Electron multiplier with improved dynode geometry for reduced crosstalk

A photomultiplier comprising:

• a transparent sealed container;
• an incident window on which light to be measured is incident, said incident window being formed on one end face of said transparent sealed container;
• first and second reflection-type photoelectric surfaces arranged in said sealed container and aligned adjacent to each other;
• respective light beam incident ports of said first and second reflection-type photoelectric surfaces, said light beam incident ports being arranged to oppose said incident window;
• and
• first and second dynode arrays, both having a respective plurality of stages of dynodes, including respective first-stage and second-stage dynodes, for multiplying photoelectrons supplied from said first and second reflection-type photoelectric surfaces, respectively, said first and second dynode arrays being provided to correspond to said first and second reflection-type photoelectric surfaces,
• wherein said first-stage dynodes are arranged in a substantially side-by-side manner, such that a direction of photoelectron emission of said first-stage dynode of said first dynode array is opposite to and away from a direction of photoelectric emission of said first-stage dynode of said second dynode array, and such that the photoelectron emission of said first-stage dynodes of said first and second dynode arrays are substantially perpendicular to a direction along which said first and second reflective-type photoelectric surfaces are aligned.