1. 1 Ultra low background characterization of Rockwell Scientific MBE HgCdTe arrays Donald N. B. Hall, University of Hawaii, Institute for Astronomy, Honolulu, Hawaii

2. 2 OUTLINE CHARACTERIZATION OF DARK CURRENT AND TOTAL NOISE IN 2Kx2K HAWAII-2RG ARRAYS UNDER JWST CONDITIONS MERITS OF SPATIAL vs TEMPORAL AVERAGING DATA CUBE FOR TEMPORAL AVERAGING TEMPERATURE DRIFT COMPENSATION

3. 3 TEST CONDITIONS MATCHED TO JWST FOUR OUTPUTS READING OUT 512 x 2048 PIXEL “STRIPES” 100 Kpxl/sec SAMPLE RATE 12 SECOND FRAME RATE 3DB NOISE BANDWIDTH FILTERED AT 160 KHz 10 TAU, > 14 BIT SETTLING PIXEL BY PIXEL RESET AT 100 Kpxl/sec OPERATING TEMPERATURE 37.000K +- <1mK ARRAY ALWAYS BEING READ OUT OR RESET DETBIAS 250 mV – Vreset 100 mV, DSUB 350 mV

4. 4 H2RG mounted to KSPEC detector module ASIC mounting socket

5. 5 4Kx4K DETECTOR MOSAIC

6. 6 NOISE MEASURD BY SPATIAL AVERAGING UH TESTING REPORTED AT MUNICH 2000 SPIE GENERATE FRAME PAIRS USING A STANDARD PROCEDURE SUBTRACT AND COMPUTE TOTAL NOISE (VARIANCE) IN DIFFERENCE FRAME TEST DATA SET CURRENTLY FIVE RAMPS, EACH CONSISTING OF TWO PIXEL BY PIXEL RESETS FOLLOWED BY 145 FRAMES CORRESPONDING FRAMES IN AJACENT RAMPS ARE DIFFERENCED TO COMPUTE TOTAL NOISE

7. 7 FEATURES OF UH SPATIAL TEST PROCEDURE SIMPLE COMPUTATION OF STRIPE AVERAGED TOTAL NOISE THE DISADVANTAGE IS THAT THERE IS NO INFORMATION ABOUT TOTAL NOISE IN INDIVIDUAL PIXELS CORRECTION WITH THE HORIZONTAL ROWS OF REFERENCE PIXELS PROVIDES SENSITIVE MEASUREMENT OF DARK CURRENT FOR INDIVIDUAL PIXELS TOTAL NOISE IS DOMINATED BY READ NOISE – DARK CURRENT CONTRIBUTION NEGLIGIBLE

8. 8 DARK CURRENT vs TEMPERATURE FOR 2.5 AND 5 UM MATERIAL

9. 9 Id0 = 0.0003 Id1 = 0.0007 Id2 = 0.0012 Id3 = 0.0009 Id4 = -0.0003 JWST- 002 at 37.00K Feb. 9, 2005 darkramp-145 x 12 sec

10. 10 Id = 0.00057 JWST- 002 at 37.00K Feb. 9, 2005 darkramp-145 x 12 sec

11. 11 TOTAL NOISE AND DARK CURRENT MEASURED BY TEMPORAL AVERAGING THE DATA SET CONSISTS OF 36 RAMPS, EACH A PAIR OF PIXEL BY PIXEL RESETS FOLLOWED BY 145 FRAMES AT 12 SECOND INTERVALS DATA CUBES 36 DEEP ARE GENERATED FOR FRAME TIME DIFFERENCES OF 384, 768 AND 1152 SECONDS AND AVERAGES OF 1, 2, 4, 8, 16 AND 32 FRAMES. ALSO RAUSCHER SLOPE FIT IN EACH OF THESE CUBES THE DC VALUES ARE USED TO DERIVE DARK CURRENT AND THE STANDARD DEVIATION OF TOTAL CHARGE TO DERIVE TOTAL NOISE FOR EVERY PIXEL COSMIC RAY CORRECTION BEING REFINED

12. 12 CDS TOTAL NOISE FOR 2.5 UM MATERIAL

13. 13 CDS TOTAL NOISE FOR 2.5 UM MATERIAL

14. 14 DARK CURRENT HISTOGRAMS for JWST-002 2.5 um 1-1 SCA at 768 seconds

15. 15 TOTAL NOISE HISTOGRAMS for JWST-002 2.5 um 1-1 SCA at 768 seconds

16. 16 1-1 CDS READ NOISE

17. 17 1-1 TOTAL NOISE for 786 seconds SIGNAL ARRAYS VERTICAL REFERENCE ARRAYS

18. 18 CONCLUSIONS FROM 1-1 CDS SPATIAL AND TEMPORAL AVERAGING METHODS SHOW GOOD AGREEMENT FOR ARRAY AVERAGES NOISE IN VERTICAL REFERENCE PIXELS AND ADJACENT SIGNAL COLUMNS IS ONLY SLIGHTLY REDUCED SHOT NOISE IN THE DARK CURRENT IS A NEGLIGIBLE COMPONENT OF TOTAL NOISE MEASUREMENTS OF SYSTEM NOISE SHOW IT TO BE A NEGLIGIBLE CONTRIBUTION

