, that black Ultima is no good. Also the dogs must be steel - no aluminum dogs for our sensitive places.

Attachment 1: drifty.png
drifty.png
  9365   Mon Nov 11 22:35:45 2013 RANAUpdateIOOPSL pointing monitoring

Since the pointing has gone bad again, I went to the PSL to investigate. Found some bad things and removed them:

1) There was a stopped down iris AGAIN in the main beam path, after the newly installed mirror mount. I opened it. Stop closing irises in the beam path.

2) The beam dump for the IOO QPD reflection was just some black aluminum. That is not a real dump. I removed it. We need two razor blade dumps for this.

3) There was an ND filter wheel (???) after one of the PMC steering mirrors. This is not good noise / optics practice. I removed it and dumped the beam in a real dump. No elog about this ?!#?

 

The attached trend shows the last 20 days. The big step ~2 weeks ago is when Steve replaced the steering mirror mount with the steel one. I don't understand the drift that comes after that.

 

Today I also spent ~1 hour repairing the Aldabella laptop. Whoever moved it from the PSL area to the SP table seems to have corrupted the disk by improper shutdown. Please stop shutting the lid and disconnecting it from the AC power unless you want to be fixing it. Its now running in some recovery mode. Lets leave it where it is next to the PSL and MC1.

I steered the MC suspensions back to where they were on the trends before the PSL mirror mount swap and then aligned the PSL beam into it by touching the last 2 steel mounts. Once the alignment was good without WFS, I centered the beams on the IOO QPDs. If it behaves good overnight, I will center the unlocked beams on the MC WFS.

 

Please stay off the PSL for a couple days if you can so that we can watch the drift. This means no opening the doors, turning on the lights, or heavy work around there.

Attachment 1: qpd.pdf
qpd.pdf
  9370   Tue Nov 12 23:48:23 2013 RANAUpdateIOOPSL pointing monitoring

Since I saw that the trend was good, I aligned the MC refl path to the existing IMC alignment:

  1. removed a broken IRIS that was clipping the reflected beam (and its mount)
  2. moved the first 1" diameter steering mirror on the high power path after the 2" diameter R=10% steering mirror. It was not centered.
  3. Moved the lens just upstream of the LSC RFPD away from the PD by ~5 mm. The beam going towards the WFS was too close to this mount and I could see some glow.
  4. Centered the beam on all optics in the WFS path and then the WFS DC.
  5. Centered beam on LSC RFPD.

The reflected spots from the PD are not hitting the dump correctly. WE need to machine a shorter post to lower the dump by ~1 cm to catch the beams.

  9400   Mon Nov 18 19:45:42 2013 RANAUpdateSUSPRM pictures

Nice camera work Steve! I will use these for publicity photos.

Now we need to get one of the video cameras hooked into the MUX so that we can see the flashing and do some image subtraction.

  9521   Mon Jan 6 18:32:17 2014 RANAUpdateIOOMC1/3 kicked this morning at 8:30

 The trend shows a big jolt to the MC1/3 pointing this morning at 8:30.

Was anyone working anywhere near there today? There is no elog.

If not, we will have to put a 'no janitor' sign on all of the 40m doors permanently to prevent mops misaligning our interferometer.

Attachment 1: kicked.png
kicked.png
  9666   Mon Feb 24 17:59:31 2014 RANAUpdateElectronicsMeasured REFL165 demod board

 

 Demod boards should be at 90 deg, not 82.7 or 12 or yellow or ****. We should re-inject the RF and then set the D Phase in the filter module to make the signals orthogonal. 165 is a challenging one to get right, but its worth it since the signals are close to degenerate already.

  7624   Thu Oct 25 15:38:06 2012 RajiUpdateAlignmentTransmitance Measurements on LaserOptik mirror

I measured the transmitted power @1064nm on one of the LaserOptik mirrors labled SN6

Here is the data

Polarization Input Angle Input Power(mW) Output Power(mW) Transmittance (%)
p 0 6.2 2.67 48
p 0 100 52 52
p 45 6.2 0.76 12
p 45 100 1,5 1
s 0 8.2 3.15 38
s 0 100 40 0.4
s 45 8.2 0.5 6
s 45 100 0.66 0.006

The mirror is not a good reflector at 0 deg.

  7644   Wed Oct 31 12:58:17 2012 RajiUpdateAlignmentTransmitance Measurements on LaserOptik mirror

Quote:

I measured the transmitted power @1064nm on one of the LaserOptik mirrors labled SN6

Here is the data

Polarization Input Angle Input Power(mW) Output Power(mW) Transmittance (%)
p 0 6.2 2.67 48
p 0 100 52 52
p 45 6.2 0.76 12
p 45 100 1,5 1
s 0 8.2 3.15 38
s 0 100 40 0.4
s 45 8.2 0.5 6
s 45 100 0.66 0.006

The mirror is not a good reflector at 0 deg.

 More data on the transmission. Measured the tranmission as a funtion of incidence angle at 1064nm

Attachment 1: Transmission-plot@1064nm.pdf
Transmission-plot@1064nm.pdf
Attachment 2: Transmission-data@1064nm.pdf
Transmission-data@1064nm.pdf
  3241   Fri Jul 16 23:53:27 2010 RanaUpdatePSLReference Cavity Insulation

From the trend, it seems that the Reference Cavity's temperature servo is working fine with the new copper foil. I was unable to find the insulating foam anywhere, but that's OK. We'll just get Frank to make us a new insulation with his special yellow stuff.

The copper foil that Steve got is just the right thickness for making it easy to form around the vacuum can, but we just have to have the patience to wrap ~5-10 more layers on there. We also have to get a new heater jacket; this one barely fits around the outside of the copper wrap. The one we have now seems to have a good heating wire pattern, but I don't know where we can buy these.

I also turned the HEPA's Variac back down to the nominal value of 20. Please remember to turn it back up to 100 before working on the PSL.

