NOISE MEASUREMENTS ON ELECTRON BEAMS AT 3000 MC

degree of Electrical Engineer. Noise measurements were made in a demountable system, on the electron beam produced by a new type of low-noise electron gun. The purpose of the investigation was to determine the effect of the dc electric field at the cathode on Haus ' noise param-eters S and II. The noise parameter S was found to be significantly influenced by the shape of the electric field in the vicinity of the cathode. Variation of S by a factor of 2 was observed at constant beam current, and by a factor of 4. 5 when the beam current was changed. Measured values for nI/S were small, the largest being 0. 16. The value of II/S was generally not found to be greatly affected by variations in the electric field at the cathode surface. However, a significantly large negative value of ll/S was produced by a field configuration that caused higher than normal cathode current density. Agreement was not found between the noise figures predicted from the minimum-noise-figure equation, Fmin = 1 + (S-il)-kT and the noise figures observed in traveling