Influence of Adsorbed Gases on the Emission of X-Rays from Exploding Tungsten Wires in Vacuum

Abstract

Undegassed and degassed tungsten wires, initially coated with a thin impurity layer consisting of tungsten oxide (WO₃) and graphite, have been exploded in vacuum, 2 × 10⁻⁶ torr. The 0.1-μF capacitor was discharged at an initial voltage of 20 kV. The loop inductance of the short-circuited system was 150 nH. Correlated measurements of x-ray emission from the “anode side” and dI/dt show that the emission of x-rays starts prior to the shunting discharge. The hard x-ray burst emitted is extremely short (half amplitude width of about 25 nsec) and reproducible both in time and intensity, provided the initial conditions are kept constant. Explosions of undegassed and degassed wires give maximum x-ray photon energies of 23 keV and 11.5 keV, respectively. The dI/dt signals obtained from both kinds of explosions are identical; i.e., the gases initially adsorbed by the wire surface affect the emission of x-rays but not the main discharge current. On the other hand, the main discharge current but not the hard x-ray emission is influenced by the impurity layer. Finally, the x-ray output versus the pressure of the surrounding medium has been investigated. It is found that the x-ray burst is reproducible inside the pressure interval 10⁻⁶ torr to 1 × 10⁻³ torr.