An ionization instability is any one of a category of plasma instabilities which is mediated by electron-impact ionization. In the most general sense, an ionization instability occurs from a feedback effect, when electrons produced by ionization go on to produce still more electrons through ionization in a self-reinforcing way.
Ionization instabilities have been seen in such plasma physics apparatus as glow discharges, [1] [2] Penning discharges, [3] magnetic nozzles, [4] [5] [6] and MHD generators. [7] [8] [9] Ionization instabilities may occur in magnetized or unmagnetized [10] plasma. They occur mostly when the plasma is relatively cold and only partially ionized, so that there is a lot of neutral gas mixed in with the plasma.
A glow discharge is a plasma-containing apparatus in which the plasma is formed by a large voltage placed across a rarefied gas. Glow discharges are used for electric lighting and materials processing. In a glow discharge, ionization instability takes the form of striations, [1] or bands of enhanced and suppressed light production. The distance between each striation is the distance required for an electron to gain enough energy to ionize a neutral gas particle.
A magnetic nozzle is an apparatus through which plasma flows, in which the plasma is constricted by a magnetic field. Magnetic nozzles are used in electric propulsion to enhance the thrust produced by a stream of plasma. In magnetic nozzles, ionization instability is caused by ionization downstream of the nozzle, causing electrons born there to migrate upstream, counter to the direction of flow. This causes the plasma flow rate and energy through the nozzle to oscillate. [4] [5] [6]
An MHD generator is an apparatus through which hot gas flows, in which the gas is ionized and a magnetic field is used to extract flow energy as electrical energy. MHD generators were studied mostly in the 1960s and 1970s to increase the efficiency of fossil-fueled and nuclear-fission power plants. [11] In MHD generators, the specific kind of magnetized ionization instability is called the electrothermal instability. It was discovered by Evgeny Velikhov in 1962. The added electrical resistance caused by ionization instability thwarted a research effort to lower the required temperature by heating electrons preferentially. [11]
In plasma physics, plasma stability concerns the stability properties of a plasma in equilibrium and its behavior under small perturbations. The stability of the system determines if the perturbations will grow, oscillate, or be damped out. It is an important consideration in topics such as nuclear fusion and astrophysical plasma.
A magnetohydrodynamic drive or MHD accelerator is a method for propelling vehicles using only electric and magnetic fields with no moving parts, accelerating an electrically conductive propellant with magnetohydrodynamics. The fluid is directed to the rear and as a reaction, the vehicle accelerates forward.
An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines.
Inertial electrostatic confinement, or IEC, is a class of fusion power devices that use electric fields to confine the plasma rather than the more common approach using magnetic fields found in magnetic confinement fusion (MCF) designs. Most IEC devices directly accelerate their fuel to fusion conditions, thereby avoiding energy losses seen during the longer heating stages of MCF devices. In theory, this makes them more suitable for using alternative aneutronic fusion fuels, which offer a number of major practical benefits and makes IEC devices one of the more widely studied approaches to fusion.
A glow discharge is a plasma formed by the passage of electric current through a gas. It is often created by applying a voltage between two electrodes in a glass tube containing a low-pressure gas. When the voltage exceeds a value called the striking voltage, the gas ionization becomes self-sustaining, and the tube glows with a colored light. The color depends on the gas used.
A magnetohydrodynamic generator is a magnetohydrodynamic converter that transforms thermal energy and kinetic energy directly into electricity. An MHD generator, like a conventional generator, relies on moving a conductor through a magnetic field to generate electric current. The MHD generator uses hot conductive ionized gas as the moving conductor. The mechanical dynamo, in contrast, uses the motion of mechanical devices to accomplish this.
A field-reversed configuration (FRC) is a type of plasma device studied as a means of producing nuclear fusion. It confines a plasma on closed magnetic field lines without a central penetration. In an FRC, the plasma has the form of a self-stable torus, similar to a smoke ring.
A nonthermal plasma, cold plasma or non-equilibrium plasma is a plasma which is not in thermodynamic equilibrium, because the electron temperature is much hotter than the temperature of heavy species. As only electrons are thermalized, their Maxwell-Boltzmann velocity distribution is very different from the ion velocity distribution. When one of the velocities of a species does not follow a Maxwell-Boltzmann distribution, the plasma is said to be non-Maxwellian.
