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A finite-sized barium (Ba) photoplasma is generated through a two-step resonant photoionization method by shining laser pulses onto an atomic beam of Ba. The photoionization yield is estimated from the ratio of photoion density to neutral atom density measured in the laser–atom interaction region. The neutral atom density in the atomic beam is measured by an optical absorption technique where a Ba hollow cathode lamp (Ba-HCL) is used as an emission source. Since the photoplasma has a finite volume and it is pulsed in nature, the photoion density in the photoplasma is estimated through the collection of charge from the photoplasma. The measured ionization yield is compared with the calculated value that is obtained from an in-house developed code. It is observed that the values are in good agreement. [ABSTRACT FROM AUTHOR]

A new design of indirectly heated solid cathode based electron gun (200 kW, 45 kV, 270° bent strip type electron gun) has been presented. The design issue addressed is the uniformity of temperature on the solid cathode using (a) a multi-segmented filament with variable height as the primary heat source and (b) trapezoidal shaped single long filament as the primary heat source. The proposed design in this paper is based on computer simulation and validated by extensive experimentations. The design emphasis is on maintaining uniform temperature on the solid cathode. The designed multi-segment filament and the single long filament provide a temperature uniformity on the solid cathode of about 250 K and 110 K, respectively. The better temperature uniformity inspite of the thermal expansion, in case of a single long filament tightly clamped at two ends, has been possible due to shaping of the single filament with a number of constituent sections such that the thermal expansion of different sections forming the actual filament takes care of not only the mechanical stability but also does not affect the emitting surface of the filament. Experiments show that the modified design achieves a one to one correspondence of the solid cathode length and the electron beam length emitted from the solid cathode. [ABSTRACT FROM AUTHOR]

This article discusses the simulation, design and performance of an 80 kW strip electron gun. Electrons from an electrically heated, multisegmented tantalum filament are electrostatically focused to provide a sheet of electrons in the postanode region, that when bent through 270° along a circle of radius 120 mm by a uniform magnetic field, focuses on the target. This gun has been tested up to 80 kW (45 kVx1.8 A), and delivers power densities on the target in the range of 20 kW cm-2. The linear current density is uniform up to 20%, over a focal spot of dimension 80x5 mm2. Good correspondence between filament geometry and focal spot image of the electron beam on the target has been obtained, which is desirable in applications involving metal vapor coatings. This design is scaleable along the length of the focal spot without sacrificing uniformity, which is not possible in scanning or multiple pencil-type of electron guns. Experimental measurement of gun parameters such as position of filament in relation to the cathode opening, distribution of current along the length of the beam, focal spot size, extraction efficiency, etc., along with data concerning electron beam quality as a function of various parameters, are presented. The performance of this gun under different experimental conditions, as well as the simulation and modeling using an in-house three-dimensional beam dynamics code, is discussed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Atomic beams can easily be produced by allowing atoms to effuse through a channel. In an earlier investigation [A. Majumder et al., Vacuum 83, 989 (2009)], we had designed, fabricated, and characterized an effusive metal-vapor source using collinear-array of multi-channel. In this note, we describe the theoretical basis of designing the source. Atom density in atomic beam has been estimated using a set of analytical expressions for long-channel operated in transparent mode. Parametric studies on aspect ratio of channel, inter-channel separation, beam width, and vertical distance from the source are carried out. They are useful in providing physical picture and optimizing design parameters. [ABSTRACT FROM AUTHOR]