40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Author Typedown Category Subject
  2622   Thu Jul 29 13:11:17 2021 KojiSummaryCryo vacuum chamberCooling progress: Update

The current cooling curve suggests that the radiative cooling factor Fe (black body =1) increased from 0.15 to 0.5.

Update: The test mass temp is reaching 200K at ~27hrs. cf previously it took 50hrs
Update: The test mass temp is 170K at ~41.5hrs.


OSEM illumination & photodetector efficiency has been kept increasing @41.5hrs

Attachment 1: temp_log_cool_down_20210728_1830.pdf
temp_log_cool_down_20210728_1830.pdf
Attachment 2: cooling_model1.pdf
cooling_model1.pdf
Attachment 3: cooling_model2.pdf
cooling_model2.pdf
Attachment 4: OSEM_cooling.pdf
OSEM_cooling.pdf
  2625   Fri Jul 30 12:22:56 2021 KojiSummaryCryo vacuum chamberCooling curve comparisons

In all aspects, the latest cooling shows the best performance thanks to better thermal connection, thermal isolation, and the black paint.

- The cold head cooling is faster and cooler

- The inner shield cooling is faster

- The test mass cooling is faster

Attachment 1: comparison_cold_head.pdf
comparison_cold_head.pdf
Attachment 2: comparison_inner_shield.pdf
comparison_inner_shield.pdf
Attachment 3: comparison_test_mass.pdf
comparison_test_mass.pdf
  2629   Sun Aug 1 22:22:00 2021 KojiSummaryCryo vacuum chamberCooling update

The test mass temperature indicates 121K@100hr but there seemed a few sensor glitches for the test mass (𝛥=-4.2K) and the inner shield (𝛥=-0.43K).
So the actual test mass temperature could be 125K.

The temp was read to be 119K@114hr (Attachment 1)

There was very little cooling capability left for the test mass (Attachment 2)

The OSEM reading is now stable @12.3V (Attachment 3)

The raw temp data and the minimal plotting code are attached (Attachment 4)

Attachment 1: temp_log_cool_down_20210728_1830.pdf
temp_log_cool_down_20210728_1830.pdf
Attachment 2: cooling_meas.pdf
cooling_meas.pdf
Attachment 3: OSEM_cooling.pdf
OSEM_cooling.pdf
Attachment 4: cooldown_210728.zip
  2645   Sun Aug 15 00:33:15 2021 KojiSummaryCryo vacuum chamberAquadag painting on the inner shield

[Stephen Koji]

We applied Aquadag painting on the inner side of the inner shield.

  • Upon the painting work, we discussed which surfaces to be painted. Basically, the surface treatment needs to be determined not by the objects but by the thermal link between the objects.
    • We want to maximize the heat extraction from the test mass. This means that we want to maximize the emissivity factor between the test mass and the inner shield.
    • Therefore the inner barrel surface of the inner shield was decided to be painted. The test mass was painted in the previous test.
    • For the same reason, the lid of the inner shield was painted.
    • It is better to paint the cold plate (table) too. But we were afraid of making it too messy. We decided to place the painted Al foil pieces on the table.
       
    • The outer surface of the inner shield and the inner surface of the outer shield: Our outer shield is sort of isolated from the cold head and the steady-state temp is ~240K. Therefore we believe that what we want is isolation between the inner and outer shields. Therefore we didn't paint these surfaces. (note that in Mariner and beyond, the outer shield will be cooled, not isolated, and the radiative link to the outer shield would be strong by design)
    • I believe that this is not the ideal condition for the inner shield. We need to model the cryo stat heat load and take a balance between the isolation and the conduction between the outer shield and the cold head so that we gain the benefit of the outer shield as a "not so hot" enclosure.
       
  • OK, so we painted the inner barrel of the inner shield, the lid of the inner shield, and some Al foils (shiny side).
  • Stephen made the Aquadag solution. The solution was 2 scoops of Aquadag concentrate + 6 scoops of water, and the adhesion/runniness test was done on a piece of aluminum foil.
  • The barrel and the lid were painted twice. Attachment 1 shows the painting of the inner shield cylinder. Attachment 2 shows a typical blemish which necessitates the second coat.
  • To accelerate the drying process, we brought the heat gun from the EE shop --> (update - returned to EE shop, see Attachment 3)
     
  • We took some photos of the process. They are all dumped in the QIL Cryo Vacuum Chamber Photo Dump album in the ligo.wbridge account.
Attachment 1: IMG_9636.JPG
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Attachment 2: IMG_9632.JPG
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Attachment 3: IMG_9646.JPG
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  2675   Sun Oct 3 08:22:49 2021 AidanSummary2micronLasersStarting data taking and second test of JPL PD A1
  • Output going to JPL_PD/data/A1_test2 and DAQ
  • Test commenced at 8:20AM and cryo cooler started shortly afterwards
  • Once trhough the loop takes about 20 minutes
  • Cryocooler on at 8:42AM
  2676   Wed Oct 6 13:50:18 2021 AidanSummary2micronLasersStarting data taking and second test of JPL PD A1
  • Turned cryocooler off around 1317588441 (about 1:46PM)
  • Restarted measurement with output going to JPL_PD/data/A1_test3
  • Room is noticeably quieter without the cryocooler on.
Quote:
  • Output going to JPL_PD/data/A1_test2 and DAQ
  • Test commenced at 8:20AM and cryo cooler started shortly afterwards
  • Once trhough the loop takes about 20 minutes
  • Cryocooler on at 8:42AM

 

  2677   Thu Oct 7 08:07:03 2021 AidanSummary2micronLasersStarting data taking and second test of JPL PD A1
  • We're at 164K as of 8AM this morning.
  2678   Mon Oct 11 08:35:21 2021 AidanSummary2micronLasersStarting data taking and second test of JPL PD A1

Terminated the data taking at 8:35Am this morning. The termperature traces of the cryo chamber show a couple of discontinuities in the gradient. I don't know what the cause is,

Quote:
  • We're at 164K as of 8AM this morning.

 

Attachment 1: Screenshot_from_2021-10-11_08-36-06.png
Screenshot_from_2021-10-11_08-36-06.png
  2679   Mon Oct 18 15:25:14 2021 AidanSummary2micronLasersStarting data taking and second test of JPL PD A1

Initial running of analysis code puts the max QE at ~62 + /- 1% around 130-150K. I want to explore this temperature regime manually and see if we're saturating the PD or not.

