 Thu May 23 01:42:46 2019, Koji, Optics, Characterization, C30665 high power test 
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An Excelitas C30665 PD with the cap removed (SN07 in Case H slot #2) was exposed to the beam with the optical power of 1.4mW to 334mW.
After each illumination, the dark current and the dark noise level were tested. Also the photo image of the PD surface was taken each time.
- No significant change of the dark current after each illumination. |
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Thu May 23 23:27:38 2019, Koji, Optics, Characterization, IGHQEX3000 high power test
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LaserComponents IGHQEX3000 (Cage B2: Serial# B1-23) was exposed to the beam with the optical power from 1.6mW to 332mW.
After each illumination, the dark current and the dark noise level were measured. Also the photo image of the PD surface was taken each time.
- No significant change of the dark current after each illumination. |
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Mon Jul 1 12:38:49 2019, Koji, Optics, Characterization, A and M prisms perpendicularity measurement 6x
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[Stephen, Koji]
The perpendicularity of some of the A and M prisms were tested.
Results |
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Mon Jul 1 12:49:42 2019, Koji, Optics, Characterization, Scattering measurement of A and C mirrors
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| Liyuan's scattering measurement for the A and C mirrors. |
 Thu Aug 22 12:35:53 2019, Stephen, Optics, Characterization, Wedging of the debonded PZTs 2019 August
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Wedge and thickness measurements of PZTs 12 and 13 took place after debonding and cleaning - results are shown in the first image (handwritten post-it
format).
These thickness measurements seem to have come back thinner than previous measurements. It is possible that I have removed some PZT material |
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Fri Aug 23 11:11:44 2019, shruti, Optics, Characterization, Finding the curvature bottom
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I attempted to fit the data taken by Koji of the beam spot precession at the CCD in order to find the location of the curvature bottom in terms
of its distance (d) and angle () from the centre of the mirror. This was done using
the method described in a previous similar measurement and Section 2.1.3 of |
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Thu Aug 29 11:51:49 2019, shruti, Optics, Characterization, Wedging of the debonded PZTs - Calculation
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Using the measurements of PZTs 12,13 taken by Stephen, I estimated the wedging angle and orientation following Section 2.3.1 of T1500060. The results
can be found in Attachment1 and is summarised as follows.
For PZT 12, PZT 13 respectively: |
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Thu Oct 8 19:55:22 2020, Koji, General, Characterization, Power Measurement of Mephisto 800NE 1166A
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The output of Mephisto 800NE (former TNI laser) was measured.
The output power was measured with Thorlabs sensors (S401C and S144C). The reference output record on the chassis says the output was 837mW at 2.1A
injection. |
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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 |
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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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Wed Jul 15 22:23:17 2015, Koji, Electronics, AM Stabilized EOM Driver, E1400445 first look
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This is not an OMC related and even not happening in the OMC lab (happening at the 40m), but I needed somewhere to elog...
E1400445 first look
LIGO
DCC E1400445 |
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Sat Jul 18 11:37:21 2015, Koji, Electronics, AM Stabilized EOM Driver, D0900848 power board ~ oscillation issue solved 6x
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Power Supply Board D0900848 was oscillating. Here is the procedure how the issue was fixed.
PCB schematic: LIGO DCC D0900848
0. Extracting the power board. |
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Wed Jul 22 09:43:01 2015, Koji, Electronics, AM Stabilized EOM Driver, Power supply test of the EOM/AOM Driver
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Serial Number of the unit: S1500117
Tester: Koji Arai
Test Date: Jul 22, 2015 |
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Wed Jul 22 10:15:14 2015, Koji, Electronics, AM Stabilized EOM Driver, RF test of the EOM/AOM Driver S1500117
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7) Make sure the on/off RF button works,
=> OK
8) Make sure the power output doesn't oscillate, |
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Sat Jul 25 17:24:11 2015, Koji, Electronics, AM Stabilized EOM Driver, RF test of the EOM/AOM Driver S1500117 7x
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(Calibration for Attachment 5 corrected Aug 27, 2015)
Now the test procedure fo the unit is written in the document https://dcc.ligo.org/LIGO-T1500404
And the test result of the first unit (S1500117) has also been uploaded to DCC https://dcc.ligo.org/LIGO-S1500117 |
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Tue Jul 28 18:36:50 2015, Koji, Electronics, AM Stabilized EOM Driver, RF test of the EOM/AOM Driver S1500117
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Final Test Result of S1500117: https://dcc.ligo.org/LIGO-S1500117
After some staring the schematic and checking some TFs, I found that the DAQ channels for MON2 have a mistake in the circuit.
