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 Type Category Subject
  2487   Tue Feb 25 15:12:22 2020 Raymond, Chris, Koji, Chub, AidanLab InfrastructureHVACHVAC work concluded for today

Facilities workers replumbed the water lines feeding the air handler units in the QIL. Tomorrow they plan to come back for about an hour to insulate the lines. We'll keep the tables wrapped up until that's complete.

  2486   Mon Feb 24 18:41:06 2020 RaymondLab InfrastructureHVACTable Shielding for 2020-02-25 HVAC repairs

[Raymond, Chris, Koji, Chub, Aidan, Duo]

Both tables were surrounded with plastic shielding in preparation for the HVAC maintenance/repairs to be performed tomorrow, Tuesday 24/02/2020. The IR Lab cryostat roughing and turbo pumps were turned off to avoid overheating while inside their new plastic cocoon. Sticky floor mats were placed in the oil-slick area in front of the flammables cabinet to improve safety for all foot traffic in the area, as well as to mitigate the urge to boogie while working in the lab. 

Attachment 1: QIL_HVACshielding1_2020-02-24.JPG
QIL_HVACshielding1_2020-02-24.JPG
Attachment 2: QIL_HVACshielding2_2020-02-24.JPG
QIL_HVACshielding2_2020-02-24.JPG
Attachment 3: QIL_HVACshielding3_2020-02-24.JPG
QIL_HVACshielding3_2020-02-24.JPG
Attachment 4: QIL_HVACshielding4_2020-02-24.JPG
QIL_HVACshielding4_2020-02-24.JPG
  2485   Thu Feb 13 11:04:47 2020 Ian MacMillanLab InfrastructureHVACRecent temperature fluctuations

Here is the data for the last week. The temperature for the Northside is noticeably higher than the Southside. This is probably a calibration error in the North sensor because there is not a noticeable temperature difference when walking across the room. I would guess the south sensor is more accurate in its overall temperature reading because it feels more like 22 degrees than 24.

Attachment 1: HVAC-B265B.pdf
HVAC-B265B.pdf
Attachment 2: Jan_2020_Qil_Temp_Measurments.zip
  2484   Tue Feb 4 14:18:24 2020 Ian MacMillanLab InfrastructureHVACRecent temperature fluctuations

Got data from the HOBO temperature recorders. The temperature has been fluctuating between about 80 degrees F to 60 degrees F. The Temperature has been fluctuating wildly in the last month that the recorder was on. I will restart the HOBO monitors to get more current data.

*Note the HOBO app changed how it reports the time data. The updated code is attached which uses the AM and PM 12 hour .csv file generated by the app.

Attachment 1: HVAC-B265B_20200402.pdf
HVAC-B265B_20200402.pdf
Attachment 2: Qil_Lab_Temperature.zip
Attachment 3: HVAC-B265B.pdf
HVAC-B265B.pdf
  2483   Fri Dec 20 22:26:19 2019 KojiUpdatePD QEPD TEC driver / A2P6 aligned / Lens moved

The QEs were measured at 293K, 239K, 232K, and 293K again. The cooling was provided by the PD TEC.  At each temperature, the incident power was changed from 30uW to 1mW to see the dependence of the QE on the incident power to check the possible saturation.

The QE was 79~81% (the window T=96.6% was already compensated). I'm not 100% sure this 1% variation in the plateau is real or due to insufficient calibration of the REF PD.
The REF PD was calibrated at 1mW at 100mA injection current to the laser.

No obvious saturation was observed.

We can cool the PD with LN2 and we should make a careful alignment of the beam at each temperature.

Attachment 1: Sb3513_A2P6_DarkCurrent_293K.pdf
Sb3513_A2P6_DarkCurrent_293K.pdf
Attachment 2: Sb3513_A2P6_DarkCurrent_239K.pdf
Sb3513_A2P6_DarkCurrent_239K.pdf
Attachment 3: Sb3513_A2P6_DarkCurrent_232K.pdf
Sb3513_A2P6_DarkCurrent_232K.pdf
Attachment 4: Sb3513_A2P6_DarkCurrent_293K_2.pdf
Sb3513_A2P6_DarkCurrent_293K_2.pdf
Attachment 5: Sb3513_A2P6_DarkCurrent_Comparison.pdf
Sb3513_A2P6_DarkCurrent_Comparison.pdf
Attachment 6: 191220_3513A2P6.zip
  2482   Fri Dec 20 21:58:14 2019 KojiUpdatePD QEPD TEC driver / A2P6 aligned / Lens moved

== Currently, A2P6 is aligned ==


1) I've brought another TEC driver fro the PD temp control. This unit was borrowed from the 2um ECDL setup. Eventually, we need to return this to ECDL. (Attachment 1)
The PID loop of the TEC control works. But it is not well optimized yet. If you change the target temp too quickly, the TEC out seemed oscillating. Watch the TEC out carefully and change the temp setpoint slowly.
So far I have tried to cool the thermister up to 30kOhm (~232K) and I_TEC was 0.33A.
I did not try further. I felt it was better to cool the PD base for further trial.

2) A part of the alignment study, the beam is aligned to A2P6. Also, the lens position was investigated, and I decided to move the lens ~1 inch away from the window.  (Attachment 2)
    In fact, this allowed us to insert the power meter between the lens and the window. 

Attachment 1: P_20191220_192440_vHDR_On.jpg
P_20191220_192440_vHDR_On.jpg
Attachment 2: P_20191220_180929_vHDR_On.jpg
P_20191220_180929_vHDR_On.jpg
  2481   Fri Dec 20 13:20:53 2019 AidanSummaryPD QEQE results from A2P6 (500um) and A2P2 (1mm)

The QE measurements from the first couple of photodiodes are attached below.