3:30PM - Chamber is still under vacuum. Cryocooler turned back on.

Quote:

Terminated the data taking at 8:35Am this morning. The termperature traces of the cryo chamber show a couple of discontinuities in the gradient. I don't know what the cause is,

Quote:
  • We're at 164K as of 8AM this morning.

 

 

  2691   Wed Oct 27 10:18:33 2021 Aidan, StephenSummaryCryo vacuum chamberInspection of Megastat post 408K event and pumping timeline

[Aidan]

I've attached a timeline of our inspection this afternoon along with today's pumping timeline,

Here is a brief summary of observations from previous pumping timelines. Today's pump down is consistent with previously observed timelines.


 

2:17PM – Assessing the impact of the 408K event in the MegaStat

Coldhead reached 363K (90C)

Innershield reached 403K (130C)

 

2:24PM – Aquadag E service temperature (149C)

https://www.laddresearch.com/index.php/lanotattachments/download/file/id/40/store/1/

Maximum service temperature in air* : 300°F (149°C) 

*Service temperature under vacuum conditions is significantly higher. Contact Acheson for specifics. 

2:25PM – Bringing Megastat back up to air for initial inspection

2:37PM – chamber is at air

 

2:41PM – removing bolts

 

 

3:13PM – initial inspection looks normal. No elevated amount of black particulates found on surfaces – consistent with or less than the amount seen last time we opened.

Stephen detected faint smell different from last time (“campfire”?)

  • One RTD connector did delaminate Aquadag from the inner shield

3:14PM - Stephen reattaching the RTD wiring that had delaminated. I wiped up visible particulates with isoproponal soaked wipe.

 

3:21PM – putting lid back on

3:30PM – lid on. Screws in finger tight

 

3:35PM – screws tight – ready to pump

3:40PM – pumping station on

 

Time (minutes) Pressure (Torr) Notes
0 7.5E2 Pirani gauge initially
1 7.5E2  
2 7.5E2  
4 7.5E2  
5 7.5E2  
7 7.5E2  
9 7.5E2  
10 7.5E2  
11 7.5E2  
12 4.3E2 Gauge starts reading decrease
13 2.2E2  
14 9.8E1  
15 5.5E1 Turbo ON
16 2.9E1  
17 1.6E1 Turbo at 44%
18 9.4E0  
19 4.9E0  
20 1.8E0 Turbo at 58%
21 3E-2 Turbo at 70%
22 1.1E-3 ION gauge readings from here. Turbo at 91%
23 7.5E-4 Turbo at 100%
24 6.3E-4  
25 5.9E-4  
26 5.5E-4

 (Cryo-cooler normally turned on around this time)

Not in this instance though

27 5.0E-4  
28 4.59E-4  
29 4.26E-4  
30 4.05E-4  
     

 

Attachment 1: IMG_5407.jpg
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Attachment 8: IMG_5415.jpg
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  2692   Fri Nov 12 08:21:22 2021 AidanSummary2um PhotodiodesResults from JPL PD: A1-Test3

[Aidan]

Here is the analyzed data from Test 3 of the A1 JPL PD.

Note about the QE measurement: 

  • HOM beam QE was performed during the warm up phase. Collimating lens was fixed and beam pointing was optimized at 100mA before each measurement. Likely that not all power was on PD but that distribution was constant throughout measurement. Therefore, good proxy for shape of QE response.
  • Manual QE was performed with 25mA current, optimized collimating lens position (and thus the beam size on the PD). The data corresponds to 8.0mm between the lens mount and fiber mount. The beam pointing was optimized before each measurement at 25mA.
  • QE projection scales the "HOM beam QE" result to the manual QE measurements to project out expected QE performance vs temperature

Dark current is the output from the Keithley scan - the vertical scale is correct in Amps [ignore question mark]

Dark noise spectra are included for different bias levels and at different temperatures. Stll need to add ADC noise floor for these plots.

Notes from Test 3

~/JPL_PD/data/A1_test3/README

6-Oct-2021: done with cryocooler off and temperature increasing

PREAMP GAIN = 1E3

SR560 gain = 500

LD temp set point = 20.2kOhm

 

 

 

Attachment 1: A1_test3_nominal_QE.pdf
A1_test3_nominal_QE.pdf
Attachment 2: A1_test3_darkcurrent.pdf
A1_test3_darkcurrent.pdf
Attachment 3: A1_test3_noise_spectra_rev.pdf
A1_test3_noise_spectra_rev.pdf A1_test3_noise_spectra_rev.pdf A1_test3_noise_spectra_rev.pdf A1_test3_noise_spectra_rev.pdf A1_test3_noise_spectra_rev.pdf
  2693   Fri Nov 12 10:54:55 2021 ranaSummary2um PhotodiodesResults from JPL PD: A1-Test3

IT would also be good if you could plot the RMS noise around 10 Hz and 100 Hz as a function of the bias and temperature, so we can see what the trends are. And how about post the data and scripts to the elog so we can munge data later?

  2703   Thu Dec 16 17:57:15 2021 Radhika, StephenSummaryCryo vacuum chamberMegastat geometric parameters

This ELOG serves as a compilation of known/measured geometric parameters of Megastat. This is informative for thermal modeling of the system, so I wanted to create a centralized reference. A reference to these dimensions has been added to the Wiki page

Chamber specs
   Outer Radius = 0.3048 m (12")
   Wall thickness = .00477 m (.188")
   Height = 0.3048 m (12")
   Flange thickness = .0254 m (1")

Outer shield specs
   Outer Radius = 0.2794 m (11")--> CAD .265 m (10.433")
   Height = 0.2286 m (9") --> CAD .206 m (8.110")
   Thickness = 2.90 mm (0.114") (CAD nominally 3 mm, but 9 gauge aluminum is standard)

Inner shield specs:
   Outer Radius = 0.244983 m (9.645") --> CAD .225 m (8.858")
   Height = 0.205994 m (8.11") --> CAD .192 m (7.559")
   Thickness = 2.90 mm (0.114")

Cold plate specs:
   Radius = CAD .254 m (10")
   Thickness = CAD .01498 m (.5897")

Test mass specs: (confirmed)
   Radius = 0.0508 m (2")
   Length = 0.1016 m (4")

Copper bar specs:
   Length = 0.508 m (20") --> note that center to center length is .440 m in CAD
   Width1 = 0.03175 m (1.25") (bulk cross section, could be approximated accross full length)
   Width2 = 0.049784 m (1.96") (cross section at cold head bolting interface)
   Thickness = 0.011684 m (0.46")

Coldhead specs:
   Radius = 0.03175 m (1.25")
   Thickness = .0516 m

CAD (.EASM) is located at https://caltech.app.box.com/folder/131056505764 (File path: Voyager > Mariner > CryoEngineering). Screenshot of current state is added as Attachment 1.

