Michael Coppins

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The charging of a large dust grain immersed in a flowing plasma is important for the study of several phenomena and in many applications. It is shown that in order to understand the charging mechanism of large dust grains, it is of great importance to take into account and calculate the effect of plasma flows on the sheath that develops around them.
The development of the m = 0 instability in a Z pinch was followed and the measured growth rates compared with 2D MHD simulations. Where MHD is valid, the measured growth rates agree well with simulation. Where the ions are magnetized, i.e., where the ion-cyclotron frequency is smaller than the ion-collision frequency and the ratio of the ion Larmor radius(More)
A misty plasma is defined as a plasma containing small liquid droplets. In such a system, the droplets will undergo total electrostatic breakup if their charge exceeds the well-known Rayleigh limit. This imposes a minimum size on the droplets. Electrostatic breakup is a significant mechanism limiting droplet survival in a wide range of plasma applications,(More)
A dust grain in a plasma has a fluctuating electric charge, and past work concludes that spherical grains in a stationary, collisionless plasma have an essentially Gaussian charge probability distribution. This paper extends that work to flowing plasmas and arbitrarily large spheres, deriving analytic charge probability distributions up to normalizing(More)
Interesting wake effects are found in simulations of dust grains in supersonically flowing plasma. A Mach cone is formed at an angle to the flow determined by the ratio of flow to Bohm speed. The latter is well approximated by [k(T(e)+γT(i))/m(i)](1/2) with γ=3. For ion temperatures significantly lower than the electron temperature, a second (inner) cone(More)
Dust immersed in plasma quickly charges to a potential where the ion and electron currents to its surface balance; this is the floating potential. In order to accurately determine dust behavior, the floating potential must be known. The charging of dust grains that are small with respect to electron Debye length (λ(D)) may be adequately approximated using(More)
This essay describes the current state of research into micrometre-scale liquid droplets in an ionised gas, usually referred to as a plasma. Such systems are a common occurrence in industrial processes, but have received little interest until recently. Electrostatic breakup is a significant mechanism for disrupting these droplets, but the effect of many(More)
Dust produced in tokamaks is an important issue for fusion. Dust particles can introduce health and safety issues when in the same time can have an impact on reactor performance. Apart from the associated problems there are also potential benefits that make the better understanding of their behavior important. In this work the dust transport code Dust in(More)
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