Results of the Recirculator Project at LLNL

The Heavy Ion Fusion Group at Lawrence Livermore National Laboratory has for several years been developing the world's first circular induction accelerator designed for space charge dominated ion beams. Experiments on one quarter of the ring have been completed. The accelerator extended ten half-lattice periods (HLP) with induction cores for acceleration placed on every other HLP. A network of Capacitive Beam Probes (C-probes) was also enabled for beam position monitoring throughout the bend section. These C-probes have been instrumental in steering experiment, implementation of the acceleration stages and the dipole pulser, and the first attempts at coordinated bending and acceleration. Data from these experiments and emittance measurements will be presented

Research on high density tomography

The project goal is to define the beam transport system and pulsed power architecture for an advanced radiography machine that would permit obtaining a temporal sequence of multipleline-of-sight views of a given dynamic event. A long (200ns-1000ns) beam pulse would be split temporally by fast kicker ``coils`` and made to travel down separate beamlines to illuminate a target from two to four different angles. The beam pulse could be repeated at intervals down to 1 microsecond. The beam transport system and pulsed power architecture for this machine have been scoped out

Optical control, diagnostic and power supply system for a solid state induction modulator

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. 8 refs., 6 figs., 1 tab

Integrated power conditioning for laser diode arrays

This compact modulator has demonstated its ability to efficiently and accurately drive a laser diode array. The addition of the crowbar protection circuit is an invaluable addition to the integrated system and is capable of protecting the laser diode array against severe damage. We showed that the correlation between measured data and simulation indicates that our modulator model is valid and can be used as a tool in the design of future systems. The spectrometer measurements that we conducted underline the imprtance of current regulation to stable laser operation

MHz Repetition Rate Solid-State Driver for High Current Induction Accelerators

A research team from the Lawrence Livermore National Laboratory and Bechtel Nevada Corporation is developing an all solid-state power source for high current induction accelerators. The original power system design, developed for heavy-ion fusion accelerators, is based on the simple idea of using an array of field effect transistors to switch energy from a pre-charged capacitor bank to an induction accelerator cell. Recently, that idea has been expanded to accommodate the greater power needs of a new class of high-current electron accelerators for advanced radiography. For this purpose, we developed a 3-stage induction adder that uses over 4,000 field effect transistors to switch peak voltages of 45 kV at currents up to 4.8 kA with pulse repetition rates of up to 2 MHz. This radically advanced power system can generate a burst of five or more pulses that vary from 200 ns to 2 µs at a duty cycle of up to 25%. Our new source is precise, robust, flexible, and exceeds all previous drivers for induction machines by a factor of 400 in repetition rate and a factor of 1000 in duty cycle