Differential driver U14 and U15 of D0900848 are intended to have the gain of +10 and -10 for the pos and neg outputs. |
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Mon Aug 10 02:11:47 2015, Koji, Electronics, AM Stabilized EOM Driver, RF AM Measurement Unit E1500151
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This is an entry for the work on Aug 3rd.
LIGO DCC E1500151
Power supply check |
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Mon Aug 10 11:39:40 2015, Koji, Electronics, AM Stabilized EOM Driver, RF AM Measurement Unit E1500151
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Entry for Aug 6th, 2015
I faced with difficulties to operate the RF AM detectors.
I tried to operate the RF AM detector. In short I could not as I could not remove the saturation of the MON outputs, no matter how jiggle the |
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Mon Aug 10 11:57:17 2015, Koji, Electronics, AM Stabilized EOM Driver, RF AM Measurement Unit E1500151
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Spending some days to figure out how to program CPLD (Xilinx CoolRunner II XC2C384).
I learned that the JTAG cable which Daniel sent to me (Altium JTAG USB adapter) was not compatible with Xilinx ISE's iMPACT.
I need to use Altium to program the CPLD. However I'm stuck there. Altium recognizes the JTAG cable but does not see CPLD. (Attachment 1) |
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Mon Aug 10 12:09:49 2015, Koji, Electronics, AM Stabilized EOM Driver, RF AM Measurement Unit E1500151
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Still suffering from a power supply issue!
I have been tracking the issues I'm having with the RF AM detector board.
I found that the -5V test point did not show -5V but ~+5V! It seemed that this pin was not connected to |
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Fri Aug 28 01:08:14 2015, Koji, Electronics, AM Stabilized EOM Driver, RF AM Measurement Unit E1500151 ~ Calibration
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Worked on the calibration of the RF AM Measurement Unit.
The calibration concept is as follows:
Generate AM modulated RF output
Measure sideband amplitude using a network anayzer (HP4395A). This gives us the SSB |
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Fri Aug 28 02:14:53 2015, Koji, Electronics, AM Stabilized EOM Driver, RF AM Measurement Unit E1500151 ~ 37MHz OCXO AM measurement
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In order to check the noise level of the RFAM detector, the power and cross spectra for the same signal source
were simultaneously measured with the two RFAM detectors.
As a signal source, 37MHz OCXO using a wenzel oscillator was used. The output from the signal source |
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Tue Sep 8 10:55:31 2015, Koji, Electronics, AM Stabilized EOM Driver, RF AM Measurement Unit E1500151 ~ 37MHz OCXO AM measurement
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Test sheet: https://dcc.ligo.org/LIGO-E1400445
Test Result (S1500114): https://dcc.ligo.org/S1500114 |
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Thu Apr 18 20:47:54 2019, Joe, Optics, , OMC initial alignment and locking
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[Joe, Phillip, Koji, Stephen]
*draft post, please add anymore info if I missed something*
made initial alignment of the cavity. To do this we used the periscope mirrors to aim the incoming beam at the centre of the |
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Fri Apr 19 09:21:07 2019, Philip, Optics, , Cleaning of OMC optics
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ach[Joe, Phillip, Koji, Stephen]
Work from 17.04.2019
First contact cleaning of OMC optics |
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Fri Apr 19 09:35:28 2019, Joe, General, , Adjusting cavity axis, re-alignment of OMC and locking
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[koji,philip, joe, liyuan, steven]
*still need to add photos to post*
PZT 11 was removed and inspected for so dust/dirt on the bottom of the prism. We saw a spot. We tried to remove this with acetone, |
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Fri Apr 19 11:34:19 2019, Koji, Optics, , OMC initial alignment and locking
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The spot on CM1 was found displaced by 3.4mm (horiz.) and 3.0mm (vert.) in the upper right direction looking from the face side.
The spot on CM2 was found displaced by 1.2mm (horiz.) and 1.8mm (vert.) in the upper left direction looking from the face side.
The drawing on the left side of the attachment shows the estimated misalignment when we think they all come from the curved |
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Mon Apr 22 09:54:21 2019, Joe, General, , Shortening cavity (A5,A14,PZT11,PZT22) to get closer to design FSR
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[Koji,Joe,Philip,stephen]
in units 20um per div on the micrometer [n.b. we reailised that its 10um per div on the micrometer]
CM1 inner screw pos: 11.5 |
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Mon Apr 22 19:54:28 2019, Koji, General, , OMC(004): Spot positions at the end of Apr 22nd
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