Pulsed high-current electron source: Final report

The objective of this investigation was to investigate ways to realize the cathode's potential as a source for high power pulse operation. The questions that needed to be studied were those of large area coverage, maximum emission that the cathode arrays are capable of producing practically, uniformity of emission over large areas, and the ability to operate with high voltage anodes. 9 figs

Application of microfabrication technology to thermionic energy conversion. Progress report No. 6, November 1, 1980-January 31, 1981

Effort was directed toward the fabrication of a micron-spaced thermionic converter diode. This technique demonstrated that interelectrode spacings down to 1.5 ..mu..m could be obtained. Several methods of duplicating the emitter and collector surfaces were also investigated. Two new techniques are proposed; both stem from an earlier idea of using evaporation, photolithography, and etching techniques. These two fabrication methods yielded a one-piece diode structure with a thick-film copper collector, eliminating the need to physically duplicate the electrode surfaces and realign the electrodes. Effort has also been directed toward a more detailed theoretical analysis of micron-spaced thermionic converter performance. Taking into account heat losses through the interelectrode support structure, it is likely that the maximum energy conversion efficiency may be greatest at a spacing somewhat larger than 1 micron (..mu..m), but less than 10 ..mu..m

RECENT PROGRESS IN LOW-VOLTAGE FIELD-EMISSION CATHODE DEVELOPMENT

Nos récents progrès dans le développement de réseaux de cathodes à émission de champ ont permis d'atteindre des densités de courant supérieures à 100 A/cm2.Recent progress in field emission cathode array development has yielded current densities greater than 100 A/cm2

Application of microfabrication technology to thermionic energy conversion. Final report, 1 April 1979-31 March 1981

The first-year effort emphasized study of the kind of microstructures that could improve the performance of thermionic converters. Two ideas considered to have a fair chance of success emerged from this study: (1) use of a very closely spaced diode to eliminate the space-charge limitation of electron flow from emitter to collector, cesium vapor being used to control the work function of the emitter; and (2) use of field emission electrons, injected into a relatively large diode gap from microcathodes built into the collector, to produce ions to neutralize the space charge. The gas in the diode gap would be a mixture of cesium (to control the emitter work function) and xenon to optimize the ionization. A number of schemes were attempted to build closely spaced diodes with spacing in the 1 to 5 ..mu..m range, which overcame the problems of lateral differential expansion, surface irregularities on the electrodes, and heat loss down the pillars holding the gap spacing. Theoretical studies on using field emitter electrons to produce the space charge neutralizing ions showed that this approach was feasible. However, the program was terminated before any experimental work could be initiated in this area

FIELD EMITTER ARRAYS APPLIED TO VACUUM FLUORESCENT DISPLAY

In this paper we describe recent progress in the development of a thin vacuum-fluorescent display utilizing a matrix-addressable array of groups of Spindt-type field-emission cathodes1,2. The array consists of a matrix having 100 lines/inch in one direction and 300 lines/inch in the other. Each picture element (pixel) in the matrix is made up of an array of emitter tips sharing a common, individually addressable base electrode (one of the 100 lines) and three separately addressable control or gate electrodes in the orthogonal direction (one for each of the basic colors : red, green, blue). Each color element has about 100 emitter tips. The current emitted from the array is averaged over the 100 tips, and good uniformity of emission from color element to color element and pixel to pixel can be obtained, because of the averaging effect

High-resolution simulation of field emission

High-resolution simulations of field emission electron sources have been made using the electron optics program EGN2. Electron emission distributions are made using the Fowler-Nordheim equation. Mesh resolution in the range of 1-5 {angstrom} is required to adequately model surface details that can result in emission currents in the range found experimentally. A typical problem starts with mechanical details with dimensions of about 1{mu}. To achieve high resolution a new boundary is defined by the tip, a nearby equipotential line, and a pair of field lines. The field lines (one of which is normally the axis of symmetry) define Neumann boundaries. This new boundary is then used by the boundary preprocessor POLYGON to create an enlarged version of the problem, typically by a factor of ten. This process can be repeated until adequate resolution is obtained to simulate surface details, such as microprotusion, that could sufficiently enhance the surface electric fields and cause field emission. When simulating experimental conditions under which emission of several microamperes per tip were observed, it was found that both a locally reduced work function and a surface protrusion were needed to duplicate the experimental results. If only a local region of reduced work function is used, the area involved and the extent of the reduction both need to be very large to reproduce the emission. If only a surface protrusion is used, it is possible to get the observed emission current with a reasonable protrusion of length a few times radius, but then the resulting beam spreads over a very large solid angle due to the strong local radial electric fields. 8 refs., 14 figs., 1 tab