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Quantum Efficiency Measurements of a NIRSpec infrared sensor in the ODL*
Peter McCullough, Project P. I.
Mike Regan, ODL Lead
Kevin Lindsay
Eddie Bergeron
Thanks to Bernie Rauscher and Don Figer, et al.
Presented to TIPS at STScI
by McCullough
Mar 15, 2007
*ODL = Operations Detector Lab at STScI and JHU
See JWST-STScI-001053 for details.
Monochromator
Lockin and cable for PbSe diode
Lamp
Optical Coupling
Blackbody
R
8
Image of Blackbody
•Blackbody
•Window
•Filter
•Pinhole
•Detector
•Dewar
Simple Predictable
Contours are in counts (ADUs)
Insert Integrating Sphere to make flat fields
Flat Field 4.5 um
(Subsampled to 512x512)
White: QE=1.05
Black: QE<0.85
Bad pixels: << 1% by number
Corners have low QE
Reference pixels visible as black edges
Flat Field 3.9 um
(Subsampled to 512x512)
White: QE=1.05
Black: QE<0.85
Bad pixels: << 1% by number
Corners have low QE
Reference pixels visible as black edges
(Same caption as previous slide, just different wavelength).
Gain requires accurate nonlinearity correction
0.8 um photons give differentgain than 1.8 um photons.Interpreted as due to a quantumyield. Analysis in preparation.
Wavelength (um)0.8 2.7
Gain versus wavelength and binning
1
2345
Bin factor
1
2
0
Apparent Gain depends on binning, due to interpixel
capacitance.
(circuit diagram from Finger et al. 2005)
1-4z
z
z z
z
0
00
0
Summary• Rockwell (Teledyne) 2kx2k sensor H2RG-S010 tested in Operations Detector Lab at STScI.
• Median QE = 95% within 5% (1 sigma) at tested wavelengths (3.38, 3.9, 4.5 microns).
• Interpixel capacitance (IPC) is significant and blurs images due to the 2.5% crosstalk to each of the 4 nearest-neighbor pixels. Neglecting this crosstalk would cause the QE to be overestimated by 2*4*2.5% = 20%. This is apparently typical for epoxy-filled H2RG devices.
• New analysis (binning method) invented to account for IPC in measurement of system gain; alternative to autocorrelation method previously used. Intuitive and more resistant to EMI.
• Analysis of measurements from 0.5 to 6.0 um in preparation.
JWS
T-S
TS
cI-0
0105
3