  3280   Fri Jul 23 16:02:16 2010 RanaUpdatePSLReference Cavity Insulation

This is the trend so far with the copper foil wrapping. According to Megan's calculation, we need ~1 mm of foil and the thickness of each layer is 0.002" (1/20th of a mm), so we need ~20 layers. We have ~5 layers so far.

As you can see the out-of-loop temperature sensor (RCTEMP) is much better than before. We need another week to tell how well the frequency is doing -

the recent spate of power cycles / reboots of the PSL have interrupted the trend smoothness so far.

Attachment 1: Untitled.png
Untitled.png
  3282   Fri Jul 23 21:14:29 2010 RanaUpdatePSLReference Cavity Insulation

I wrapped another ~3 layers onto there. It occurs to me now that we could just get some 2mm thick copper plates made to fit over the stainless steel can.

They don't have to completely cover it, just mostly. I also took the copper circles that Steve had made and marked them with the correct beam height

and put them on Steve's desk. We need a 1" dia. hole cut into these on Monday.

To compensate for the cooling during my work, I've set the heater for max heating for 1 hour and then to engage the temperature servo.

I also noticed the HEPA VARIAC on the PSL was set to 100. Please set it back to 20 after completing your PSL work so that it doesn't disturb the RC temperature..

  7869   Fri Dec 21 16:50:30 2012 RanaUpdateSUSTT in vac DB25 pin swapping

[Koji, Rana, Nic, Steve]

We went to the 25-pin D cable which connects to the TT1 quadropus and succeeded eventually in swapping pins 12/24 into the 13/25 positions.

  1. The D-sub connector is a custom made LIGO part and so it doesn't at all work to use the standard pin extractor tools to move the pins out; we should have investigated this before spending all this time poking at and possibly damaging the existing connector.
  2. To move the pins, we have to partially dis-assemble the connector and fish the pins/wires through the appropriate holes. Unfortunately, the design is such that we nearly lose all of the pins when trying to do this. Pictures describe the story better than words.
  3. After the swap we tried to test the TT, but again wasted some time because the vac feedthrough was incorrectly labeled. The 25-pin feedthrough labeled as "PZT1" does not, in fact, connect to the TT. Instead, its the one slightly above it that is labeled "Pico". I have moved the PZT1 sticker up to match the actual connector. In order to discover this, we beeped through several stages of the coil driver, cable system. WE need to order some in-line D-sub breakouts for 25pin, 37pin, and 9pin which are similar to the ones we have now for 15pin. These are better than the green terminal block breakouts.
  4. After this, we were able to see the TT move, but elected to leave the final piece of the work (determining which microD goes with which coil) to when Jamie gets back.
  5. The TT screen is not good: it needs to be just like the usual sus screen so that we can put in offsets, excitations, etc. Perhaps also the ASC-TT screen can link to the TT:SUS screens. We can just copy the eLIGO TT screens to get going.
  8395   Tue Apr 2 21:11:42 2013 RanaUpdateoptical tablesOptical Table Toolboxes Update

Quote:

A heavy duty plastic box is the likeliest candidate for the optical table toolbox. It measures 5 9/16 in. x 11 5/8 in. x 4 5/8 in. and fits all the tools comfortably. ( http://www.mcmaster.com/#plastic-bin-boxes/=m4yh4m  ,  under Heavy Duty Plastic Bin Boxes)

The list of tools has been updated to include a pen and a wire cutter as well as everything previously stated.

In addition, Steve has recommended that boxes should be secured to the walls or surfaces near the optical tables as opposed to the optical tables themselves, as to keep the tables from wobbling when tools are being exchanged.

A diagram of tentative box placements will go out soon.

 No, the small boxes must be attached to the optical tables. They won't be heavy enough to change the table tilt.

Also, all tools must be color coded according to the optical table using the 3M Vinyl table color code:

http://www.3m.com/product/images/Vinyl-Electrical-Color-Tape-300.jpg

  9316   Wed Oct 30 03:33:17 2013 RanaUpdateLSCLSC demod boards need some thought

 

 0309.png

I worked on the script SPAG4395A.py tonight with Masayuki's help. This sets up the parameters on the Agilent 4395A and then acquires the spectrum data. It had a couple of bugs before: no matter what channel you requested, you always got channel R. It also would disobey any requests to reduce the attenuation and left the Auto Atten ON. The version now in the SVN allows you to choose the channel and the attenuation.

It then makes this plot using matplotlib. The attached image is from the REFL165 pickoff at a time tonight when the arm powers were ~5-10. I have converted the spectrum from RF electrical Watts into Volts (V = 50*sqrt(W)). To go from the analyzer input to the demod board input we should scale this spectrum by a factor of ~15 (to account for the 20 dB from the coupler and the 3 dB of the splitter and a little more for losses). On the oscilloscope we see Vpp ~5 mV, so that's ~75 mVpp at the output of the BBPD which we're using for REFL165. Perhaps we can handle another factor of ~2-3 ? I'm not sure what we have in terms of linearity measurements on this thing.

EDIT: Evan is right, its V = sqrt(50*W), not V = 50*sqrt(W). ignore y-axis above

  16061   Wed Apr 21 11:01:37 2021 RanaUpdateCDS40m LSC simPlant model

The controller would be in the c1sus model, and connects to the c1sup plant model. So the controller doesn't go in the plant model.

Both the controller and the plant can be modeled using a single filter module in each separate model as you've drawn, but they go in separate models.

 

  1954   Wed Aug 26 19:58:14 2009 Rana, AlbertoUpdatePSLReference Cavity Temperature Control: MINCO PID removed

Summary: This afternoon we managed to get the temperature control of the reference cavity working again.

We bypassed the MINCO PID by connecting the temperature box error signal directly into EPICS.

We couldn't configure the PID so that it worked with the modified temperature box so we decided to just avoid using it.

Now the temperature control is done by a software servo by using the channel C1:PSL-FSS_MINCOMEAS as error signal and driving C1:PSL-FSS_TIDALSET (which we have clip-doodle wired directly to the heater input).