CAD (source file, .sldasm - SolidWorks 2021) may be accessed via the PDM Vault (File path: llpdmpro > voyager > rnd qil cryostat)

Attachment 1: D2000310_y-003_20211222.png
D2000310_y-003_20211222.png
  2714   Fri Jan 28 10:31:15 2022 ranaSummaryTutorial videooh no, stap the units madness, aaaaahhhh!!! noooooo!!!!

What if I told you SI-units is way harder to miscalculate with - Matrix  Morpheus | Make a Meme

 

  2772   Wed May 25 14:32:12 2022 RadhikaSummaryEmissivity estimationList of Megastat upgrades for emissivity estimation

This post will serve as a running list of modifications for Megastat for emissivity estimation (brain dump). It is divided into categories:

Category 1: Inner shield / cold plate

We want to cover the cold plate with Aquadag, either directly or by placing aquadag-coated tiles or Al foil on top of the cold plate. It seems the latter approach is preferable, to avoid directly removing and coating the cold plate. Stephen has prepared aquadag-coated aluminum foil which we will soon assess for this purpose. If for some reason it doesn't seem to be sufficient, we will need to identify/design tiles or chunks of aluminum that we can paint with aquadag and lay on top of the cold plate. While we're coating things with aquadag, there are some spots on the inner shield that could use a touch-up.

Category 2: Suspension of sample

There are several options for suspending a 2" Si wafer or 1" optic.

1. RTD lead suspension

This method would involve wrapping the RTD wires around the sample and somehow hanging or dangling the sample from another surface. The wire would be strain-relieved around another component, like a post, before being varnished to the sample. I will have to play around and try out various configurations to determine if this is feasible / would not strain the RTD contact. This approach would not require additional components in the chamber. 

2. Insulating posts 

In the case where we cannot achieve RTD lead suspension, we will need to rest the sample on support posts while minimizing conductive heat transfer through said posts. Stephen suggested using ceramic ball bearings bolted down to the cold plate. Further modeling is needed to calculate conduction through these supports. Using a bunch of tiny "pins" was also suggested, but these would need to be similarly modeled, and eventually procured. 

Category 3: Heat actuation on sample

There are several options for applying heating power to the suspended sample, each with its own drawbacks.

1. Wire-wound resistor

Binding this directly to the sample will be challenging, especially if the sample is wire-suspended. The resistor will occupy a non-negligible amount of area on the sample, which is not ideal for maximum thermal coupling between the sample and the inner shield. Furthermore, since the emissivity an uncoated Si wafer is quite low (low bulk absorption given thin wafer), the emissivity of the heater body (or the varnish/epoxy) could dominate the coupling and lead to an inaccurate fit for sample emissivity. 

2. Lamp source + parabolic reflector

The lamp and reflector would be placed and mounted inside the chamber and directed towards the sample. I found parabolic reflectors in the TCS lab and would need to purchase a suitable light source. Here is an example from my search: https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=7541. Its emission is broadband and could probably be modeled as a blackbody, but I would need to look into this further. I don't know how efficient the heat transfer to the sample would be, i.e. how much heating power would actually hit the sample. This would also make the control of heating power much more difficult.

3. Laser heating source

A laser could be set up outside Megastat and send its beam through one of the viewports to hit the sample. There would be some reflection from the viewport glass, but the transmission would directly heat the suspended sample without crowding the inside of the chamber. The heating power reaching the sample could more easily be determined and controlled in this method, although a laser would need to be sourced for this purpose. This would also require uncovering an additional viewport, which could contribute more heat leakage into the enclosure. 

  2773   Thu May 26 13:12:25 2022 RadhikaSummaryEmissivity estimationList of Megastat upgrades for emissivity estimation

I think this flashlight would work

Quote:
 

2. Lamp source + parabolic reflector

The lamp and reflector would be placed and mounted inside the chamber and directed towards the sample. I found parabolic reflectors in the TCS lab and would need to purchase a suitable light source. Here is an example from my search: https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=7541. Its emission is broadband and could probably be modeled as a blackbody, but I would need to look into this further. I don't know how efficient the heat transfer to the sample would be, i.e. how much heating power would actually hit the sample. This would also make the control of heating power much more difficult.

  2775   Fri May 27 17:33:24 2022 RadhikaSummaryEmissivity estimationList of Megastat upgrades for emissivity estimation

[Stephen, Radhika]

Today we further discussed ideas for the enclosure, suspension/support, and heat actuation for wafers in Megastat. 

Enclosure: We re-painted the inner surface of the inner shield with aquadag, including the top side of the bottom lip [Attachments 1,2]. The folded sheets of aluminum foil covering the apertures were unbolted and also painted with aquadag [Attachment 3]. 

Wafer support and heat actuation: Attachment 4 shows sketches and a plan forward (drawn by Stephen). The first round of upgrades includes the components underlined in blue: a baseplate to house the points of contact to the wafer, the ceramic ball bearings which will serve as the points of contact, an aquadag-painted sheet metal insert that will bolt down to the coldplate, and a mount for a Maglite mini flashlight. 

We will obtain more wire-wound resistors to serve as a back-up to flashlight heating, if the need arises.

Attachment 1: IMG_3493.jpeg
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Attachment 2: IMG_3494.jpeg
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Attachment 3: IMG_3492.jpeg
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Attachment 4: IMG_1633.jpeg
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  2011   Tue Jan 5 14:48:08 2016 ranaSafetyLab InfrastructureHVACheating and cooling

As noticed by Kate a few times last year, the north side of the lab has hot air comiing out of the HEPA vents and the south side has cold air. This seems to be a problem with the setpoints for the sensors or the hot water actuators.

