  The fabrication and operation of V-based superconducting nanorefrigerators is
reported. Specifically, electrons in an Al island are cooled thanks to
hot-quasiparticle extraction provided by tunnel-coupled V electrodes.
Electronic temperature reduction down to 400 mK starting from 1 K is
demonstrated with a cooling power ~20 pW at 1 K for a junction area of 0.3
micron^2. The present architecture extends to higher temperatures refrigeration
based on tunneling between superconductors and paves the way to the
implementation of a multi-stage on-chip cooling scheme operating from above 1 K
down to the mK regime.
