We report a study of materials recovered from a uranium-containing plasma generated by an electric arc. The device used to generate the arc is capable of sustaining temperatures of an eV or higher for up to 100 μs. Samples took the form of a 4 μm-thick U238 film deposited onto 8 pairs of 17 μm-thick Cu electrodes supported on a 25 μm-thick Kapton backing and sandwiched between glass plates. Materials recovered from the glass plates and around the electrode tips after passage of an arc were characterized using scanning and transmission electron microscopy. Recovered materials included a variety of crystalline compounds (e.g., UO2, UC2, UCu5,) as well as mixtures of uranium and amorphous glass. Most of the materials collected on the glass plates took the form of spherules having a wide range of diameters from tens of nanometers to tens of micrometers. The composition and size of the spherules depended on location, indicating different chemical and physical environments. A theoretical analysis we have carried out suggests that the submicron spherules presumably formed by deposition during the arc discharge, while at the same time the glass plates were strongly heated due to absorption of plasma radiation mainly by islands of deposited metals (Cu, U). The surface temperature of the glass plates is expected to have risen to ∼2300 K thus producing a liquefied glass layer, likely diffusions of the deposited metals on the hot glass surface and into this layer were accompanied by chemical reactions that gave rise to the observed materials. These results, together with the compact scale and relatively low cost, suggest that the experimental technique provides a practical approach to investigate the complex physical and chemical processes that occur when actinide-containing material interacts with the environment at high temperature, for example, during fallout formation following a nuclear detonation.

Summary form only given. Dense Plasma Focus (DPF) Z-pinches are copious sources of radiation including neutrons, x-rays, and MeV level electron and ion beams. Energetic protons and deuterons up to 10 MeV have been observed from ~cm long pinches indicating average acceleration gradients up to 1 GV/m. Corresponding electron beams with lower particle energy are also emitted. These beams contribute significantly to the neutron and x-ray output of the device. However, the mechanisms behind these gradients are not completely understood and hence a true predictive capability required for optimization or application is not currently available. At LLNL we are assembling a DPF experiment with a unique 4 MV ion probe beam designed to measure these gradients directly and to examine the possibility of using the DPF as a high-gradient acceleration stage. These unique data along with fully kinetic simulation of the DPF z-pinch will form an integrated simulation and experimental approach to understanding the DPF. In this poster we will review the design, construction, and initial operations of a 4 kJ modular DPF. We will also discuss how the probe beam will be used to measure the acceleration gradients in the plasma.

The Beam Research Program at Lawrence Liver-more National Laboratory is continuing development of the dielectric wall accelerator (DWA), a type of accelerator which uses stacked pulse-forming lines (PFLs) to apply an accelerating field directly to the beam through a nonconducting vacuum boundary. Here, we report operation of a DWA as an electron diode using a surface flashover plasma cathode. Peak perveances in excess of 6 x 10(-6) A/V-3/2 were measured, with current extraction and pulse train format depending on flashover source timing and PFL switching speed.

Compact dielectric wall (DWA) accelerator technology is being developed at the Lawrence Livermore National Laboratory. The DWA accelerator uses fast switched high voltage transmission lines to generate pulsed electric fields on the inside of a high gradient insulating (HGI) acceleration tube. Its high electric field gradients are achieved by the use of alternating insulators and conductors and short pulse times. The DWA concept can be applied to accelerate charge particle beams with any charge to mass ratio and energy. Based on the DWA system, a novel compact proton therapy accelerator is being developed. This proton therapy system will produce individual pulses that can be varied in intensity, energy and spot width. The system will be capable of being sited in a conventional linac vault and provide intensity modulated rotational therapy. The status of the developmental new technologies that make the compact system possible will be reviewed. These include, high gradient vacuum insulators, solid dielectric materials, SiC photoconductive switches and compact proton sources. Applications of the DWA accelerator to problems in homeland security will also be discussed.

A new type of compact induction accelerator is under development at the Lawrence Livermore National Laboratory that promises to increase the average accelerating gradient by at least an order of magnitude over that of existing induction machines. The machine is based on the use of high gradient vacuum insulators, advanced dielectric materials and switches and is being developed for a variety of applications. Research describing an extreme variant of this technology aimed at producing a compact, variable output linear accelerator for proton therapy for cancer will be described along with the technical challenges and issues. The goal of the development is to produce a proton accelerator that will fit in a standard linac vault and deliver intensity modulated proton therapy. Tomotherapy, Inc. has licensed the new accelerator technology from the Lawrence Livermore National Laboratory and the Compact Particle Acceleration Corporation (CPAC) is supporting development of the system. Research sponsored by Tomotherapy, Inc. and CPAC. Conflict of Interest: Some of the co‐authors have a financial interest in Tomotherapy, Inc. and/or CPAC.

Large aperture plasma electrode pockels cells (PEPC) are an enabling technology in the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory. The Pockels cell allows the NIF laser to take advantage of multi-pass amplifier architecture, thus reducing costs and physical size of the facility. Each Pockels cell comprises four 40-cm times 40-cm apertures arranged in a 4times1 array. The combination of the Pockels cell and a thin-film polarizer, configured in a 4times1 array, form an optical switch that is key to achieving multi-pass operation. Solid-state Plasma Pulse Generators (PPGs) and high current high voltage solid-state Switch Pulse Generators (SPGs) have been developed for use in the PEPC. The solid-state plasma pulse generators initiate and maintain plasma within the cells; each pulser is capable of delivering 60 J of energy to each plasma channel. Deployment of the solid-state PPGs has been completed in NIF. The MOSFET-switched SPG is capable of delivering a requisite fast rise time, 17 kV flattop pulse to the cells' nonlinear crystals. A complete software and hardware control system has been developed and is currently being tested for use on the solid-state SPGs. Also a transmission line modeling, development, and testing effort is in process, in support of NIFs' Advanced Radiographic Capabilities (ARC). Work is scheduled for completion by the end of the calendar year.

