 Sat Nov 21 13:58:30 2020, Koji, Electronics, Characterization, Dark Current Measurement for InGaAs QPDs 
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Dark current measurement for InGaAs QPDs (OSI FCI-InGaAs-Q3000) has been done using Keithley 2450 and Frank's diode test kit. Frank's setup uses
various custom instruments which are no longer exist, therefore the kit was used only for switching between the segments.
The diodes were serialized as 81, 82, 83, 84, continuing the numbering for the OMC QPDs. The numbers are engraved at the side and the back of |
 Sun Nov 22 13:49:12 2020, Koji, Electronics, Characterization, Impedance Measurement for InGaAs QPDs
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To know any anomaly to the junction capacitance of the QPD segments, the RF impedances were tested with a hand-made impedance measurement.
All segments look almost identical in terms of capacitance.
Measurement setup: |
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Mon Nov 23 23:17:19 2020, Koji, Electronics, Characterization, The dark noise of the Q3000 QPDs
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The dark noise levels of the four Q3000 QPDs were measured with FEMTO DLPCA200 low noise transimpedance amp.
The measurement has been done in the audio frequency band. The amp gain was 10^7 V/A. The reverse bias was set to be 5V and the DC output of
the amplifier was ~40mV which corresponds to the dark current of 4nA. It is consistent with the dark current measurement. |
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Tue Nov 24 10:45:07 2020, gautam, Electronics, Characterization, The dark noise of the Q3000 QPDs
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I see that these measurements are done out to 100 kHz - I guess there is no reason to suspect anything at 55 MHz which is where this QPD will be reading
out photocurrent given the low frequency behavior looks fine? The broad feature at ~80 kHz is the usual SR785 feature I guess, IIRC it's got to do
with the display scanning rate. |
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Tue Nov 24 12:27:18 2020, Koji, Electronics, Characterization, The dark noise of the Q3000 QPDs
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The amplifier BW was 400kHz at the gain of 1e7 V/A. And the max BW is 500kHz even at a lower gain. I have to setup something special to see the RF band
dark noise.
With this situation, I stated "the RF dark noise should be characterized by the actual WFS head circuit." in the 40m ELOG. |
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Fri Feb 5 07:40:37 2021, Stephen, Supply, General, OMC Unit 4 Build Machined Parts
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OMC Unit 4 Build Machined Parts are currently located in Stephen's office. See image of large blue box from office, below.
Loaned item D1100855-V1-00-OMC08Q004
to Don Griffith for work in semi-clean HDS assy. |
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Wed Jul 7 14:21:50 2021, Stephen, Supply, General, OMC Unit 4 Build Machined Parts
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More explicit insights into the inventory for the Unit 4 build. Image of inventory included below.
Machined Parts:
New fabrication = Contents of Storage-11112 are consistent with |
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Thu Jun 23 21:03:33 2022, Koji, Facility, General, Moving the small optical table to CAML (TCS Lab)
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I've cleared the small optical table and wondered how to move it out of the room. Fortunately, the north side of the big table had wide enough clearance
and let the 36" wide table go through. This was easy without moving other heavy stuff.
From here to the door, a bit of work is required. A possibility is to roll the laser blocking wall to the south side of the big table. This will |
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Tue Jun 28 16:13:34 2022, Koji, General, General, The small optical table not small enough to get out
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The table width was an inch too large compared to the door width. We need to tilt the table and it seemed too much for us. Let's ask the transportation
for handling.
Photo courtesy by Juan |
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Thu Jul 21 13:21:27 2022, Koji, General, Configuration, Windows laptop for WincamD Beam'R2 recovery
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The Windows laptop for WincamD/Beam'R2 (DELL Vostro3300) was not functional.
- Windows 7 got stuck in the starting up process (Google "startup repair loop")
- The battery can't charge and the adapter connection is flaky |
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Thu May 20 17:03:50 2021, Koji, General, General, SRS LCR meter SRS720 borrowed from Downs
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Item loan: SRS LCR meter SRS720 borrowed from Downs. The unit is at the 40m right now for testing with an excelitas PD. Once it is done, the setup will
be moved to the OMC lab for testing the high QE PDs |
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Sun May 30 15:17:16 2021, Koji, General, General, DCPD AF capacitance measirement
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Attachment 1: System diagram. The reverse bias voltage is controlled by DS335. This can produce a voltage offset up to 10V. A G=+2 opamp
circuit was inserted so that a bias of up to +15V can be produced. The capacitances of the photodiodes were measured with SR720 LCR meter with a probe.
DS335 and SR720 were controlled from PC/Mac via serial connections. |
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Sun May 30 15:32:56 2021, Koji, General, General, DCPD AF capacitance measirement
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Measurement result:
The capacitance at no bias was 460~500pF. This goes down to below 300pF at 1.0~1.5V reverse bias. At maximum +15V, the capacitance goes down
to 200~220pF. |
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Fri Jul 22 17:41:01 2022, Koji, General, General, SRS LCR meter SRS720 returned to Downs
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SRS LCR meter SRS720 was returned to Downs as before.
