Enhanced dielectric-wall linear accelerator

• US 5,811,944 A
• Filed: 12/18/1996
• Issued: 09/22/1998
• Est. Priority Date: 06/25/1996
• Status: Expired due to Term

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: United States Of America As Represented By The Department Of Energy
• Inventors: Caporaso, George J., Sampayan, Stephen E., Kirbie, Hugh C.
• Primary Examiner(s): O'Shea, Sandra L.
• Assistant Examiner(s): Patidar, Jay M.
• Application Number:
  US08/773,804
• Time in Patent Office: 643 Days
• Field of Search: 315/505, 315/500, 315/507, 315/5.42, 315/5.41, 315/5.47, 315/5.46, 315/5.16, 315/359.1, 315/360.1
• US Class Current: 315/505
• CPC Class Codes: H05H 7/00 Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
• CPC Class Codes: H05H 9/00 Linear accelerators

Abstract

A dielectric-wall linear accelerator is enhanced by a high-voltage, fast e-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface.

Claims

1. A linear accelerator (linac), comprising:

a first plane with a first flat planar conductor having a first central hole, and connected to a common potential;

a second plane adjacent to and parallel with the first plane and having a second flat planar conductor with a second central hole that shares an axis with said first central hole, and switchable to both said common potential and a high voltage potential;

a third plane adjacent to and parallel with the second plane and having a third flat planar conductor with a third central hole that shares said axis with said first and second central holes, and connected to a common potential;

a first dielectric volume that fills the space separating said first and second planar conductors and that comprises a first layered insulator assembly with a first dielectric constant;

a second dielectric volume that fills the space separating said second and third planar conductors and that comprises a second layered insulator assembly with a second dielectric constant that is substantially greater than the dielectric constant of said first material, wherein a substantial difference in electrical signal wavefront propagation velocity exists between the first and second dielectric volumes from the outside perimeters of the first through third flat planar conductors and their respective first through third central holes;

a laser directed to focus a fluence of photons on the outside edges of said first through third flat planar conductors for repeated initiation of a short circuit of a high voltage, wherein, an accelerating field is momentarily created in one direction along said axis through said first through third central holes; and

a dielectric sleeve fitted through the inside diameters of said first through third central holes as a hollow tube open to pass a particle beam along said axis;

wherein the dielectric sleeve comprises alternating layers of metals and dielectrics in planes orthogonal to said axis.

2. The linac of claim 1, wherein:

the dielectric sleeve further comprises a lamination of alternating sheets of electrically isolated conductors and insulators in a stack is such that each pair of conductor and insulator sheets has a thickness that does not exceed one millimeter.

3. The linac of claim 1, wherein:

said first through third flat planar conductors have circular outside perimeters and the whole linac combines to form a solid cylinder with a coaxial cylindrical hole, said first through third flat planar conductors comprise inner and outer conductive rings between which the electrical length between said inner and outer conductive rings is extended.

4. The linac of claim 1, further comprising:

a dielectric sleeve fitted through the inside diameters of said first through third central holes as a hollow tube open to pass a particle beam along said axis.

5. The linac of claim 4, wherein:

the dielectric sleeve comprises, in overall bulk, a third material with a dielectric constant that is four times that of said first material;

wherein the dielectric constants of said first through third materials have a ratio of 1;

9;

4.

6. The linac of claim 1, wherein:

said first through third flat planar conductors have circular outside perimeters and the whole linac combines to form a solid cylinder with a coaxial cylindrical hole.

7. The linac of claim 1, further comprising an initiation switch that includes:

a pair of electrodes providing for the application of a high voltage potential;

an insulator assembly disposed between the pair of electrodes and having at least one surface between the pair of electrodes exposed to a vacuum; and

light source means for directing a flux of photons to fall on said surface between the pair of electrodes exposed to said vacuum for precipitating an electrical current flashover between the pair of electrodes.

8. The linac of claim 7, wherein:

the light source means includes a frequency multiplied Nd-YAG laser (1.06μ

) that provides a prompt flux through a port and lenses that is thrown to a line focus approximately one millimeter by one centimeter along said surface between the pair of electrodes exposed to said vacuum.

9. The linac of claim 7, wherein:

the laser means includes a bundle of fiber optic cables for directing a plurality of prompt photon fluxes independently to a plurality of places on said surface between the pair of electrodes exposed to said vacuum.

10. The linac of claim 7, wherein:

the laser means includes a bundle of fiber optic cables for directing a plurality of prompt photon fluxes independently to a plurality of places on said surface between the pair of electrodes exposed to said vacuum;

wherein different lengths of said fiber optic cable are associated with individual switches to provide for a plurality of time phasings between switch closures for a single pulsed operation of a laser light source.

11. A linear accelerator (linac), comprising:

a plurality of Blumlein modules arranged in a coaxial stack;

a high-voltage, fast rise-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators;

means for applying a high voltage between the electrodes; and

a light source focused along at least one line along the edge surface of said laminated alternating layers of isolated conductors and insulators extending between said electrodes, wherein the initiation of a surface breakdown is accomplished by a fluence of photons, thus causing the switch to electrically close very promptly; and

a dielectric sleeve coaxially disposed within the coaxial stack of Blumlein modules that comprises a lamination of alternating sheets of electrically isolated conductors and insulators in a stack is such that each pair of conductor and insulator sheets has a thickness that does not exceed one millimeter.

12. The linac of claim 11, further comprising:

phasing means for delivering said fluence of photons at a sequence of different times to each Blumlein module.

13. The linac of claim 12, wherein:

the phasing means is such that said time delivery sequence is controlled by adjusting the length of a set of fiber optic cables that carry the laser light to the insulator surface.

14. The linac of claim 12, wherein:

each of said Blumlein modules includes both a first and a second type of insulator, wherein said first type has a dielectric constant that is nine times the dielectric constant of said second type.

15. The linac of claim 12, wherein:

the light source is a frequency multiplied type laser coupled in with a fiber optic bundle.