Waveguide for a particle accelerator

Patent metadata

Field	Value
Publication number	US-12317405-B2
Application number	US-202117997714-A
Country	US
Kind code	B2
Filing date	Apr 30, 2021
Priority date	May 1, 2020
Publication date	May 27, 2025
Grant date	May 27, 2025

Abstract

Disclosed herein is a waveguide cell having a helical cavity. The waveguide cell has a central axis and a cavity having a transverse cross section whose rotational position about the central axis varies along the central axis. There is also disclosed a method a determining the shape of a waveguide cell.

First claim

The invention claimed is:

1. A waveguide cell comprising:
a helical cavity; and
a central axis, wherein the helical cavity includes a transverse cross section whose rotational position about the central axis varies along the central axis, wherein a longitudinal cross section of the waveguide cell in a first plane and a longitudinal cross section of the waveguide cell in a second plane, orthogonal to the first plane, are a same shape 180 degrees out of phase relative to each other, wherein the transverse cross section is a polar coordinates conversion of an iris-to-iris 2D cartesian cell shape, and wherein the longitudinal cross section of the waveguide cell viewed in a first plane is the iris-to-iris 2D cartesian cell shape, and wherein the longitudinal cross section of the waveguide cell viewed in a second plane, orthogonal to the first plane is an equator-to-equator 2D cartesian cell shape.

2. The waveguide cell of claim 1 , wherein the transverse cross section is continuously helically rotated along a length of the waveguide cell.

3. The waveguide cell of claim 2 , wherein the transverse cross section is rotated at a fixed rotation rate along the length of the waveguide cell.

4. The waveguide cell of claim 2 , wherein the transverse cross section is helically rotated along the length of the waveguide cell through at least 180 degrees.

5. The waveguide cell of claim 1 , in combination with one or more additional waveguide cells in a series arrangement.

6. The waveguide cell of claim 1 , wherein the longitudinal cross section in the first plane has a periodic structure, and wherein the longitudinal cross section in the second plane has the periodic structure 180 degrees out of phase relative to the first plane.

7. A method of generating a three-dimensional (3D) shape of a waveguide cell, the method comprising:
identifying a two-dimensional (2D) cross section of the waveguide cell, wherein identifying a 2D cross section comprises:
identifying a Cartesian 2D cross section of the waveguide cell in Cartesian coordinates; and
generating a polar 2D cross section in polar coordinates by converting the 2D Cartesian cross section into polar coordinates defining a θ direction between 0 and L/2π;

helically rotating the (2D) cross section around a central axis along a length (L) of the waveguide cell to generate a 3D shape, wherein helically rotating the 2D cross section around the central axis along the length of the cell to generate a 3D shape comprises:
extruding the 2D polar coordinates shape back in a z axis of the Cartesian coordinate system with a twist rate of π/L; and

outputting the 3D shape.

8. The method of claim 7 wherein helically rotating the cross section comprises rotating the cross section along the length of the waveguide cell through 180 degrees.

9. The method of claim 7 , wherein identifying a 2D cross section comprises:
identifying a periodic Cartesian 2D cross section of the waveguide cell, wherein the periodic Cartesian 2D cross section defines a periodic function f(z);
and wherein helically rotating the cross section around the central axis along the length of the waveguide cell to generate a 3D shape comprises:
transforming the periodic function f(z) into a new function F(θ) in a helical coordinate system, wherein one or more z values are converted by a twist rate π/L and a value of θ ranges from 0 to L/2π.

10. The method of claim 7 , wherein the Cartesian 2D cross section of the cell comprises an iris-to-iris cell shape, and wherein a longitudinal cross section of the waveguide cell in a first plane is the iris-to-iris Cartesian cell shape, and in a second plane, orthogonal to the first plane, is an equator-to-equator Cartesian cell shape.

11. The method of claim 10 , wherein the Cartesian 2D cross section is the longitudinal cross section of a known cavity shape and wherein the known cavity shape comprises one of:
a pillbox shape, an elliptical shape, an Ichiro shape or a Tesla shape.

12. A linear accelerator comprising:
a waveguide, the waveguide including:
a waveguide cell, the waveguide cell including:
a central axis; and
a helical cavity, wherein the helical cavity includes a transverse cross section, wherein a rotational position of the transverse cross section about the central axis varies along the central axis, wherein a longitudinal cross section of the waveguide cell in a first plane and a longitudinal cross section of the waveguide cell in a second plane, orthogonal to the first plane, are a same shape 180 degrees out of phase relative to each other, wherein the transverse cross section is a polar coordinates conversion of an iris-to-iris 2D cartesian cell shape, and wherein the longitudinal cross section of the waveguide cell viewed in a first plane is the iris-to-iris 2D cartesian cell shape, and wherein the longitudinal cross section of the waveguide cell viewed in a second plane, orthogonal to the first plane, is an equator-to-equator 2D cartesian cell shape.

13. The linear accelerator of claim 12 , wherein the transverse cross section is continuously helically rotated along a length of the waveguide cell.

14. The linear accelerator of claim 13 , wherein the transverse cross section is rotated at a fixed rate of rotation along the length of the waveguide cell, and wherein the transverse cross section is helically rotated along the length of the waveguide cell through 180 degrees.

Assignees

• Elekta ltd

Inventors

• Shinton Ian

Classifications

• H05H2277/11

  Radiotherapy · CPC title

• H01P3/127

  with a circular, elliptic, or parabolic cross-section · CPC title

• A61N5/1077

  Beam delivery systems · CPC title

• H05H7/22

  Details of linear accelerators, e.g. drift tubes (H05H7/02 - H05H7/20 take precedence) · CPC title

• H05H9/00

  Linear accelerators · CPC title