  • plot_JPL_diode_results.m - A2P6 analysis
  • plot_JPL_A2P2_diode_results.m - A2P2 analysis

QE = [I_photocurrent]/[P_PD] * h *nu/e

P_PD = Power incident on photodetector = 0.966*power_incident on cryo window

Power incident on cryo window = F(voltage on reference PD)

Attachment 1: PC_DC_v_T.pdf
PC_DC_v_T.pdf
Attachment 2: A2P2_001_test.pdf
A2P2_001_test.pdf
Attachment 3: PC_DC_v_T.pdf
PC_DC_v_T.pdf
Attachment 4: A2P6_001_test.pdf
A2P6_001_test.pdf
Attachment 5: plot_JPL_diode_results.m
% load JPL data
f0 = dir('*dark*.txt');
f1 = dir('*photo*.txt');
f2 = dir('*cond*.txt');

% get temperature vs time
tempList = [];
pList = [];
for ii = 1:numel(f2)-1
... 102 more lines ...
Attachment 6: plot_JPL_A2P2_diode_results.m
close all 
clear all
% load JPL data
f0 = dir('*dark');
f1 = dir('*bright*');

% get temperature vs time
tempList = [];
refPDList = [];
for ii = 1:numel(f1)
... 113 more lines ...
  2480   Mon Dec 16 18:16:31 2019 RaymondDailyProgressPD QECryostat wiring fixes

Opened the cryostat to resolder the heater and re-wrap the thermal anchor for the sample RTD and PD connection. All connections are working as expected at room temperature. A2 is still in the sample mount. 

  2479   Fri Dec 13 01:51:15 2019 RaymondDailyProgressPD QECryostat wiring fixes
  • Monitored an autorun of the photocurrent for A2P6 from about 77K-300K and adjusted the laser alignment as necessary. I've not yet looked through the data, as I was keen on fixing the assorted wiring issues in time to pump down for tomorrow. Chris found the laser power issue rooted in my sub-optimal diode-collimator mating connection, ie I didn't fully plug back in the laser. I've learned my lesson and will simply shield the fiber with Al foil for future nitrogen pouring endeavours .
  • Opened the cryostat and confirmed the pin assignments (see attached list).
  • Cathode 2 was shorting on the thermal anchors for the PD plug. I re-wrapped the quad twist wire around the bobbins and this has fixed the issue, though I did not see any portion of the quad twist wires that was missing the Formvar insulation. 
  • The DT-670 silicon diode thermometer was busted, this was likely the case from the start and should have been checked (by me) prior to wiring. I've replaced this diode with another 4-lead platinum resistor, it is plugged into input 3 on the CTC100 (still labeled 'PDdiode'). 
  • The thermistor on A2P6 is still intact, showing about 1.9 kΩ at room temp

Still to do:

  • Move the radiation shield PT RTD to the outer shield
  • Re-wire the baseplate pins in the DSUB9 connection to the CTC100 temp controller (switched V+ and V-)
  • Check feasibility of adding 25Ω heater to the sample mount to stabilize the temp of the PD rather than measuring while sweeping 

 

Attachment 1: 18_32malepinsinairAssigned.pdf
18_32malepinsinairAssigned.pdf
  2478   Thu Dec 12 02:10:37 2019 Raymond, ChrisDailyProgressPD QEPD test dry run

(Raymond, Chris)

  • Baseplate and shield RTD temperature sensors are working, and digitally recorded.  The temperature sensing diode on the PD mount seems to be unconnected.
  • We made dark current vs bias measurements on the P6 and P2 elements at room temperature.  We also checked P3 but it appears to be unconnected.  Then, after realigning the P6 element, we measured its photocurrent vs bias at room temperature.  The photocurrent and dark current data looks much like what Koji previously reported at room temperature.
  • Going from 77 K to room temperature, the beam had to be moved downward to correct the alignment.  The magnitude was about 1 clockwise turn of the vertical alignment knob on the steering mirror.  The horizontal shift was very small.
  • Armed with this knowledge, we re-wetted the cryostat with LN2, bringing the baseplate and shield temperatures down into the 80 K range.  Our plan was to let it warm up overnight while running an automated test series of dark current and photocurrent vs bias and temperature.  We offset the vertical alignment by a half turn, in hopes of having the PD well aligned near the expected QE sweet spot of 150-200 K.
  • The procedure for adding LN2 to the cryostat involves temporarily disconnecting the fiber coupler.  Sadly, it appears in our haste we did not fully recover the alignment after this step, or else the calibration somehow shifted by a lot.  The photocurrent is at the 0.1 mA level instead of the ~1 mA we expect.  Accordingly, this run will primarily be useful as a test of the automation, as an indication of dark current vs temperature, and as a very rough, qualitative indication of QE vs temperature.
  • The script is running on qil-ws1 in a screen session.  It can be interrupted with screen -RAad autorun to connect to the session, followed by Ctrl-C to kill the script.
  • In the morning, we need to decide whether to open the cryostat and fix the wiring, or to repeat this run with tighter control over the alignment.
  2477   Wed Dec 11 19:50:25 2019 ranaHowtoCryo vacuum chamberProcedure to record photodiode output vs temperature

don't we also want to record the dark noise spectrum as a function of T and V_Bias ? I would guess that the dark noise doesn't always scale with dark current at low frequencies since its probably more like a random walk than shot noise.

