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The paper describes experiments on the generation and transport of a low energy (70–120 keV), high intensity (10–30 A/cm2) 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 ji∼10–20 A/cm2 at the anode surface, was ballistically focused to a current density in the focal plane of 50–80 A/cm2. 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 ∼ 50% with an IB current density of 20 A/cm2. Two-dimensional computer simulations of post-MID IB transport supported the optimization of system parameters.

Numerous approaches to the production of intense beams of highly charged heavy ions are compared and contrasted. The competing processes of ionization and electron capture are described and evaluated to explore ways to further improve upon the encouraging recent results from electron-beam (E-MEVVA) and low-impedance Z-discharge (LIZ-MeV) variations on the venerable metal vapor vacuum arc (MEVVA) ion source.

The low inductance Z-discharge metal vapor (LIZ-MeV) ion source, which uses a magnetized Z-pinch, is a pseudo-spark device capable of producing intense currents (several kA) of highly chargedgold or other ions. Typical operations produce an extracted charge-state distribution with a range in gold ion charge state from 4 to 19. Time-of-flight (TOF) spectra (excluding contributions from impurities) indicate that charge states at least as high as Au +12 were generated. Various TOF spectra are presented here to support this conclusion. Although the results are preliminary, LIZ-MeV shows great potential. Existing heavy-ion sources can produce either high beam currents, but low charge states (e.g., the metal-vapor vacuum arc) or high charge states, but low beam currents (e.g., the electron beamion source). For ion beam injection our goal has been to develop an ion source that produces both high charge states and high beam currents. The existing LIZ-MeV has sufficiently large electron impact energies and electron current densities, but performance is limited by charge exchange with ambient gas and short confinement times. Plans are underway to add another Z-pinch stage to both lengthen confinement times and to minimize charge-state reducing processes. Such an enhanced LIZ-MeV should eventually produce even larger currents of more highly ionized heavy metal ions for accelerator applications.

Summary form only given. This paper extends earlier studies, on the transport of intense, wide cross-section neutralized H/sup +/ plasma (PB) and ion beams (IB) with translational energies in the range of /spl sim/0.1 to /spl sim/100 keV, respectively, through various combinations of vacuum, ambient plasma and/or transverse B-fields ranging from 0.1 to 1.6 kG. Particle densities and temperatures for the ambient plasma and PB were of the same order in magnitude (/spl sim/10/sup 13/ cm/sup -3/ and a few eV) while the IB was two orders lower in density and more than one order higher in temperature (/spl sim/10/sup 11/ cm/sup -3/ and hundreds of eV). For the PB, depending on the B-field strength, the ratio of beam width to Larmor radius, d/R, ranged from 1 to 10 and the ratio of beam energy density to B-field pressure, /spl beta/, ranged from 10/sup -2/ to 1. For the IB, these values ranged from 10/sup -1/ to 1 and 10/sup -1/ to 10, respectively. Based on the transport criteria used in, at low B-fields (/spl les/0.4 kG) in vacuum, the PB was mainly diamagnetic, whereas for higher B-fields (/spl ges/0.6 kG), the PB propagated by ExB drift with pronounced peripheral layer loss and beam "braking" due to virtual anode formation. Slowing down of the PB front caused the beam to bunch and consequently the density of the central part of the PB increased by more than one order in magnitude. In the case of the IB, similar peripheral beam loss was not accompanied by beam braking or the enhancement of its central part indicating an ExB mechanism of transport without the formation of a virtual anode. The propagation of the IB in ambient plasma across B-field agrees with the picture of efficient shorting of the polarization E-field with subsequent beam deflection corresponding to a one-particle orbit of an H/sup +/ with respective average beam energy. Differing from this picture, the PB in similar conditions propagated without any noticeable deflection, though bunching and "pealing off" was much less pronounced compared with its propagation in vacuum. A possible cause for this dissimilarity may be insufficient ambient plasma density for the PB and therefore an incomplete shorting of the polarization E-field.

Summary form only given, as follows. Streak measurement of the inverse Brumstrahlun absorption of the laser light in a Z-pinch provides information about the stability and temperature evolution of a high density pinch with high time and spatial resolutions. Our experiment uses the UCI staged pinch with peak parameters: 50 kV, 63 kJ, 1.7 msec rise time, and 2 MA maximum current. A 20 mW He-Ne laser (633 nm, single mode) backlights the plasma and a Hamammatsu 1370 streak-camera records the image. A double cylindrical lens collimator before the plasma increases the probe light intensity which is focused to a 1 mm line in the midplane of the pinch. A 10 mm filter and narrow slit placed at the light focus reduces the influence of plasma self-luminosity, these shots were accompanied by a two frame nitrogen laser shadow pictures, (/spl lambda/=337 nm). These images were separated in time by /spl sim/15 ns, with /spl sim/1 ns exposure.

Recently substantial enhancement of high ion charge states was clearly observed in both the HCEI and ITEP E-MEVVA ion sources. These experimental setups have two different methods of measuring the ion charge state distributions. The results can be considered as a proof of the E-MEVVA principle. These results sparked discussions regarding which physics effects are dominant. Basic physics seems straightforward, an ion charge state in E-MEVVA is determined by the number of collisions with fast electrons versus the number of encounters with neutrals and lower charge state ions during an ion dwell time in the drift channel. However, the fluxes of fast electrons, lower charge state ions, and neutrals encountered by an ion may be a consequence of numerous effects. Factors determining neutral fluxes might be poor vacuum conditions, desorption of adsorbed gas by the electron beam directly or indirectly due to stacking (E-beam reflection) and/or instabilities that cause heating and desorption. Flux and energy of the fast electrons is primarily determined by the electron gun output. But significant contributions from electron beam stacking, instabilities, as well as plasma electron heating, are possible. The various contributions are evaluated to account for past results and to guide future progress.