 

We 'successfully' used ezcaservo to stabilize the temperature:

ezcaservo -r C1:PSL-FSS_MINCOMEAS -s 26.6 -g -0.00003 C1:PSL-FSS_TIDALSET

 

We also recalibrated the channels:

C1:PSL-FSS_RMTEMP

C1:PSL-FSS_RCTEMP

C1:PSL-FSS_MINCOMEAS

with Peter King on the phone by using ezcawrite (EGUF and EGUL) but we didn't change the database yet. So please do not reboot the PSL computer until we update the database.

 

More details will follow.

Attachment 1: rc.png
rc.png
  8776   Thu Jun 27 22:52:38 2013 Rana, Gabriele, FrancescoSummaryComputer Scripts / ProgramsLIGO-DV installed

I installed ligoDV in the /ligo/apps/ligoDV/

Now, by pointing the tool at the local NDS2 server (megatron:31200) you can access the recent local data (raw, trends, etc.)

by running /ligo/apps/ligoDV/ligodv from the command line.

Attachment 1: ldv.png
ldv.png
  8387   Tue Apr 2 10:22:37 2013 Rana, Gabriele, JenneUpdateLSCPRMI lock

We locked the PRMI, this time really on the sidebands, using the two REFL55 signals.

Here are the parameters: triggering on POP22_I in at 140, out at 20. No normalization. MICH gain -0.15, PRCL gain 0.1

It seems that the lock is not very stable. It seems likely to come from some large angular motion of one of the mirrors. We'll need to calibrate the optical lever signals to understand which one is moving too much.

 

Attachment 1: lock_prmi_sb.pdf
lock_prmi_sb.pdf
  2465   Tue Dec 29 13:57:20 2009 Rana, Kiwamu, and HaixingUpdatePhotosPhotos of video switch box

Before we installed the video switch box, we also took some photos of it. We uploaded them onto the 40m Picasa.

Video Matrix

The first photo is the an entire view of the switch box. The following four photos are the details of the switch matrix.

 The slideshow below is a dump of the last several months of photos from the Olympus. The originals have been deleted.

  3102   Wed Jun 23 12:28:34 2010 RazibSummaryPhase CameraWeeekly Summary

This past week I have completed the following tasks:

 

1. Built a trigger and power box for the camera GC 750M (06058) and took some test images to see whether the trigger box really works. Result: It is doing fine!

2. Went over the setup that is already sitting on the table. Ref: Aidan's elog entry

3. Attended seminars and talks given by Alan, Jahms, Koji and Rana.

4. Attended the mandatory laser safety training by Peter.

 

Expected task for this week (could be more):

1. Work out analytical expressions of the power of the carrier and sidebands going to the camera in the setup. (As suggested by Rana and Joe)

2. Work on producing beat signal to the camera using the He-Ne laser setup.

3. Move,if possible, to the Nd:YAG setup.

4. Go over the codes and paper by the past SURFers on the phase camera experiment.

 

trigger-box_circuit.png

 


 

Attachment 2: test1.png
test1.png
  3146   Wed Jun 30 12:20:49 2010 RazibUpdatePhase CameraWeekly update

This week I have completed following tasks:

1. Worked out the analytical expressions for the amount of power of the DC and oscillatory part going into the camera.

2. Realigned the He-Ne PhaseCam setup as we had to replace the first steering mirror after the laser with a silvered mirror ( one without a dielectric coating for 1064 nm).

3. Gone through the code written by a previous surfer (Zach Cummings).

4. Read the paper 'Real-time phase-front detector for heterodyne interferometers'- F. Cervantes et. el. where they talk about constructing a phase detector for LISA pathfinder mission. One interesting fact I found was that, they used InGaAs chip for their CCD Cam which has a amazing QE of 80% @ 1064 nm. Unfortunately, the one we are using (Micro MT9V022 CMOS) has only ~5% QE for 1064 nm and 50% for 633 nm. One top of it MT9V022 has a built-in infra-red filter infront of it to make it more insenstive to 1064. In such limitations, we may have to find a work-around for this issue. Any idea?

5. Read about the EOM and AOM and their vibrating (!) way to add on and alter the incident light on them. (Source: Intro to Optical Electronics-Yariv)

 

One task that we couldn't accomplish even though I planned on doing is:

1. Move,if possible, to the Nd:YAG setup.

 

Task for this week:

1. Produce breathtaking calibration of the camera at He-Ne setup.

2. Read 'Fringe Analysis'-Y.Surrel and 'Phase Lock Technique'-Gardner.

3. Modify the phasecam code.

4. Produce an alternate triggerbox using diodes instead of Op-Amp as op-amp is suspected to fail at some point driving the camera due to impedance mismatch.

5. Answer Koji's question at Aidan's ELOG .

  3167   Wed Jul 7 12:17:36 2010 RazibUpdatePhase CameraWeekly update

I have completed the following tasks:

1. Find a simplified calibration of the exposure time for the current He-Ne setup. Basically, I triggered the camera to take 20 snapshots with a 20 Hz driving signal at different exposure time beginning from 100 us (microsecond) upto 4000 us with an increment of 200 us.

    Result: The current power allows the camera to have an exposure time of ~500 us before the DC level begans to saturate.

2. Aidan and I did some alignment and connected the AOM and corrected the driving frequency of its PZT to 40 Mhz(which apparently was disconnected which in turn gets the credit of NO beat signal for me until Tuesday 07/06/2010 5:30 PST) .

    Result: I got the beat signal of 1 Hz and 5 Hz. Image follows (the colormap shows the power in arbitrary units).

