Cyclotron Autoresonance Maser Experiments Research Articles

Linear Analysis of a Cyclotron Autoresonance Maser (CARM) Operating in a Transverse Magnetic Mode

In the fast-wave devices like gyrotron, gyro-peniotron and cyclotron autoresonance maser (CARM) that generate millimeter and sub-millimeter waves, the transverse dimensions of the resonator and the output cylindrical waveguide become small. In order to prevent loss of electrons and thermal loading of the rf structure, the electron beam must be kept relatively far from the walls. The latter requirement demands smaller transverse dimensions of the helical electron beam as well. In this paper linear formulation of a CARM operating in a general transverse-magnetic (TM) mode is derived, and a detailed analysis of the influences of the parameters is presented for the TM1,1 mode CARM. It is found that, compared to the TE1,1 mode which is often employed in gyrotron traveling wave tube (gyro-TWT) and CARM experiments, the TM1,1 mode has a greater eigen value and consequently leads to a greater waveguide radius for a given cutoff wave number, and also, allows the electron beam to be settled close to the waveguide axis to have a small transverse dimension. Results show that a TM-mode CARM can reach high power and ultrahigh gain, just as a TE-mode CARM or a TE-mode gyro-TWT does.

A method of forming a high-quality electron beam for free electron masers

Abstract A new method to form a high-quality electron beam in which electrons initially move strictly along the axis without spurious transverse velocity is discussed. A two-electrode axisymmetric gun immersed in a uniform axial magnetic field is followed by a small correcting coil which compensates the dispersing action of an anode aperture and “straightens” electron trajectories. Computer simulations of a magnetically insulated diode with the space-charge-limited current proved effectiveness of this method. The use of the method in a cyclotron autoresonance maser experiment provided 30% electron efficiency enhancement.

Generation of a high-quality electron beam for application in cyclotron autoresonance maser experiments.

In this paper we report on the numerical calculations and experimental testing of a nonadiabatically electrostatic pumped beam. These initial investigations are intended to lay the groundwork for generating a high-quality electron beam, which will be used for cyclotron autoresonance maser driving. The present gun geometry produces a beam at a voltage of 500 kV in a 30-ns pulse, with total power between 150 and 300 MW The experimental data characterizing the beam properties are compared with numerical simulation results, indicating that the gun has operated essentially as predicted by theory. \textcopyright{} 1996 The American Physical Society.

Long-pulse millimeter-wave free-electron laser and cyclotron autoresonance maser experiments

Experimental results on high-power long-pulse free-electron laser (FEL) and cyclotron autoresonance maser (CARM) experiments are summarized. Single-mode operation of a free-electron laser oscillator at 27.4 GHz with a Bragg resonator has been obtained, with an output power of 990 kW for a beam energy of 320 keV and transmitted current of 30 A, corresponding to an efficiency of 10.3%. Free-electron maser (FEM) amplifier operation at 35 GHz has yielded a gain of 26 dB with an output power of 800 kW, corresponding to an efficiency of 8.6%. CARM oscillator experiments at 32 GHz with a different electron gun have yielded lower powers because of poor beam quality; planned CARM experiments are discussed.

Cyclotron autoresonance maser in the millimeter region

Results from a cyclotron autoresonance maser experiment are reported. Two maxima of the output microwave power (8 and 10 MW) at a wavelength of 5 and 5.5 mm, respectively, have been observed. The nonadiabatic beam pumping is achieved by transit of the electrons through an external magnetic-field local inhomogeneity due to the presence of a copper aperture.

Frequency-tunable, high-power microwave emission from cyclotron autoresonance maser oscillation and gyrotron interactions

The authors report experimental observations of high-power microwave emission from both the high-frequency cyclotron autoresonance maser (CARM) oscillation and the low-frequency gyrotron interaction. High-power (3-10 MW) microwave emission is attributed to the CARM mechanism, which is magnetically tunable through discrete axial cavity modes from 15 through 16.7 GHz. For the same experimental parameters, megawatt-level microwave emission is observed, which is magnetically tunable from 10 through 14 GHz, indicating low-frequency gyrotron oscillation. High-frequency microwave pulse-lengths of up to 0.2 mu s have been generated, which is a factor of five greater than those achieved in previous CARM experiments. >