Tunnel Junction Refrigerators Cooling From 300 mK to 112 mK with Large Cooling Power

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Tunnel Junction Refrigerators Cooling From 300 mK
to 112 mKwith Large Cooling Power
Galen O'Neil For Peter Lowell (his knee ?)
NIST Boulder NIS Team Peter Lowell Dan
Schmidt Jason Underwood Joel Ullom
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NIS Refrigerator
hot
Al
Al
(Al-Mn)Ox
I
Substrate (Si)
cold
Al-Mn
Al-Mn
SiO2
10 um
hot
Si
hot
I
Junction
Superconductor (Al)
cold
Normal Metal (AlMn)
hot
hot
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More options for refrigeration below 300 mK
2-stage 3He
cheapest 300 mK

ADR Moderate price 50 mK
Dilution refrigerator Most expensive 10 mK
NIS refrigerator cooling detectors? 100 mK
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Previous State of the Art
320 mK
160 mK
Tc185mK Dissipating 22 pW
230 mK
rest of chip 260mK
-NIS cooled X-Ray detector has best 6keV
resolution with cryostat above 200mK 9.4 eV _at_
6keV -Representative of a class sensors that
operate near 100mK
N
S
cold
hot
A.M Clark, et al, Appl Phys Lett 86, 1734508
(2005)? N.M. Miller, et al, Appl Phys Lett 92,
163501 (2008)
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How does it work?
Vbias.5?/e
eVbias
BCS DOS
BCS DOS
BCS DOS
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Hot Electrons Tunnel
Vbias.9?/e
eVbias
BCS DOS
BCS DOS
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Normal Metal Cools - Superconductor Heats
Vbias.9?/e
eVbias
BCS DOS
BCS DOS
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Add a Heatsink (Quasiparticle Trap)
Vbias.9?/e
eVbias
no bias on heatsink junction
BCS DOS
BCS DOS
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NIS Refrigerator Geometry
Al-Mn
hot
Al
Al
(Al-Mn)Ox
I
cold
Al-Mn
Al-Mn
SiO2
hot
Si
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Old Thermal Model
IV Power
NIS Junction Cooling Function of Tn
I2R
normal metal electrons
superconductor (fixed at bath temperature)
Payload Power
Quasiparticle Return(Small Fraction of
IV, Empirical)
Electron-Phonon Coupling
substrate/normal metal phonons (fixed at bath
temperature)
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New Thermal Model with Heatsink
IV Power
NIS Junction Cooling Function of Tn,Ts
Quasiparticle Trapping/ (Heatsink)
I2R
normal metal electrons
superconductor (QP Density vs Position)
normal metal trap electrons (T vs Position)
Payload Power
Electron-Phonon Coupling
Electron-Phonon Coupling
Quasiparticle Recombination
substrate/normal metal phonons (fixed at bath
temperature)
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Inside The Thermal Model
x
Al-Mn
Al
Al-Mn
Al-Mn
SiO2
Si
quasiparticle
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Predictions of Model
Previous 50nm
Target 25nm
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Predictions of Model
Previous Overlayer Oxide (no overlayer trap)
Target for overlayer 10 Wmm2
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Measured Cooling to 112 mK
Record NIS Cooling (Large Junction)
2008
TNISTADR
Sat July 30 2010
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Next StepNIS Cooled Cryogenic Stage

• 3mm chip -gt 0.1uW _at_ 100 mK
• 10 uW dissipated at 300mK

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• NIS Junction Cooling
• Function of Tn

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