First-stage dynode and photomultiplier tube

A photomultiplier tube, comprising:

• a photocathode;
• a plurality of stages of dynodes;
• and
• an anode,
• wherein the plurality of stages of dynodes include a first-stage dynode and a second-stage dynode arranged on a predetermined plane,
• the first-stage dynode includes:
• a bottom wall portion;
• and
• a pair of side wall portions extending from both end portions of the bottom wall portion in a predetermined direction to the photocathode side and the second-stage dynode side, the predetermined direction being perpendicular to the predetermined plane,
• in the first-stage dynode, an electron emission surface is formed by a bottom surface of the bottom wall portion on the photocathode side and the second-stage dynode side and a pair of side surfaces of the pair of side wall portions on the photocathode side and the second-stage dynode side, and
• each of the pair of side surfaces is a curved surface that is curved in a concave shape in a cross section parallel to the predetermined direction.