Accelerating cavity and method of manufacturing accelerating cavity
An accelerating cavity includes: a housing that is conductive, has a tubular shape, and is formed by joining a plurality of part members parted by a planar parting surface along a central axis; a plurality of cells that are arranged in the housing along an axial direction of the central axis of the housing, and are connected to each other by a communicating portion that allows charged particles to pass through; and a protrusion that is disposed at a position surrounding the communicating portion of each of the cells in the housing, protrudes toward an inner side of the cell in the axial direction, and has a shape becoming larger in a radial direction with respect to the central axis from a tip end portion toward a base end portion in the axial direction.
1 . An accelerating cavity comprising:
a housing that is conductive, has a tubular shape, and is formed by joining a plurality of part members parted by a planar parting surface along a central axis;
a plurality of cells that are arranged in the housing along an axial direction of the central axis of the housing, and are connected to each other by a communicating portion that allows charged particles to pass through; and
a protrusion that is disposed at a position surrounding the communicating portion of each of the cells in the housing, protrudes toward an inner side of the cell in the axial direction, and has a shape becoming larger in a radial direction from a tip end portion toward a base end portion in the axial direction as the shape is away from the parting surface in a rotating direction about the central axis, wherein
the protrusion includes a base-end side curved portion forming the base end portion, a tip-end side curved portion forming the tip end portion, and a connecting portion connecting the base-end side curved portion and the tip-end side curved portion,
the base-end side curved portion and the connecting portion are smoothly connected to each other, and the tip-end side curved portion and the connecting portion are smoothly connected to each other, and
at a position at which a predetermined angle φ from the parting surface in the rotating direction about the central axis, a connecting position between the tip-end side curved portion and the connecting portion is set so as to satisfy
α
(
φ
)
∝
(
sin
φ
)
n
where α(φ) is an angle formed by a first virtual line orthogonal to a line tangent to the connecting position and a second virtual line perpendicular to the central axis, and n is a positive real number.
2 . The accelerating cavity according to claim 1 , wherein,
in a cross-sectional view along a plane passing the central axis,
the base-end side curved portion exhibits an arc shape, and
the connecting portion includes a linear portion.
3 . A method of manufacturing an accelerating cavity including: a housing that is conductive, has a tubular shape, and is formed by joining a plurality of part members parted by a planar parting surface along a central axis; a plurality of cells that are arranged in the housing along an axial direction of the central axis of the housing, and are connected to each other by a communicating portion that allows charged particles to pass through; and a protrusion that is disposed at a position surrounding the communicating portion of each of the cells in the housing, and protrudes toward an inner side of the cell in the axial direction, the method comprising:
forming a recess corresponding to the plurality of cells and the communicating portion by machining a machined surface of a base material, the machined surface being a surface corresponding to the parting surface; and
forming a portion corresponding to the protrusion such that the portion has a shape becoming larger in a radial direction with respect to the central axis from a tip end portion toward a base end portion in the axial direction of the central axis by inserting a machining tool into the recess from a side of the machined surface, wherein
in the forming a portion corresponding to the protrusion,
the protrusion includes a base-end side curved portion forming the base end portion, a tip-end side curved portion forming the tip end portion, and a connecting portion connecting the base-end side curved portion and the tip-end side curved portion,
the base-end side curved portion and the connecting portion are smoothly connected to each other, and the tip-end side curved portion and the connecting portion are smoothly connected to each other, and
at a position at which a predetermined angle φ from the parting surface in the rotating direction about the central axis, a connecting position between the tip-end side curved portion and the connecting portion is set so as to satisfy
α
(
φ
)
∝
(
sin
φ
)
n
where α(φ) is an angle formed by a first virtual line orthogonal to a line tangent to the connecting position and a second virtual line perpendicular to the central axis, and n is a positive real number.