Scientific DetectorWorkshop, 2005 Taormina

Characterization of 1.7um cutoff detectors for SNAP

Roger Smith

Caltech

SuperNova / Acceleration ProbeA 2m class wide field survey telescope in L2 orbit…

…will use supernovae and gravitational lensing to begin to unravel the mysteries of Dark Energy and Dark Matter.

SuperNova / Acceleration Probe

Precision photometery … <2% error, including systematics

No cryogens

Mixed CCD and NIR focal plane• 36 x 2Kx2K NIR arrays

• 1.7um cutoff

• Radiative cooling to 120-140K

• 3 NIR bandpasses

• Fixed filters

• 18-20um pixels under-sample diffraction profile

Caltech U.Michigan IDTL JPL GSFC

560mm diameter

36 NIR Detectors 3 bandpasses

Guiders (4)

36 CCDs, 6

bandpasses

Spectrograph slit

QE

SNAP Spec.

Without AR Coating

Substrate removed with 1.7um AR coat

RSC

RSC WFC3-094 SUBSTRATE REMOVED (DCL)

Smaller telescope, cheaper mission

Intra-Pixel Response[Total signal from 5um spot, vs. position]

Raytheon Rockwell HgCdTe

Dark Current vs TDARK CURRENT

for various 1.7um cut-off detectors

0.01

0.1

1

10

100

80 90 100 110 120 130 140 150 160 170 180 190 200

Temperature (K)

e- / s

ec /

pix

el

RVS-HgCdTe 141

RVS-HgCdTe 09A

RVS-InGaAs

RSC-HgCdTe 038

RSC-HgCdTe 039

RSC-HgCdTe 040

RSC-InGaAs

.

GOAL

REQUIREMENT

CDS noiseCDS noise vs Temperature

0

10

20

30

40

50

60

80 100 120 140 160 180 200 220

Temperature (K)

Re

ad

no

ise

(e

-)

RSC HgCdTe-038 Temporal 1s

RSC-HgCdT Spatial 1s

RSC HgCdTe Temporal 300s

RSC HgCdTe Spatial 300s

RSC InGaAs Temporal 1s

RVS HgCdTe Temporal 1s

Fowler Sampled noise (spatial)Noise vs Sampling Depth

1

10

100

1 10 100# fowler pairs

No

ise

(e-)

CDS/sqrt(N)

RVS InGaAs 140K

RVS InGaAs 100K

RSC HgCdTe-038 140K

RSC HgCdTe-038 100K

RVS 1K HgCdTe-141 - 100K

GOAL

REQUIREMENT

Cosmic Rays

Raytheon HgCdTe Single 1000s dark (CDS)

Rockwell HgCdTe Difference of 1000s darks

Fowler 32, 80K

Best efforts so far…At 140K…. Rockwell

HgCdTeRaytheon HgCdTe

Rockwell+SU InGaAs

Raytheon+SU InGaAs

QE (no AR coat) 60-80%, substrate removed

80%, flat substrate on

75-85%, cutoff shorter at low T

Intrapixel response(p-p, 2.3um spot)

20% <2% <2%

Dark current (e-/s) 0.07 0.25* 3

Diffuse Cosmic Rays ? Yes substrate on

Yes substrate on

CDS Noise (e-), 140K 33 16 36 89

Fowler16 noise, (e-) min.exp, 100K

7.6 6.6 30

RTS Noise in mux ? Yes No

Rad hardness (mux) Excellent TBD soon

* Manufacturer’s measurement