Development of an optical trap for microparticle clouds in dilute gases

摘要

Long-duration experiments with clouds of mcroparticles are planned for the ICAPS facility on board the International Space Station ISS. The scientific objectives of such experiments are widespread and are ranging from the simulation of aerosol behaviour in Earth's atmosphere to die formation of planetes in the early solar system. It is, however, even under microgravity conditions, imposssible to sustain a cloud of free-floating, microscopic particles for an extended period of time, due to thermal diffusion and due to unavoidable external accelerations. Therefore, a trap for dust clouds is required which prevents the diffusion of the particles, which provides a source of relative velocities between die dust grains and which can also concentrate the dust to higher number densities that are otherwise not, achievable. We are planning to use the photophoretic effect for such a particle trap. First short-duration microgravity experiments on the photophoretic motion of microscopic particles show that such an optical particle-cloud trap is feasible. First tests of a two-dimensional trap were performed in the Bremen drop tower.