Experimental studies and analysis of low-voltage, grating TWT amplifiers

Summary form only given. Spontaneous emission, small signal and linear gain measurements for a low-voltage (/spl les/10 kV), sheet-beam-compatible, grating TWT Ku-band amplifier are presented. A round "probe" beam from a 10 kV, 0.25 A Pierce gun electron source is utilized for 14 GHz amplifier experiments. The spontaneous emission measurements provide a measurement of the grating-induced spontaneous emission spectrum, measurements of broad-band noise emission, and measurement of spontaneous emission in the backward-wave regime. The noise emission spectra have been correlated with experimental factors including the guide magnetic field intensity and body current. Measurements of small signal and linear gain are also compared with the theoretical prediction in the backward-wave regime. Vacuum cold test measurements of the grating dispersion relation are made by means of a moveable rf probe inserted into a slotted line by means of a spatial FFT of the resulting phase sensitive signal. An analysis of the vacuum grating dispersion characteristics for shallow and deep groove gratings is used to interpret experimental measurements of wave transmittance and growth. Results of a waveguide coupling system for linear gain measurements are also presented.