Summary form only given. A high current, high voltage, all solid-state pulse modulator has been developed for use in the Plasma Electrode Pockels Cell (PEPC) subsystem in the National Ignition Facility. The MOSFET-switched pulse generator, designed to be a more capable plug-in replacement for the thyratron-svvitched units currently deployed in NIF, offers unprecedented capabilities including burst-mode operation, pulse width agility and a steady-state pulse repetition frequency exceeding 1 Hz. Capable of delivering requisite fast risetime, 17-kV flattop pulses into a 6-Omega load, the pulser employs a modular architecture characteristic of the inductive adder technology, pioneered at LLNL for use in acceleration applications, which keeps primary voltages low (and well within the capabilities of existing FET technology), reduces fabrication costs and is amenable to rapid assembly and quick field repairs.

As the switching capabilities of solid-state devices increase, these devices are being incorporated into modulator designs for high voltage accelerator applications. Solid-state modulators based on inductive adder circuit topology have demonstrated great versatility with regard to pulse width and pulse repetition rate while maintaining fast pulse rise and fall times. Additionally, these modulators are capable of being scaled to higher output voltage and power levels. An explanation of the basic circuit operation will be presented as well as test data of several different hardware systems.

The Next Linear Collider (NLC) accelerator proposal at Stanford Linear Accelerator Center (SLAC) requires a high efficiency, highly reliable, and low cost pulsed power modulator to drive the X band klystrons. The present NLC RF compression technique needed a modulator to drive 4 Klystrons at 400kV, 1300A for 1.6 mu S at 60 PPS (> 500 megawatt pulse, 80kW average). A prototype NLC solid-state induction modulator was modified to drive this new klystron array. The prototype induction modulator utilizes a three-turn secondary with 76 single "fraction turn" primary to produce the 400kV pulse. The design, testing and operational experience will be discussed.

protection remains a critical issue along with modulator reliability, efficiency and cost. Configurations whereby multiple klystrons are paralleled on a single modulator may exacerbate the problem. The majority of this paper will discuss tests at SLAC of klystron arcs on Line-type modulators with single and double klystron loads. This talk may introduce and refer to other talks at this conference and other conferences by National and Foreign Laboratory collaborators and Industry, specifically in relation to DOE SBIR programs.

A solid-state high voltage pulse generator with multipulse burst capability, very fast rise and fall times, pulse width agility, and amplitude modulation capability for use with high speed electron beam kickers has been designed and tested at LLNL. A control system calculates a desired waveform to be applied to the kicker based on measured electron beam displacement then adjusts the pulse generators to provide the desired waveform. This paper presents the design of the control system and measured performance data from operation on the ETA-II accelerator at LLNL.

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.

A solid-state modulator with very fast rise and fall times, pulse width agility, and multi-pulse burst and intra-pulse amplitude adjustment capability for use with high speed electron beam kickers has been designed and tested at LLNL. The modulator uses multiple solid-state modules stacked in an inductive-adder configuration. Amplitude adjustment is provided by controlling individual modules in the adder, and is used to compensate for transverse e-beam motion as well as the dynamic response and beam-induced steering effects associated with the kicker structure. A control algorithm calculates a voltage based on measured e-beam displacement and adjusts the modulator to regulate beam centroid position. This paper presents design details of amplitude control along with measured performance data from kicker operation on the ETA-II accelerator at LLNL.

The ability to extract particle beam bunches from a ring accelerator in arbitrary order can greatly extend an accelerator's capabilities and applications. A prototype solid-state kicker pulser capable of generating asynchronous bursts of 50 kV pulses has been designed and tested into a 50 /spl Omega/ load. The pulser features fast rise and fall times and is capable of generating an arbitrary pattern of pulses with a maximum burst frequency exceeding 5 MHz. If required, the pulse-width of each pulse in the burst is independently adjustable. This kicker modulator uses multiple solid-state modules stacked in an inductive-adder configuration where the energy is switched into each section of the adder by a parallel array of MOSFETs. Test data, capabilities, and limitations of the prototype pulser are described.

This paper presents the physics design of the DARHTII downstream system, which consists of a diagnostic beam stop, a fast, high-precision kicker system and the xray converter target assembly. The beamline configuration, the transverse resistive wall instability and the ion hose instability modelling are presented. We also discuss elimination of spot size dilution during kicker switching and implementation of the foil-barrier scheme to minimize the backstreaming ion focusing effects. Finally, we present the target converter’s configuration, and the simulated DARHT-II x-ray spot sizes and doses. Some experimental results, which support the physics design, will be also presented.

A solid-state high voltage pulse generator for highspeed beam kicker applications has been designed and tested at Lawrence Livermore National Laboratory. This kicker pulser uses multiple stages stacked in an inductive-adder configuration where the energy is switched from each stage of the adder by a parallel array of MOSFETs. Features include pulse width, format and amplitude agility all at a high pulse-repetition rate. The modulator can drive a 50%o load at voltages up to 18 kV with +/-10% amplitude modulation at several MHz burst frequency. Rise and fall times are on the order of 10 ns, and the pulser can easily be configured for either positive or negative polarity. The presentation will include test and operational data collected from both the ETA II accelerator kicker and resistive dummy loads.

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 electro-optical x-ray imaging system, and other hydrodynamics testing systems. We will briefly describe this machine. 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 will discuss this accelerator by summarizing the overall design of the long-pulse injector and accelerator. We will also discuss the fast kicker used to separate the long-pulse beam into short bursts suitable for radiography.