Fraunhofer diffraction method를 이용한 Plasma 파동 측정에 관한 이론적 해석

Abstract

The theoretical analysis of Fraunhofer diffraction method as a new means to measure the wavenumber spectrum, spatial position and propagating direction of plasma waves is presented. A general theory of the Frauhofer diffraction method is described by using the volume-integration of electric fields indeed by individual electrons integrating with the incident beam over the diffracting volume, and can include such conditions as the oblique incidence of the electromagnetic wave and a finite width and a spatial position of plasma wave. The principle for measurement of wavenumber spectra of plasma waves is discussed by using theoretical analysis of the approximate solution of the Fraunhofer diffraction theory. In measurement of the wavenumber of the long wavelength region, the information of the wave number is easily obtained from the ratio of the intensity at u = 0 to the intensity at u = 0.75, where the normalized coordinate is given in the peak point. Further, effects of the incident angle and the plasma wave width are discussed by the intensity profile. From the envelope profile, the wavenumber, width and propagating direction of plasma waves are obtained by a process of curve fitting.