Dendritic crystal growth in pure4He

Dendritic crystal growth of pure hcp and fcc4He was observed at pressures between 210 and 6500 bar. Dendrite morphology depends on fluid supercooling and crystal phase. At large supercooling, dendrites with side arms are observed, whereas at low supercooling dendrites grow without side arms. The morphology of hcp4He dendrites is strongly influenced by crystalline anisotropy. Comparison with present theories of dendrite growth show good agreement with the power law dependencies of velocity, tip radius, and Péclet number on supercooling. Numerically, theory predicts much larger velocities than are observed. The stability parameter σ is found to be much smaller than theoretically predicted.

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