Phys. rev. appl. Phys. rev. appl. Enhancement of the Liquefaction Rate in Small-Scale Helium Liquefiers Working Near and Above the Critical Point Rillo Conrado Gabal Miguel Lozano Bernal María Pilar Universidad de Zaragoza Sesé Javier Universidad de Zaragoza Spagna Stefano Diederichs Jost Sager Ronald Chialvo Cesar Terry Jeremy Rayner Grant Warburton Richard Reineman Richard 2015 research-article