3. Finished writing my Progress Report 1 .

DC_1Hz_beat_sig.jpgDC_5Hz_beat_sig.jpg

Attachment 1: DC_1Hz_beat_sig.jpg
DC_1Hz_beat_sig.jpg
  3187   Fri Jul 9 12:07:26 2010 RazibUpdatePhase CameraWeekly update

Here are some more details about the current phasecam setup. We are using a He-Ne laser setup

phase_cam_setup_09_08_10.jpg

A crude snap shot of the setup....

mod_setup_(copy)_annotated.jpg

 

We sent light through SM2 (Steering Mirror 2)  to BS1(Beam-Splitter 1) where the laser light is split into two parts, one going to the AOM and the other to the EOM. The EOM adds 40 MHz sidebands to the incoming carrier light after SM3, and the AOM shifts the frequency of the incident light on it to 40.000 005 MHz. The purpose for doing this juggling is to intentionally create a beat signal off the reference beam from the AOM with the sidebands added at the EOM. Note that, we are driving the AOM at 7dBm and the EOM at 13 dBm with 0 (nil) modulation. The two lights are combined at the BS2 and sent off through SM5 to the camera. The CMOS of the camera contains silicon based Micro MT9V022 chip which has a quantum efficiency of 50% at 633 nm. Thus we expected a fairly good response to this He-Ne setup from the camera. 

Using a trigger circuit, we triggered the camera at 20 Hz by sending a 20Hz sinusoidal signal to it. The trigger circuit converts this to a positive square waves. Then I roughly figured out the optimum exposure time for the camera before the DC levels saturates it by writing a code for taking a series of 25 images at different exposure time. I found that 500µs seems to be a reasonable exposure time. So, using this data, I took 20 consecutive images and sent them through a short Fourier Transform segment using Matlab to see the beat signal. Note that the DC component from these processing of the images have some fringe pattern which is due to the ND 2.5 filter that we were using to reduce the light power incident on the camera. The FT method also gave us the presence of the beat signal at the corresponding bin of the FT (for example: for 5Hz beat signal, I got the DC at bin 1 of the FT and 5Hz component at bin 6 as expected). Then I changed the AOM driving frequency to 40.000 001 MHz in order to see a 1 Hz beat signal. The results for both is in my previous post. 

Quote:

I have completed the following tasks:

1. Find a simplified calibration of the exposure time for the current He-Ne setup. Basically, I triggered the camera to take 20 snapshots with a 20 Hz driving signal at different exposure time beginning from 100 us (microsecond) upto 4000 us with an increment of 200 us.

    Result: The current power allows the camera to have an exposure time of ~500 us before the DC level begans to saturate.

2. Aidan and I did some alignment and connected the AOM and corrected the driving frequency of its PZT to 40 Mhz(which apparently was disconnected which in turn gets the credit of NO beat signal for me until Tuesday 07/06/2010 5:30 PST) .

    Result: I got the beat signal of 1 Hz and 5 Hz. Image follows (the colormap shows the power in arbitrary units).

3. Finished writing my Progress Report 1 .

DC_1Hz_beat_sig.jpgDC_5Hz_beat_sig.jpg

 

  3215   Wed Jul 14 11:51:48 2010 RazibUpdatePhase CameraWork near 1Y2 yesterday

Quote:

Razib and I were attempting to get the output of a photodiode (PD55A in this case) recorded, so that we could independently measure the slow (~1-10 Hz) fluctuations of the light incident on the camera.  This would then allow us to subtract those fluctuations out, letting us get at the camera noise in the case with signal present (as opposed to just a dark noise measurement when we look at the noise with no signal present).

Originally I was thinking of using one empty patch panel BNCs used for PEM channels down by the 1Y7 rack and go through a 110B, although Alberto pointed out he had recently removed some monitoring equipment, which watched the amplitude modulation at various frequencies of the RF distribution (i.e. 33 MHz, etc).  This equipment output a DC voltage proportional to the amplitude of the RF signals.  The associated channel names were C1:IOO-RFAMPD_33MHZ, C1:IOO-RFAMPD_33MHZ_CAL, C1:IOO-RFAMPD_133MHZ, etc.  These are slow channels, so I presume they enter in via the slow computers, probably via pentek (I didn't check that, although in hindsight I probably should have taken the time to find exactly where they enter the system).  The connections them selves were a set of BNCs on the south side, half way up the 1Y2 rack.

We simply chose one, the 33 MHz channel in this case, and connected.  At around this time, the MC did become unlocked, although it looked like it was due to the MC2 watchdog tripping.  The initial theory was we had bumped the Mode Cleaner while looking around for some BNC cables, although from what Rana had to do last night, it probably was the connection.  We were able to restore the watchdog and confirm that the optic started to settle down again.  Unfortunately, I had to leave about 5 minutes later, and didn't do as thorough an investigation as was warranted.

 Before I left, I disconnected the PD55, so the 33 MHz channel wasn't physically connected to anything!!! Only one end of the wire was connected to the rack while the other was free...

So it wasn't the PD connection that is responsible for MC tripping at the later time...

  3217   Wed Jul 14 12:12:03 2010 RazibSummaryPhase CameraWeekly update

This week I was mainly interested in investigating the noise source at the phase camera. So having this issue in mind, my activities are the following:

1. I worked on producing multiple beat signal (1Hz and 5Hz). Elog entry.

2. I altered the setup so that instead of triggering the camera from the signal generator, we are now triggering it from the beat signal from the reference beam and sideband.

3. I made the nice little aluminium table for all the amplifiers, mixer and splitters to sit at one place instead of floating around.

4. I talked with Aidan and Joe and verified my calculation and extended it to further investigation of the noise source in the setup.

 

Plan for the upcoming week:

1. Measure and calibrate the camera w.r.t the power incident on it.

2. Investigate the noise source.

  3258   Wed Jul 21 12:20:58 2010 RazibUpdatePhase CameraWeekly update

This past week I have worked on the following:

1. Setting up the infrastructure to do noise analysis: We added a temporary channel on the DAQ to connect to the PD 55 which we are using to take the power measurement. Before that, I connected the PD55 to an oscilloscope and recorded the power.

    phase_cam_setup_21_07_2010.jpg

The power at PD55 as measured using the oscilloscope = 600 µV.

