Prospects of porous gold as a low-temperature heat exchanger for liquid and solid helium

We have measured the electrical resistivity of porous gold produced by selective leaching of silver from silver-gold alloys. The low-temperature thermal conductivity expected from the electrical resistivity at 4.2K and the Wiedemann-Franz law is considerably better than that of sintered platinum black, while the surface area per volume is roughly four times larger than that of sintered silver powders. These advantages over sintered platinum and sintered silver promise porous gold to be a superior material for heat exchangers in experiments where liquid and solid helium is cooled to microkelvin temperatures. (C) 2000 Elsevier Science B.V. All rights reserved.