  2476   Wed Dec 11 15:53:48 2019 Aidan, Chris, RaymondHowtoCryo vacuum chamberProcedure to record photodiode output vs temperature

[Aidan, Chris, Ray]

  1. Add LN2 to cryo-chamber
  2. Turn on heater to 25W
  3. Wait for LN2 to boil off
  4. Turn on the REFPD bias switch, and enable a 200 mV bias on the JPL PD (set C4:TST-FM13_OFFSET to 200)
  5. Switch the readout to the transimpedance amplifier (relay control output from C4:TST-FM15 at 30k ct)
  6. Turn on the laser
    1. Power up the LDC201C and set it for half-power output (50 mA), with the modulation output from C4:TST-FM12 at zero
    2. Set C4:TST-FM12_OFFSET to 1 to go up to full power
  7. Monitor the PD output on oscilloscope and adjust horizontal and vertical alignment of laser beam so that the output of the PD is maximized (also adjust TIA gain if needed so the output is not saturated)
  8. Switch the readout to the Keithley (relay control output from C4:TST-FM15 at zero)
  9. Record bright PD response
    1. Turn on laser (set C4:TST-FM12_OFFSET to 1)
    2. Scan bias voltage and record the PD response using the source meter (scripts are located in $HOME/JPL_PD/scripts on qil-ws1)
      1. ./runsweep.py triggers the Keithley to sweep the bias (range of sweep is defined in the script)
      2. ./getdata.py FILENAME downloads data from the Keithley and writes it to FILENAME
    3. Record REF PD reading
    4. Record RTD resistance
  10. Record dark PD response
    1. Turn off laser (set C4:TST-FM12_OFFSET to -1)
    2. Repeat steps 9-2 through 9-4
  11. Switch the readout to the transimpedance amplifier (relay control output from C4:TST-FM15 at 30k ct)
  12. Measure dark noise vs bias (using either the SR785 or the cymac, TBD)
  13. Wait two minutes and repeat steps 6 through 12 (there is a script ./autorun.sh which continuously repeats steps 9 and 10)
  14. Continue until RTD reaches room temperature (approximately 60-90 minutes).
  2475   Wed Dec 11 01:29:26 2019 KojiSummaryPD QESb3513 A2P6 Dark Current / QE / Dark Noise measurement @77K

[Raymond, Aidan, Chris, Koji]

P6 element (500um)^2

- We looked at the current amp (FEMTO) output. The amplifier saturated at the gain of 10^3 V/A. Looking at the output with a scope, we found that there is a huge 1.2MHz oscillation. Initially, we thought it is the amplifier oscillation. However, this oscillation is independent of the amplifier bandwidth when we tried the our-own made transimpedance amp.

- Shorting the cryostat chamber to the optical table made the 1.2MHz significantly reduced. Also, connecting the shield of the TEC/Laser controller made the oscillation almost invisible. This improvement allowed us to increase the amp-gain up to 10^7.

- Then the dominant RMS was 60Hz line. This was reduced by more grounding of the cable shields. The output was still dominated by the 60Hz line, but the gain could be increased to 10^8. This was sufficient for us to proceed to the careful measurements.

----

- The dark current was measured by the source meter, while the photocurrent (together with the dark current) was measured under the illumination of the ~1mW light on the PD.

- Attachment 1 shows the dependence of the dark current against the swept bias voltage. We had ~mA dark current at the room temp. So, this is ~10^5 improvement.

- Attachment 2 shows the dependence of the apparent QE against the swept bias voltage. The dark current was subtracted from the total current, to estimate the contribution of the photocurrent in the measurement.

- Attachment 3 shows the dark noise measurement at the reverse bias of ~0.6V. Up to 1kHz, the noise level was below the equivalent shotnoise level of 1mA photocurrent.

---------

All the data and python notebook in the attached zip file.

Attachment 1: Sb3513_A2P6_DarkCurrent_77K.pdf
Sb3513_A2P6_DarkCurrent_77K.pdf
Attachment 2: Sb3513_A2P6_QE_77K.pdf
Sb3513_A2P6_QE_77K.pdf
Attachment 3: Sb3513_A2P6_DarkNoise_77K.pdf
Sb3513_A2P6_DarkNoise_77K.pdf
Attachment 4: 191210_3513A2P6.zip
  2474   Tue Dec 10 16:35:03 2019 AidanLaser2micronLasersCalibrated cryo-PD REF PD output in units of power incident on cryo chamber window

We placed a power meter after the fiber collimator, 75mm focal length lens and HR mirror at 45 degrees - basically, we placed the power meter immediately before the input window to the cryo chamber after all the intervening optics from the fiber output.

For a series of laser diode current levels, we measured the power on the power meter and the corresponding voltage on the reference photodetector that is monitoring a 10% pick-off from the laser. The calibration is as follows:

Diode current (mA) REF PD (V) Laser Power (mW)
100.83 1.048 1.171
90.75 0.941 1.043
80.66 0.827 0.904
70.56 0.708 0.763
60.47 0.596 0.627
50.45 0.48 0.485
39.92 0.357 0.338
29.82 0.237 0.191
19.73 0.117 0.045
9.64 0.080 0.000
0.00 0.080 0.000

 

  2473   Mon Dec 9 14:45:45 2019 KojiDailyProgressPD QEToward PD testing automation

Wow. This is great, thanks Chris.

 

  2472   Mon Dec 9 14:03:52 2019 ChrisDailyProgressPD QEToward PD testing automation
  • A Keithley 2450 source meter will be used to measure QE and dark current vs bias.  It is on the QIL network as 10.0.1.130.  A command interface is available via telnet for running measurements and grabbing data.
  • A FEMTO transimpedance amp and SR785 will be used to take dark noise spectra, with bias supplied by a DAC channel filtered by an SR560.  The 785 is on the QIL network as 10.0.1.66, and the usual GPIB scripts should be sufficient.
  • A relay has been installed to control the switching between the Keithley and SR785 readouts.
  • BNC cables and breakouts connect the electronics on the table with the cymac (see table below for the channel assignments at the moment).
Cymac channel Assignment
ADC 29 Reference PD out
ADC 30 TED200C temperature out
ADC 31 ITC510 TEC temperature out
DAC 12 LDC201C laser current ctrl
DAC 13 SR560 (PD bias control for dark noise measurement)
DAC 14 ITC510 TEC temperature tune
DAC 15 Relay control (0 ct = Keithley, 30k ct = SR785)

Note: in the preceding table, channel numbers use the digital convention (numbered starting from zero), which is not the convention used by the AA/AI chassis front panel (numbered starting from one).

