M. Rosenberg

Ion- and dust-acoustic instabilities in dusty plasmas

Dust ion-acoustic and dust-acoustic instabilities in dusty plasmas are investigated using a standard Vlasov approach. Possible applications of these instabilities to various cosmic environments, including protostellar clouds and planetary rings, are briefly discussed.

Ion‐dust streaming instability in processing plasmas

An ion‐dust streaming instability is investigated for conditions representative of plasma sheath interface regions where dust grains are observed to be present in processing plasmas. Kinetic theory is used, and the effects of collisions of charged particles with neutrals is retained. It is found that an instability with growth rate of the order of the dust plasma frequency may be driven by the drift of ions relative to charged dust. Possible implication for plasma etching is briefly discussed.

Some Physical Processes in Dusty Plasmas

Ionized gases containing fine (μm to sub-μm sized) charged dust grains, referred to as dusty plasmas, occur in diverse cosmic and laboratory environments. Dust occurs in many space and astrophysical environments, including planetary rings, comets, the Earths ionosphere, and interstellar molecular clouds. Dust also occurs in laboratory plasmas, including processing plasmas, and crystallized dusty plasmas. Charged dust can lead to various effects in a plasma. In this review, some physical processes in dusty plasmas are discussed, with an emphasis on applications to dusty plasmas in space. This includes theoretical work on several wave instabilities, the role of dust as an electron source, and Coulomb crystals of positively charged dust.

Ionization equilibria in dusty plasma environments

The interaction between dust and plasma leads to a variety of physical and dynamical consequences for both the dust and the plasma. One important consequence for the plasma is the effect on its charge state. While dust could act as a sink for the plasma by providing a recombination site for the electrons and ions, it could also act as a source of electrons in numerous ways. Here we discuss this latter problem. In particular we consider the role of photoelectric emission and thermionic emission from dust in enhancing the electron density in several environments, in each case considering both a cosmic one and a terrestrial one. With regard to photoelectric emission we briefly review some of our earlier work pertaining to interstellar molecular clouds and Coulomb crystals. With regard to thermionic emission, we present preliminary results of ongoing work pertaining to hydrocarbon combustion flames and dusty circumstellar shells around carbon rich red giant stars.

Weakly ionized cosmic gas: Ionization and characterization

Since collective plasma behavior may determine important transport processes (e.g., plasma diffusion across a magnetic field) in certain cosmic environments, it is important to delineate the parameter space in which weakly ionized cosmic gases may be characterized as plasmas. In this short note, we do so. First, we use values for the ionization fraction given in the literature, wherein the ionization is generally assumed to be due primarily to ionization by cosmic rays. We also discuss an additional mechanism for ionization in such environments, namely, the photoelectric emission of electrons from cosmic dust grains in an interstellar FUV radiation field. Simple estimates suggest that under certain conditions this mechanism may dominate cosmic ray ionization, and possibly also the photoionization of metal atoms by the interstellar FUV field, and thereby lead to an enhanced ionization level.

Simulation of dust-acoustic waves

The authors use molecular dynamics (MD) and particle-in-cell (PIC) simulation methods to investigate the dispersion relation of dust-acoustic waves in a one-dimensional, strongly coupled (Coulomb coupling parameter = {Lambda} = ratio of the Coulomb energy to the thermal energy = 120) dusty plasma. They study both cases where the dust is represented by a small number of simulation particles that form into a regular array structure (crystal limit) as well as where the dust is represented by a much larger number of particles (fluid limit).

Nuclear diagnostic commissioning for the national ignition campaign

Nuclear diagnostics aiming at measuring neutron yield, ion temperature, neutron bang time and down scattered ratio are a main component of the National Ignition Campaign. Therefore in order to commission these diagnostic, polar direct drive experiments on exploding pusher target have been taking place on the National Ignition Facility (NIF) to produce neutron yield up to about 2e14 neutron. Results of the exploding pusher performance on the NIF as well as progress on the neutron diagnostic commissioning will be presented in this talk.

Dust-Plasma Interactions

The objective of our theoretical research under this grant over the past 3 years was to develop new understanding in a range of topics in the physics of dust-plasma interactions, with application to space and the laboratory. We conducted studies related to the physical properties of dust, waves and instabilities in both weakly coupled and strongly coupled dusty plasmas, and innovative possible applications. A major consideration in our choice of topics was to compare theory with experiments or observations, and to motivate new experiments, which we believe is important for developing this relatively new field. Our research is summarized, with reference to our list of journal publications.

Waves in Dusty Plasmas

Summary form only given. Dusty plasmas are ionized gases containing massive charged dust grains. The presence of charged dust in a plasma can affect the behavior of waves and instabilities and also the interaction of electromagnetic (EM) waves with the plasma. We discuss some recent theoretical work in these areas. Instabilities may play important roles in various applications in both laboratory and space dusty plasmas. First, we consider conditions for exciting dust acoustic or drift instabilities in laboratory dusty plasmas with strong magnetic fields and discuss implications for the stability of plasma crystals. Next we consider instabilities in dusty plasmas in the Earths ionosphere (associated with meteorites or rocket exhaust), along with implications for backscatter. Finally we consider beam-plasma instabilities in a strongly coupled dusty plasma in the context of suggesting experiments. The interaction of EM waves with a dusty plasma may lead to possible applications. We discuss several, including the use of dust plasma crystals as EM filters, and the applications arising from the use of dust grains that can exhibit surface plasmon resonances

Waves in dusty plasma crystals with dipole interactions

Nonsymmetrical effective interactions between dust grains in dusty plasmas can arise from a variety of mechanisms such as nonuniform charging, ion focusing and wakes, and induced grain polarization. These effects can be included by describing the total effective interaction in terms of its first two multipoles: the monopole term which corresponds to the usual screened Coulomb interaction, and the dipole term which can be either attractive or repulsive depending on the relative orientation between grains. We consider dust waves propagating along the dipole axis in such a system (in its crystalline phase) and dispersion relations are presented.