A @[email protected] with additional amplification by electron multiplication. It consists of a photocathode, a series of dynodes, called a dynode chain on which a secondary-electron multiplication process occurs, and an @[email protected] According to the desired @[email protected], transit time, time spread, gain, or low @[email protected], different types of dynode structures have been developed, e.g. circular @[email protected] structure, linear focused structure, venetian blind structure, box and grid structure. Some special dynode structures permit combination with additional electric or magnetic fields. A strip dynode photomultiplier tube consists of a photocathode followed by thin dynode material on an insulating substrate. In a continuous-strip photomultiplier, two strip dynodes are arranged in parallel. A potential applied to the ends of the two strips produces an electric field across the continuous strip dynodes, giving rise to electron multiplication along the dynodes. In a @[email protected] magnetic photomultiplier, a uniform magnetic field is applied to the planes of the strips, so that the electrons travel in the crossed electric and magnetic fields. A channel photomultiplier tube photocathode consists of a @[email protected] electron multiplier (CEM) system for the photoelectrons, and an @[email protected] to collect the final electron current. The basic part of the CEM is a tube with a semiconducting inner surface. In general it is curved in order to inhibit the @[email protected] of positive ions towards the photocathode. A number of small channels called microchannels can be constructed in arrays for imaging applications.