Breakdown voltage reliability improvement in gas-discharge tube surge protectors employing graphite field emitters J. Appl. Phys. 111, 083301 (2012) Effect of sputtered lanthanum hexaboride film thickness on field emission from metallic knife edge cathodes J. Appl. Phys. 111, 063717 (2012) Space charge and quantum effects on electron emission J. Appl. Phys. 111, 054917 (2012) Enhanced electron field emission from plasma-nitrogenated carbon nanotips J. Appl. Phys. 111, 044317 (2012) Field-emission properties of individual GaN nanowires grown by chemical vapor deposition

Simple expressions for sheath and presheath potentials are provided for anode, cathode and electrically floating plasma-facing surfaces. The expressions are developed using a fully kinetic theory that includes the effects of secondary or thermionic electron emission from the plasma-facing surface. The emission can be space-charge limited and a criterion is provided for the onset of space-charge saturation.

A two-dimensional theory for calculating an upper bound for the space-charge limited current of relativistic electron beams is extended to coaxial drift tubes. The theory applies to annular beams of arbitrary radius, thickness and length travelling in a grounded coaxial drift tube of circular cross section. Poisson’s equation for space-charge limited flow is replaced with a Sturm–Liouville-type eigenvalue problem. The problem reduces to numerically solving a determinantal equation rather than a partial differential equation. Under limiting cases, closed-form analytical expressions are derived.

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MACH2 is a general purpose MHD code that previously has been used to simulate a wide variety of pulsed power plasma devices. Recent extensions to the code permit accurate tracking of moving material interfaces. The code has been used to simulate the evolution of an explosively formed fuseS consisting of a thin cylindrical aluminum shell that is driven into a Teflon die by an explosion. The resulting rapid increase of the fuse resistance operates as an opening switch to transfer stored magnetic field energy into a load. The simulation included the initiation and propagation of the explosive detonation wave and tracked the extrusion of the fuse into the Teflon die. The transient fuse resistance was determined from the changing inductance and the ohmic heating of the fuse. The code predicted that the fuse resistance increased by approximately three orders of magnitude during a time of approximately 1 microsecond. The increase in resistance was due to the lengthening and thinning of the fuse material and the rise of temperature caused by the ohmic heating. The simulation results will be compared with recent experimental measurements performed at Los Alamos National Laboratory.In a circuit interruption process of an SF6 circuit breaker, there remains a post-arc channel with temperatures below 6000 K between the electrodes. The post-arc channel is exposed to high electric field induced by a transient recovery voltage. The high electric field can elevate the kinetic energy of electron, resulting in higher electron temperature T, than gas temperature Tg. It causes properties to differ from those under the condition of local thermal equilibrium. This paper describes the influence of applied electric field on properties of SF, post-arc channel. First, electrical conductivity, enthalpy and mass density of electron and heavy particles in an SF, plasma were calculated as a functions of T, and Tg Secondly, using the data derived above, time variations in T, and Tg were computed in an SF6 plasma to which high electric field was applied. The calculated results revealed that applied electric field increased T, and caused deviation from local thermal equilibrium.Finally, time evolution of electrical conductivity D of SF, plasma exposed to electric field was also calculated. It was found that CT was enhanced by increasing T, particularly at initial temperature ranges 3000-3500 K and 5500-6500 K. 150