Millimeter Wave ESR Using Gyrotron as a Light Source

光谱学的研究在毫米波区域并不活跃，主要是由于缺乏可用的光源。本课题利用为等离子体加热和诊断而研制的回旋管作为毫米波ESR的光源，设计并制作了用于W和D波段ESR谱仪的小尺寸高Q腔回旋管。尽管发生了超导磁体低温恒温器漏气、超导磁体电源故障、高压Transformer损坏等事故，但研制的回旋管仍能产生93.9GHz-146.2GHz的强辐射，可用于ESR。在毫米波区，ESR主要是通过传输过程中的吸收来观测的，但本系统采用法布里-珀罗谐振腔，可以在W和D波段进行精确测量 ...更多信息 .作为初步试验，我们用反向振荡器代替回旋管，在室温下观察了一些低维晶格反铁磁体的ESR谱和DPPH的参考谱。所获得的粉末图案与各向异性的g-因子是高度解析的X波段光谱的相同的标本相比。在本光谱仪中，法布里-珀罗谐振器的镜间距通过施加AC调制电压到铁电致动器来精细地调节。具有调制的检测器的相干输出被反馈到致动器的驱动器，以便保持谐振器的谐振条件，从而从所获得的吸收光谱中排除色散分量。处理后的信号真实的实时显示和记录在计算机存储器中的软件已准备就绪，从而使回旋管光源的毫米波ESR装置接近完成。用该装置对回旋管高压Transformer进行修理后，很快就能获得分辨良好的W和D波段ESR谱。少

Spectroscopic studies have not been so active in millimeter wave region mainly due to the lack of available light sources. In this project, the gyrotron developed for the plasma heating and diagnosis was utilized as the light source of the millimeter wave ESR.A gyrotron with small size electron gun and high Q cavity was designed and manufactured for ESR spectrometer of W and D bands. In spite of many accidents such as air leakage of the cryostat for the superconducting magnet, trouble of the power supply of the superconducting magnet and damage of the high voltage transformer, the developed gyrotron was proved to yield strong radiation of 93.9GHz-146.2GHz in W and D bands available for ESR. Some modes of oscillation may be excited continuously with attainable low cathode current as much as lOOmA.ESR in millimeter wave region has been mostly observed by the absorption during transmission, but the present system utilizes Fabry-Perot resonator for the precise measurements in W and D bands … More . For the preliminary test, a backward oscillator, instead of gyrotron, was used to observe ESR spectra at room temperature of some low dimensional lattice antiferromagnets together with a reference spectrum of DPPH. The obtained powder patterns with anisotropic g-factors are highly resolved compared with X band spectra of the same specimens. In the present spectrometer, the mirror spacing of the Fabry-Perot resonator is adjusted finely by applying an AC modulated voltage to a ferroelectric actuator. The coherent output of the detector with the modulation is fed back to the driver of the actuator so as to maintain the resonance condition of the resonator to exclude the dispersion component from the obtained absorption spectra. The software to display the processed signal in real time and to record in the memory of computer is ready for use.Thus, the millimeter wave ESR apparatus with light source of a gyrotron is near the completion. With the apparatus well resolved ESR spectra in W and D bands will be soon obtained after the high voltage transformer of the gyrotron will be repaired. Less