The geyser effect in the vacuum expansion of solid 3He0.54/4He0.46 and the determination of the Poisson ratio

Periodic bursts, also called the geyser effect, previously observed in the vacuum expansion of pure and < 1% He-3-doped solid He-4, are shown to occur also in solid He-3-He-4 alloys. Results are reported for (He0.54He0.46)-He-3-He-4 for the temperature range of 1.73-2.13K and pressures up to 92 bar, and then compared with the results for pure solid He-4. The geyser period is found to increase with pressure much faster in the mixed solid than in pure solid He-4. A direct measurement of the internal pressure exerted on the lateral walls of the source chamber provides the first information on the Poisson ratio of polycrystalline pure and mixed solids