HAWAII-2RG NOISE SNAP Collaboration Meeting

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HAWAII-2RG NOISESNAP Collaboration Meeting

• M.Bonati, D.Guzman, R.Smith
• Caltech

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The questions
Requirement / Goal 8e- / 5e- _at_ fowler 16
...yes

• Is detector material limiting noise performance?
• Is this a property of the 1.7 ?m cutoff
  material/process, or the higher operating
  temperature?
• Is the problem with the noise floor or the
  starting CDS noise?

both
CDS too high
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Confusing effects

• Is detector noise floor masked by dark current,
  mux glow, or particle hits?
• Is mux degrading detector noise?
• Is controller degrading mux noise?

particle hits in substrate are a concern.
not now. RTS may intrude later.
slightly. Upgradeable, but not urgent.
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How do we know detector material limits noise
performance?

• Image pixel noise gtgt bare mux, ref pixels
• Dependence on T, not seen in ref pixels.
• Excess noise goes away when reset switch is
  closed.

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Temporal noise map showsreference pixels are
much quieter than image

• Need gt400 samples to see intrinsic width of
  histogram

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Temporal Noise Histograms vs. T
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Fowler Noise at 140K

• Excess noise goes away when reset switch is
  closed.

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Is it just the temperature?
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• At 77K CDS noise is still much higher than for
  2.5?m HgCdTe.
• True fowler limit may be due to mux glow, dark
  current, drift or Cosmic Rays.

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Dark current vs. Temperature

• Modal dark current is negligible.
• 0.2e-/read mux glow has small effect at Fowler
  64.

Dewar showed no light leak previously, but this
has not been tested recently.
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Sample Up the Ramp

• Average of all channels is quite linear but
  individual channels sho considerable scatter.
• .Drifts?
• .Cosmic ray hits?

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Dark images vs T
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Cosmic Rays ?

• Difference of successive 300s dark images
• 100K
• Fowler 32

Some are very diffuse
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Long darks show flat field pattern
Dark
Flat
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e-/ADU vs T
Inverse Gain

• 4 rise from 85 to140K

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Bare mux performance

• .Not currently a limitation.

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Bare mux 006, ch 1, optimum biasesCDS noise (ADU)
PREVIOUS RESULTS
Reset mode Image pixels spatial temporal Image pixels spatial temporal Reference pixels spatial temporal Reference pixels spatial temporal
Line, Pulsed 16.8 7.2
Global 10.1 11.8 6.3 8.8
Global dummy before reset 10.2 6.8
Global dummy after reset 9.7 6.2
Line, Continuous 5.8 6.8 5.8 6.8
gain 1.1 to 1.4 e-/ADU
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(No Transcript)
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To reduce bias sensitivity
Vload
BiasPower
BG tracks BP so bias current constant. Can use
32 ch readout
VddA
375?
BiasGate
Vo
Vishay J508 2.4mA, 700K?, 0.05/C
Vreset
Col Sel
Row Sel
RG
Column bus
Ci
CellDrain
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Bare mux029 -- CDS noise
Noise in ADU, gain 1.1 to 1.4
e-/ADU Continuous line reset, all pixels on ch
1, 1 sec/read. BP3.3V, BG2.4V, VR0.6,
Configuration Spatial noise min.exp 300s Spatial noise min.exp 300s Temporal (mode) min.exp 300s Temporal (mode) min.exp 300s
?BG ?BP VddA BP 5.2 5.7 6.0
?BG ?BP Independent VddA 5.25 5.6
ANU bias board ?BG?BP, VddABP 5.8 6.0 5.4
ANU bias board Separate BP, BG, VddA 6.4 7.1 5.9 6.1
Mux030, SDSU biases, ?BG?BP, 4.9 5.0 4.6
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DRIFTS in CDS frames
RMS variation of mean in ADU. gain 1.1 to 1.4
e-/ADU Continuous line reset, all pixels on ch
1, 1 sec/read. BP3.3V, BG2.4V, VR0.6
Configuration Drift (ADU) RMS of means for 200 frames Min.exp 300s Drift (ADU) RMS of means for 200 frames Min.exp 300s
SDSU biases ?BG?BP, VddABP 4.3 36
ANU bias board ?BG?BP, VddABP 1.4 16
ANU bias board Separate BP, BG, VddA 0.9 1.6
Mux030, SDSU biases, ?BG?BP, 1.5 4.9
Drift reduced by shield installation? less
convection around JFET currrent source?
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ANU bias loopback tests

• ANU drift and noise are dominated by the Leach 8
  channel video board drift and noise, so they are
  indeed very good.
• We plan to improve the drift of the Leach board
  by a factor of two by a component change, and
  will then remeasure.