Lawrence Livermore National Security, LLC

Opcondys, Inc.

University of California

The United States of America As Represented by the United States

The United States of America As Represented by the Department of Energy

George James Caporaso

Stephen E Sampayan

Steven Anthony Hawkins

Yu-Jiuan Chen

Scott D Nelson

David M Sanders

Kristin Cortella Sampayan

Hugh C Kirbie

Hoang Tan Nguyen

James S Sullivan

Brian R Poole

Clifford C Shang

Lars F Voss

Adam M Conway

Rebecca J Nikolic

Mihail Bora

John Richardson Harris

Li-Fang Wang

Hugh Kirbie

William J Orvis

Daniel S Prono

Sangtae Park

Arthur C Paul

Ted F Wieskamp

Richard J Briggs

Jim Sullivan

Methods, devices and systems for ultra-high dose radiotherapy are disclosed. The described techniques rely in-part on active switching control of a photoconductive switch during the time the accelerator is accelerating charged particles to produce the output radiation at the desired dose rates. One radiotherapy system includes a particle accelerator configured to receive charged particles from a pulsed source. The particle accelerator includes a pipe configured to allow the charged particles to pass through as a beam, a magnetic core positioned proximate to the pipe and coupled to the pulsed source, and at least one multilayer insulator positioned adjacent to the pipe and the magnetic core. The system also includes a photoconductive switch coupled to the particle accelerator and configured to supply the particle accelerator with a plurality of voltage pulses.

Flash radiotherapy accelerator system

Methods, devices and systems for ultra-high dose radiotherapy are described that rely in-part on active switching control of a photoconductive switch when the accelerator is accelerating charged particles to produce output radiation at desired dose rates. One example method for producing output radiation in a flash radiotherapy system includes receiving, at a particle accelerator, a charged particle beam, where the particle accelerator system also includes a photoconductive switch coupled to the particle accelerator. The photoconductive switch can operate in a linear mode and includes a doped crystalline material that receives a voltage to establish an electric field across the crystalline material. The method includes producing a plurality of voltage pulses by the photoconductive switch in response to receiving light incident on the doped crystalline material, and accelerating the charged particles by the particle accelerator based on the plurality of voltage pulses to produce the output radiation beams for flash radiotherapy.

Flash radiotherapy accelerator

Methods, devices and systems for ultra-high dose radiotherapy are disclosed. The described techniques rely in-part on active switching control of a photoconductive switch during the time the accelerator is accelerating charged particles to produce the output radiation at the desired dose rates. One flash radiotherapy system includes an induction accelerator, and a controllable switch coupled to the induction accelerator. The switch is operable to produce a plurality of voltage pulses to drive the induction accelerator. The radiotherapy system also includes a radiation measurement device to measure output radiation produced by the radiotherapy system and provide feedback to the controllable switch. The controllable switch is operable to, based on the received feedback, modify an amplitude, shape, spacing, number or width of the voltage pulses that are supplied to the particle accelerator to deliver the desired output radiation.

A photoconductive switch is disclosed having a substrate, an electrode formed on the substrate, and a dielectric formed adjacent to the substrate and the electrode. The dielectric, the electrode and the substrate each have a portion cooperatively defining an interface area. The interface area of the dielectric has a doping making the interface area of the dielectric electrically conductive to suppress a charge collection at the interface area when the photoconductive switch is electrically energized through an input signal irradiating the electrode. In one embodiment the electrode may have a curvilinear or spherical shape, and the substrate may have a boundary edge surface which extends normal to the surface of the electrode, and with the dielectric having an edge surface that matches the contour of the substrate edge surface.

Conformal photoconductive switch package

Methods, systems, and devices are disclosed for photoconductive switch package configurations. In some aspects, a photoconductive switch package includes of a wide bandgap photoconductive material (e.g., GaN, ZnO, diamond, AlN, SiC, BN, etc.), a source for energetic photons (e.g., a laser), a mechanism to couple the laser into the switch, and a mechanism for high voltage to enter and leave the switch package. In some implementations, the disclosed photoconductive switch packages can be configured as a three terminal device, e.g., similar to transistors, with one of the terminals being laser input or the voltage input to the laser system.

Photoconductive switch package configurations having a profiled resistive element

A photoconductive switch consisting of an optically actuated photoconductive material, e.g. a wide bandgap semiconductor such as SiC, situated between opposing electrodes. The electrodes are created using various methods in order to maximize reliability by reducing resistive heating, current concentrations and filamentation, and heating and ablation due to the light source. This is primarily accomplished by the configuration of the electrical contact geometry, choice of contacts metals, annealing, ion implantation, creation of recesses within the SiC, and the use of coatings to act as encapsulants and anti-reflective layers.

