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 Thu Aug 5 09:20:44 2021, Aidan, Laser, 2um Photodiodes, Optical design for 2um PD in new cryo chamber 
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 Thu Aug 5 12:39:56 2021, Aidan, Laser, 2um Photodiodes, Optical design for 2um PD in new cryo chamber
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Thu Aug 5 14:29:42 2021, Stephen, Laser, 2um Photodiodes, Optical design for 2um PD in new cryo chamber
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Tue Aug 24 15:01:25 2021, Stephen, Laser, 2um Photodiodes, 2um PD in new cryo chamber
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Thu Aug 26 14:31:46 2021, Aidan, Stephen, Laser, 2um Photodiodes, Incident power calibration of 2um PD in new cryo chamber
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Fri Aug 27 17:57:30 2021, Stephen, DailyProgress, 2um Photodiodes, Start of PD pumpdown
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Sat Aug 28 07:01:21 2021, Aidan, DailyProgress, 2um Photodiodes, Start of PD pumpdown
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Sun Aug 29 11:17:43 2021, Aidan, DailyProgress, 2um Photodiodes, Start of PD pumpdown
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Mon Aug 30 08:04:52 2021, Aidan, DailyProgress, 2um Photodiodes, Monday morning observation of JPL A1 PD cool down
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Message ID: 2651
Entry time: Thu Aug 26 14:31:46 2021
In reply to: 2650
Reply to this: 2654
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| Author: |
Aidan, Stephen |
| Type: |
Laser |
| Category: |
2um Photodiodes |
| Subject: |
Incident power calibration of 2um PD in new cryo chamber |
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We're getting close to running this (2um beam is focussed onto the PD and we have piezo mirror steering and beam size tuning). However, all DAC channels are currently non-responsive. I'm going to rebooting the front-end.
Incident power calibration was performed with a S148C power meter head placed directly in front of the PD. For varying current levels, I recorded the pick-off PD voltage and the power meter reading.
| Current (mA) |
REF PD (V) |
Power Meter (mW) |
| 101.04 |
1.01 |
0.803 |
| 101.03 |
1.012 |
0.805 |
| 100.41 |
1.01 |
0.805 |
| 93.11 |
0.935 |
0.735 |
| 85.03 |
0.846 |
0.664 |
| 79.97 |
0.792 |
0.618 |
| 75.01 |
0.74 |
0.573 |
| 69.97 |
0.684 |
0.524 |
| 65 |
0.629 |
0.478 |
| 55.01 |
0.52 |
0.384 |
| 44.96 |
0.405 |
0.284 |
| 35 |
0.291 |
0.1834 |
| 25 |
0.176 |
0.0844 |
| 20 |
0.119 |
0.0348 |
| 0.03 |
0.079 |
3.00E-04 |
POW [mW] = 0.862[mW/V]*REF_PD [V] -0.067[mW]
| Quote: |
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[Aidan, Stephen]
Worked toward aligning and characterizing beam on PD. Will complete next session.
Log:
Some difficulty aligning to the 2um beam, which is sensed by a thermal card. Aidan intends to upgrade with a fiber coupled visible laser, which could then be swapped interchangably for alignment.
The 1" mirror at the top of the periscope doesn't make sense, given larger apertures in shields and viewport. We looked for a nearby 2" replacement but did not have luck. Ended up swapping back in the gold-coated 2" mirror, even though it is thin enough to be a pain to mount.
Instrumented connector pins to DB9 pins using the following translation (ref Aidan's drawing for connector / PD pinout, ref drawing from QIL/2639)
DB9 - 1 6 2 7 3 8
Connector - 2 3 4 5 6 7
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