An apparatus for determining the secondary electron emission properties of nonconductors
The apparatus described allows the measurement of the secondary emission coefficient and the secondary electron energy distribution from nonconducting surfaces. The potential of the nonconducting surface is stabilized by a cathode very close to it. The use of an oscillatory primary beam allows a measurement of the secondary emission coefficient. The application of a sinusoidally modulated voltage sawtooth allows the determination of the emitted electron energy distribution and measures the potential of the emitting surface. The performance of the apparatus is demonstrated by results obtained from an amorphous magnesium oxide coating.
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 × 10-7torr, 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.
Verstärkung von photoströmen durch emission von sekundärelektronen
Summary In vacuum photocells the current from the cathode (K) may amplified about 7 × by secondary emission from a third electrode (B) of th same material as the cathode. For the coefficient of secondary emission (δ) values up to 9 were found; there was no well-defined correlation between δ and the photoelectric sensibility. These secondary emission cells show a practically constant dynamic response to light variations up to at least 20 kilocytes. The relative value of the shot effect (“noise to signal ratio”) is higher than in vacuum cells of the same photocurrent but smaller than in gasfilled cells with the same photocurrent and the same amplification; probably it decreases with increasing energy of the primary electrons. With gasfilled secondary emission cells a large amplification may be reached at very low gas pressures; this effect is ascribed to the to and fro movement of the secondary electrons.