Noise reduction in space charge limited thermionic diodes

Abstract

Theoretical studies of the space charge reduction of noise in a thermionic diode predict a much greater suppression of the low frequency shot noise than is actually observed. A lower limit to the observed reduction of the shot noise is proposed to be due to modulation of the diode spacing by thermal elastic fluctuations in the length of the cathode. Combining the classical Langmuir diode and Debye vibrational theories, yields results that agree quantitatively with experiment. The theory makes a number of predictions as to how the measured space charge reduction factor varies with the relevant parameters, which need to be verified.