HAWAII2RG 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
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,
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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
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.