Let's remember to call physical plant after the current roof leaking situation settles down.

  2169   Tue Aug 22 11:59:56 2017 awadeSafetyGeneralLeak in the ATF Lab

Tue Aug 22 11:57:33 2017

We found water pooling next to the computer/CDS rack in the ATF lab (Room 265B). There is not a lot, may be 500 mL, but we don't know how long its been going.

It looks like its a slow dribble from some of the piping coming down the wall.

 

  2170   Thu Aug 24 13:47:00 2017 AidanSafetyGeneralLeak in the ATF Lab

Yesterday the leak was worse. And there was a smell of foul effluent in the lab. And some brown water by the bottom of the rack. This was later discovered to be drain water rather than sewage.

The custodians cleaned up the clear water. I filed a Service Request and the plumbers came out and cleared up the brown water with disinfectant. They subsequently spotted a leak in the pipe itself - about 8 feet up the pipe. This is scheduled to be fixed. Eric G informs me that there is duct tape on leak right now. I spoke to the service center and they're going to do a permanent repair (replacing the pipe) sometime in the near future. If the pipe leaks again in the interim, they said to contact them and they'll expedite the replacement.

Attachment 1: IMG_0673_(1).jpg
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  2738   Mon Mar 28 14:29:22 2022 shrutiSafetyCleanlinessLab flooding

When I went into QIL today there was a lot of flooding from water dripping from the ceiling at several places in the lab. Images attached.

Attachment 1: Flooding.zip
  2739   Mon Mar 28 16:09:57 2022 AidanSafetyCleanlinessLab flooding

Some photos of affected areas in B265A and B265B (elog shows some preview photos - click on PDF for full set).

Stephen did a great job cleaning up and drying up. Most equipment is powered off and we're leaving it off for a couple of days to dry completely. We'll want to check the stuff on the red lab cart thoroughly. 

Quote:

When I went into QIL today there was a lot of flooding from water dripping from the ceiling at several places in the lab. Images attached.

 

Attachment 1: Flood_in_sub-basement-20220328.pdf
Flood_in_sub-basement-20220328.pdf Flood_in_sub-basement-20220328.pdf Flood_in_sub-basement-20220328.pdf Flood_in_sub-basement-20220328.pdf Flood_in_sub-basement-20220328.pdf Flood_in_sub-basement-20220328.pdf Flood_in_sub-basement-20220328.pdf Flood_in_sub-basement-20220328.pdf
  2740   Mon Mar 28 18:00:43 2022 KojiSafetyCleanlinessLab flooding

Flood photo album: https://photos.app.goo.gl/BZAG8DyQzFVTfMNz6 (This link is read-only who has no access to the account)

 

  2741   Tue Mar 29 09:13:20 2022 AidanSafetyCleanlinessLab flooding

Facilities placed a blower and dehumidifier in B265B. I checked the airflow and the air around the tables is comparitively still. The North table is covered and the South table is over pressurized by HEPA filters, so there should be little risk of dust being stirred up.

Quote:

Flood photo album: https://photos.app.goo.gl/BZAG8DyQzFVTfMNz6 (This link is read-only who has no access to the account)

 

 

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  2742   Wed Mar 30 10:46:49 2022 RadhikaSafetyCleanlinessLab flooding

[Radhika, Shruti]

This morning, facilities removed all the porous ceiling panels that had been soaked/damaged by water (in B265B: above WS1 and WS2, see Attachments 1+2; In B265A, see Attachment 3). Specifically in B265A, an enclosure was created (Attachment 4) and a dehumidifier was placed inside. All monitors/equipment underneath the panels were thoroughly covered, and the floors were swept up afterward.

No work was done above the North table in the QIL. I asked about it and facilities said they would look into it, but it wasn't on the schedule for today. A member of facilities also pointed out that the sink in the QIL was running black liquid (Attachment 5). It looks like soil/dirt entered the water pipes? This seemed to also be outside of their scope for today. 

Attachment 1: IMG_3227.jpeg
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  2743   Wed Mar 30 16:25:06 2022 KojiSafetyCleanlinessLab flooding

Muddy Waters is not new, but if the facility can fix it we'd take it.

 

  2744   Fri Apr 1 13:53:02 2022 RadhikaSafetyCleanlinessLab flooding

Facilities will be returning on Monday 4/4 between 8-9 AM to remove all ceiling panels above the workstations in B265B (QIL). Replacement of the panels is not yet scheduled, but in the meantime the open ceiling will be covered and the workstations will still be accessible. 

  2745   Mon Apr 4 17:05:20 2022 RadhikaSafetyCleanlinessLab flooding

Pictures attached. WS1 and WS2 have been turned back on, since the replacement for the ceiling panels will not arrive for another few weeks according to Facilities.

Quote:

Facilities will be returning on Monday 4/4 between 8-9 AM to remove all ceiling panels above the workstations in B265B (QIL). Replacement of the panels is not yet scheduled, but in the meantime the open ceiling will be covered and the workstations will still be accessible. 

 

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  2307   Wed Mar 20 15:57:55 2019 AnjaliNoise Budget2micronLasersNoise budget for the frequency discriminator

I was trying to prepare the noise budget for the frequency stabilisation setup for 2 micron laser. In this test, we use a fiber based Mach-Zehnder interferometer as a frequency discriminator to convert frequency noise to amplitude(voltage) fluctuations. The different noise sources to be considered in this analysis are the following

