Page 1 Science Payload and Advanced Concepts Office STJs as Photon Detectors.
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Transcript of Page 1 Science Payload and Advanced Concepts Office STJs as Photon Detectors.
Page 1 Science Payload and Advanced Concepts Office
STJs as Photon DetectorsSTJs as Photon Detectors
Page 2 Science Payload and Advanced Concepts Office
STJs: principle of operationSTJs: principle of operation
• photon with energy E breaks Cooper pairs quasiparticles
for Ta: ~0.7 meV N0 ~ 850 / eV
• multiple tunneling detected charge:
• resolving power limited by statistics of QP generation and tunneling:
Ta: E ~ 2.0 eV @ E=500eV
Additional resolution degradation:- electronics noise, infrared background- non-uniform detector response
Δ1.7E(E)
0N
(E)0
Nn N(E)tunnel
τloss
τn
n11F1.7EΔ2.355TδE
Page 3 Science Payload and Advanced Concepts Office
STJs: energy resolving powerSTJs: energy resolving power
10
100
1000
10000
1 10 100 1000 10000
photon energy (eV)
reso
lvin
g p
ow
er
20x100 micron Ta DROID
25x25 micron Ta STJfrom 6x6 array
50x50 micron Ta/Al STJ
Hf
Mo
Ta
Nb
Tc (K) gap (meV)Nb 9.2 1.55Ta 4.5 0.67Mo 0.92 0.14Hf 0.13 ~0.02
Page 4 Science Payload and Advanced Concepts Office
Ta-based STJs (for UV/visible)Ta-based STJs (for UV/visible)
• Ta layers: 100 nmBase: epitaxial (RRR~45)
• Al layers: 30 nm
• Nb wiring (QP out diffusion)
• AlOx barrier: ~1 nm tunnel time ~ 0.5-1 s low leakage: <0.1 pA/m2
• detector area: 10x10 - 100x100 m2
Al
Ta
Ta
Sapphire substrate
SiOx
Nb
Back-illumination
Front-illumination
Page 5 Science Payload and Advanced Concepts Office
S-Cam 3 Detector: 10x12 Ta/Al S-Cam 3 Detector: 10x12 Ta/Al STJsSTJs
371
m =
8.9
”
446m =
10.7”
S-Cam 3: 10x12 pixels ; 33x33 m2 FOV = 9x11 arcsec
top electrodecontact wires
25x25 m2
STJ
commonreturnwire
a)
170m = 4”
170m =
4”
S-Cam 2:
Page 6 Science Payload and Advanced Concepts Office
S-Cam 3 Detector S-Cam 3 Detector 120 pixels120 pixels
ALL subgap currents ~100 pA low noise operation
Uniform responsivity across array
Fiske modesResidual Jc
Bias region
Page 7 Science Payload and Advanced Concepts Office
S-Cam 3 image (9”x11”)S-Cam 3 image (9”x11”)
Page 8 Science Payload and Advanced Concepts Office
S-Cam 6: improved spectral resolutionS-Cam 6: improved spectral resolutionAluminium STJs:
• Tc=1.2K T<100mK (ADR)
• expected resolution 2x better than Ta
• Measured resolution ~ Ta
(mechanism and solution
under investigation)
Next step:
molybdenum STJs:
• Tc=0.9K
• better efficiency than Al
Page 9 Science Payload and Advanced Concepts Office
Distributed Read Out Imaging Devices Distributed Read Out Imaging Devices (DROIDs)(DROIDs)
absorber with 2 STJs for readout:
• Position sensitivity: S1 - S2• Photon energy: S1 + S2
sapphire substrate
SiOx
Al (65 nm) AlOx
Nb contacts
Ta top electrode
200 m50 m
- - -- - - - - - - Ta absorber
Page 10 Science Payload and Advanced Concepts Office
100x20 m2 absorber with 20x20 m2 STJs
E=2.4 eV (FWHM) at E=500 eV
DROIDs as X-ray detectorsDROIDs as X-ray detectors
Page 11 Science Payload and Advanced Concepts Office
100x100 m2 absorber
with 20x20 m2 STJs
2D DROIDs as X-ray detectors2D DROIDs as X-ray detectors
10 keV diffraction pattern
from 5 m pinhole
with 2-D DROID
Page 12 Science Payload and Advanced Concepts Office
Detection efficiency for 500nm thick Detection efficiency for 500nm thick DROIDsDROIDs
0
0.2
0.4
0.6
0.8
1
10 100 1000 10000photon energy (eV)
eff
icie
nc
y
Ta
Mo
Page 13 Science Payload and Advanced Concepts Office
Possible detector layout for NFI1 on XEUSPossible detector layout for NFI1 on XEUSArray of DROIDs
0.5x1.7 arcmin
FL=30m 4.4x15mm
750x75 micron DROIDs 6x200 DROIDs
1.7’ = 15mm = 200 DROIDs
0.5’ = 4.4mm
= 6 DROIDs
Page 14 Science Payload and Advanced Concepts Office
Latest Ta/Al STJs for opticalLatest Ta/Al STJs for optical
• Ta layers: 100 nmBase: epitaxial (RRR~30)
• Al layers: 30 nm
• Nb wiring (QP out diffusion)
• AlOx barrier: ~1 nm tunnel time ~ 0.5-1 s low leakage: <0.1 pA/m2
• detector area: 10x10 - 100x100 m2
Page 15 Science Payload and Advanced Concepts Office
Latest Ta/Al STJs for opticalLatest Ta/Al STJs for optical
0 1 2 3 4
IR ~2 micron
lambda=500nm R~23
30x30 micron
Page 16 Science Payload and Advanced Concepts Office
Latest Ta/Al STJs for optical: resolving Latest Ta/Al STJs for optical: resolving powerpower
MUL169.D3 #6 (30x30) FIR=9.0kHz, w=0.85
0
5
10
15
20
25
30
35
40
0.0 1.0 2.0 3.0 4.0 5.0 6.0
Photon Energy (eV)
Re
so
lvin
g P
ow
er
bulk Ta 0.70meV, G=1
Ta 0.50meV, G=0.45
Ta 0.50meV, G=1
Ta 0.50meV, G=0 (Fano)