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LTD 10, July 7, 2003, GenoaDay et al.
Peter Day, Rick LeDucJet Propulsion Laboratory
Ben Mazin, Tasos Vayonakis, Peter Mason, Jonas Zmuidzinas
Caltech
Microwave Kinetic Inductance Detectors (MKIDs): Background and First Results on Photon Detection
CALTECH
LTD 10, July 7, 2003, GenoaDay et al.
Superconducting Kinetic Inductance DetectorsSQUID readout :
McDonald and Sauvageau (IEEE Trans. Magn. 25, 1331 (1989)).
Near Tc operation.
Grossman, McDonald and Sauvageau (IEEE Trans. Magn. 27, 2677 (1991)).
Equilibrium and non-equilibrium response.
Bluzer (PRB 44, 10222 (1991), JAP 78, 7340 (1995)).
Sergeev and Rizer (Int. J Mod. Phys. 10, 635 (1996)); Sergeev, Mitin and Karasik (APL 80, 817 (2002)).
Advantages of T<<Tc operation
Microwave readout :
VanVechten et. al. (Nucl. Instrum. Meth. A370, 34 (1996)).
Non-resonant, transmission loss
LTD 10, July 7, 2003, GenoaDay et al.
Pair-Breaking Detectors
• Finite gap energy
–Quasiparticle lifetime tqp ~ 1/nqp 10-6 – 10-3 sec–Thermal quasiparticle density scales as nqp ~ exp(- D /kT)
–Fundamental sensitivity set by quasiparticle generation-recombination noise, scales as (nqp / tqp)1/2 ~ exp(- D/kT)
LTD 10, July 7, 2003, GenoaDay et al.
• For AC currents:• Accelerative response of supercurrent: • Allows kinetic energy storage in supercurrent• B penetrates a distance l into the surface
! magnetic energy storage.• “kinetic inductance” effect: surface inductance Ls= m0l
• Surface impedance Zs = Rs + i Xs = Rs + iwLs
• Xs >> Rs, for T << Tc
Kinetic Inductance and Surface Impedance
EtJS
rr=∂∂Λ
LTD 10, July 7, 2003, GenoaDay et al.
Surface Impedance vs. Quasiparticle Density
" δXs , Rs, nqp all decrease exponentially with temperatures" δXs , Rs have nearly constant response to changes in nqp
(in a
lum
inum
)
LTD 10, July 7, 2003, GenoaDay et al.
Measurement of Surface Impedance with a Microwave Resonator
λ/4
sLsLf
QsLsL
IK
clcf
totk
kgeomtot
/
/f/ffraction) ..(/
)(,/4
0
21
0
2/10
δαθδ
δαδα
=
−=
≡
+=== −
LLLLL
LC
• Quarter wave resonator• resonance ‘dip’
• Response scales with Q
LTD 10, July 7, 2003, GenoaDay et al.
Multiplexing
Frequency domain muliplexing
Excite with a ‘comb’Can use single cryogenic amplifierMultiplexing factor
determined by Q, cross talk, lithographic precision
See talk Y02-
-
-
-
LTD 10, July 7, 2003, GenoaDay et al.
A Test DeviceCPW 0.2mm aluminum on sapphireL = 3mm ! 10 GHzQ = 55,000; a = 0.04; V=2000mm3
LTD 10, July 7, 2003, GenoaDay et al.
Rough Estimate of Responsivity
550
3
0
102/1103~/||
meV171.0,m2000,04.0
/2
/||
/~/ 0
−− ×=>×→
≈∆=≈
=
∆
Qff
VsLsLff
NnsLsLqp
δ
µα
δαδ
δδ
For a 5.9 keV photon
• Large frequency shifts expected
LTD 10, July 7, 2003, GenoaDay et al.
Readout Circuit
MIXER 90 HYBRID AMPLIFIER
LTD 10, July 7, 2003, GenoaDay et al.
X-Ray Events
6 keV, 55Fe source
LTD 10, July 7, 2003, GenoaDay et al.
I-Q trajectory
θ
40mK 216 243
268
297
LTD 10, July 7, 2003, GenoaDay et al.
Decay Times
LTD 10, July 7, 2003, GenoaDay et al.
Decay Times
LTD 10, July 7, 2003, GenoaDay et al.
0 5 10 15 200
20
40
60
80
100
120
140
160
Number of thermal quasiparticles (millions)
phas
e ch
ange
(rad
ians
)
‘Thermal’ Calibration of Responsivity• Measure response to temperature changes• thermally excited quasiparticles
LTD 10, July 7, 2003, GenoaDay et al.
Noise Measurements• Amplifer noise can be measured off resonance• On resonance noise exceeds the readout noise
LTD 10, July 7, 2003, GenoaDay et al.
Noise Measurements
eV11~)(
4355.22/1
02FWHM
−∞
=∆ ∫ ω
ωd
NEPE
total
amplifer
G-R
oscillator
)1()()(NEP 20
2
2
qp
02 τωθητωω θ +
∂∂
∆=
−
NS
LTD 10, July 7, 2003, GenoaDay et al.
Coupling
• Use absorbers with higher D• Quasiparticle diffusion / trapping
• Antenna coupling
LTD 10, July 7, 2003, GenoaDay et al.
Ultimate Sensitivity
NEP
(W/ H
z1/2 ) D
E FWH
M(eV
)
aQ / V (mm-3)
• Assume amplifier limited noise (with TN = 5K)• Assume readout power scales inversely with aQ / V
LTD 10, July 7, 2003, GenoaDay et al.
Conclusions
• MKIDs appear to be very interesting for large-format detector arrays (103-104 pixels, or larger ?)
• Basic detector physics has been demonstrated• Observed single-photon X-ray pulses with high SNR• Much work remains to be done !
