SITCOMTN-148
LSST Camera Electro-Optical Test Results#
Abstract
‘This note collects results from the LSST Camera electro-optical testing prior to installation on the TMA. We describe the CCD and Focal Plane optimization and the resulting default settings. Results from eo_pipe are shown for standard runs such as B-protocols, Dense and SuperDense PTCs, gain stability, OpSim runs of Darks, and Darks with variable delays. We also describe features such as e2v Persistence, ITL phosphorescence in coffee stains, remnant charge near Serial register following saturated images, vampire pixels, ITL dips, and others.
Electro-optical setup#
Run 7 Optical modifications#
hello world.
This section describes run 7 optical changes to the CCOB, projector, etc.
refresh of setup with items the same as IR2 (CCOB, no narrow-beam)
diffuser install
projector
Projector spots#
hello world.
This section describes the spots and rectangles tested with the 4k projector
Projector background
Spots on many amps
Spots on one amp
Optical setup
FCS development#
hello world.
This section describes FCS operation and intervention.
Activity with the FCS
Fault at end of september & documentation
autochanger known light leak
Running FCS in emulator mode (OCS)
Characterization#
Dark current and light leaks#
This section describes dark current and light leaks in Run 7 testing.
One of the first tests we attempted with the camera was measuring dark current and sources of light leaks in the camera body.
Light leak mitigation with shrouding the camera body#
Sources of light leak with the autochanger#
After completing the shroud of the camera, we proceeded with several long dark exposures using different filter and shutter conditions to establish our baseline dark condition for testing.
We acquired 900s darks with different shutter conditions and the empty frame filter in place.
We acquired 900s darks in different filters with the shutter open
Shutter condition impact on darks#
Filter condition impact on darks#
Final measurements of dark current#
Baseline characterization#
hello world.
This section describes baseline characterization and reverification
first B protocols and PTCS
comparison to IR2 metrics
new features in any baseline runs?
Guider operation#
hello world.
This section describes guider operation.
initial guider operation
power cycling the guiders to get to proper mode
synchronization
guider roi characterization
Tree rings#
hello world.
This section describes tree rings.
Tree rings without diffuser
Tree rings with diffuser
Camera Optimization#
Sequencer Optimization#
hello world.
This section describes sequencer optimization.
No-pocket conclusions
Overlap conclusions
Serial flush conclusions
Persistence optimization#
hello world.
Trying new voltages
impact on persistence
impact on full-well
impact on other parameters
Thermal Optimization#
hello world.
This section describes thermal optimization.
Background
Idle flush off & it’s stability
impact on other parameters
Camera stability#
Defect stability#
hello world.
This section describes defect stability.
Bright defects
Dark defects with picture frame
Bias stability#
Bias instabilities (typically above the 1-ADU level) are observed over a significant number of sensors for both ITL and e2v CCDs. The main issues are referred as:
The ITL bias jumps : large variation of the column-wise structure from exposure to exposure.
The e2v yellow corners : residual 2D shape of the bias even after 2D-overscan correction. These residuals depend on the acquisition sequence and of the exposure time.
Both issues were observed and deeply studied in Run 6 EO data. The ITL issue is believed to be phase shifts in clocks between Readout Electronics Boards (REB) because REBs rely on the frequency converted from their natural frequency. We tried to mitigate the e2v issue by optimizing the acquisition configuration in Run 7.
For the baseline acquisition configuration (see conclusion), three relevant stability runs were recorded:
Run E2136: 15s darks with some very long delays throughout the run
Run E2236: 50 15s darks, 50 biases recorded with 30s delays between exposures
Run E2330: 15s and 30s darks with variables delays between exposures
To process these runs, the eo_pipe bias stability task is used: for the ISR part, a serial (‘mean_per_row’) overscan correction and a bias subtraction (computed from the corresponding B-protocol run) are applied. The final data product is the mean of the per-amplifier science image over the full set of exposures of the run. Two typical examples from Run E2136 are shown in the figures below. In the stable case, the variations are typically at the 0.1 ADU level; in the instable case, the variations go up to 4 ADUs.
