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Abstract:
The pulsed flow of solid 4He through a narrow capillary in a flow system which issues into vacuum is
investigated at temperatures between 1.64 and 2.66 K and pressures between 54 and 104 bars. After each pulse
three different capillary flow regimes are observed as the upstream pressure decreases: an oscillatory [mini-geyser
(MG)] regime, a constant flow (CF) regime with a linearly decreasing pressure difference, and a nonresistant
(NR) regime. A quantitative analysis of the three regimes suggests that the flow of solid 4He is driven by a
counterflow of excess vacancies, which are injected downstream of the capillary at the solid/liquid interface near
the micrometric orifice exposed to vacuum. The CF regime, where the flow velocity is found to be independent
of the pressure difference, and the NR regime, where the solid flows as a Bernoulli fluid, suggest a new dynamic
phase of solid helium induced by a steady influx of vacancies.
