K. Sakamoto et al., A STUDY OF WAVE-GUIDE MODE-IDENTIFICATION IN A FEL EXPERIMENT, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 341(1-3), 1994, pp. 101-104
The modes of FEL radiation propagating in a drift tube and their spati
al growth rate were determined experimentally. A high growth rate of 6
0 dB/m was observed for the main mode (TE11 circular). Besides this, t
he higher modes TE31, and TE51 were also detected. The spatial growth
rates are 50 dB/m and 45 dB/m, respectively, and power saturation is o
bserved at the same position for all modes.