Dust trajectories and diagnostic applications beyond strongly coupled dusty plasmas

Abstract

Plasma interaction with dust is of growing interest for a number of reasons. On the one hand, dusty plasma research has become one of the most vibrant branches of plasma science. On the other hand, substantially less is known about dust dynamics outside the laboratory strongly coupled dusty-plasma regime, which typically corresponds to 1015m−3 electron density with ions at room temperature. Dust dynamics is also important to magnetic fusion because of concerns about safety and potential dust contamination of the fusion core. Dust trajectories are measured under two plasma conditions, both of which have larger densities and hotter ions than in typical dusty plasmas. Plasma-flow drag force, dominating over other forces in flowing plasmas, can explain the dust motion. In addition, quantitative understanding of dust trajectories is the basis for diagnostic applications using dust. Observation of hypervelocity dust in laboratory enables dust as diagnostic tool (hypervelocity dust injection) in magnetic fusion. In colder plasmas (∼10eV or less), dust with known physical and chemical properties can be used as microparticle tracers to measure both the magnitude and directions of flows in plasmas with good spatial resolution as the microparticle tracer velocimetry.

Existing and new applications of micropellet injection (MPI) in magnetic fusion

“…Application of hypervelocity dust injection to high-temperature plasma diagnostics was discussed previously (Wang & Wurden 2003, 2004; Wang et al. 2007; Ticos et al. 2008).…”

High-speed imaging of dust particles in plasma

“…Some examples are the DicamPro used at Los Alamos in plasma fusion experiments (Wang et al 2007), the PCI 1024 FastCam, the Kodak Motion Coder, and Phantom cameras used in tokamaks experiments (Roquemore et al 2007;Rudakov et al 2008). To be able to observe particles of a few microns in size at several tens of centimeters, a good close-up lens is required.…”

Hypervelocity Dust Storm Launched With a Coaxial Plasma Gun

“…where k B is the Boltzmann constant, T i is the ion temperature, n i is the plasma density and w=( [11][12]15]. Electron drag is neglected here due to small electron mass.…”

“…A microparticle accelerator based on a coaxial plasma gun [8] has multiple advantages: it has a compact size and operates with voltages of a few kV compared to electrostatic accelerators which occupy large volumes and require MV, it can use different gases although the plasma flow speed may vary, depending on the ions mass [9], and it can accelerate several microparticles simultaneously, regardless of their shape or size. The plasma flow can exert sufficient drag force even on grains with a radius of a hundred microns, and impart accelerations as large as a d =500g (g=9.81 m/s 2 ) [10][11]. The acceleration process is usually accompanied by intense heating of the grains due to the dense plasma particle fluxes colliding with the grains.…”