  2471   Mon Dec 9 12:34:14 2019 KojiDailyProgressPD QE 

I can see some screws are not vented. You also need to use a vented screw for the additional temp sensor if the face screws of the PD mounts are not vented.

You can use a bunch of clean clamps and screws I brought. They are in a mylar bag.
If you need more vented screws, please specify the size and length. I can grab some from the 40m cleanroom.

  2470   Mon Dec 9 02:15:39 2019 RaymondDailyProgressPD QEIR Labs Cryostat

The IR Labs cryostat has its internals wired and attached to the baseplate. PD A2 was clamped and the vacuum pumps turned on for the first cooling test.

[in the morning I will update with a detailed pin-out and label the attached photo (labeled 12/13, pin out in separate post)]

Attachment 1: IRLabscryointernals.pdf
IRLabscryointernals.pdf
  2469   Fri Dec 6 00:13:12 2019 ChrisComputingCDSarbitrary waveform streaming on the cymac

Recently Duo wanted to make an arbitrary waveform excitation using the QIL cymac, but it wasn't working.  An excitation would die after 10 seconds or so, with awgtpman reporting that the data was too far in the future.

It turns out this was caused by a missing leap second in the RTS software.  It is now fixed upstream, and we're running a patched version of awgtpman on fb4, until the change propagates to the packaged version.
 

  2468   Thu Dec 5 13:50:59 2019 KojiSummaryPD QEDark current measurement with the sourcemeter

I borrowed KEITHLEY 2450 source meter from Rich. The unit comes with special coaxial cables and banana clips. Most of the peripherals are evacuated in the OMC lab.

The dark current of A2P2, A2P3, A2P6 were measure with different temperatures (300K, 270K, 254K). The plot combined with the previous measurement ELOG QIL 2425.


== How to use the source meter ==

- Two-wire mode: Connect the wires to the diode

- Over voltage protection: [MENU] button -> SOURCE / SETTINGS->Over Voltage Protectiuon 2V

- Sweep setting: [MENU] button -> SOURCE / SWEEP -> e.g. Start -750mV, Stop +500mV, Step 10mV, Source Limit 1mA -> Select Generate

- Graph View: [MENU] button -> VIEWS / GRAPH

- Start measurement: Note: The response of [TRIGGER] button is not good. You need to push hard
  This starts the sweep, or a menu shows up if your push is too long -> Select "Initiate ..."

- Data Saving: [MENU] button -> MEASURE / READING BUFFERS -> Save to a USB stick

Attachment 1: InAsSb_DarkCurrent_markedup.pdf
InAsSb_DarkCurrent_markedup.pdf
  2467   Wed Dec 4 13:54:04 2019 RaymondLab InfrastructureGeneralMoved IR Labs cryostat into QIL from Cryo Lab

Update on the 32 pin female connector:

Mouser's overnight delivery was rejected on 12/3 by mail services for being soaked in an "unkown liquid" and was therefore taken away by the courier for return to Mouser. This was the last one in stock, so I ordered a replacement through Digikey for express delivery this morning 12/4, but it has not yet arrived. I've called Fedex and the package was sorted at the LA facility but not given to the courier for morning delivery. It is now estimated for delivery this afternoon. 

  2466   Tue Dec 3 15:32:39 2019 KojiSummaryPD QEPD TEC cooling test

The quantities we want to measure as a function of the temperature:

- Temperature: 2.2k thermister resistance / 100ohm platinum RTD

- QE (Illuminating output / Dark output / Reference voltage / Reference dark output)

- Dark current (vs V_bias) -> Manual measurement or use a source meter

- Dark noise (PSD) 100kHz, 12.8k, 1.6kHz, 100Hz

 

  2465   Tue Dec 3 13:52:04 2019 KojiUpdatePD QESocket soldering test piece made

[Raymond and Koji]

We dunked the PD socket test piece into LN2 and repeated heat cycle 8 times. No obvious change was observed. Then the wires were pulled to find any broken joint or etc.
None of the solder joints showed the sign of failure.

For cleanliness, we are going to use In-Ag solder (no flux) for the actual wiring.

Attachment 1: Frozen connector

Attachment 2-4: Inspection after thawing.

Attachment 1: PC029784.jpeg
PC029784.jpeg
Attachment 2: PC029788.jpeg
PC029788.jpeg
Attachment 3: PC029786.jpeg
PC029786.jpeg
Attachment 4: PC029787.jpeg
PC029787.jpeg
  2464   Sun Dec 1 01:32:19 2019 KojiSummaryPD QEPD TEC cooling test

While I'm still waiting for the proper connector for the vacuum feedthru of the IRLabs cryostat, I have connected to the Dsub9/15 split cable to another Dsub9 connector so that I can test the cooling of the InAsSb sensor in air. Also, the 2004nm laser, a fiber-coupled faraday isolator, and 90:10 beam splitter was moved to the cryostat table and fixed on a black al breadboard. [Attachment 1]

The InAsSb TEC was controlled by the TEC controller of ITC-50. I didn't change the PID parameters of the controller but the temperature nicely setteled to the setpoint. The sensor has a 2.2kOhm thermister. And the max current for the TEC was unknown. The TEC driver had the current limiter of 0.3A and it was not changed for now. With this current limit, the thermistor resistance of 10Kohm was realized. This corresponds to the temperature of about -20degC. According to the data sheet given by Alex, the resistance/temperature conversion is given by the formula

1/T = 7.755e-4 + 3.425e-4*log(R)+1.611e-13*log(R)^3

Questions:

  • What is the max current for the TEC?
  • What is the calibration formula of the thermister (TB04-222) at cryogenic temperature?
    -> Thermistor datasheet link (pdf)

To satisfy the curiosity, the dark current of a (500um)^2 element was measured between -250K and -300K. At -254K, the dark current went down to the level of 40uA (1/15 of the one at the room temp). For the measurement, the bias voltage was set to be 0.5 and 0.6V. However, it was dependent on the diode current. (Probably the bias circuit has the output impedance). This should be replaced by something else.

