Dendritic solidification of krypton

We have measured the tip growth velocity $v_{\mathrm{tip}}$ and the tip radius $R$ of krypton dendrites growing into a supercooled melt in the supercooling range $0.005<\mathrm{}\Delta T<\mathrm{}0.25\mathrm{}$ K. The experimental results can be fitted by $v_{\mathrm{tip}}=3.1\mathrm{}\times {10}^{-2\mathrm{}}{\Delta T}^{1.73}$ cm/s and $R=6.7\mathrm{}\times {10}^{-4\mathrm{}}{\Delta T}^{-0.68\mathrm{}}$ cm which is compatible with $v_{\mathrm{tip}}R\propto \Delta T$. Our experimental data do not confirm the stability hypothesis according to which $v_{\mathrm{tip}}{R}^2=\mathrm{const}$. The dendrites show four fins equal in shape and size in the dendrite tip region, indicating anisotropic attachment kinetics and corresponding influence on the growth rate.