K. S. Ketola

Third sound and mass adsorption studies of4He on C60

We report preliminary third sound and quartz crystal resonance data from experiments in progress on the properties of4He adsorbed on C60.

Novel behavior of3He-4He mixture films on a cesium coated substrate at low temperatures

We report quartz crystal measurements of the adsorption of3He —4He mixture films to gold and cesium substrates as a function of temperature and concentration. Measurements for higher concentrations than reported earlier show steps in the adsorption at low temperatures. Speculations as to the origin of these steps are presented.

The influence of3He on the wetting of4He to a cesiated substrate

We report preliminary measurements of the influence of3He in the adsorption of4He to a cesiated substrate by the use of quartz crystal resonance techniques. When compared with the case of pure4He, the presence of3He in the apparatus induces the wetting of the mixture film to Cesium at low temperatures. The wetting is hysteretic, beginning at a concentration-dependent Tc on cooling with continued wetting for T>Tc on warming. The temperatures Tc are given as a function of the total concentration of3He in the apparatus.

Amplitude saturation of pulsed third sound on glass

Abstract We report a study of the amplitude and width of third sound pulses as a function of the energy deposited by a square wave thermal drive. Amplitude saturation is observed and discussed.

Amplitude Saturation and Non-Linearity of Pulsed Third Sound on a Glass Substrate

The amplitude of third sound has been measured as a function of the amplitude and width of a pulsed thermal drive for 4He film thickness values in the range 3–20 layers at T=1.11, 1.35 and 1.50 K. Saturation of the third sound amplitude and non-linearity were measured for large drive powers. The critical velocity of film flow is estimated from the saturated amplitude.

Third sound and quartz crystal resonance studies of helium adsorbed to C60

Abstract We report comparison measurements of the adsorption and properties of 4 He on 400, 800 and 1000A˚thick C 60 films and on glass and silver plated quartz by the techniques of pulsed third sound and quartz crystal resonance. No marked difference in the superfluid transition or adsorption behavior is observed among the several substrates.

Anomalous wetting of helium on cesium

We report studies of the anomalous wetting of a cesium substrate by a liquid helium film by means of the technique of third sound. A hysteretic pre-wetting transition is observed as a function of the amount of helium in the experimental cell.

Observation of third sound pulses in collision

Abstract We report measurements of collisions of third sound pulses which propagate through each other in a head-on scattering geometry. The amplitude of the waves can be measured throughout the scattering process.