To Do

  • 2um laser beam setup (w=100um beam)
  • Bias circuit
  • Quick check of the QE and dark noise at -20degC

 

Attachment 1: 20191129191814_IMG_9146.JPG
20191129191814_IMG_9146.JPG
Attachment 2: cooling_dark_current.pdf
cooling_dark_current.pdf
  2463   Wed Nov 27 20:38:57 2019 KojiSummaryPD QESystem Diagram

The external Dsub cable is ready except for the 32pin connector to be plugged-in to the chamber. See QIL ELOG 2460 for the pin assignment.

 

Attachment 1: P_20191127_203612_vHDR_On.jpg
P_20191127_203612_vHDR_On.jpg
  2462   Tue Nov 26 18:49:11 2019 KojiUpdatePD QESocket soldering test piece made

Normal solder (Sn63 Pb37): with flux, wetting o

Pure Indium - In 99.995: no flux, wetting x, low melting temp, like paste

Pb93.5 Sn5 Ag1.5: with flux, wetting o, high melting temp (soldering iron setting 380~430F)

Cryo solder In97 Ag3: no flux, wetting x, low melting temp, like paste

Attachment 1: IMG_9118.jpeg
IMG_9118.jpeg
Attachment 2: IMG_9120.jpeg
IMG_9120.jpeg
Attachment 3: IMG_9121.jpeg
IMG_9121.jpeg
Attachment 4: IMG_9123.jpeg
IMG_9123.jpeg
Attachment 5: IMG_9125.jpeg
IMG_9125.jpeg
Attachment 6: socket.pdf
socket.pdf
  2461   Tue Nov 26 15:36:59 2019 RaymondLab InfrastructureGeneralMoved IR Labs cryostat into QIL from Cryo Lab

The IR Labs cryostat is now pumping down. The thor labs posts are necessary for centering the optical port at a height of 5.5". The orange cabinet used to elevate the pumping station was relocated from next to the computer (was, and still is, empty). The power supply is for the wide range vacuum gauge attached to the pumping line. 

I've ordered a liquid nitrogen dewar for arrival Monday morning.

For future reference, the gauge communicates via a VGA port, for which the pin-to-wire association is as such: 1-Black; 2-Brown; 3-Red; 4-Orange; 5-Yellow; 6-Green; 7-Blue; 8-Purple; 9-Grey; 10-White; 11-Pink; 12-Cyan; 13-Black/White; 14-Brown/White; 15-Red/White  (MKS 901P non-ethercat wiring diagram)

edit by RXA: replaced multi GB PDF w a reasonable JPG.

Attachment 1: IRLabsQIL.jpg
IRLabsQIL.jpg
  2460   Mon Nov 25 21:46:56 2019 KojiSummaryPD QESystem Diagram

System diagram of the PD QE test with the IRLabs cryostat.

 

PT-SE (MS/PT-SE) connector data sheets

Connector/receptacles/tools https://www.peigenesis.com/images/content/pei_tabs/amphenol/pt-ptse-series/new-thumbs/123-146_pt_series.pdf
Amphenol catalog http://www.amphenol-industrial.com/images/catalogs/PT.pdf

Detoronics Hermeic Sealed Connectors (DT02H-18-*PN) http://www.hselectronics.com/pdf/Detoronics-Hermetic-Connectors.pdf

AF8 crimping tool (expensive!) https://www.mouser.com/ProductDetail/DMC-Tools/AF8?qs=gvhpkjpQEVSjrLbsepewjg%3D%3D
AF8 alternative https://www.jrdtools.com/?gclid=Cj0KCQiA2vjuBRCqARIsAJL5a-IQ9ztCEYKdo645v_RhUBJS3eMIars1LubjlKZoorS-lnx6ClDDiMUaAlZiEALw_wcB

 

Thermistor link: https://www.tec-microsystems.com//Download/Docs/Thermistors/TB04-222%205%25%20Thermistor_Specification_upd2018.pdf

TEC spec: Mounted TEC type: 2MD04-022-08/1 https://www.tec-microsystems.com/products/thermoelectric-coolers/2md04-series-thermoelectric-coolers.html
2MD04-022-08/1 dTmax = 96, Qmax = 0.4W, Imax = 0.7A,  Umax = 2.0, ACR = 2.29 Ohm

Attachment 1: cryo_pd_test.pdf
cryo_pd_test.pdf cryo_pd_test.pdf
Attachment 2: InAsSb_PD_mount_short.PDF
InAsSb_PD_mount_short.PDF
Attachment 3: PD_pin.pdf
PD_pin.pdf
  2459   Mon Nov 25 15:03:34 2019 KojiUpdatePD QEIn solder and PD mounts are in

The PD mounts were delivered from ProtoLabs. The order was sent on Tue last week and it's here on Monday. Excellent!
And the quality looks pretty good.

The surfaces are sandblasted. Do we want to do any process on the bottom surface to reduce the thermal resistance?

An indium solder string also came in.

