SURFACE EXPLOSIONS ON SOLIDS BY HIGH-DENSITY ELECTRON BOMBARDMENT
Abstract
The object of this study is to investigate surface explosions and the structural changes of matter caused by high temperatures, large temperature gradients, and fast quenching rates connected with electron bombardment. An existing high perveance electron gun with a high area convergence ratio was adapted for the experiments. Since the energy density in the bombarded spot is inversely proportional to the cathode area at a given maximum emission density, a cathode diameter of 0.6 cm or an area of 0.5 sq. cm was chosen. This results in a specific cathode load of 9.2 amperes/sq. cm at 15,000 volts. To draw such a current, the pure tantalum cathode is heated to about 2750 K by electron bombardment. At the beginning of the pulse, the exposed area is equal to the electron beam cross-section in vacuum, but is reduced very rapidly by additional ion focusing caused by evaporation of the target material. Because of this, the effective energy density is increased by at least an order of magnitude. The tantalum particles, being at temperatures around the melting point, emit electrons readily and charge positive in an electrostatic field. In the inhomogeneous axial symmetric field around wires particles were trapped in orbit during a series of experiments. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1962
- Accession Number
- AD0292108
Entities
People
- Oskar Heil
- Siegfried Vogel