摘要
This work discusses the feasibility of gyrotron amplifiers using TM modes by investigating their dispersion relations starting with the relativistic Vlasov equation. For an input signal carrying a real frequency ω, the complex wave number k solved from the dispersion relation tells us the growth rate and the bandwidth of an amplifier. Three modes (TE , TM , and TM ) operating at the fundamental cyclotron harmonic (s = 1) with the same cutoff frequency will be discussed. The results show that the TM - and TM -mode gyrotrons require much higher beam current than the TE -mode gyrotron traveling-wave tube (gyro-TWT) amplifier. The TM modes are unsuitable for the gyro-TWT amplifier as discovered by other authors. The gyrotron backward-wave (gyro-BW) amplifier is also examined. The dispersion relations indicate that the TM modes are as good as the TE modes. The gain and bandwidth of the TM -mode gyrotron backward-wave amplifier (gyro-BWA) are studied by changing either the magnet field or the beam voltage. The TM mode is suitable and has a decent bandwidth for the operation of the gyro-BW amplifier.