Secondary electron multipliers (SEM) are electronic devices for amplifying (multiplying) the flow of electrons based on secondary electron emission.
Open SEMs are vacuum tube devices which are used for direct detection of electromagnetic radiation or particles. The device is used in facilities operating under natural vacuum conditions (in space) and in high-vacuum measuring instruments at pressures which do not normally exceed 10-3 Pa.
Depending on the design, SEMs are divided into two main groups: (1) with discrete dynode systems in which electron fluxes are multiplied on separate electrodes – dynodes, with potentials of dynodes in such SEMs increasing in a stepwise manner, and (2) with distributed (continuous) dynode systems in which electron fluxes are multiplied along the surfaces with a continuous change in potential (channel electron multiplier, microchannel plates).
VTC Baspik produces channel SEMs (SEM-6M and SEM-6C) and SEMs with a chevron stack of two MCPs (SEM-7B in various versions).