Attachment 1: PB259778.JPG
PB259778.JPG
Attachment 2: PB259780.JPG
PB259780.JPG
Attachment 3: PB259781.JPG
PB259781.JPG
  2458   Sat Nov 23 13:00:06 2019 KojiLab InfrastructureOpticsOptical window transmission measurement

The power transmission of the optical window for the IRLab cryostat was measured to be 0.966+/-0.002 at 2004nm. (Attachment 1)

A chopper powermeter was set to the QE measurement setup (Attachment 2). The window was held with a mount as shown in Attachmnent 3. The laser source was excited with the pumping current of 101.04mA. The output power was  monitored with a Thorlabs DET10D (PD#2 with Amp#2) attached at the 10% side of the 90:10 beamsplitter. The detected photocurrent after subtracting the dark current of 15.7uA was 152uA. The power meter detected the power around 0.95mW, while the power with the window inserted was around 0.91~0.92.


PD1       Window   No Window
[V]       [mW]     [mW]
-0.855    0.913    0.944
-0.855    0.906    0.951
-0.855    0.914    0.947
-0.855    0.922    0.950
-0.855    0.913    0.949
-0.855    0.912    0.948
-0.855    0.920    0.946
-0.855    0.915    0.946
-0.855    0.916    0.951
-0.855    0.915    0.952
-0.855    0.919    0.947
-0.855    0.921    0.944
-0.855    0.916    0.948

Note: PD1 had the dark output of -0.0809V.
Note2: The power meter readings had the fluctuation of +/-0.005 mW

Attachment 1: optical_window_T.pdf
optical_window_T.pdf
Attachment 2: P_20191122_183426_vHDR_On.jpg
P_20191122_183426_vHDR_On.jpg
Attachment 3: P_20191122_183436_vHDR_On.jpg
P_20191122_183436_vHDR_On.jpg
  2457   Fri Nov 22 15:33:40 2019 KojiLab InfrastructureGeneralMoved IR Labs cryostat into QIL from Cryo Lab

Salvaged an assort of vented/non-vented screws, washers, spring washers, and clamps for #4-40 & 1/4-20 from the 40m cleanroom stock. They are clean enough for the cryostat use.

Attachment 1: P_20191122_150845_vHDR_On.jpg
P_20191122_150845_vHDR_On.jpg
  2456   Fri Nov 22 13:21:26 2019 RaymondLab InfrastructureGeneralMoved IR Labs cryostat into QIL from Cryo Lab

Removed the IR Labs cryostat window for testing. It's on the cryocooler bench, see attached photos

Attachment 1: IMG_0497.JPG
IMG_0497.JPG
Attachment 2: IMG_0498.JPG
IMG_0498.JPG
  2455   Thu Nov 21 21:58:27 2019 RaymondDailyProgressCryo vacuum chamberTank Update

Update of our available electrical feedthroughs:

2 x 19 pin round with corresponding internal connectors and external connectors

2 x 15 D sub 

- re-tapped the PEEK support pieces to 1/4-20 to match the bottom of the tank, added them with vented socket set screws. These will need to be replaced with brass or aluminum to better match thermal contraction (steel screws likely to crack the PEEK upon cooling)

- Drilled holes (attached, highlighted in orange) in the pump station base in order to utilize the more robust shock absorbers that came with the oil pump. 

- Noticed significant flaking of the nuts/bolts when removing the tank lid. Suggested using anit-seize compound on the tank lid bolts but Chris advised against anything lube-like on the system. Just a note to remember to check the integrity of the bolts going forward before tightening the lid to avoid bolt seizing. 

Attachment 1: IMG_0490.JPG
IMG_0490.JPG
Attachment 2: IMG_0491.JPG
IMG_0491.JPG
Attachment 3: DiaphragmAdapt.pdf
DiaphragmAdapt.pdf
  2454   Thu Nov 21 21:45:10 2019 RaymondLab InfrastructureGeneralMoved IR Labs cryostat into QIL from Cryo Lab

Ordered the electrical feedthrough from IR Labs on overnight shipping. I've attached the diagram of the feedthrough, 32 pin is the only available configuration for this size feedthrough. 

Will attempt to use my makeshift 12 pin feedthrough if the proper one does not arrive tomorrow (thanks Koji for the 40m drill bit tip). I'll clear the bench of the IR Labs carcasses tomorrow.

UPDATE: feedthrough will arrive by 10:30 on Monday the 25th

Attachment 1: DT02H_18_32PN.pdf
DT02H_18_32PN.pdf
  2452   Wed Nov 20 17:44:10 2019 KojiLab InfrastructureGeneralMoved IR Labs cryostat into QIL from Cryo Lab

Here you are.

Attachment 1: P_20191120_174034_vHDR_On.jpg
P_20191120_174034_vHDR_On.jpg
Attachment 2: P_20191120_174040_vHDR_On.jpg
P_20191120_174040_vHDR_On.jpg
  2451   Wed Nov 20 12:25:58 2019 KojiLab InfrastructureGeneralMoved IR Labs cryostat into QIL from Cryo Lab

The large cryostat has 1/4-20 holes on a 2 inch grid

The IR labs cryostat has 4-40 holes on a 1 cm grid

I'll check the 40m for a bit (5/8-3/4")

  2450   Wed Nov 20 11:59:17 2019 KojiLab InfrastructureGeneralMoved IR Labs cryostat into QIL from Cryo Lab

Ah, I have designed the PD holder with the venting targeted for 1/4-20 holes with 1" grid...

The dog clamps to hold the PD units also need to be compatible with 4-40 screws.

How big the hole diameter should be? Can you find a suitable drill at the 40m?

 

  2449   Wed Nov 20 11:51:27 2019 RaymondMiscHVACDueling vents

In the QIL and noticed that the vent above the cryo chamber is heating the lab while the vent above the 2um laser bench is blasting AC. Both have been running continuously since I first entered the lab (~10:30)

  2448   Tue Nov 19 20:16:40 2019 RaymondLab InfrastructureGeneralMoved IR Labs cryostat into QIL from Cryo Lab

The cold plate breadboard holes are indeed 4-40.