19. 19 DARK CURRENT HISTOGRAMS for JWST-002 2.5 um 8-8 SCA at 768 seconds

20. 20 TOTAL NOISE HISTOGRAMS for JWST-002 2.5 um 8-8 SCA at 768 seconds

21. 21 8-8 CDS READ NOISE

22. 22 8-8 TOTAL NOISE for 786 seconds SIGNAL ARRAYS VERTICAL REFERENCE ARRAYS

23. 23 8-8 AVERAGE MEASUREMENTS AT ~ 5.2 RMS e-, TOTAL 8–8 CDS OF MEETS NIRSPEC REQUIREMENT FOR BOTH DARK CURRENT AND TOTAL NOISE, SPATIAL AND TEMPORAL MEASUREMENTS ARE IN GOOD AGREEMENT TOTAL NOISE IN REFERENCE PIXELS AND AJACENT PIXELS IS ONLY SLIGHTLY LOWER THAN IN THE FULL BODY OF THE ARRAY

24. 24 DARK CURRENT HISTOGRAMS for JWST-002 2.5 um 32-32 SCA at 768 seconds

25. 25 TOTAL NOISE HISTOGRAMS for JWST-002 2.5 um 32-32 SCA at 768 seconds

26. 26 H2RG-NIRCam-002-BernieMean-1008sec

27. 27 H2RG-NIRCam-002-BernieSig-1008sec

28. 28 CONCLUSIONS REGARDING 32-32 AND SLOPE 32 – 32 AVERAGED CDS IS WELL MATCHED TO THE OPTIMUM 1/3 RAMP AVERAGING OVER A RAMP OF 88 SAMPLES EMPIRICALLY THE 32 – 32 CDS TECHNIQUE GIVES A SIGNIFICANT GAIN IN TOTAL NOISE ( 3.35 rms e- vs 4.87 rms e-) OVER SLOPE DETERMINATION

29. 29 HAWAII-2RG TEMPERATURE SENSITIVITY AT 37 K IN ALL UH TESTS, THE TEMPERATURE OF THE DETECTOR WAS HELD CONSTANT TO <+- 1 Mk NIRCAM NEEDS TO SPECIFY THE ACCURACY TO WHICH TEMPERATURE MUST BE HELD (+- 50 Mk GOAL)TO MEET REQUIREMENTS THE REF PIXELS FULLY COMPENSATE SUPPLY AND SIGNAL CHAIN VOLTAGE CHANGES dV/dT IS LARGE (800 e-/K), THE REF PIXEL dV/Dt IS DIFFERENT TO THAT OF THE SIGNAL PIXELS AND VARIES MARKEDLY ACROSS THE ARRAY THE COEFFICIENT IS LINEAR FOR EACH PIXEL

30. 30 KPEC Temperature Stability

31. 31 ULBcam Temperature Stability

32. 32 Temperature Stability of 36 Ramp Data Cube

33. 33 THERMAL PROFILE of TEMPERATURE DRIFT TEST

34. 34 100mK UP RAMP (36.95K to 37.05K)

35. 35 100mK UP RAMP (36.95K to 37.05K)

36. 36 CDS of 100mK UP RAMP (36.95K to 37.05K) Logarithmic Linear

37. 37 100mK DOWN RAMP (37.05K to 36.95K)

38. 38 100mK DOWN RAMP (37.05K to 36.95K)

39. 39 CDS of 100mK DOWN RAMP (37.05K to 36.95K) Logarithmic Linear

40. 40 TEMPERATURE DRIFT CORRECTION (TDC) TEMPLATE CREATE A TEMPLATE BY FORMING 128 CDS FRAMES BY SUBTRACTING FRAMES AT 36.4K FROM CORRESPONDING FRAMES AT 37.6K REF PIXEL CORRECT EACH AND CO-ADD TO FORM THE TDC TEMPLATE. MEASURE THE TEMPERATURE OF EACH FRAME IN AN OBSERVATION SCALE THE TEMPLATE TO THE ΔT FROM 37K AND SUBTRACT FROM THE REF PIXEL CORRECTED OBSERVED FRAME

41. 41 THERMAL PROFILE of TEMPERATURE DRIFT CORRECTION

42. 42 H2RG-NIRCam4-UP-Template

43. 43 H2RG-NIRCam4-DOWN-Template

44. 44 H2RG-NIRCam4- UP T36.95 to 37.05K-corrected-Template

45. 45 H2RG-NIRCam4-UP T36.95 to T37.05K -Template corrected

46. 46 CDS of 100mK UP RAMP (36.95K to 37.05K) Logarithmic Linear

47. 47 CDS of 100mK UP RAMP (36.95K to 37.05K) Temperature Drift Compensated Logarithmic Linear

48. 48 H2RG-NIRCam4-DOWNT37.05 toT36.95K-Template-corrected

49. 49 H2RG-NIRCam4-DOWN T37.05 to T36.95K template corrected

50. 50 CDS of 100mK DOWN RAMP (37.05K to 36.95K) Logarithmic Linear

51. 51 CDS of 100mK DOWN RAMP (37.05K to 36.95K) Temperature Drift Compensated Logarithmic Linear

52. 52 CONCLUSIONS SPATIAL AND TEMPORAL AVERAGING ARE IN GOOD AGREEMENT REGARDING PIXEL DARK CURRENT AND FRAME AVERAGED TOTAL NOISE TEMPORAL AVERAGING DATA CUBE ALLOWS DETERMINATION OF TOTAL NOISE PER PIXEL TOTAL 8 – 8 NOISE OF <6 RMS e- MEETS SPEC AT ~ 0.001 e-/sec, DARK CURRENT IS NEGLIGIBLE NOISE SOURCE TEMPLATE APPROACH CORRECTS 90% THERMAL DRIFT – 0.8 e-/Mk TO 0.08 e-/mK