  1. Shot noise
  2. Dark current noise
  3. Room thermal noise
  4. Fiber thermal noise
  5. Fiber acoustic noise
  6. Laser intensity noise
  7. Photothermal noise
  • Attachment #1 shows the magnitude spectrum of the transfer fucntion for the frequency discriminator. I assumed the delay fiber length in one of the arms of the Mach-Zehnder interferometer is 10 m. This corresponds to a time delay of 50 ns. The corner frequency is inversely proportional to the time delay.
  • The transfer fucntion can be interpreted as, if the frequency variation is very slow- it can't be distiguished by the discriminator and we dont get any signal.
  • Attachment # 2 and # 3 shows the shot noise and fiber thermal noise respectively in rad/rtHz
  • The shot noise is calculated  considering thorlabs DET10D detector with a responsivity of 1.2 A/W at 2 micron. The laser output power from Eblana laser is assumed to be 2 mW and the power reaching the detector is estimated to be 1.23 mW.
  • The fiber thermal noise is calculated based on Wanser, K. H. (1992). Fundamental phase noise limit in optical fibres due to temperature fluctuations. Electronics letters28(1), 53-54.
  • The dark current noise and room thermal noise are calculted to be a constant value (3.97x10-12 rad/rtHz and 1.20x10-12 rad/rtHz respectively)- but this is not correct
  • The noise in rad/rtHz is converted to Hz/rtHz by mutiplying with the frequency (f) and it is shown in attachment #4
Attachment 1: High_pass_transfer_function.pdf
High_pass_transfer_function.pdf
Attachment 2: Shot_noise.pdf
Shot_noise.pdf
Attachment 3: Thermoconductive_noise_of_fiber_Glenn_parameter.pdf
Thermoconductive_noise_of_fiber_Glenn_parameter.pdf
Attachment 4: noise_budget_combined_log_log.png
noise_budget_combined_log_log.png
  2308   Wed Mar 20 19:17:50 2019 ranaNoise Budget2micronLasersNoise budget for the frequency discriminator

I think the dark noise should be very close to the shot noise and also have the same transfer function.

Also, the room temperature fluctuations are probably large at low frequencies. What PSD for room temperature did you use?

 

  2309   Thu Mar 21 00:49:35 2019 AnjaliNoise Budget2micronLasersNoise budget for the frequency discriminator

I didn't use the transfer funtion in the calculation of dark current noise thinking dark current noise is a characteristic of the detector alone

Regarding room thermal fluctuation, I was plotting the thermal noise of the detector which is given in A/rtHz as 

=\sqrt{\frac{4k_bT}{R_f}}

  2310   Thu Mar 21 09:43:19 2019 AnjaliNoise Budget2micronLasersNoise budget for the frequency discriminator

Also, I have a doubt that whether the transfer function should be of low pass in nature. So, if the laser phase is fluctuating faster than the time it takes to propagate throught the delay fiber, we will not be able to discriminate .

If that is the case, the noise budget looks like as shown in attachment #1

Attachment 1: Noise_budget_with_low_pass_transfer_function.pdf
Noise_budget_with_low_pass_transfer_function.pdf
  2311   Fri Mar 22 10:00:30 2019 AnjaliNoise Budget2micronLasersNoise budget for the frequency discriminator

Attachement #1 shows the modified noise budget with modification on dark current noise.

I still have to find out the PSD for room temperature to plot the room thermal noise

 

Attachment 1: Noise_budget_modified.pdf
Noise_budget_modified.pdf
  2312   Mon Mar 25 09:40:16 2019 AnjaliNoise Budget2micronLasersNoise budget for the frequency discriminator
  • Different fiber parameters are very important in determining the thermal noise of the fiber. I was considering SM1950 fiber for the calculations, but all the characteristic parameters for this fiber are not known.
  • Glenn ( IEEE Journal of Quantum Electronics25(6), 1218-1224 ) and Jing Dong (Applied Physics Letters108(2), 021108) had given the set of fiber parameters. Attachment #1 shows the comparison of thermoconductive noise of the fiber with fiber parameters taken from Glenn and Jing Dong. The parameters from Jing Dong are for Corning standard SMF 28 fibers and they are the recent resuts compared to Glenn. Hence I think it would be good to follow the parameters given in Jing Dong's paper.
  • It is also found that the thermal noise of fiber has contributions from the thermoconductive noise (https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=255919) and thermomechanical noise (https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5614023) . Thermoconductive noise  (in rad/rtHz) predicts a frequency independent characteristics at lower frequencies where as thermomechanical noise (in rad/rtHz) has a 1/f characteristics over a certain frequency range. The thermomechanical noise is of concern only over a certain frequency range it is given by the ratio of velocity of sound with the total length of the fiber. This indicates that, in the case of thermomechanical noise, the fluctuation of concern is much slower than the time it takes for the sound wave to travel across the length of the fiber. 
  • Attachment #2 shows the noise budget including the thermomechanical noise of the fiber. With 10 m length of the fiber, the thermoconductive noise is of concern for frequencies lower than 364 Hz . Thus a low pass transfer function is assumed with corner frquency of 364 Hz in the calculation of thermomechanical noise. 
Attachment 1: Comparison_of_thermoconductive_noise_in_Hz_per_rtHz.pdf
Comparison_of_thermoconductive_noise_in_Hz_per_rtHz.pdf
Attachment 2: Noise_budget_with_thermomechanical_noise.pdf
Noise_budget_with_thermomechanical_noise.pdf
  2333   Sun May 5 15:17:33 2019 AnjaliNoise Budget2micronLasersFrequency noise measurement of 2 micron source

We are going to start the heterodyne configuration for the frequency noise measurement of 2 micron laser source. The schematic of the same is shown in attachment #1. The initial plan was to separate the photodetector output to in phase , quadrature component and then extract the frequency noise information from the same. The new plan suggested is to use a phase locked loop for the demodulation part. We can use IFR Marconi 2023A as a VCO and SR560 as the amplifier. The RF generator for the AOM and the VCO need to be locked through Rubidium frequency standard (FS725). One of the issues is that the band width of the photodetector that we have is 14 MHz and the AOM is at 80 MHz. The response of photodetector at 80 MHz is about 20 % of that at DC.I have modified the noise budget after discussing with Anchal. Attachment #2 shows the noise budget. The Marconi data is taken from Anchal. The data plotted in attachment #2 corresponds to Marconi #539 at 48 MHz and actuation slope of 500 Hz. We may have to find the actual numbers based on our settings for the experiment.  From the data sheet, the input noise of SR 560 is 4nV/rtHz. The frequency mixer (Minicircuit ZAD-1-1+) has a conversion loss of 4.83 dB and the thermal noise of it is not given in the data sheet and thus it is not included in the noise budget. The length of the fiber considered for MZI is 10 m.

