Generation and propagation of electromagnetic waves resonantly excited by a heating wave near the electron cyclotron frequency.

在磁海滩位形中的电子回旋加热（ECH）中，平行波数的发散增加和共振回旋电子数的同步加速是两个复杂的共振过程。在本课题中，我们对强单色加热波在回旋区激发的电磁波的频谱分析进行了新的尝试，建立了一个紧凑、灵敏的诊断系统，适用于串列镜中窄空间的热等离子体诊断。我们在观测上证实了单个热电子回旋辐射的宽带谱，新的发现是在加热波频率以上几个百分点处有一个强窄带谱。峰值频率和宽度随加热波功率的增加而减小，并且谱结构取决于磁场剖面。我们的结论是，这种窄带波是由一组共振电子产生的，这些电子在ECU下的速度空间中进行相位调制，并在磁斜坡中空间聚束，以在局部回旋频率下产生相干发射。

In electron cyclotron heating (ECH) of tenuous plasmas in a magnetic beach configuration, two resonant processes complicates physical analyses, i.e. divergent increase of the parallel wave number and synchronized acceleration of increasing number of resonantly gyrating electrons. In this task, we have made a new trial to look into the process in terms of frequency-spectrum-analyses of electromagnetic waves excited in the cyclotron range under the stimulation of a strong monochromatic heating wave.We have constructed a compact sensitive diagnostic system that fit in a narrow accessible pace for diagnoses of a hot plasma in a tandem mirror, We have observationally confirmed a broad-band spectrum that is attributable to cyclotron emissions by individual hot electrons.New finding in this research is a strong narrow band spectrum at a few per-cent above the heating wave frequency. The peak frequency and the width decreases with increasing power of the heating wave, and the spectral structure depends on the magnetic field profile. We conclude that this narrow-band wave is generated by a resonant group of electrons which are phase-modulated in the velocity space under ECU and spatially bunched in the magnetic slope to generate coherent emissions at the local cyclotron frequency.