Handbook of Vacuum Physics, Volume 2: Physical Electronics, Parts 2 and 3 focuses on the processes, methodologies, and reactions involved in thermionic emission and secondary electron emission. The publication first offers information on the theory of thermionic cathodes and measurements on thermionic cathodes. Discussions focus on emission equation and velocity distribution of emitted electrons, surface phenomena and work function, band theory of solids, electrical conductivity, and measurements in special devices and practical tubes. The text then ponders on various types of thermionic cathodes, as well as core metal, compounds used for coating and their preparation, decomposition and activation, properties of oxide cathodes, and evaporation of oxide-coated cathodes. The manuscript takes a look at secondary emission of metals and insulators. Topics include energy distribution of secondary electrons from insulators; stability of secondary emission yield from insulators; influence of temperature on the total yield; electron bombardment induced conductivity; and variation of secondary emission with angle of incidence of primaries. The book then examines the technology of secondary emitting materials, including surfaces for use in electron multipliers and preparation of secondary emitting surfaces for use in storage tubes. The publication is a valuable reference for readers interested in in thermionic emission and secondary electron emission.