Quasiparticle behavior in tunnel junction refrigerators

We present simulations of quasiparticle creation, propagation, and loss in the superconducting electrode of a normal-insulator-superconductor tunnel j unction refrigerator. We calculate the electronic temperature in the superc onducting electrode from self-consistent solutions to the diffusion equatio n. We then calculate the power load on the normal electrode due to recombin ation phonons and the reduction in cooling power due to the elevated temper ature of the superconductor. Our calculations explain the degraded cooling performance observed in 20 mu m sized Ag/AlOx/Al junctions. (C) 2000 Elsevi er Science B.V. All rights reserved.