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A solid-state Marx modulator is under development to supply regulated voltage and current to a high-power magnetron. A primary goal of this design is for the modulator to have low volume and low weight. The modulator is required to provide 5-/spl mu/s-wide rectangular pulses of approximately 45 kV and 145 A at a repetition frequency of 120 Hz. The Marx is composed of 12 circuit boards, with 4 IGBT switched Marx stages per board, for a total of 48 stages. The IGBT Marx switches can be closed and then opened at full-load current, allowing the production of a rectangular pulse from a Marx generator. Single boards and three-board stacks have been tested into a resistive load at operational voltages and currents. Results of the resistive load test are shown.

The Dual-Axis Radiographic Hydrodynamics Test (DARHT) facility will employ two perpendicular electron linear induction accelerators to produce intense, bremsstrahlung X-ray pulses for flash radiography. We intend to produce measurements containing three-dimensional information with sub-millimeter spatial resolution of the interior features of very dense, explosively driven objects. The facility will be completed in two phases with the first phase having become operational in July 1999 utilizing a single-pulse, 20 MeV, 2 kA, 60 ns accelerator, a high-resolution electrooptical X-ray imaging system, and other hydrodynamics testing systems. We describe this machine and discuss its current operating status. The first electron beams will be generated in the second phase of DARHT this year. The second DARHT accelerator consists of a 18.4 MeV, 2 kA, 2-microsecond pulse-width accelerator. Four short electron micropulses of variable pulse-width and spacing will be chopped out of the original, long accelerator pulse for producing time-resolved X-ray images. The second phase also features an extended, high-resolution electro-optical X-ray system with a framing speed of about 2 MHz. We discuss this accelerator by summarizing the overall design of the long-pulse injector and accelerator as well as some component test results. We also discuss the fast kicker used to separate the long-pulse beam into short bursts suitable for radiography.

The Dual-Axis Radiographic Hydrodynamics Test (DARHT) facility will employ two perpendicular electron linear induction accelerators to produce intense, bremsstrahlung X-ray pulses for flash radiography. The first DARHT accelerator became operational in July 1999 producing a single electron beam pulse at 20 MeV, 2 kA, and 60 ns pulse. The second DARHT accelerator consists of a 18.4 MeV, 2 kA, 2 microsecond pulse-width accelerator. Four short electron micropulses of variable pulse-width and spacing will be chopped out of the original, long accelerator pulse for producing time-resolved X-ray images. The first electron beam in this machine will be produced this year. We discuss the pulsed power systems associated with this machine. These include an injector driven by a Marx consisting of 88 type-E PFN stages driving a matched load at 3.2 MV with a 500 ns risetime, 2 microsecond e-beam pulse. The Metglas-filled induction cells making up the accelerator are described. Each induction cell is driven by a cell-driver that contains 4, 7-section E-network PFNs in a Marx configuration with a 20 /spl Omega/ impedance that delivers flattop of greater than 2 microseconds into a resistive load of 5 /spl Omega/ for a total drive current of 10 kA at 200 kV. The principal element of the electron beam transport system is the fast deflector, or kicker, used to generate four micropulses from the primary beam. The kicker modulator generates bi-polar 18 kV pulses of arbitrary pulse width and spacing using solid-state circuitry that is described. Component test data from the injector, accelerator, and kicker system is discussed.

A new high speed optical control, diagnostic and power supply system has been developed for a solid state induction modulator. The modulator consists of a large array of field effect transistors (FETs) that switch a high-voltage pulse across a tape-wound magnetic core. The FETs within the modulator are mounted on numerous circuit boards that are stacked in series for high-voltage operation. The new optical system overcomes the issue of voltage isolation by supplying each circuit board with optically coupled control power and high bandwidth signal information. An optical fiber is used to transmit laser light to a custom photovoltaic cell that provides DC power to the on-board control circuits. Optical fiber technology is again used to convey a pulse that contains detailed analog features to the FET gate controls. Diagnostic data and status information are also obtained from each board by similar optical methods.

The Laser Program at Lawrence Livermore National Laboratory (LLNL) pioneered the use of large-scale glass lasers to heat inertial-fusion targets. Today, that same exploratory spirit applies to the latest laser-fusion effort-the National Ignition Facility (NIF). The NIF has the potential to pave the way to commercial power extraction from inertial fusion, as long as the generating system is affordable and it operates repetitively. These fundamental issues of cost and repetition rate have stimulated a search for alternative fusion-target drivers to replace large, single-shot lasers. The authors are developing an ion approach whereby converging beams of heavy ions act as the driver. Like lasers, the ions impart their energy to the target and produce fusion temperatures. The difference lies in the ability of particle accelerators to generate repetitive bursts of ions with a higher efficiency at a lower cost.