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HAWAII-2RG NOISE SNAP Collaboration Meeting

HAWAII-2RG NOISE SNAP Collaboration Meeting. M.Bonati, D.Guzman, R.Smith Caltech. The questions. Requirement / Goal = 8e- / 5e- @ fowler ~16. Is detector material limiting noise performance?

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HAWAII-2RG NOISE SNAP Collaboration Meeting

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  1. HAWAII-2RG NOISESNAP Collaboration Meeting M.Bonati, D.Guzman, R.Smith Caltech

  2. The questions Requirement / Goal = 8e- / 5e- @ fowler ~16 • 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? ...yes …both …CDS too high

  3. 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.

  4. How do we know detector material limits noise performance? • Image pixel noise >> bare mux, ref pixels • Dependence on T, not seen in ref pixels. • Excess noise goes away when reset switch is closed.

  5. Temporal noise map showsreference pixels are much quieter than image • Need >400 samples to see intrinsic width of histogram

  6. Temporal Noise Histograms vs. T

  7. Fowler Noise at 140K Excess noise goes away when reset switch is closed.

  8. Is it just the temperature?

  9. 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.

  10. 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.

  11. Average of all channels is quite linear but individual channels sho considerable scatter. ….Drifts? ….Cosmic ray hits? Sample Up the Ramp

  12. Movie 115K Hot pixels frozen out 140K lots of hot pixels Many diffuse cosmic ray hits Dark images vs T

  13. Movie Cosmic Rays ? • Difference of successive 300s dark images • 100K • Fowler 32 Some are very diffuse

  14. Movie Long darks show flat field pattern Dark Flat

  15. e-/ADU vs T 4% rise from 85 to140K Inverse Gain

  16. Bare mux performance ….Not currently a limitation.

  17. Bare mux 006, ch 1, optimum biasesCDS noise (ADU) PREVIOUS RESULTS gain = 1.1 to 1.4 e-/ADU

  18. Rload OutputDrain VddA = BP eliminates body effect, but… …. VddA still acts like phantom gate connection here so VddA=BP increases net effect of VddA drift. 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

  19. 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. BP=3.3V, BG=2.4V, VR=0.6,

  20. 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. BP=3.3V, BG=2.4V, VR=0.6 Drift reduced by shield installation? …less convection around JFET currrent source?

  21. 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.

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