 

Attachment 1: schmeatic_heterodyne.png
schmeatic_heterodyne.png
Attachment 2: Noise_budget_modified.pdf
Noise_budget_modified.pdf
  2334   Sun May 5 20:52:16 2019 ranaNoise Budget2micronLasersFrequency noise measurement of 2 micron source

Looks good! A few comments:

  1. The LPF should be a 1.9 MHz LP from Mini-circuits
  2. The SR560 should be set with a 1 MHz low pass only
  3. No Rubidium needed. We just want to use two IFR/Marconi synthesizers so that they can share the same time standard.
  4. We will need a RF Amp to drive the AOM hard enough - check the manual and see what level is required to get the max diffraction.
  2372   Mon Jul 22 20:21:33 2019 ShalikaNoise Budget2micronLasersNoise Analysis of Circuit using SR785 Spectrum Analyzer and Zero Simulation

The transimpedance amps, differential circuit and the whitening filter for the 2um Extended InGaAs detectors were made and their noise level was evaluated. The examination of noise was done without the diodes. For every analysis, SR785 spectrum analyzer was used and a simulation using zero in python was also done. The SR785 was controlled using the python program to get the data. The input was AC coupled and Hanning window function was used during the task of getting data.

**The noise of SR785 spectrum analyzer is also mentioned, which was measured by deploying a terminator at one channel. The noise labelled as SR785noise mentions the spectrum analyzer noise alone.

**The noise of the components, with SR785 mentioned along with them, indicates the noise observed using the Spectrum analyzer.

Attachment 1: The circuit diagram

The usual transimpedance configuration was made using the OP27 IC. There are two TIA as we will be using two PD in our final circuit. The two TIA are connected to Whitening Filter respectively. The Whitening filter has a gain of 10. Apart from that, the output of the two TIA is connected to a differential circuit and whose output is in turn connected to another independent whitening filter.

Attachment 2: The amplifier noise Part I

The noise of TIA1 was analyzed using the SR785 spectrum analyzer and also by simulating the circuit using zero in python. 

Attachment 3: The amplifier noise Part II

The noise of TIA2 was analyzed using the SR785 spectrum analyzer and also by simulating the circuit using zero in python. It was observed to be exactly similar to that observed of TIA1.

Attachment 4: The differential circuit noise levels

The noise level of the differential circuit was measured by shorting both the input terminals and observing the output at the pin6 of IC.

Attachment 5: The Whitening Filter noise level.

The noise of the Whitening filter was measured by grounding the input terminal (pin 3) at taking the measurement at the output. The gain of the filter is 10. 

Attachment 6: The TIA and Whitening Filter, connected together, noise level.

The TIA and Whitening filter were connected in series and the noise was observed at the output of the whitening filter.

Attachment 7: The Simulation of Circuit in Zero

The complete circuit was configured using zero. It will help us analyze the noise that we are not expecting. Please open it using Jupyter Notebook.

Attachment 1: full_circuit.pdf
full_circuit.pdf
Attachment 2: Noise_at_node_naout.pdf
Noise_at_node_naout.pdf
Attachment 3: Noise_at_node_nbout.pdf
Noise_at_node_nbout.pdf
Attachment 4: Noise_at_node_ndout.pdf
Noise_at_node_ndout.pdf
Attachment 5: Noise_at_node_nout.pdf
Noise_at_node_nout.pdf
Attachment 6: Noise_at_node_nw1out.pdf
Noise_at_node_nw1out.pdf
Attachment 7: noise_simulation.zip
  2384   Thu Aug 8 17:19:12 2019 Shalika SinghNoise Budget2micronLasersNoise Analysis of TIA using SR785 Spectrum Analyser and Zero Simulation

Input Referred noise to be calculated for trans-impedance.

Attachment 1: The Circuit Diagram on paper,

>>  the TIA with a gain of 5.1k

Attachment 2: Noise across TIA 

The input-referred current noise across the TIA was measured using SR785 and was compared against the graph obtained from ZERO simulation.

** This time, I divided the measurements into 7 parts, 0-800, 800-2.4k, 2.4k-5.6k, 5.6k-12k, 12k-24.8k, 24.8k-50.4k, 50.4k-101.6k. The number of points for each was 800. Hanning Window function was used in the template file and the Input channels were grounded. 

Attachment 3: Noise across TIA 

The input-referred current noise across the TIA was measured using SR785 and was compared against the graph obtained from ZERO simulation.

** This time, I divided the measurements into 1 part, 10-6.4k. The number of points for each was 800. Hanning Window function was used in the template file and the Input channels were grounded. 

** To measure the noise the output was measured at the pin6 of the OpAmp.

** A source of 1V was applied to the circuit by keeping a 10k in series with the input of the circuit when Transfer Function was being measured.

** It's difficult to avoid 60Hz harmonics with a circuit kept in open as this one. Lots of its effects are visible in the plot.

 

Attachment 4: Noise of the power supply used

The power supply was observed to be used to be noisy. 

Attachment 1: TIA.pdf
TIA.pdf
Attachment 2: Noise_across_TIA.pdf
Noise_across_TIA.pdf
Attachment 3: Noise_across_TIA.pdf
Noise_across_TIA.pdf
Attachment 4: powersupply.pdf
powersupply.pdf
  2385   Fri Aug 9 21:10:48 2019 Shalika SinghNoise Budget2micronLasersNoise Analysis of Circuit using SR785 Spectrum Analyser and Zero Simulation

Input Referred noise is calculated for the circuit that is to be used for characterization of photodiodes. For the biasing 12V was used from SR560 as it provides cleaner voltage as compared to other voltage supplies. 

 

Attachment 1: The Circuit Diagram TIA

>>  the TIA with a gain of 5.1k

Attachment 2: Input Referred noise of TIA 

The input-referred current noise across the TIA was measured using SR785 and was compared against the graph obtained from ZERO simulation.

Attachment 3: Differential Circuit

>> gain of 100

Attachment 4: Input Referred noise of Differential Circuit

The input-referred voltage noise measured using SR785 and was compared against the graph obtained from ZERO simulation. 

Attachment 5: Whitening Filter Circuit

>> gain of 10

Attachment 6: Input Referred noise of Whitening Filter Circuit

The input-referred voltage noise was measured using SR785 and was compared against the graph obtained from ZERO simulation.

Some points that were observed: 

*** I am observing deviation from simulated results at higher frequencies. Presently, I am unable to understand the cause of this deviation. 

