Tunnel Junction Refrigerators Cooling From 300 m K
- Slides: 18
Tunnel Junction Refrigerators Cooling From 300 m. K to 112 m. K with Large Cooling Power Galen O'Neil For Peter Lowell (his knee ) NIST Boulder NIS Team Peter Lowell Dan Schmidt Jason Underwood Joel Ullom
NIS Refrigerator (Al-Mn)Ox Al Al hot I Substrate (Si) cold 10 um hot Superconductor (Al) hot Junction hot I cold Normal Metal (Al. Mn) hot Al-Mn Si. O 2 Si
More options for refrigeration below 300 m. K 2 -stage 3 He cheapest ~ 300 m. K ADR Moderate price 50 m. K Dilution refrigerator Most expensive 10 m. K + NIS refrigerator cooling detectors 100 m. K
Previous State of the Art 320 m. K 160 m. K Tc=185 m. K Dissipating 22 p. W 230 m. K rest of chip = 260 m. K -NIS cooled X-Ray detector has best 6 ke. V resolution with cryostat above 200 m. K: 9. 4 e. V @ 6 ke. V -Representative of a class sensors that operate near 100 m. K A. M Clark, et al, Appl Phys Lett 86, 1734508 (2005) N. M. Miller, et al, Appl Phys Lett 92, 163501 (2008) S N cold hot
How does it work? Vbias=. 5Δ/e e. Vbias BCS DOS
Hot Electrons Tunnel Vbias=. 9Δ/e e. Vbias BCS DOS
Normal Metal Cools - Superconductor Heats Vbias=. 9Δ/e e. Vbias BCS DOS
Add a Heatsink (Quasiparticle Trap) Vbias=. 9Δ/e e. Vbias no bias on heatsink junction BCS DOS
NIS Refrigerator Geometry Al-Mn hot (Al-Mn)Ox Al Al I cold Al-Mn Si. O 2 hot Si
Old Thermal Model IV Power NIS Junction Cooling Function of Tn I 2 R superconductor (fixed at bath temperature) normal metal electrons Quasiparticle Return (Small Fraction of IV, Empirical) substrate/normal metal phonons (fixed at bath temperature) Payload Power Electron-Phonon Coupling
New Thermal Model with Heatsink Quasiparticle Trapping/ (Heatsink) IV Power NIS Junction Cooling Function of Tn, Ts I 2 R normal metal trap electrons (T vs Position) superconductor (QP Density vs Position) Electron-Phonon Coupling normal metal electrons Quasiparticle Recombination substrate/normal metal phonons (fixed at bath temperature) Payload Power Electron-Phonon Coupling
Inside Thermal Model x Al-Mn Si. O 2 Si quasiparticle:
Predictions of Model Previous 50 nm Al-Mn Target 25 nm hot (Al-Mn)Ox Al Al I Al-Mn cold Al-Mn Si. O 2 hot Si
Predictions of Model Previous Overlayer Oxide (no overlayer trap) Target for overlayer 10 Wmm 2 Al-Mn hot (Al-Mn)Ox Al Al I Al-Mn cold Al-Mn Si. O 2 hot Si
Measured Cooling to 112 m. K Record NIS Cooling (Large Junction) 2008 300 m. K ↓ 112 m. K =T S I TN R D A Sat July 30 2010
Next Step: NIS Cooled Cryogenic Stage • 3 mm chip -> 0. 1 u. W @ 100 m. K • 10 u. W dissipated at 300 m. K
NIS Junction Cooling Function of Tn