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Mon Jul 25 18:25:04 2022, Koji, General, General, A/C Filter was replaced
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New filter PN
Grainger
TK70457312T Mini-Pleat Air Filter, Style - Air Filters Box, Performance Rating MERV 14, Nominal Filter Size 12x24x2
Previous |
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Fri Jul 15 22:14:14 2022, Koji, General, General, OMC Lab recovery for the OMC #002 test
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- The lab is chilly (18degC)
- Cleaned the lab and the optical table a bit so that the delicate work can be done. The diode test rig (borrowed from Downs - see OMC
ELOG 408 and OMC ELOG 409) was removed from the table and brought to the office (to return |
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Tue Jul 26 00:01:59 2022, Koji, General, General, OMC #002 delamination check 2
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More epoxy delamination check:
DCPD R (Attachment 1): Found half delaminated
DCPD T (Attachment 2): Found half delaminated |
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Mon Jul 18 14:20:09 2022, Koji, General, General, OMC #002 Plan Portal
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== Initial Preparation ==
[Done] OMC #002 placement
[Done] OMC #002 locking
Details OMC
ELOG 414
== Measurements == |
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Tue Jul 19 03:17:56 2022, Koji, General, General, OMC #002 Power Budget before mirror cleaning
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o Power Budget (2022/07/18)
NPRO ADJ -50 (min)
Fiber incident 62.8mW |
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Thu Jul 21 02:55:06 2022, Koji, General, General, OMC #002 Power Budget after mirror cleaning
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o Power Budget after FirstContact cleaning (2022/07/20)
NPRO ADJ -50 (min)
Fiber incident --.-mW |
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Thu Jul 21 14:35:35 2022, Koji, General, General, Bond reinforcement blocks for the invar brackets
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Bond reinforcement blocks for the invar brackets:
Attachment 1: CLASS A glass prisms (the surplus of the 2016 repair)
Attachment 2: Dirty
reiforcement bars made of Aluminum
There are also many dirty prisms in the kit obtained from Stephen
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Thu Jul 21 14:55:48 2022, Koji, General, General, Optics bonding for the backscatter measurement
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The backscatter beam is supposed to appear in the backpropagation path. The transmission of the OMC has a couple of optics, it's not easy to access
that beam.
To try to deflect the beam either horizontally or vertically, small optical pieces were made. (Attachment) |
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Thu Jul 21 17:47:00 2022, Koji, General, General, The profile of the beam incident on the fiber input coupler
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The profile of the beam incident on the fiber input
The fiber input was deflected by a 45deg mirror. The beam profile was measured with WincamD. The beam was too strong (~60mW) even at the smallest
pump power (ADJ -50) of the NPRO. So the two ND20 filters were added to the lens right before the 45 deg mirror and the camera. |
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Fri Jul 22 00:31:17 2022, Koji, General, General, OMC #002 backscatter measurement
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Measure the power ratio between the forward-propagating and reverse-propagating beams.
Place a small deflecting mirror at the transmission.
Place a flat mirror at the deflected transmission. When the alignment
of this mirror is adjusted to retroreflect this beam, the DC of the cavity reflection PD increases, and also the CCD shows spurious fringes.
This |
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Fri Jul 22 17:47:38 2022, Koji, General, General, C&B request for the reinforcement blocks
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OMC Reinforcement blocks
1. P/N D1600316; Version v4; Type 01; Qty 30; Source Chemistry Machine Shop
2. P/N D1600316; Version v4; Type 02; Qty 15; Source Chemistry Machine Shop |
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Tue Jul 26 00:12:58 2022, Koji, General, General, High QE PD: QE measurements
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- Installed the High QE PDs to OMC #002
B1-22@Cage B1 was installed to the transmission DCPD
B1-23@Cage B1 was installed to the reflection
DCPD
Upon the installation, the legs of the PDs were cut by 3mm. Also, the tab of the PD could not be embedded in the DCPD housing. |
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Wed Jul 27 10:34:09 2022, Koji, General, General, High QE PD: QE measurements 2
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- DLPCA-200 trans-impedance amplifier was calibrated.
Keithley source meter 2450 was connected to the amp. Provide current and read the output voltage with the precision digital voltage meter
(Agilent/Keysight). |
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Wed Jul 27 10:09:51 2022, Koji, General, General, 4+4 wire clamp in hand
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Regarding: D1200971
- 4 CLASS A wire clamp obtained from the OMC spare
- 4 more DIRTY wire clamp obtained from WB experiments (they no longer use these) |
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Wed Jul 27 10:34:30 2022, Koji, General, General, OMC #002 Protective FirstContact Paint
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The optical surfaces were coated with FirstContact to keep them clean / somewhat protected during the transportation.
The PD aperture was sealed with FirstContact "caps" (made by Kate in 2016?). |
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Wed Jul 27 23:52:18 2022, Koji, General, General, OMC #002 Cable bracket replacement (1)
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Parts check
- D1300052-V3 SN001 is going to be used (Attachment 1)
- This is the PEEK version of the cable bracket (Attachment 2). The side thread holes have no Helicoils inserted. This |
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Thu Jul 28 00:28:15 2022, Koji, General, General, OMC #002 Cable bracket replacement (2)
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Connector unmounting
- (Attachment 1) The connector nut rings were removed using an angled needle nose plier. The connector shell has a tight dimension
relative to the hole on the bracket. But of course, they could be extracted. |
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Thu Jul 28 00:46:47 2022, Koji, General, General, Subject: OMC #002 Cable bracket replacement (3)
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Checking the spare parts
- Conclusion for OMC#2: need PEEK cable ties
- for more OMCs: need more BHCS / PEEK cable ties / Helicoils |
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Wed Aug 10 18:42:27 2022, Koji, General, General, OMC #002 Cable bracket replacement (4)
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[Stephen Koji]
Now we got the C&Bed parts to continue to work on the cable bracket replacement.
1) Helicoil insertion |
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Thu Aug 11 15:24:57 2022, Koji, General, General, OMC #002 Cable bracket replacement (4)
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- The hole size extension is going forwared now.
- Madeline and Chub are cleaning (sonicating) a drill (29/64=0.4531") |