James S. Sullivan

High gradient induction accelerator

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 stimulated by the desire for compact flash X-ray radiography sources. Research describing an extreme variant of this technology aimed at proton therapy for cancer will be described. Progress in applying this technology to several applications will be reviewed.

Development of a Compact Radiography Accelerator Using Dielectric Wall Accelerator Technology

We are developing an inexpensive compact accelerator system primarily intended for pulsed radiography. Design characteristics are an 8 MeV endpoint energy, 2 kA beam current, a cell gradient of approximately 3 MV/m (for an overall accelerator length is 2-3 m), and <

Solid-state kicker pulser for DARHT-2

1/Volt capital costs. Such designs have been made possible with the development of high specific energy dielectrics (>10J/cm3), specialized transmission line designs and multi-gap laser triggered low jitter (<1 ns) gas switches. In this geometry, the pulse forming lines, switches, and insulator/beam pipe are fully integrated within each cell to form a compact, stand-alone, stackable unit. We detail our research and modeling to date, recent high voltage test results, and the integration concept of the cells into a radiographic system.

TH‐C‐AUD‐09: A Proposal for a Novel Compact Intensity Modulated Proton Therapy System Using a Dielectric Wall Accelerator

To replace a hard tube design, a solid-state kicker pulser for the Dual-Axis Radiographic Hydrodynamic Test facility (DARHT-2) has been designed and tested. 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. The modulator features very fast rise and fall times, pulse width agility and a high pulse-repetition rate in burst mode. The modulator can drive a 50 /spl Omega/ load with voltages up to 20 kV and can be easily configured for either positive or negative polarity. The presentation includes test and operational data.

Status Of The Dielectric Wall Accelerator For Proton Therapy

Purpose: A novel compact CT‐guided intensity modulated protonradiotherapy (IMPT) system is introduced. The system is being designed to deliver motion‐managed IMPT to large target volumes. The system will be ideal for large and complex target volumes in young patients. Method and Materials: The basis of the design is the dielectric wall accelerator (DWA) system being developed at Lawrence Livermore National Laboratory (LLNL). The DWA will use fast switched high voltage transmission lines to generate pulsed electric fields on the inside of a high gradient insulating (HGI) acceleration tube. High electric field gradients are achieved alternating insulators and conductors and short pulse times. The system will produce individual pulses that can be varied in intensity, energy and spot width, all of which will be optimized in the IMPT planning system. It is anticipated that no magnets will be required and the neutron contamination will be very low. The system will be capable of being sited in a conventional linac vault. Results: The design specifications have been met in some component tests. Gradients of 100 MV/m have been achieved in small HGI samples. Optical switches based on fast laser switched SiC has been achieved. Feasibility tests of an optimization system for selecting the position, energy, intensity and spot size for a collection of spots comprising the treatment are underway. A prototype is being designed and concept designs of the envelope and environmental needs of the unit has commenced. Conclusion: The DWA accelerator represents breakthrough technology for intensity modulated proton therapy. The system is being designed from the ground up to be capable of CT‐guided intensity modulated proton therapy and to be housed in a conventional linac vault. Conflict of Interest:Some of the authors have financial interest in TomoTherapy Inc., which has licensed the DWA technology from LLNL.

Electromagnetic and thermal simulations for the switch region of a compact proton accelerator

The Dielectric Wall Accelerator (DWA) offers the potential to produce a high gradient linear accelerator for proton therapy and other applications. The current status of the DWA for proton therapy will be reviewed. Recent progress in SiC photoconductive switch development will be presented. There are serious beam transport challenges in the DWA arising from short pulse excitation of the wall. Solutions to these transport difficulties will be discussed.

Developmeno f Compact Pulsed Power for thet Dielectric Wall Accelerator (DWA)

A compact proton accelerator for medical applications is being developed at Lawrence Livermore National Laboratory. The accelerator architecture is based on the dielectric wall accelerator (DWA) concept. One critical area to consider is the switch region. Electric field simulations and thermal calculations of the switch area were performed to help determine the operating limits of silicon carbide (SiC) switches. Different geometries were considered for the field simulation including the shape of the thin indium solder meniscus between the electrodes and SiC. Electric field simulations were also utilized to demonstrate how the field stress could be reduced. Thermal simulations results were analyzed to find the average power capability of the switches.

ULTRA‐COMPACT ACCELERATOR TECHNOLOGIES FOR APPLICATION IN NUCLEAR TECHNIQUES

We are developing compact pulsed power systems for various defense missions. Although the system is primarily intended for pulsed radiography, its modularity makes it well suited for compact neutron sources for explosives detection and as an HPM driver for various DOD missions. To date, we have performed extensive research at the component level and are now pursuing the integration of the technology into a single accelerator cell. Cost is <

MO‐D‐BRD‐02: Dielectric Wall Accelerators for Proton Therapy

0.50/volt. As part of this effort, we are also pursuing advanced development of high specific energy dielectrics (>10J/cm3), specialized transmission line designs, HGI insulator technology, multi-gap low jitter (<1 ns) switches, and high voltage SiC photoconductive switching. We detail the progress of our overall research to date, recent high voltage test results, and the integration concept into a compact accelerator cell

Optically-initiated silicon carbide high voltage switch

We report on compact accelerator technology development for potential use as a pulsed neutron source quantitative post verifier. The technology is derived from our on‐going compact accelerator technology development program for radiography under the US Department of Energy and for a clinic sized compact proton therapy systems under an industry sponsored Cooperative Research and Development Agreement. The accelerator technique relies on the synchronous discharge of a prompt pulse generating stacked transmission line structure with the beam transit. The goal of this technology is to achieve ∼10 MV/m gradients for 10 s of nanoseconds pulses and ∼100 MV/m gradients for ∼1 ns systems. As a post verifier for supplementing existing x‐ray equipment, this system can remain in a charged, stand‐by state with little or no energy consumption. We describe the progress of our overall component development effort with the multilayer dielectric wall insulators (i.e., the accelerator wall), compact power supply technology,...