Torsion Pendulum for the Study of Thin 3He Films

We report on the design of a torsion pendulum that can resolve the mass loading from 5×10 ^{17 3} He atoms (equivalent to a 1000Å film) with a 0.1% resolution. The oscillator is fabricated from coin silver alloy, and the working surfaces are two highly polished coin silver discs, each with well-characterized surface roughness, that are diffusion welded together using a copper gasket. We report on the cell's temperature dependent background. The cell will be used to examine the evolution of the superfluid density and transition temperature as a function of film thickness as well as the normal fluid behavior.