A two electron gun technique for the measurement of secondary emission characteristics of a variety of materials

A new technique and apparatus are described whereby the secondary emission ratio of a variety of materials can be measured. The experimental setup employs two electron guns in a demountable vacuum system and associated electronics. The system, which operates at a pressure of about 5 × 10 -7 torr, has the advantage of taking data under steady-state conditions rather than employing pulsing techniques. Conductors, semiconductors, and dielectrics can be tested in the demountable. The principal features of this technique are 1) use of a flood electron gun to place the target surface at some fixed voltage, and 2) the use of an amplitude modulated probing electron beam and a narrow-band amplifier centered at the probing beam modulating frequency, to measure the collected probing current at the target. Secondary emission measurements on semiconductors are described for primary energies from zero through first crossover to approximately 50 eV above maximum. Modification of the system to enable measurements up to 10 kilovolts is also explained. Advantages of this apparatus as an important laboratory tool for the measurement of the secondary emission characteristic of materials for use in camera tubes, image converters, storage tubes, electron multipliers, and other devices, are emphasized.