Then I tried to calibrate the channel by sending up a signal from the function generator and measuring up the offset.. However, the channels seems noisy enough, especially due to electronics noise as suggested by the measurements and FFT calculation.

2. I worked on trying to sync the data acquisition of the PD and the CAM. After sometime spent on fiddling with the software method such as taking images at stamped time and then lining them up with the daq timestamps, I found a hardware method as suggested by Aidan. It was putting up a shutter (Uniblitz shutter and driver VMMD1) in the setup. I synced the shutter with the camera for which I had to tear apart the previously made trigger box and add a sync output from the camera (took a while as I also had to make a new cable).

3. I worked (still working) on making a differential amplifier to blow up the signal from the PD.

 

 

 

  3309   Wed Jul 28 13:06:47 2010 RazibUpdatePhase Camera 

Attached are some calculation that I did previously for the phasecamera setup. This shows the nature of the beat signal that we are measuring.

I am also trying to characterize the noise source of the camera also. Following images shows the mean dark noise (with no light on the camera) and the standard deviation for 100 snaps at an exposure time of 500 µs.

mean_100_snaps.pngstd_100_snaps.png

My target now is to measure the response gain of each pixel and how they vary over intensity. I already have a simplified setup on the table and will work on it today. Details will follow at the end of the day.

Attachment 3: phase_cam_calc.pdf
phase_cam_calc.pdf phase_cam_calc.pdf phase_cam_calc.pdf
  3411   Thu Aug 12 16:52:02 2010 RazibUpdatePhase CameraSideband power measurement (updated)

I made some measurement of the SCR (signal to contrast ratio) from the signal from the EOM and the AOM.

The recipe for that was:

1. Trigger the camera at 20 Hz (from function generator).

2. Take a series of 20 images.

3. Do FFT to take out the DC component.

4. Extract the beat signal out of the FFT'd data.

5. Block the EOM.

6. Take another set of images of the AOM beam.

7. Take more(!) images, but this time of the background (blocking both EOM and AOM).

 

So the SCR is calculated by the ratio of the FFT'd DC and the 5 Hz signal. Using the CCD, I obtained the SCR to be 0.075 ± 0.01. Previously, we expected our SCR to be 0.09 as in the previous e-log entry.

The plot for that is:

SCR.jpg

 After measuring the SCR, I also measured the amplitude of the sideband and made an amplitude profile of the 40 MHz sideband.

The amplitude measurement is done as follows:

We know that the our 5 Hz signal consists of,

Sig = A_r * A_sb    where A_r = amplitude of the reference beam, A_sb= amplitude of the sideband

So, A_sb = Sig / A_r .

But,  A_r = sqrt ( P_AOM - Background),

Thus  A_sb = Sig / sqrt( P_AOM - Background) .

So the amplitude profile is done by taking the 5 Hz beat signal and dividing by the square root of the AOM beam minus the background light.

The plots looks like this:

DC_sig_sideband_profile.jpg

The solo sideband profile looks like this:

sideband_profile.jpg

Next we plan to trigger the camera with a 1 KHz signal and take snaps at n* T/4 (where n=0,1,2,3) of the period of the beat signal. So the plan is to trigger the camera at the point where the red dots appear in following cartoon.

sine_trig.jpg

Some more details of this setup will be posted later.

  

Quote:
 

 

Attachment 4: sine_trig.jpg
sine_trig.jpg
  3413   Thu Aug 12 17:28:28 2010 RazibUpdatePhase CameraSideband power measurement (updated)

Quote:

This sounds very relieving although this could be a lower bound of the number.
Why didn't you use the output on the PD which just give us the direct observation of your so-called SCR.

Quote:

So the SCR is calculated by the ratio of the FFT'd DC and the 5 Hz signal. Using the CCD, I obtained the SCR to be 0.075 ± 0.01. Previously, we expected our SCR to be 0.09 as in the previous e-log entry. 

 

 The SCR was at first measured using the output of the PD. That was exactly from where we got our 0.09 (previous elog entry). The second measurement was from the CCD.

  3360   Wed Aug 4 16:52:59 2010 Razib, AidanUpdatePhase CameraSideband power measurement (updated)

Aidan and I made some attempt to measure the power of the sidebands so that we can calculate our expected signal strength.

Our setup looks like the following:

Setup_08_04_2010.jpg

 

As light from the laser is split into two at BS1, the transmitted beam has higher power as our BS1 is only coated for 1064nm. We get two reflected beams from BS1, one reflected of the front surface and the other from the back surface. We took the stronger back reflected beam to the EOM driven at 40 MHz (also at 25 MHz at  a later time). The AOM produced a reference beam with 40 .000 005 MHz offset which we recombined with the sidebands obtained from the EOM. The beat produced is sent off to PDA 10CF connected to 4395A spectrum analyzer.

The plots for 40MHz sidebands and 25 MHz sidebands looks like this:

power_40MHz.png

From the above spectra, at 40 MHz sideband regime:

Power of the carrier @ 40 MHz = -39.72 dBm

Power of the sideband @ 80 MHz = -60.39 dBm

 

 

power_25MHz.png

At 25 MHz sideband regime,

Power of the carrier @ 40 MHz = -40.22 dBm

Power of the upper sideband @ 65 MHz = -61.72 dBm

Power of the lower sideband @ 15 MHz = -60.99 dBm

 

Power Measurement:

We made some necessary power measurement using a PD connected to a voltmeter after the EOM and the AOM when the EOM is driven at 40 MHz:

___________________________________________________________

Dark :  0.025 V

AOM on: 4.10 V    (EOM blocked)

EOM : 2.425 V      (AOM blocked)

___________________________________________________________

 From the earlier calculation (ref: Elog entry July 28) the power that we expect to see at the PD is,

P= A_c ^2 + A_r^2 + A_(-sb)^2+ A_sb ^2 +2* A_r* A_sb * cos ( w_(r,sb) t ) ,                         where A_c= carrier;   A_r= reference beam;     A_sb=Upper sideband;    A_(-sb)= Lower sideband,     w_(r,sb) = w_r - w_sb

P = A_c ^2 + A_r^2 + A_(-sb)^2+ A_sb ^2 +2* A_r* A_sb  , letting cos (w_(r,sb) go to 1) is order to approximate the maximum signal

So the signal that we expect to see relative to the DC ( i.e    A_c ^2 + A_r^2 + A_(-sb)^2+ A_sb ^2,    the first four terms of the power equation) is,

Sig = 2* A_r* A_sb    / { A_c ^2 + A_r^2 + A_(-sb)^2+ A_sb ^2 },

Since the modulation index is small, the power in the sideband is very small compared to carrier and the reference beam. So we can ignore the sideband power for the signal expression.

