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Summary form only given. As part of a continuous research effort into the development of high brightness flash radiographic sources, Sandia National Laboratories is developing a suite of advanced diagnostics that will aid in the characterization of these high-intensity electron-beam diodes. There are various time dependent beam transport features that inhibit the stable operation of these sources. A scintillator based time resolved spot size diagnostic (TRSD) was developed to quantify these beam variations. Preliminary results demonstrated beam centroid tracking as well as time dependent beam spot size measurements. Detailed characterization of the TRSD, including an assessment of the temporal and spatial resolution of the system is underway. Results of these tests as well the improvements and modifications being incorporated into a 2nd generation TRSD design are detailed in this paper.

Summary form only given. Traditionally, the paraxial radiographic diode has relied on a gas-filled chamber to focus an electron beam into a small spot for the purpose of generating X-rays. Focusing is provided by the electron beam-produced plasma whose density increases during the course of the beam pulse. Simulations using Lsp, a particle-in-cell code, have shown that the location of the electron beam focus wanders during the timescale of the pulse in this case, resulting in a larger radiographic spot than is desirable. Lsp simulations have also shown that replacing the gas-filled focusing chamber with a fully-ionized plasma of density on the order of 10/sup 16/ cm/sup -3/ will prevent the spot from significantly wandering, hence resulting in a smaller, more stable spot size. Sandia National Laboratories is implementing a plasma prefilled paraxial diode on the RITS-3 accelerator. The plasma-filled cell will be created using a z-discharge in a hydrogen fill. Laser interferometry is used to assess the plasma density on bench-top experiments, and plans are underway to perform the diagnostics during RITS-3 experiments. Details of the plasma source, its characterization in a bench-top setting, and plans for investigation during RITS-3 operation are presented.

Summary form only given. The self-magnetic-pinch diode is being developed as an intense electron beam source for high-power X-ray radiography. The diode uses an 8-mm-diameter hollow-cylindrical cathode with a rounded tip from which a high current electron beam is emitted. The beam self-focuses in its own magnetic field as it propagates across a /spl sim/1-cm vacuum gap where it deposits its energy on a planar high-atomic-number target from which bremsstrahlung radiation is produced. This diode has been experimentally optimized for electrical operating parameter ranges of 1-5 MV,>50 kA, and pulse widths of 20-50 ns. Experimental data suggests that the hollow cathode region significantly extends the impedance lifetime by providing electrode plasmas produced in the vicinity of the pinch a place to expand. The hybrid particle-in-cell code LSP is used to study the evolution of cathode and anode plasmas in several of the experimentally tested cathode configuration. Comparisons with available experimental results are made.

Summary form only given. In this paper we discuss the design of RITS-6 including the dimensions of the MITL, the cathode, anode and vacuum flow currents, and voltage at each stage of the MITL/voltage adder. RITS-6 output operating conditions for diode impedances less than 85.5 ohms where an over-insulation wave propagates back up the MITL from the diode was presented. Particle-in-cell simulations (LSP) of the power flow from the cell to the load was compared with parapotential flow predictions. LSP simulations based on RITS-3 PFL water output switch jitter data was used to estimate the expected range of vacuum insulator voltages on RITS-6 if water PFL switches are employed.

Summary form only given. The magnetically immersed diode is being developed as an intense electron beam source for high power X-ray radiography. Electrons are emitted from a needle cathode of 0.5-5 mm diameter and confined in a 10-50 Tesla solenoidal field. These electrons, striking a high atomic number anode converter, can potentially deliver a high brightness source of X-rays for flashradiography. In recent experiments on the 150-kA, 4-MV RITS-3 accelerator at Sandia National Laboratories, using

Summary form only given. Sandia National Laboratories is investigating and developing high-dose, high-brightness flash radiographic sources. One of the candidate sources being developed is the magnetically immersed diode. These diodes employ large-bore, high-field solenoid magnets to help produce an intense electron beam from a needle-like cathode "immersed" in the strong Bz field of the magnet. Sandia's RITS-3 accelerator (4-MV, 150-kA, 70-ns) has been used to fully characterize the diode behavior and radiographic performance of Sandia's 20-T large bore immersed diode over a wide range of diode parameters including cathode diameter, A-K gap, magnetic field strength, anode materials, base vacuum pressures and accelerator pre-pulse. Key results from this extensive survey are described.

Summary form only given. Recent theoretical work to model the final longitudinal and radial compression of a HIF beam is summarized in this paper. The three-dimensional electrostatic particle-in-cell (PIC) code WARP3d is used to study beam transport in the drift-compression section, while transport in the fusion chamber is modeled in using the electromagnetic PIC code LSP. Possible low-energy near-term experiments are investigated, as well as full-scale fusion drivers, and for each accelerator category, we examine how transport and error sensitivity scale with the major beam and lattice parameters.

Summary form only given, as follows. We have investigated the conditions for a nonthermal dissipative quasisteady state of a bean-penetrated plasma, in which the primary unstable space-charge waves transfer power to nonlinearly-induced secondary space charge waves and density fluctuations (cavitons), and in which nonthermal randomly accelerated plasma electrons created by these nonlineanties provide and represent greatly enhanced Landau damping of the sccondaly waves. The power balance of the energized nonthermal hat electrons and the three wave populations is studied for astrophysical applications, and used to allow some inference about beam-plasma properties from potential radiation spectrum observation.