Accelerating cavity and method of manufacturing accelerating cavity

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 o 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.