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Pulse heating of materials by highly concentrated electron beams

Electron bombardment provides a means of heating with high local energy concentration and definition. The object is to investigate surface explosions and structural changes of matter caused by high temperatures, large temperature gradients and fast quenching rates connected with electron bombardment. It is intended to operate close to the absolute limits of energy concentration in electron beams. A theoretical study was made of the mechanism of electron beam focusing to determine the maximum obtainable beam compression. Results show that for low perveance beams the compression limit is set by the laws of thermodynamics. For high perveance beams, the thermodynamic limit cannot be reached because the electric and/or magnetic fields required become technically impossible. A numerical example illustrates this. An existing high perveance electron gun with a high area convergence ratio was adapted for the planned experiments. (Author).

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  • "Electron bombardment provides a means of heating with high local energy concentration and definition. The object is to investigate surface explosions and structural changes of matter caused by high temperatures, large temperature gradients and fast quenching rates connected with electron bombardment. It is intended to operate close to the absolute limits of energy concentration in electron beams. A theoretical study was made of the mechanism of electron beam focusing to determine the maximum obtainable beam compression. Results show that for low perveance beams the compression limit is set by the laws of thermodynamics. For high perveance beams, the thermodynamic limit cannot be reached because the electric and/or magnetic fields required become technically impossible. A numerical example illustrates this. An existing high perveance electron gun with a high area convergence ratio was adapted for the planned experiments. (Author)."@en
  • "An existing high perveance electron gun with a high area convergence ratio was adapted for the experiments. A cathode diam. of 0.6 cm or an area of 0.5 sq. cm was chosen. This resulted in a specific cathode load of 5 amperes/sq cm at 10,000 volts. Such a current was drawn from a pure Ta surface heated to 2600 K by electron bombardment. The electron energy was uniformly absorbed in a layer of material with a thickness corresponding to 2.6 x 10 to the -4th power g/sq cm. At the beginning of the pulse, the exposed area of this layer corresponded to the vacuum electron beam cross-section, but was reduced very rapidly by additional ion focusing caused by material evaporation. Experiments were performed using a condensor discharged through the gun for bombarding solid Ta as well as thin Ta foils. Craters and surface explosions on the targets were observed. Thin foils were punctured by the beam producing a liquid film. A jet of evaporating Ta then accelerated, by its recoil force, the film in the direction of the beam. The film was torn apart forming a series of small droplets. (Author)."@en

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  • "Pulse heating of materials by highly concentrated electron beams"@en

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