The Effect of 3He Impurities on Anomalous Oscillations in the Expansion of Solid 4He

The geyser effect in the vacuum expansion of solid3He0.544He0.46and the determination of the Poisson ratio

“…In a subsequent study [4], it was shown that small concentrations of 3 He ( 1% down to 15 p.p.m.) are sufficient to completely remove the anomalies.…”

“…In recent years, much experimental and theoretical effort has been devoted to understanding the low-temperature physical nature of solid pure 4 He, largely stimulated by the claimed observation of superfluidity [1]. The most recent consensus view indicates that the anomalies observed in the non-classical rotational inertia, shear modulus and the specific heat are not due to superfluidity of the ideal commensurate solid, but rather they must be related to vacancies and other intrinsic defects such as grain boundaries or dislocations, or extrinsic factors such as the 3 He impurity level [2].…”

“…The most recent consensus view indicates that the anomalies observed in the non-classical rotational inertia, shear modulus and the specific heat are not due to superfluidity of the ideal commensurate solid, but rather they must be related to vacancies and other intrinsic defects such as grain boundaries or dislocations, or extrinsic factors such as the 3 He impurity level [2]. Defects of a similar nature have been invoked to explain a phenomenon called the geyser effect, observed in the expansion of solid 4 He through a small orifice into vacuum under constant source pressure (P 0 ) and temperature (T 0 ). The flow, which in itself was unexpected, was dominated by periodic intensity bursts [3].…”

Solid 4He and the Supersolid Phase: from Theoretical Speculation to the Discovery of a New State of Matter? –A Review of the Past and Present Status of Research–

“…It is also interesting to remember a study on the free expansion of solid 4 He into vacuum 99,100) from a hole of diameter in the range 1-5 mm in the container. First, a sequence of periodic intensity bursts was observed with a very regular period, which increases with increasing pressure or decreasing temperature, the so-called geyser effect.…”

“…Closer to the melting curve the flow is continuous in time and pure Bernoulli liquid flow is observed for a pressure of about 2 bar above the melting curve, suggesting that the solid closest to the melting curve possesses different ''flow'' properties. 99) Low concentrations of 3 He, from 1 down to 0.1%, are sufficient to completely remove the ''anomalous'' behaviour near the melting curve, and the geyser effect is always observable at the melting curve down to the lowest measured temperature, about 1.3 K. 100) In this experiment the system is far from equilibrium, and excess vacancies were proposed by the authors as a possible mechanism for the geyser effect, but even if these vacancies could play a role in the geyser effect, the different flow properties close to the melting line remain unexplained. We believe that it will be important to extend these experiments to a lower temperature, in the region of NCRI.…”