Processes near the plasma-metal boundary under disruptive conditions in plasma focus systems

The authors investigate experimentally and consider theoretically a complex of interrelated phenomena occurring under disruptive conditons: interaction of the plasma with the metal, acceleration of the current sheath, formation of a strong electron flux, generation of hard X-rays, appearance of high-energy deuterons and blistering of the back of the anode. The time and space characteristics of the bremsstrahlung, the integrated energy spectra of the high-energy component of the deuterons and of the hard X-rays, and their dependence on the discharge parameters are determined. With the method used for treating the hard X-ray spectra it is possible to reconstruct the spectrum of the primary electrons of the flux. From metallographic investigations based on structural changes in the anode material, an estimate is made of the pulsed electron beam pressure on the anode bearing in mind that the entire discharge current is transmitted as a directed electron flux. On the basis of the data presented, the authors propose a model according to which formation of the electron beam and hence acceleration of the electrons and deuterons occur in an electric field developing in a disruption of the current caused by a thin layer of metal vapour above the anode surface