*** At low frequencies deviation from simulated results is perhaps caused due to 60Hz harmonics and 1/f noise.

Attachment 1: TIA.png
TIA.png
Attachment 2: Noise_across_TIA.pdf
Noise_across_TIA.pdf
Attachment 3: Differential_Circuit.png
Differential_Circuit.png
Attachment 4: Noise_across_Differential_Circuit.pdf
Noise_across_Differential_Circuit.pdf
Attachment 5: Whitening_Filter.png
Whitening_Filter.png
Attachment 6: Noise_across_Whitening_Filter.pdf
Noise_across_Whitening_Filter.pdf
  2386   Sun Aug 11 01:22:04 2019 Shalika SinghNoise Budget2micronLasersNoise Analysis of voltage regulator using SR785 Spectrum Analyser

A comparison between the types of voltage regulators was done in order to know which should be preferred to provide a clean bias supply.

Attachment 1: The Circuit Diagram of the voltage regulator 

Tere are 3 types of voltage regulators that were tested. 

a. LM317

b. LM7915

c. LM7815

Attachment 2: Output Voltage noise of all 3 voltage regulators

A voltage of 12V(+/-) was provided using SR560 to the respective input of the regulator IC and the output noise across each were measured using the SR785.

LM317 will be a better choice to make a voltage regulator for the circuit mentioned in elog entry 2381.

Attachment 1: regulator.pdf
regulator.pdf
Attachment 2: Noise_across_Voltage_Regulator_Circuit.pdf
Noise_across_Voltage_Regulator_Circuit.pdf
  2387   Sun Aug 11 14:35:41 2019 KojiNoise Budget2micronLasersNoise Analysis of voltage regulator using SR785 Spectrum Analyser

Questions:

1) Has the DC output voltages of the regulators checked?

2) What's the target voltages of the regulator circuits? And how the voltages were supplied from the power supply port of the SR560? 7815 is the regulator meant for +15V and 7915 is for -15V. So the input voltages need to have at least 3V larger voltages than the target voltages (like +18V for 7815, -18V for 7915). If the +/-12V are naitvely applied, the regulators don't reach the operating point.
Check "Voltage Drop" descriptions in the data sheets of the regulator chips.

3) What's the purpose of these diodes? I believe they are for the regulator protection against the transient sign flip during power switching etc as well as over voltageprotection. The circuit of the 7915 has the larger potential difference (like -18V) while the output has -15V. This means the diode will always be on. If this is just a typo in the figure, it's not a big deal. If this is the real situation, it is a big problem.

4) Why were there such huge 60Hz lines? Was the SR560 properly operated with its battery?

  2388   Sun Aug 11 19:15:32 2019 Shalika SinghNoise Budget2micronLasersNoise Analysis of voltage regulator using SR785 Spectrum Analyser

Answers:

1. For LM317 I received the output of 11.2V and for LM7915 -10V and for LM7815 at 10.4V

2. I did a mistake with the supply. Next time I won't use SR560 and will use a voltage supply instead. 

3. The diode is for protection purpose. How should I use the diode for 7915, should I put it in forward bias or not use it at all?

4. I did check the voltage supply provided by SR560 using a multimeter, they were 12V.

Quote:

Questions:

1) Has the DC output voltages of the regulators checked?

2) What's the target voltages of the regulator circuits? And how the voltages were supplied from the power supply port of the SR560? 7815 is the regulator meant for +15V and 7915 is for -15V. So the input voltages need to have at least 3V larger voltages than the target voltages (like +18V for 7815, -18V for 7915). If the +/-12V are naitvely applied, the regulators don't reach the operating point.
Check "Voltage Drop" descriptions in the data sheets of the regulator chips.

3) What's the purpose of these diodes? I believe they are for the regulator protection against the transient sign flip during power switching etc as well as over voltageprotection. The circuit of the 7915 has the larger potential difference (like -18V) while the output has -15V. This means the diode will always be on. If this is just a typo in the figure, it's not a big deal. If this is the real situation, it is a big problem.

4) Why were there such huge 60Hz lines? Was the SR560 properly operated with its battery?

 

  2389   Sun Aug 11 22:34:50 2019 KojiNoise Budget2micronLasersNoise Analysis of voltage regulator using SR785 Spectrum Analyser

3. You need to flip the direction of the diode.

1&2 OK, so the circuits were not fucntioning. Use a dual voltage supply (in a proper cascading setting) and give +/-18V.

4. When you use SR560 as a power supply, you need to disconnect the AC power supply. Otherwise, the AC power, which charges the +/-12V lead battery, contaminates the output voltage with the 60Hz lines.

  2390   Mon Aug 12 11:37:36 2019 Shalika SinghNoise Budget2micronLasersNoise Analysis of Circuit using SR785 Spectrum Analyser and Zero Simulation

Referring to elog entry 2385. I did the measurements again because mistakingly I had been using the SR560 with it's AC supply on. This time I used the 12V supply with no connection to the AC supply.

Attachment 1: The Circuit Diagram TIA

>>  the TIA with a gain of 5.1k

Attachment 2: Input Referred noise of TIA 

The input-referred current noise across the TIA was measured using SR785 and was compared against the graph obtained from ZERO simulation.

Attachment 3: Differential Circuit

>> gain of 100

Attachment 4: Input Referred noise of Differential Circuit

The input-referred voltage noise measured using SR785 and was compared against the graph obtained from ZERO simulation. 

Attachment 5: Whitening Filter Circuit

>> gain of 10

Attachment 6: Input Referred noise of Whitening Filter Circuit

The input-referred voltage noise was measured using SR785 and was compared against the graph obtained from ZERO simulation.

Attachment 7: The Scripts

All the scripts and data used in the measurement.

** I did notice a reduction in 60Hz harmonics but I still see a deviation from simulated results at higher frequencies and at frequencies below 10Hz.

Attachment 1: TIA.png
TIA.png
Attachment 2: Noise_across_TIA.pdf
Noise_across_TIA.pdf
Attachment 3: Differential_Circuit.png
Differential_Circuit.png
Attachment 4: Noise_across_Differential_Circuit.pdf
Noise_across_Differential_Circuit.pdf
Attachment 5: Whitening_Filter.png
Whitening_Filter.png
Attachment 6: Noise_across_Whitening_Filter.pdf
Noise_across_Whitening_Filter.pdf
Attachment 7: Noise.zip
  2391   Mon Aug 12 11:51:38 2019 Shalika SinghNoise Budget2micronLasersNoise Analysis of Voltage Regulator using SR785 Spectrum Analyser

Referring to elog entry QIL:2387. I did the correction with the voltage supply and now provided a supply of 18V(+/-) to LM7815 and LM7915. The position of diodes was also corrected for LM7915. The Electrolytic Capacitors(100uf) I am using are getting heated when using with LM7915 only. I didn't find any tantalum capacitors of 100uf in EE shop. Should they be replaced with some other capacitors?

