Micro-Particles as Probes for Laboratory Plasmas

Summary form only given. To diagnose plasmas with least perturbation, while still achieving good spatial resolution, one of the most common and simple approaches is to use small physical probes, which still have a long dimension out to the wall for data transmission. An alternative, which is truly miniature in all three dimensions, is to use microparticles (~10^-6 m). The concept of injecting microparticles for plasma diagnostics was first introduced to measure internal magnetic field topology in 500-eV-temperature plasmas [Wang and Wurden, Rev. Sci. Instrum. 74, 1887 (2003)]. Here we suggest that, combined with laser sheet-beam and fast cameras, use of microparticles can be extended to measure plasma flow and turbulence structures by carefully choosing geometry, size, materials, and physical properties of microparticles. Because the surface-to-volume ratio of a microparticle scales like ~1/r, where r is the characteristic dimension, surface conditions will play important role in data interpretation. In the mean time, microparticle charging, electron and ion fluxes, electric and magnetic fields can induce other effects, such as rocket effects. Furthermore, experimental data about microparticles in plasmas may be used as inputs for cosmic dust modeling. It is also interesting to study the effects of the plasma Debye length relative to the dust size. In summary, this talk will discuss the complexity of microparticle-plasma interactions, including both challenges and opportunities for microparticle applications to plasmas.