TORSIONAL OSCILLATOR EXPERIMENTS WITH HIGH-STABILITY AND REPRODUCIBILITY

We report experiments of the torsional oscillator to observe the super fluid transition in He-4 films in porous glass (the pore diameter is 1 mu m). Stability and reproducibility of the oscillator which quite of ten is problematic in previous experiments, is essential for a quantit ative analysis of observations in different conditions. It follows tha t the friction of the superfluid films and the energy dissipation of t he solid films are derived from comparisons of measurements for differ ent film thickness.