So,

Sig = 2* A_r* A_sb  /  ( A_c ^2 + A_r^2 )

So if we want to maximize this signal w.r.t the reference then,

d (sig)/ d(A_r) = 2 { ( A_c ^2  - A_r^2) *A_sb } / {( A_c^2 + A_r^2)} ^2

Thus, the signal is maximized when,

A_r^2 = A_c^2

 

We adjusted the AOM to be driven at + 7.7 dBM so that the new power at the AOM matched the EOM power, which is 2.397 in the voltmeter.

So the power at both the AOM and the EOM are:

P_AOM = ( V_AOM - V_dark) / (PD responsitivity * Transimpedance gain)

               = ( 2.397 - 0.025 ) / ( 0.45  * 1.5 x 10 ^5 )

               = 3.51 x 10 ^ - 5  W

P_EOM = (V_EOM - V _dark) / (PD responsitivity * Transimpedance gain)

               = ( 2. 425 - .0.025) / ( 0.45 * 1.5 x 10 ^5 )

               = 3.55 x 10^ - 5  W

 

From the spectra of the 40 MHz sideband above, the ratio of the carrier and the sideband amplitude is:  A_c / A_sb = 10.8 .

P_EOM = A_c ^2 + 2 A_sb ^2

Therefore, A_sb = sqrt ( P_EOM / 118.64) = 5.47 x 10^ - 4   V/m

Thus,     A_c = 5.908 x 10^ -3   V/m

and    A_r = sqrt ( P_AOM) = 5.92 x 10 -3    V/m.

 

This measurement can be used to calculate the signal to contrast ratio (SCR) that we expect to see:

SCR = 2 A_r * A_sb  / ( A_c^2  + A_r^2 )  = 0.09

 

Our next step is to measure the actual signal to constrast ratio as seen by the camera. Details of that will be posted soon.

  10221   Wed Jul 16 21:24:41 2014 ReetikaUpdateElectronicsVCO Driver inside 40m

  

I found the VCO driver, that Rana asked me to locate, inside the 40m. I already have one VCO from PSL lab. Now, I have kept both of them inside the 40m lab(one on the cart in the side of the Y-arm and the other near the X-arm electronics table).

  7747   Mon Nov 26 19:27:59 2012 RijuHowTo Testing AG4395A+GPIB

Riju, Jenne

We have checked the transfer function of a bandpass filter using AG4395A network analyzer and retrieved the data through GPIB. The RF out signal of AG4395A had been divided by splitter with two outputs of the splitter going to through R and the filter which was connected to the A channel of the network analyzer. The GPIB data came in complex data format, from which the absolute value and phase had to be retrieved. 

 

The plot for the TF is as following

Attachment 1: tfmag.jpg
tfmag.jpg
Attachment 2: tfphase.jpg
tfphase.jpg
  7756   Tue Nov 27 19:06:16 2012 RijuUpdate Testing AG4395A+GPIB

 I ve tested another bandpass filter today with similar set-up. This time I took the data with corrected reference level. To set this reference-level the filter was disconnected and the cable was connected "thru" according to the instructions provided in the manual of AG4395A at http://cp.literature.agilent.com/litweb/pdf/04395-90040.pdf, page 3-10. The transfer functions are as follows 

Attachment 1: tfmag1.jpg
tfmag1.jpg
Attachment 2: tfphase1.jpg
tfphase1.jpg
  7794   Wed Dec 5 17:38:41 2012 RijuHowTo Photodiode transimpedance

I have started making the circuit to measure the transimpedance for the photodiode PDA10CF using Jenne's laser. I will continue it tomorrow.

  7817   Wed Dec 12 17:26:47 2012 RijuUpdate Testing AG4395A+GPIB

I repeated my experiment to get noise level. To get that I disconnected the bandpass filter SBP-10.7  from channel A of network analyzer AG4395A and terminated both the open ends (open end of filter and open end of channel A) with 50ohm terminator.

Reference level had been corrected, signal and noise data had been collected separately w.r.t that level.

Command for GPIB:   ./netgpibdata.py -i 192.168.113.105 -d AG4395A -a 10 -f filename

The result is as follows

 

Attachment 1: TFbandpassfilter.pdf
TFbandpassfilter.pdf
  7834   Fri Dec 14 14:40:31 2012 RijuUpdate Photodiode transimpedance

Photodiode PDA10CF was under test. The RF out signal of AG4395A had been divided by splitter with one output of the splitter going to R channel of the network analyzer and the other to the laser. The splitted laser beams - splitted with beam splitter - fall on two photodiodes - one reference and the other on PDA10CF. The outputs of these two photodiodes go to channel B and A respectively of the network analyzer. The measured transimpedance data had been collected using the GPIB connection.

The result is as follows:

Attachment 1: PDA10CF.pdf
PDA10CF.pdf
  7870   Fri Dec 21 19:49:39 2012 RijuUpdate Photodiode transimpedance

I have repeated the transimpedance measurement of PDA10CF. Also made the dark current noise measurement by connecting the PDA10CF output to the A channel of network analyzer.  The results are as follows. I I started to take the reading for shot noise intercept current using a light bulb in front of the PD, changing the current through the bulb, but at higher current the bulb filament got broken, so the experiment is incomplete.

