ALICE, AN INSTRUMENT FOR THE ANALYSIS OF FLUIDS CLOSE TO THE CRITICAL-POINT IN MICROGRAVITY

The ALICE instrument is dedicated to the study of phase transitions and mass and heat transport phenomena in fluids near their critical point in microgravity conditions. The core of the instrument is a thermostat that creates a thermically stable environment inside its three thermal shields. This thermostat encloses the Sample Cell Unit (SCU), that contains the two experimental samples. This SCU is a copper block with apertures, for the light path and the experimental samples. The samples are studied by means of six optical diagnostics: interferometry, observation of the complete sample, microscopy, direct transmission of the laser beam, small angles diffusion, and observation of the density gradients by means of a lattice inserted in the optical path. The light sources (laser and LEDs) are integrated in a hermetic block and the light is collected in another hermetic block that contains two CCDs, a photodiode, and different optical elements. The video signal is recorded on a video recorder, and the tapes are taken back to Earth by the cosmonaut. The whole instrument is managed by an electronic block that reads the instructions on a program cassette introduced in the instrument before each experimental run by the cosmonaut.