Tunnel Junction Refrigerators Cooling From 300 mK to 112 mKwith Large Cooling Power
Galen O'NeilFor Peter Lowell(his knee )
NIST Boulder NIS TeamPeter LowellDan Schmidt
Jason UnderwoodJoel Ullom
NIS Refrigerator
Si
Al-MnAl-MnSiO2
AlAl(Al-Mn)Ox
Superconductor(Al)
Normal Metal (AlMn)
Junc
tion
Substrate (Si)
10 um
I
I
hot
hothot
hot
hot
cold
cold
More options for refrigeration below 300 mK
Dilution refrigeratorMost expensive10 mK
2-stage 3He
ADRModerate price50 mK
NIS refrigerator cooling detectors 100 mK
cheapest~ 300 mK
+
Previous State of the Art
hot
S N
A.M Clark, et al, Appl Phys Lett 86, 1734508 (2005)N.M. Miller, et al, Appl Phys Lett 92, 163501 (2008)
-NIS cooled X-Ray detector hasbest 6keV resolution with cryostat above 200mK:9.4 eV @ 6keV-Representative of a class sensors that operate near 100mK
230 mK
320 mK
160 mK
rest of chip = 260mK
cold
Tc=185mKDissipating 22 pW
How does it work?Vbias=.5Δ/e
eVbias
2
BCS DOS BCS DOSBCS DOS
Hot Electrons TunnelVbias=.9Δ/e
eVbias
2
BCS DOS BCS DOS
Normal Metal Cools - Superconductor HeatsVbias=.9Δ/e
eVbias
2
BCS DOS BCS DOS
Vbias=.9Δ/e
eVbias
2
BCS DOS BCS DOS
no bias on heatsinkjunction
Add a Heatsink (Quasiparticle Trap)
NIS Refrigerator Geometry
Si
Al-MnAl-Mn
SiO2
AlAl(Al-Mn)Ox
I
hot
hot
cold
Al-Mn
Old Thermal Model
normal metalelectrons
substrate/normal metalphonons (fixed at bath temperature)
superconductor(fixed at bathtemperature)
NIS Junction CoolingFunction of Tn
Electron-Phonon Coupling
IV Power
I2R
PayloadPower
Quasiparticle Return(Small Fraction of IV,Empirical)
New Thermal Model with Heatsink
normal metalelectrons
substrate/normal metalphonons (fixed at bath temperature)
superconductor(QP Density vsPosition)
NIS Junction CoolingFunction of Tn,Ts
Electron-Phonon Coupling
IV Power
I2R
normal metaltrap electrons(T vs Position)
Quasiparticle Trapping/(Heatsink)
Electron-Phonon Coupling
QuasiparticleRecombination
PayloadPower
Inside The Thermal Model
Si
Al-MnAl-MnSiO2
Al-Mn
x
Al
quasiparticle:
Si
Al-MnAl-MnSiO2
AlAl(Al-Mn)OxI
hot
hot
cold
Al-Mn
Predictions of Model
Previous 50nm
Target 25nm
Predictions of Model
Previous OverlayerOxide(no overlayer trap)
Target for overlayer10 m2
Si
Al-MnAl-MnSiO2
AlAl(Al-Mn)OxI
hot
hot
cold
Al-Mn
Measured Cooling to 112 mK
Record NIS Cooling(Large Junction)
T NIS=T ADR
Sat July 30 2010
2008
300 mK ↓
112 mK
Next Step:NIS Cooled Cryogenic Stage
•3mm chip -> 0.1uW @ 100 mK•10 uW dissipated at 300mK
NIS Junction Cooling Function of Tn