I've installed a new o-ring and vacuum valve, but I've scoured the labs for any piece that fits the open port on the side of the cryostat and have come up empty-handed. I've attached a photo with all of the IR labs input pieces found thus far (except duplicates or ones that match these same dimensions), none fit the drill pattern or counter sunk hole of the cryostat port. I tried but could not find mention of this specific port's removal in the elog history. 

Spent a while trying to make a Franken-stat from the innards and limbs of the other decommisioned IR lab cryostats but nothing allowed for a correct optical path. So I then started to make a custom port with a 122 o-ring and an old ISO blank flange, but I need a drill bit larger than 0.5" for the center electrical feedthrough and am having ID card issues accessing the student shop over in CES.

I will call IR labs tomorrow and see if they have an a standard piece for this feedthrough. 

Attachment 1: IMG_0483.JPG
IMG_0483.JPG
  Draft   Mon Nov 18 17:17:29 2019 DuoSummary Restart model in QIL lab

Here are the commands.

ssh fb4
sudo /sbin/rmmod c4tst c4iop && cd /opt/rtcds/caltech/c4/target/c4iop/scripts/

./startupC4rt && cd ../../c4tst/scripts/ && ./startupC4rt && systemctl start rts-awgtpman@c4iop.service && systemctl start rts-awgtpman@c4tst.service && systemctl restart daqd@standiop.service

  2446   Fri Nov 15 20:10:00 2019 KojiSummary2micronLasersInAsSb PD Mounts designed

LIGO-Number Title Author(s) Topic(s) Last Updated
E1900369-v1 InAsSb Photodiode Mount (Short) Assembly Koji Arai Assembly
Basic R&D
15 Nov 2019
E1900368-v1 InAsSb Photodiode Mount Assembly Koji Arai Assembly
Basic R&D
15 Nov 2019
D1900490-v1 InAsSb Photodiode Mount Face Plate Koji Arai Basic R&D 15 Nov 2019
D1900489-v1 InAsSb Photodiode Mount (short) Koji Arai Basic R&D 15 Nov 2019
D1900488-v1 InAsSb Photodiode Mount Koji Arai Basic R&D 15 Nov 2019

  2445   Fri Nov 15 17:29:14 2019 RaymondLab InfrastructureGeneralMoved IR Labs cryostat into QIL from Cryo Lab

See attached photos for the internal layout of Zach's cantilever cryostat (all internal components left in cryo lab (except the heater)) The holes are on a 1cm grid and, I believe, are threaded for 4-40 (will check Monday). The internal 'window' is about an inch off the colplate. There is ~2 inches of space from the colplate to the first radiation shield lid. 

The external optical port on the vacuum tank is 1.75" from the bench and is 0.75" in diameter. The cryostat is missing the lid o-ring, electrical feedthrough vacuum port, and intermediary valve between the vacuum space and the vacuum pumps. I will search for these on Monday.

Attachment 1: IMG_0270.JPG
IMG_0270.JPG
Attachment 2: IMG_0269.JPG
IMG_0269.JPG
  2444   Tue Nov 12 17:44:39 2019 RaymondDailyProgressCryo vacuum chamberTank Update

Last week I moved the upper portion of the crane to the new, bolted crane support stand. Chub removed the wheeled lower section from the lab shortly thereafter. I also re-threaded the nylon lifting strap to remove slack and level the lid a bit better during lifting and moved one of the side tables next to the crane so the lid can be safely lowered after being lifted off the tank (see first photo). 

Opened the tank today to check internal dimensions. It is now closed (top bolts finger tight) but not under vacuum. The diaphragm pump was dispatched today, so will replace the dirty pump and pull vacuum again upon arrival. 

Attached a photo of the baseplate for future drill pattern reference. Note there are three anomalous holes, this is where the PEEK support poles should go. It was discovered today that these holes are 1/4-20 tapped but the PEEK pillars are dirlled/threaded for a smaller bolt.

I've attached a rough cartoon of the cold plate height relative to the optical ports and the tank wall. The outer rad shield is not shown and is slightly misaligned, but it can be easily aligned with a ~1.5 mm shim (better for thermal isolation anyways). 

Attachment 1: IMG_0258.JPG
IMG_0258.JPG
Attachment 2: IMG_0257.JPG
IMG_0257.JPG
Attachment 3: IMG_0259.JPG
IMG_0259.JPG
  2443   Tue Nov 12 03:40:39 2019 KojiLaserPD QEPD EQE vs Spot size

The QE of the (500um)^2 element has been tested with a half-power (0.51mW) instead of 0.92mW.
It is clear that the central dip depth is reduced by the lower power density.

 

Attachment 1: QE_vs_spotsize_half_power.pdf
QE_vs_spotsize_half_power.pdf
  2442   Mon Nov 11 22:19:09 2019 RaymondDailyProgressCryo vacuum chamberChanges to preserve long strap for internal chamber use

I've attached a photo of some changes to the cryocooler-tank connection design. We can save money and space by removing the 45 degree 1.33" conflat ports from the custom CH104 to 6" conflat adapter and using zero length conflat reducers at the unused 4 way cross ports, ie replace the 4-way piece blanks with holes for the vacuum line and gauge. The primary goal for these changes is to shorten the path from the cooler's heat station to the tank so that we keep the long thermal strap for use inside the tank. Also, the height is reduced from 89 cm to 59 cm.

A slightly different cupper adapter is needed to accomodate the thick strap, but no adapter will be needed anymore between the heat station and the thermal strap (same diameter round mates(new holes will need to be drilled though)).