Fig. 1 Stable case (R21 S21)#
Fig. 2 Instable case (R23 S22)#
A comparison of the results for an instable CDD is shown below for the three runs.
Fig. 3 Run E2136, R33 S02#
Fig. 4 Run E2236, R33 S02#
Fig. 5 Run E2330, R33 S02#
In order to highlight the 2D shape differences, a 2D-overscan correction is applied. A few exposures illustrating the variations of the 2D shape for an instable CCD are shown below. The 2D shape of the image in amplifier C01 is different in the 3 cases.
Fig. 6 Bias exposure, run 1880, R33 S02#
Fig. 7 15-s dark exposure, run E2136 in ‘stable’ conditions, R33 S02#
Fig. 8 15-s dark exposure, run E2136 after a 3-minute delay, R33 S02#
In order to quantify the number of e2v instable amplifiers, a stability metric d is defined from the eo_pipe stability task data products. More precisely, d is defined, for a given amplifier in a given run, as the difference between the 5th and 95th percentiles of the image mean over all the exposures. The distribution of d for run E2136 is shown below. Applying a threshold at 0.3, 51 amplifiers are identified as instable (see the corresponding mosaic). This corresponds to ~3% of the e2v amplifiers.
Fig. 9 Distribution of the stability metric for the e2v amplifiers in run E2136#
Fig. 10 Mosaic of e2v amplifiers identified as instable (white color) in run E2136#
Further studies are required in order to converge on the best mitigation strategy for the start of the LSST survey.
Gain stability#
hello world.
This section describes gain stability.
No temp variation, fixed flux
no temp variation, variation in flux
Temp variation, fixed flux
Sensor features#
ITL Dips#
hello world.
This section describes ITL Dips.
Vampire pixels#
First observations#
Vampire pixels were first observed in ComCam observations [need more info to properly give context] - Andy’s study on Oct. 8 - Agnes masking effort
LSSTCam vampire pixel features#
The vampire pixels have distinct features, both on the individual defect level, and across the focal plane
Individual vampire features#
General size
Radial kernel
uniformity
Vampire features across the focal plane#
sensor type
static or dynamic
higher concentrations? Particularly bad sensors?
Current masking conditions#
Bright pixels
Dark pixels
Jim’s task
Analysis of flats#
LED effect
Intensity effect
Analysis of darks#
Previous LED effect
Intensity of LED effect
dark cadence and exposure times
Current models of vampires#
Tony & Craig model
Others?
Serial remnants#
hello world.
This section describes incomplete serial flush.
Background
Mitigation with sequencers
discussion of different clears
Phosphorescence#
hello world.
This section describes phosphorescence.
phosphorescence background
phosphorescence on flat fields
phosphorescence on spot projections
Observatory integration#
Shutter activity#
hello world.
This section describe shutter activity
Shutter test
Shutter profiles
shutter failures
OCS Integration#
hello world.
This section describes OCS Integration with LSSTCam.
OpSim with darks
OpSim with shutter control
OCS Mock calibrations#
hello world.
This section describes mock calibrations taken through OCS.
Calibration acquisition
DM processing
Chiller activity#
hello world.
This section describes failures with the L1 chiller.
History of chiller degradation starting in mid october
Catalogue of events over week of Nov. 9
solution (eventually…)
Conclusions#
Run 7 final operating parameters#
This section describes the conclusions of run 7 optimization and the operating conditions of the camera. Decisions regarding these parameters were decided based upon the results of the voltage optimization, sequencer optimization, and thermal optimization.
Voltage conditions#
Parameter |
E2V Quantity |
ITL Quantity |
|---|---|---|
pclkHigh |
2.0 |
3.3 |
pclkLow |
-6.0 |
-6.0 |
dpclk |
8.0 |
9.3 |
sclkHigh |
3.55 |
3.9 |
sclkLow |
-5.75 |
-5.4 |
rgHigh |
5.01 |
6.1 |
rgLow |
-4.99 |
-4.0 |
rd |
10.5 |
11.6 |
od |
22.3 |
23.4 |
og |
-3.75 |
-3.4 |
gd |
26.0 |
26.0 |
Sequencer conditions#
Detector type |
File name |
|---|---|
E2V |
FP_E2V_2s_l3cp_v30.seq |
ITL |
FP_ITL_2s_l3cp_v30.seq |
v30 sequencers are identical to the FP_ITL_2s_l3cp_v29_Noppp.seq and FP_E2V_2s_l3cp_v29_NopSf.seq. All sequencer files can be found in the github repository.