Evgeny Pavlovich Velikhov is a physicist and scientific leader in the Russian Federation. His scientific interests include plasma physics, lasers, controlled nuclear fusion, power engineering, and magnetohydrodynamics. He is the author of over 1500 scientific publications and a number of inventions and discoveries.
The Ayaks is a hypersonic waverider aircraft program started in the Soviet Union and currently under development by the Hypersonic Systems Research Institute (HSRI) of Leninets Holding Company in Saint Petersburg, Russia.
A Q-machine is a device that is used in experimental plasma physics. The name Q-machine stems from the original intention of creating a quiescent plasma that is free from the fluctuations that are present in plasmas created in electric discharges. The Q-machine was first described in a publication by Rynn and D'Angelo.
The electrothermal instability is a magnetohydrodynamic (MHD) instability appearing in magnetized non-thermal plasmas used in MHD converters. It was first theoretically discovered in 1962 and experimentally measured into a MHD generator in 1963 by Evgeny Velikhov.
"This paper shows that it is possible to assert sufficiently specifically that the ionization instability is the number one problem for the utilization of a plasma with hot electrons."
Plasma is one of four fundamental states of matter characterized by the presence of a significant portion of charged particles in any combination of ions or electrons. It is the most abundant form of ordinary matter in the universe, mostly in stars, but also dominating the rarefied intracluster medium and intergalactic medium. Plasma can be artificially generated, for example, by heating a neutral gas or subjecting it to a strong electromagnetic field.
The Spitzer resistivity is an expression describing the electrical resistance in a plasma, which was first formulated by Lyman Spitzer in 1950. The Spitzer resistivity of a plasma decreases in proportion to the electron temperature as .
The Princeton field-reversed configuration (PFRC) is a series of experiments in plasma physics, an experimental program to evaluate a configuration for a fusion power reactor, at the Princeton Plasma Physics Laboratory (PPPL). The experiment probes the dynamics of long-pulse, collisionless, low s-parameter field-reversed configurations (FRCs) formed with odd-parity rotating magnetic fields. FRCs are the evolution of the Greek engineer's Nicholas C. Christofilos original idea of E-layers which he developed for the Astron fusion reactor. The PFRC program aims to experimentally verify the physics predictions that such configurations are globally stable and have transport levels comparable with classical magnetic diffusion. It also aims to apply this technology to the Direct Fusion Drive concept for spacecraft propulsion.
A sawtooth is a relaxation that is commonly observed in the core of tokamak plasmas, first reported in 1974. The relaxations occur quasi-periodically and cause a sudden drop in the temperature and density in the center of the plasma. A soft-xray pinhole camera pointed toward the plasma core during sawtooth activity will produce a sawtooth-like signal. Sawteeth effectively limit the amplitude of the central current density. The Kadomtsev model of sawteeth is a classic example of magnetic reconnection. Other repeated relaxation oscillations occurring in tokamaks include the edge localized mode (ELM) which effectively limits the pressure gradient at the plasma edge and the fishbone instability which effectively limits the density and pressure of fast particles.
A magnetohydrodynamic converter is an electromagnetic machine with no moving parts involving magnetohydrodynamics, the study of the kinetics of electrically conductive fluids in the presence of electromagnetic fields. Such converters act on the fluid using the Lorentz force to operate in two possible ways: either as an electric generator called an MHD generator, extracting energy from a fluid in motion; or as an electric motor called an MHD accelerator or magnetohydrodynamic drive, putting a fluid in motion by injecting energy. MHD converters are indeed reversible, like many electromagnetic devices.
James F. Drake is an American theoretical physicist who specializes in plasma physics. He is known for his studies on plasma instabilities and magnetic reconnection for which he was awarded the 2010 James Clerk Maxwell Prize for Plasma Physics by the American Physical Society.
Ravindra Nath Sudan was an Indian-American electrical engineer and physicist who specialized in plasma physics. He was known for independently discovering the whistler instability in 1963, an instability which causes audible low-frequency radio waves to be emitted in the magnetosphere in the form of whistler waves. He also pioneered the study of the generation and propagation of intense ion beams, and contributed to theories of plasma instabilities and plasma turbulence.
William Henry Matthaeus is an American astrophysicist and plasma physicist. He is known for his research on turbulence in magnetohydrodynamics (MHD) and astrophysical plasmas, for which he was awarded the 2019 James Clerk Maxwell Prize for Plasma Physics.