Attachment 1: ShortAdapter.png
ShortAdapter.png
  2441   Wed Nov 6 17:05:33 2019 RaymondDailyProgressCryo vacuum chamberConflat flange tightening

Tightened all of the vacuum ports on the chamber so that the flange interfaces are all now metal-to-metal, ie full copper gasket compression. All of the ports required at least two star pattern passes before reaching this point, except for the bellows line to the turbo/backing pumps which was already at complete compression. Prior to tighening, the wide range gauge gave a pressure reading of 5.8x10-6 Torr and the ion-gauge showed 5.75x10-6 Torr. After tightening the wide range flange the reading dropped to 5.6x10-6 ; after tightening the ion-gauge flange the gauge reading dropped to 5.69x10-6

For future reference: the 4.625" flanges use 5/16" torx bolts and 1/2" nuts, and the 2.75" flanges use a 1/4" torx bolt and 7/16" nuts. 

  2440   Tue Nov 5 20:06:36 2019 RaymondUpdateCryo vacuum chamberCooler to tank connection

Attached is a drawing of the first phase (minimal vibration isolation) cryocooler attachment, where the main tank connects via the blue rimmed feedthrough. Boxed/circled components are those that will require custom fabrication:

  1. Copper adaptor from heat station to thermal strap
  2. 5.25" outer diameter 2-153 o-ring connection to conflat adapter (DN75 (4-5/8" outer diameter, 3" tube OD) pictured, but am comparing this with the DN100 (6" OD, 4" tube diameter))
  3. Conflat to ASA o-ring adapter
  4. a + b: Copper adapter from the flat strap connector to the round copper vacuum feedthrough (closeup shown in second figure)

Currently there are only two connections that require viton o-ring rather than conflat connections (cooler to piece 1, piece 3 to HV feedthrough). 

Attachment 1: CoolerCartoon.pdf
CoolerCartoon.pdf
Attachment 2: Screen_Shot_2019-11-05_at_20.25.54.png
Screen_Shot_2019-11-05_at_20.25.54.png
  2439   Fri Nov 1 12:47:18 2019 KojiLaserPD QEPD EQE vs Spot size

Clipping and saturation were investigated by the semi-analytical model. In the analysis, the waist radius of 20um at the micrometer position of 8mm is used.

1) Clipping

Firstly, the clipping loss was just geometrically calculated. Here the saturation issue was completely ignored. The elements P6, P3, and P2 have the sizes of (500um)^2, (750um)^2m, and (1000um)^2, respectively. However, these numbers could not explain the clipping loss observed at the large spot sizes. Instead, empirically the effective sizes of (350um)^2, (610um)^2, and (860um)^2 were given to match the measurement and the calculation. This is equivalent to have 70um of an insensitive band at each edge of an element (Attachment 1). These effective element sizes are used for the calculation throughout this elog entry.

2) Saturation modeling

To incorporate the saturation effect, set a threshold power density. i.e. When the power density exceeds the threshold, the power density is truncated to this threshold. (Hard saturation)

Resulting loss was estimated using numerical integration using Mathematica. When the threshold power density was set to be 0.85W/mm^2, the drop of QE was approximately matched at the waist (Attachment 2). However, this did not explain the observed much-earlier saturation at the lower density. This suggests that the saturation is not such hard.

In order to estimate the threshold power density, look at the beam size where the first saturation starts. The earlier sagging of the QE was represented by the threshold density of 0.1W/mm^2. (Attachment 3)

Attachment 1: QE_vs_spotsize_no_saturation.pdf
QE_vs_spotsize_no_saturation.pdf
Attachment 2: QE_vs_spotsize_saturation_0_85.pdf
QE_vs_spotsize_saturation_0_85.pdf
Attachment 3: QE_vs_spotsize_saturation_0_1.pdf
QE_vs_spotsize_saturation_0_1.pdf
  2438   Thu Oct 31 18:31:10 2019 KojiLaserPD QEPD EQE vs Spot size

InAsSb PD QE Test

The relationship between the spot radius and the apparent QE (EQE) was measured.

1) The spot size was checked with DataRay Beam'R2. The beam scanner was mounted on the post with a micrometer stage in the longitudinal direction. (Attachment1 upper plot)
It was confirmed that the beam is focused down to ~22um. The incident power was about 0.9mW.

2) The InAsSb detector (Sb3513A2) was mounted on the PD holder and then mounted on the stage+post. The photocurrent was amplified by a FEMTO's transimpedance amp (V/A=1e3Ohm). The dark current and the total photocurrent were measured at each measurement point with the beam aligned to the PD every time. The estimated EQEs were plotted in the lower plot of the attachment.

Note that P2, P3, and P6 elements have the size of (500um)^2, (750um)^2, and (1000um)^2, respectively.

The absolute longitudinal position of the sensor was of course slightly different from the position of the beam scanner. So the horizontal axis of the plots was arbitrary adjuted based on the symmetry.

The remarkable feature is that the QE goes down with small spot size. This is suggesting a nonlinear loss mechanism such as recombination loss when the carrier density is high.

With the present incident power, the beam size of 100um is optimal for all the element sizes. For the larger elements, a bigger beam size seems still fine.

The next step is to estimate the clipping loss and the saturation threshold with the Gaussian beam model.

Attachment 1: QE_vs_spotsize.pdf
QE_vs_spotsize.pdf
  2437   Thu Oct 24 11:58:27 2019 ChrisElectronicsCDSnew QIL AA boards

The anti-alias boards in the QIL AA chassis have been replaced with newer ones I found in the EE shop (serial numbers S1200217, S1200274, S1200275, S1200277).

The new boards (D070081-v4) have input buffers and a reasonably high input impedance (20k), unlike the old boards (D070081-v1).  However, according to the DCC revision notes, they may suffer from some excess low frequency noise caused by LT1492 opamps.  If it becomes a problem for us, we can replace those opamps.

The low input impedance of the original boards explains the anomalous ADC/DAC loopback measurement Jon made several months ago.  It should now be close to 0.5 ADC ct per DAC ct.  I have checked the DC gain for the first few channels, but have not exhaustively tested the new boards.  (Perhaps Jon has a script to automate this?)

ELOG V3.1.3-