Patent ID: 7602122

Claim:
A photomultiplier comprising: an outer casing whose interior is maintained in a vacuum state; a photocathode accommodated in said outer casing, said photocathode emitting electrons into the interior of said outer casing in accordance with light taken in via said outer casing; an electron multiplier section accommodated in said outer casing, said electron multiplier section having: a base which has a main surface facing said photocathode such that the electrons from said photocathode directly reach; and a plurality of wall portions for guiding, on the main surface of said base, the reached electrons in a predetermined direction, each of said wall portions extending along the predetermined direction while being in direct contact with the main surface of said base; and an anode accommodated in said outer casing, said anode taking out, from among electrons resulting from cascade multiplication at said electron multiplier section, reached electrons as signals, wherein one or more protrusions, each having a secondary electron emitting surface formed on the surface thereof to perform cascade multiplication of the electrons from said photocathode, are provided on the respective surfaces of the adjacent wall portions which face each other, and wherein an interval between the adjacent wall portions which face each other seesaws along a direction from said photocathode to said anode.