Attachment 1: PDA10CFrepeat.pdf
PDA10CFrepeat.pdf
Attachment 2: darknoiseVpda10cf.pdf
darknoiseVpda10cf.pdf
Attachment 3: darknoiseApda10cf.pdf
darknoiseApda10cf.pdf
Attachment 4: PDA10CF_z.pdf
PDA10CF_z.pdf
  7874   Thu Jan 3 20:34:43 2013 RijuUpdate Photodiode transimpedance

Today I have measured the transimpedance and dark-noise of the MC-REFL PD.

For transimpedance measurement I first collected the data of the reference Newfocus PD connecting it at channel B of Network-analyzer using the set-up of Jenne's laser. The data for the MC-REFL PD had been collected by connecting it to the A channel of Network Analyzer. To do that I shifted the Jenne's Laser to the table of MC-REFL PD, I moved the laser output on the table and fixed a lens and a mirror on the table. Taking the ratio of the two sets of datas I got the required trans-impedance.

Dark-noise readings were taken keeping the laser off.

I will upload the corresponding plots tomorrow.

  7880   Tue Jan 8 14:01:21 2013 RijuUpdate Photodiode transimpedance

 Here I upload the plots corresponding to my last day's measurements.

 

Attachment 1: TFreflpd.pdf
TFreflpd.pdf
Attachment 2: REFL_z.pdf
REFL_z.pdf
Attachment 3: darknoiseVreflpd.pdf
darknoiseVreflpd.pdf
Attachment 4: darknoiseAreflpd.pdf
darknoiseAreflpd.pdf
  7881   Tue Jan 8 14:07:04 2013 RijuUpdateElectronicsPhotodiode transimpedance

Quote:

You have to correct this transimpedance ratio by correcting for the different levels of DC photocurrent in the two devices.

For the dark noise, you must always include a trace showing the noise of the measurements device (i.e. the analyzer noise must be less than the dark PD noise) with the same input attenuation setting.

 Hi,

The correction for different levels of DC photocurrent in the two devices had been taken care by one MATLAB code, the code that originally was made by Koji.

The analyzer noise I had not recorded; today I am going to record it.

Riju

  7882   Tue Jan 8 15:28:41 2013 RijuUpdateElectronicsPhotodiode transimpedance

Quote:

Quote:

You have to correct this transimpedance ratio by correcting for the different levels of DC photocurrent in the two devices.

For the dark noise, you must always include a trace showing the noise of the measurements device (i.e. the analyzer noise must be less than the dark PD noise) with the same input attenuation setting.

 Hi,

The correction for different levels of DC photocurrent in the two devices had been taken care by one MATLAB code, the code that originally was made by Koji.

The analyzer noise I had not recorded; today I am going to record it.

Riju

 Here is the data for AG4395A network/spectrum analyzer noise data. I collected the data by putting 50ohm terminator on channel A with same input attenuation setting (0dB attenuation).

Attachment 1: analyzernoiseV.pdf
analyzernoiseV.pdf
  7887   Wed Jan 9 19:32:24 2013 RijuUpdate Photodiode transimpedance

Summary:

Today I have tested the MC transmission-end RF photodiode PDA255 for transimpedance and dark noise using Jenne's Laser and AG4395A network/spectrum analyzer. The dark noise voltage distribution for the transmission and reflection PDs of MC and the analyzer has been compared.

Motivation:

I am to do the input mode cleaner cavity mode scan. The electronic and shot noise of the components used , particularly photodiode noise, will affect the peak position  of the modes, indicating the uncertainty in the measured frequencies of the modes. That will in turn give the uncertainty in the measured change of radius of curvature of the mirrors in presence of the laser beam, from which we will be able to calculate the uncertainty in the mirror-absorption  value.

Method:

For PD transimpedance measurement I used Jenne's laser along with AG4395 network analyzer. The RF out signal of AG4395A had been divided by splitter with one output of the splitter going to R channel of the network analyzer and the other to the laser. The splitted laser beams - splitted with beam splitter - fall on two photodiodes - one reference(Newfocus1617? PD, the DC and RF transimpedance values were taken from its datasheet ) and the other on PDA255. The outputs of these two photodiodes go to channel B and A respectively of the network analyzer. The measured transimpedance data had been collected using the GPIB connection. It had been ensured that the PD under test is not going to saturation, for that the source power level was kept to -40dBm. transimpedance measurements were compensated by the ratio of DC photocurrent.

For dark noise measurement the output of the PD was connected to the A channel of the AG4395A, when there was no light falling on it. The response is collected using GPIB. The attenuation of channel A was made 0dB. ( AG4395A was kept in Spectrum analyzer mode in Noise Format).

Results:

The plots corresponding to the measurements are attached.

Discussion:

The comparison for the dark noise voltage levels of the MC transmission PD (PDA255) with MC REFL PD has been made with analyzer dark noise voltage. It is shown in the attachment (I will upload the dark noise current comparison too....since the output darknoise depends on the gain of the circuit, it is important to divide this voltage spectra by transimpedances.)

Attachment 1: PDA255.pdf
PDA255.pdf
Attachment 2: PDA255_z.pdf
PDA255_z.pdf
Attachment 3: darknoiseVpda255.pdf
darknoiseVpda255.pdf
Attachment 4: darknoiseApda255.pdf
darknoiseApda255.pdf
Attachment 5: darknoise_comparison.pdf
darknoise_comparison.pdf
  7907   Wed Jan 16 18:58:08 2013 RijuUpdate Photodiode transimpedance

Today I have taken the reading for shot noise intercept current for the PDA255 - MC transmission RF PD. To do that I have put an incandescent bulb (JKL lamps, 222 bulbs, voltage and current rating 2.25V and 0.25A) in front of the PD and varied the current through it from 0A to 0.29A at 2.2V. I measured the corresponding DC voltage and took the noise data (4395A spectrum analyzer/ format noise, channel attenuation 0dB) through GPIB .

I will process the data and upload the result soon.

