Field enhancement of the photoelectric and secondary electron emission from CsI

We have measured the electron emission from a CsI‐coated multiwire cathode, induced by ultraviolet photons and electrons, in vacuum at high electric fields. We found an enhancement in quantum efficiency of a factor of 1.5 at 160 nm, 3 at 185 nm, and 25 above 200 nm, at a field of 500 kV/cm. At the short wavelengths the amplitude of the effect is a linear function of the square root of the field strength. The enhancement of the electron‐induced secondary electron emission yield is dependent on the primary electron energy: for energies above 1 keV it varies by a factor of 2 to 10. A simple model of the field enhancement of the photoemission is suggested. Practical applications are discussed.

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