Attachment 1: The Circuit Diagram Voltage regulator

The component used                   Input Voltage                              Output Voltage

a. LM7915                                    -18 V                                  -15.1 V

b. LM7815                                    18 V                                    14.86 V

c. LM317                                      18 V                                    17 V      

Attachment 2: Output Voltage noise of regulator circuit

The noise observed using SR785 at the output of each regulator.

 

Attachment 1: regulator.pdf
regulator.pdf
Attachment 2: Noise_across_Voltage_Regulator_Circuit.pdf
Noise_across_Voltage_Regulator_Circuit.pdf
  2393   Mon Aug 12 15:17:05 2019 KojiNoise Budget2micronLasersNoise Analysis of Voltage Regulator using SR785 Spectrum Analyser

1. Heat: Check the polarity of the electrolytic or tantalum caps. 

2. Add 0.1uF high-K ceramic caps in pararel to these electrolytic or tantalum caps.

3. Why does LM317 have only one volt drop? It requires minimum 3V mergin between the input and output voltages. (See the datasheet) 

 

  2395   Tue Aug 13 17:59:25 2019 Nathan HollandNoise Budget2micronLasersPhase Noise of Mach Zehnder with VCO.

Following up from my previous post I measured the phase noise of the Mach Zehnder setup with the AOM driven properly with its VCO. The setup is shown in attachment 1, and compressed data in attachment 2 (goto here to get the python library to decompress this data). The value of M for this data shown is +0.85 V, though I have data for other voltages - however it should affect the performance. Using the low frequency preview I was able to see that I would need to coherently subtract the phase measurements of both measurements, which restricted me to a maximum sampling frequency of 15 kHz.

The measured data is shown in attachment 3. Already you can see that the phase noise of the VCO limits the measured phase from the IFO. This also tells me that previously, when I was modulating the VCO, the AM was affecting the measured phase. When I convert this difference into frequency noise the result can be seen in attachment 4. One upside of this setup is that the signal from the IFO is much more robust, so the PLL can stay locked for longer. This is a consquency of increased drive, 24 dB more, on the AOM.

To me this demonstrates that the way forward is to replace the VCO driving the AOM with a RF amplifier, driven by a low noise (or lower noise) signal generator. The Moku is able to drive at 80 MHz. We have a Mini Circuits ZHL-5W-1 (ZHL--5W) amplifier in the laboratory. This has 46.4 dB of gain, and a maximum power output of 37 dBm. The maximum power that can be input into the AOM is 27.8 dBm (0.6 W). Thus with an appropriate setup this miniciruits amplifier should be a viable repalcement for the current VCO.

Attachment 1: 20190813__Phase_Noise_Measurement_VCO_setup.pdf
20190813__Phase_Noise_Measurement_VCO_setup.pdf
Attachment 2: MachZehnder_w_AOM_Driver_085_20190813_102449.li
Attachment 3: 20190813__MachZehnder_w_VCO-phase_noise.pdf
20190813__MachZehnder_w_VCO-phase_noise.pdf
Attachment 4: 20190813__MachZehnder_w_VCO-frequency_noise.pdf
20190813__MachZehnder_w_VCO-frequency_noise.pdf
  2396   Tue Aug 13 19:03:05 2019 Shalika SinghNoise Budget2micronLasersNoise Analysis of Voltage Regulator Circuit using SR785 Spectrum Analyzer

As it was observed that normal voltage supply is noisy and not suitable for our circuit, we plan to use a voltage regulator that will help us provide a clean supply. Referring to previous elog entries the corresponding corrections were made( polarity of electrolytic capacitors, ceramic cap in parallel to electrolytic, 3V difference between input and output of respective regulators).

Attachment 1: The Circuit Diagram of Voltage regulator

The component used                   Input Voltage                              Output Voltage

a. LM7915                                    -18 V                                  -15.1 V

b. LM7815                                    18 V                                    14.86 V

c. LM317                                      18 V                                   14.96 V      

Attachment 2: Output Voltage noise of regulator circuit

The noise observed using SR785 at the output of each regulator is shown. It clearly shows that LM317 manifests less noise in comparison to LM7915 and LM7815. It will be therefore a good idea to use this to provide 15V bias in our circuit.

Attachment 3: The Scripts

Find all the scripts and data used in this measurement.

Attachment 1: regulator.pdf
regulator.pdf
Attachment 2: Noise_across_Voltage_Regulator.pdf
Noise_across_Voltage_Regulator.pdf
Attachment 3: regulator.zip
  2399   Wed Aug 14 19:50:37 2019 Shalika SinghNoise Budget2micronLasersNoise analysis of Sallen Key filter using SR785 and Zero simulation

The photodiode needs a 1V bias so for a clean bias we have decided to use a sallen key low pass filter with a cut off frequency at 1Hz. The quality factor of the designed sallen key filter is 0.707.

Attachment 1: The Circuit Diagram of Sallen Key filter

The gain of the circuit is 1. 

Attachment 2: The transfer function of the filter

We can see the cut off frequency at 1Hz

Attachment 3: The Input Referred Noise of filter

The input-referred voltage noise was obtained using SR785 and compared with zero simulation. It deviates a lot from the simulated results by a factor of 100.

Attachment 4: Scripts

Find all the data and scripts used for the measurements.

NOTE: Noise plot below had inconsistent units; please ignore.

 

Attachment 1: sallenkeyfilter.pdf
sallenkeyfilter.pdf
Attachment 2: Transfer_function_of_sallen_key.pdf
Transfer_function_of_sallen_key.pdf
Attachment 3: Noise_across_SallenKey.pdf
Noise_across_SallenKey.pdf
Attachment 4: sallenkey.zip
  2401   Thu Aug 15 08:03:13 2019 ranaNoise Budget2micronLasersNoise Analysis of Voltage Regulator Circuit using SR785 Spectrum Analyzer
I'm glad to see that the voltage regulators can give good noise performance. I wish I understood what the gain peaking features came from - maybe the choice of capacitors?
ELOG V3.1.3-