Generation and transport of a low energy intense ion beam

The paper describes experiments on the generation and transport of a low energy (70-120 keV), high intensity (10-30 A/cm(2)) microsecond duration H+ ion beam (IB) in vacuum and plasma. The IB was generated in a magnetically insulated diode (MID) with an applied radial B field and an active hydrogen-puff ion source. The annular IB, with an initial density of j(i)similar to10-20 A/cm(2) at the anode surface, was ballistically focused to a current density in the focal plane of 50-80 A/cm(2). The postcathode collimation and transport of the converging IB were provided by the combination of a "concave" toroidal magnetic lens followed by a straight transport solenoid section. With optimized MID parameters and magnetic fields in the lens/solenoid system, the overall efficiency of IB transport at the exit of the solenoid 1 m from the anode was similar to 50% with an IB current density of 20 A/cm(2). Two-dimensional computer simulations of post-MID IB transport supported the optimization of system parameters. (C) 2004 American Institute of Physics

Wire Array Z-Pinch Insights for Enhanced X-Ray Production

Comparisons of measured total radiated x-ray power from annular wire-array z-pinches with a variety of models as a function of wire number, array mass, and load radius are reviewed. The data, which are comprehensive, have provided important insights into the features of wire-array dynamics that are critical for high x-ray power generation. Collectively, the comparisons of the data with the model calculations suggest that a number of underlying dynamical mechanisms involving cylindrical asymmetries and plasma instabilities contribute to the measured characteristics. For example, under the general assumption that the measured risetime of the total-radiated-power pulse is related to the thickness of the plasma shell formed on axis, the Heuristic Model [IEEE Trans. Plasma Sci., 26, 1275 (1998)] agrees with the measured risetime under a number of specific assumptions about the way the breakdown of the wires, the wire-plasma expansion, and the Rayleigh-Taylor instability in the r-z plane, interact. Likewise, in the high wire-number regime (where the wires are calculated to form a plasma shell prior to significant radial motion of the shell) the comparisons show that the variation in the power of the radiation generated as a function of load mass and array radius can be simulated by the 2-D Eulerian-radiation-magnetohydrodynamics code (E-RMHC) [Phys. Plasmas 3, 368 (1996)], using a single random-density perturbation that seeds the Rayleigh-Taylor instability in the r-z plane. For a given pulse-power generator, the comparisons suggest that (1) the smallest interwire gaps compatible with practical load construction and (2) the minimum implosion time consistent with the optimum required energy coupling of the generator to the load should produce the highest total-radiated-power levels