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

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