  7926   Tue Jan 22 17:29:29 2013 RijuUpdate Photodiode transimpedance

Riju

Summary:  I am stuck with the measurement of shot-noise-intercept-current of PDA255. Seeking help.

Motivation: It is to measure the shot noise intercept current for PDA255 - the MC transmission RF photodiode to get an idea for the noise current for the detector.

Method: It is as described in the elog  7907 

Result: The plot is attached here.

Discussion: The result I got is really unexpected, the noise voltage should increase with the DC current level that corresponds to the increment of light level too. But actually it is decreasing. Three times I have repeated this experiment and got the same result. I want some suggestion on this regard.

Attachment 1: pda255shotnoiseintercept.pdf
pda255shotnoiseintercept.pdf
  7929   Wed Jan 23 11:43:19 2013 RijuUpdate Photodiode transimpedance

Quote:

- The data should be plotted in a log-log scale.
- The data points were only taken in the high current region.

- The plot may suggest that the amplifier saturate at the RF.

PDA255 has the nomial transimpedance gain of 10^4 Ohm.
The DC current of 10^-3 gives the output of 10V.
This plot may tell that the saturation starts even at the 1/10 of the full DC range.

The plot doesn't have many points below 0.1mA.
Consult with my plots for the similar measurements.
The measured points are logarithmically spaced. Use the same technique.

- It is also very unknown that how the noise level is calculated. No info is supplied in the plot or the elogs.

 Here I am attaching the plot in loglog scale. I have taken the data-points from no light condition to the maximum light condition, the minimum variation possible in the current supply was 0.01A. The noise was visibly decreasing at higher light level.

For the noise level calculation I took the average of total noise in the range 7-60MHz. For each range the formula used was

noisevalue= sqrt(data(:,2)*100)/sqrt(2)/sqrt(channel BW);     -- this conversion is needed since the data was collected in the 2 column format: frequency, spectrum(W).

Attachment 1: pda255shotnoiseintercept1.pdf
pda255shotnoiseintercept1.pdf
  7933   Wed Jan 23 20:27:05 2013 RijuUpdate Photodiode transimpedance

Today I have repeated the expt for shot noise intercept current. Koji found that the Spectrum analyzer is going to saturation, so we have used one DC blocker (MCL - 15542 model) in PD signal.

I will analyze the data and report.

Ed by Koji: DC BLOCK is  BLK-89-S

  7946   Mon Jan 28 17:59:02 2013 RijuUpdate Photodiode transimpedance

Summary: Measurement and plot of shot-noise-intercept-current for PDA255.

Motivation:It is to measure the shot noise intercept current for PDA255 - the MC transmission RF photodiode to get an idea for the noise current for the detector

Result: The final plot is attached here. The plot suggests that the value of shot-noise-intercept current is 3.06mA

Discussion:

The plot is for the measured data of Noise voltage (V/sqrt(Hz)) vs DCcurrent(A). The fitted plot to this measured data follows the noise equation

Vnoise = gdet* sqrt[ 2e (iDC+idet)] ,  where gdet= transimpedance of the PD in RF region as described in manual of PDA255 (i.e. 5e3 when it is not in High-impedance region).

On the other hand for DCcurrent calculation we must use the high-impedance value for the transimpedance i.e. 1e4 Ohm. idet is the shot noise intercept current.

For the rough calculation of the noise level we may use the following formulae:

Vnoise = gdet*sqrt[2e (iDC+idet)] = gdet*sqrt(2e in), when in=iDC+idet;

For say, in1=1mA; Vnoise1=gdet*sqrt(2e *in1)

and sqrt(2e *in1)~18pA/sqrt(Hz)

In current case dark noise is ~1.5e-7 V/sqrt(Hz)

Therefore dark current(in2) ~dark noise voltage/RF transimpedance = 30pA/sqrt(Hz)

i.e. sqrt(2e *in2)=30pA/sqrt(Hz)

i.e. sqrt(in2/in1)=30/18

therefore, in2~3mA (since in1=1mA)

For, iDC=0, in=idet.

Therefore the shot-noise-intercept current will be ~3mA

Then Vdc = in2*1e4 = 30V

According to the experiment  and also from the PDA255 manual the DC voltage level never goes beyond ~10V. Therefore following the photodiode characteristics(we work in reverse bias) we may infer that it can never become shot noise limited.

Also, from PDA255 manual, at 1650nm the dark noise is 30pW/sqrt(Hz) and the responsivity is 0.9A/W. Therefore the noise current level will be = noise power* responsivity ~27pA/sqrt(Hz). The value matches well with our expectation.

 

Attachment 1: shotnoiseinterceptpda255.pdf
shotnoiseinterceptpda255.pdf
  7956   Tue Jan 29 18:40:20 2013 RijuUpdate Photodiode transimpedance

Today I have taken data for shot noise intercept current for PDA10CF. I will process the data and report.

Note: GPIB address changed, new command for AG4395A network/spectrum analyzer: ./netgpibdata.py -i 192.168.113.108 -d AG4395A -a 10 -f filename

  7972   Thu Jan 31 12:44:42 2013 RijuUpdate Photodiode transimpedance

Today I collected the data for shot noise intercept current for MC REFL PD. I didn't get many data points at higher DC voltage of the photodiode, cause the incandescent bulbs get burnt at that level; two bulbs I have burnt today. I will process the data and report.

  7976   Thu Jan 31 15:34:22 2013 RijuUpdateRF SystemPhotodiode transimpedance

Quote:

Quote:

Today I collected the data for shot noise intercept current for MC REFL PD. I didn't get many data points at higher DC voltage of the photodiode, cause the incandescent bulbs get burnt at that level; two bulbs I have burnt today. I will process the data and report.

 This work was done in-situ, so no optics on the AS table were moved.  The PSL shutter was blocked since the IR beam was not necessary, and would scatter off the bulb Riju put in front of the PD. 

 Thanks Jenne.

ELOG V3.1.3-