Reliable electrical contacts for high power photoconductive switches

A photoconductive switch having a wide bandgap material substrate between opposing electrodes, and a doped dielectric filler that is in contact with both the electrodes and the substrate at the triple point. The dielectric filler material is doped with a conductive material to make it partially or completely conducting, to minimize the field enhancement near the triple point both when the substrate is not conducting in the 'off' state and when the substrate is rendered conducting by radiation in the 'on' state.

High voltage photoconductive switch package

A photoconductive switch is formed of a substrate that has a central portion of SiC or other photoconductive material and an outer portion of cvd-diamond or other suitable material surrounding the central portion. Conducting electrodes are formed on opposed sides of the substrate, with the electrodes extending beyond the central portion and the edges of the electrodes lying over the outer portion. Thus any high electric fields produced at the edges of the electrodes lie outside of and do not affect the central portion, which is the active switching element. Light is transmitted through the outer portion to the central portion to actuate the switch.

Photoconductive switch package

The devices, systems and techniques disclosed here can be used to reduce undesired effects by magnetic field induced eddy currents based on a diamagnetic composite material structure including diamagnetic composite sheets that are separated from one another to provide a high impedance composite material structure. In some implementations, each diamagnetic composite sheet includes patterned conductor layers are separated by a dielectric material and each patterned conductor layer includes voids and conductor areas. The voids in the patterned conductor layers of each diamagnetic composite sheet are arranged to be displaced in position from one patterned conductor layer to an adjacent patterned conductor layer while conductor areas of the patterned conductor layers collectively form a contiguous conductor structure in each diamagnetic composite sheet to prevent penetration by a magnetic field.

Diamagnetic composite material structure for reducing undesired electromagnetic interference and eddy currents in dielectric wall accelerators and other devices

In a structure or device having a pair of electrical conductors separated by an insulator across which a voltage is placed, resistive layers are formed around the conductors to force the electric potential within the insulator to distribute more uniformly so as to decrease or eliminate electric field enhancement at the conductor edges. This is done by utilizing the properties of resistive layers to allow the voltage on the electrode to diffuse outwards, reducing the field stress at the conductor edge. Preferably, the resistive layer has a tapered resistivity, with a lower resistivity adjacent to the conductor and a higher resistivity away from the conductor. Generally, a resistive path across the insulator is provided, preferably by providing a resistive region in the bulk of the insulator, with the resistive layer extending over the resistive region.

Resistive foil edge grading for accelerator and other high voltage structures

A virtual, moving accelerating gap is formed along an insulating tube in a dielectric wall accelerator (DWA) by locally controlling the conductivity of the tube. Localized voltage concentration is thus achieved by sequential activation of a variable resistive tube or stalk down the axis of an inductive voltage adder, producing a 'virtual' traveling wave along the tube. The tube conductivity can be controlled at a desired location, which can be moved at a desired rate, by light illumination, or by photoconductive switches, or by other means. As a result, an impressed voltage along the tube appears predominantly over a local region, the virtual gap. By making the length of the tube large in comparison to the virtual gap length, the effective gain of the accelerator can be made very large.

Virtual gap dielectric wall accelerator

A system and method for producing modulated electrical signals. The system uses a variable resistor having a photoconductive wide bandgap semiconductor material construction whose conduction response to changes in amplitude of incident radiation is substantially linear throughout a non-saturation region to enable operation in non-avalanche mode. The system also includes a modulated radiation source, such as a modulated laser, for producing amplitude-modulated radiation with which to direct upon the variable resistor and modulate its conduction response. A voltage source and an output port, are both operably connected to the variable resistor so that an electrical signal may be produced at the output port by way of the variable resistor, either generated by activation of the variable resistor or propagating through the variable resistor. In this manner, the electrical signal is modulated by the variable resistor so as to have a waveform substantially similar to the amplitude-modulated radiation.

System and method of modulating electrical signals using photoconductive wide bandgap semiconductors as variable resistors

An improved photoconductive switch having a SIC or other wide band gap substrate material, such as GaAs and field-grading liners composed of preferably SiN formed on the substrate adjacent the electrode perimeters or adjacent the substrate perimeters for grading the electric fields.

Optically-initiated silicon carbide high voltage switch

A dispersion-free radial transmission line ('DFRTL') preferably for linear accelerators, having two plane conductors each with a central hole, and an electromagnetically permeable material ('EPM') between the two conductors and surrounding a channel connecting the two holes. At least one of the material parameters of relative magnetic permeability, relative dielectric permittivity, and axial width of the EPM is varied as a function of radius, so that the characteristic impedance of the DFRTL is held substantially constant, and pulse transmission therethrough is substantially dispersion-free. Preferably, the EPM is divided into concentric radial sections, with the varied material parameters held constant in each respective section but stepwise varied between sections as a step function of the radius. The radial widths of the concentric sections are selected so that pulse traversal time across each section is the same, and the varied material parameters of the concentric sections are selected to minimize traversal error.

Growing community of inventors

Livermore, CA, United States of America

George James Caporaso