HgI2 nucleation experiments performed in the SL1 and SL3 (space laboratory) flights

Abstract

These experiments, each in sets of three quartz ampoules loaded with HgI2 and a host vapour were, performed in space laboratories, one in the SL1 and two in the SL3. Each experiment was reproduced twice after the flight. The experimental technique and results are presented in this paper. The Stefan flow and thermal diffusion without effect of gravity account for the HgI2 concentration profile as detected by nucleation in the SL3 and corresponding ground based experiments. On the contrary, with the quasi-equilibrium conditions used in the SL1, the HgI2 nucleation is shown to be sensitive to gravity. Nucleation is as difficult to control in space as on the ground.