Emission phenomena and dynamics of a controlled plasma focus

The Plasma Focus is a device for the production of dense plasmas with high energy density and power density. In a high-current discharge within hydrogen or deuterium gas an approximately cylindrical plasma is compressed by its own magnetic fields, reaching high electron densities and emitting electromagnetic radiation. Electrons and ions are accelerated up to several MeV. In the relatively small Plasma Focus device at Darmstadt, a prepared rather 'pure' plasma state (homogenized, symmetrical, almost free of macroscopic filamentations) the resulting high current densities show that an extreme non-equilibrium condition of the system is of utmost importance for the observed emission phenomena. The following phenomena were observed: Missing magnetic confinement; quasi-periodic modulation of the electron beam (in picosecond range) emitted towards the anode, estimated by a beam-plasma model describing the nonlinear coherent coupling of three plasma waves; electron emission in the direction of the cathode (40-200 keV); emission of oriented soft X-radiation at the time of the electron emission. A model description of the focus phase was developed, especially considering the influence of the magnetic field and the cyclotron motion of the electrons at the beginning of the focus phase. (AH)