Other camera conditions#
Idle flush disabled
Record runs#
This section describes run 7 record runs.
All runs use our camera operating configuration, unless otherwise noted.
Run Type |
Run ID |
Links |
Notes |
|---|---|---|---|
B protocol |
E1880 |
||
E2233 |
Identical to E1880. Acquired after CCS subsystem reboot |
||
PTCs |
E1886 |
Red LED dense. Dark interleaving between flat pairs |
|
E1881 |
Red LED dense. No dark interleaving between flat pairs |
||
E748 |
nm960 dense |
||
E2237 |
Red LED dense. Acquired after CCS subsystem reboot. |
||
E2016 |
Super dense red LED. HV Bias off for R13/Reb2. jGroups meltdown interrupted acquisitions, restarted |
||
Long dark acquisitions |
E1117 |
||
E1116 |
|||
E1115 |
|||
E1114 |
|||
E1075 |
|||
Projector acquisitions |
E1558 |
Flat pairs, fine scan in flux from 1-100s in 1s intervals. E2V:v29_NoP, ITL:v29_NoPP |
|
E1553 |
Flat pairs, coarse scan in flux from 5-120s in 5s interval.E2V:v29_NoP, ITL:v29_NoPP |
||
E1586 |
One 100s flat exposure, spots moved to selected phosphorescent regions.E2V:v29_NoP, ITL:v29_NoPP |
||
E2181 |
Flat pairs from 2-60s in 2s intervals. Two 15s darks interleaved after flat acquisition. Rectangle on C10 amplifier.E2V:v29_NoP, ITL:v29_NoPP |
||
E2184 |
10 30s dark images to capture background pattern |
||
OpSim runs |
E1717 |
Long dark sequence, no filter changes |
|
E2330 |
Short dark sequence, filter changes in headers through OCS |
||
E1414 |
30 minutes OpSim run with shutter control, filter change, and realistic survey cadence |
||
E2328 |
Flats with shutter-controlled exposure |
||
E1657 |
10 hour OpSim dark run, ~50% of darks were acquired properly |
||
Phosphorescence datasets |
E2015 |
10 flats at 10ke- followed by 10x15s darks |
|
E2014 |
1 flat at 10ke- followed by 10x15s darks |
||
E2011 |
20 flats at 10ke- followed by 10x15s darks |
||
E2012 |
10 flats at 1ke- followed by 10x15 s darks |
||
E2013 |
10 flats at 10ke- followed by 10x15s darks. Interleaved biases with the darks |
||
Tree ring flats |
E1050 |
||
E1052 |
|||
E1053 |
|||
E1055 |
|||
E1056 |
|||
E1021 |
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E1023 |
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E1024 |
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E1025 |
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E1026 |
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Gain stability runs |
E1955 |
||
E2008 |
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E1968 |
|||
E1367 |
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E1362 |
|||
E756 |
|||
E1496 |
|||
Persistence datasets |
E1503 |
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E1504 |
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E1505 |
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E1506 |
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E2286 |
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E1502 |
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E1501 |
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E1500 |
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E1499 |
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E1498 |
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E1494 |
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E1493 |
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E1492 |
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E1490 |
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E1491 |
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E1489 |
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E1488 |
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E1487 |
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E1486 |
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E1485 |
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E1478 |
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E1477 |
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E1479 |
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E1483 |
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E1484 |
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Guider ROI acquisitions |
E1510 |
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E1518 |
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E1519 |
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E1508 |
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E1509 |
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E1520 |
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E1511 |
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E1521 |
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E1512 |
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E1513 |
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E1514 |
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E1517 |