Plasma dragged microparticles as a method to measure plasma flows

Abstract

The physics of microparticle motion in flowing plasmas is studied in detail for plasmas with electron and ion densities ne,i∼1019m−3, electron and ion temperatures of no more than 15eV, and plasma flows on the order of the ion thermal speed, vf∼vti. The equations of motion due to Coulomb interactions and direct impact with ions and electrons, of charge variation, as well as of heat exchange with the plasma, are solved numerically for isolated particles (or dust grains) of micron sizes. It is predicted that microparticles can survive in plasma long enough, and can be dragged in the direction of the local ion flow. Based on the theoretical analysis, we describe a new plasma flow measurement technique called microparticle tracer velocimetry (mPTV), which tracks microparticle motion in a plasma with a high-speed camera. The mPTV can reveal the directions of the plasma flow vectors at multiple locations simultaneously and at submillimeter scales, which is hard to achieve by most other techniques. Thus, mPTV can be used to study plasma flows produced in the laboratory.

Survivability of dust in tokamaks: Dust transport in the divertor sheath

“…Our model includes a dust charging equation, the dust equation of motion, the dust heating equation and an equation for dust mass loss in the framework of the OML theory, and is similar to other dust transport models used in the literature [13][14][15][16][17]30].…”

Modeling of dust-particle behavior for different materials in plasmas

“…The model for calculating the penetration of a hypervelocity dust beam into the plasma including dust charging and heating by plasma was recently developed in Ref. 19. The analysis based on a high-speed multiview camera system can be used for plasma flow measurements in the scrape-off layer and divertor regions of tokamaks.…”

“…Dust also can be an important contributor to impurity contamination of the core and scrape-off-layer ͑SOL͒ plasmas in tokamak fusion devices, [1][2][3][4] which may increase radiation loss from the plasmas and affect recycling regimes in the divertor regions. Thus, novel experimental and theoretical studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] on dust composition; mechanisms of dust formation; dust thermochemical, electrical, magnetic and radiative properties; statistical distribution of dust particles over sizes, shapes, porosity, etc. ; and dust transport in fusion plasma devices have started.…”

Charging and Heat Collection by a Positively Charged Dust Grain in a Plasma

“…Experiments showing the formation of ordered structures with positively charged dust are reported in laboratory [11,12] and in microgravity [13]. Since charging is governed by the characteristic length of the body relative to the plasma Debye length or the electron gyroradius, there is no conceptual difference between the examples above and in what follows we will use the term dust broadly.A charging theory is a necessary ingredient of any model of dust transport and destruction/survival in a plasma [4,6,7,9,[14][15][16][17][18][19]. It calculates the dust charge/potential, momentum and heat collection due to the dust-plasma interaction.…”

“…A charging theory is a necessary ingredient of any model of dust transport and destruction/survival in a plasma [4,6,7,9,[14][15][16][17][18][19]. It calculates the dust charge/potential, momentum and heat collection due to the dust-plasma interaction.…”