Instabilities Within Complex Plasmas

Summary form only given. Instabilities within plasmas have long been of interest to physicists working in the plasma field. In recent experiments both in microgravity and on Earth, it has been shown that under appropriate conditions such condensed states can form adjacent to regions containing liquid like dust phases. Under these circumstances, the complex plasma will often spontaneously form a stable, local, dust-free region having sharp boundaries called a void. Voids are typically small, relatively robust (stable) and can form in a variety of manners. For example, in the laboratory when dust grains are grown in situ, formation of the void is often preceded by the sudden onset of a filamentary mode while in microgravity, they often appear without any observable initial instability. In all cases, void size appears to be dependent upon RF power. Various mechanisms have been proposed to explain the underlying physics behind the formation of filamentary or void modes. The majority of these treat the dust system as either a one or two dimensional fluid with the ion drag, thermophoretic force, ionization instabilities or some other attractive potential between the dust grains proposed as a possible formation mechanism for the void. Recently within CASPER, an entirely new mechanism for creating instabilities has been discovered. This method allows the experimental generation of void-like structures within the sheath region above the lower electrode of a RF plasma discharge. This method will be discussed briefly along with recent experimental results. Theoretical results modeling the above will also be presented