The effect of space charge on bunching in a two-cavity klystron

The effect of space charge on bunching in a two-cavity klystron has been analyzed by many investigators, but no rigorous theory exists for large-signal bunching in a finite beam klystron. The various available theories are reviewed and compared with new experimental data on the subject. It is found that there is 25 per cent loss of bunching efficiency at the drift length which is currently accepted as optimum, namely, 90 degrees of an effective plasma wavelength. It is shown that to reduce this loss to 5 per cent, drift length should vary from 65 degrees of an effective plasma wavelength at
\gamma b
= 0.5 to 45 degrees at
\gamma b
= 2. Reasoning qualitatively from these measurements, the optimum drift lengths for a multicavity klystron are suggested to be: 90° : 90° : ... : 65°-45° : 30°.