45 Riverside Way
The photomultiplier detects light at the photocathode (k) which emits electrons by the photoelectric effect. These photoelectrons are electrostatically accelerated and focused onto the first dynode (d1) of an electron multiplier. On impact each electron liberates a number of secondary electrons which are in turn, electrostatically accelerated and focused onto the next dynode (d2). The process is repeated at each subsequent dynode and the secondary electrons from the last dynode are collected at the anode (a). The ratio of secondary to primary electrons emitted at each dynode depends on the energy of the incident electrons and is controlled by the inter-electrode potentials. By using a variable high voltage supply, the amplitude of photomultiplier output can cover a wide dynamic range.