Measuring of electric fields in the discharge of the microwave plasmatron

Abstract

Summary form only given. Paper is devoted to experimental investigations of the electromagnetic field distribution in a discharge induced by the coaxial microwave plasmatron (f=10 GHz, microwave power of 1/spl divide/12 W). It has been shown in that electron temperature of the plasma is 10/sup 4//spl deg/K, temperature of gas at plasma flame axis is 600-1000/spl deg/K, concentration of electrons in plasma reaches over 10/sup 14/ cm/sup -3/. It is significant that electric parameters of plasma in the microwave plasmatron satisfy the condition of surface electromagnetic waves propagation in plasma. High strength of electric field is assumed existing in plasma, however, until the present time any information about direct measurements of electromagnetic fields in such microwave plasmatrons was absent. Because of small dimensions of discharge (d/spl Lt//spl lambda/, L/spl ap//spl lambda/) the electric field measurements are difficult to perform. Moreover, there are not so many techniques of microwave field investigation in free space, where microwave discharge takes place. A new method has been proposed for measurement of electromagnetic field directly in discharge. The method is based on usage of vibration string as a small perturbing body, which placed into the discharge. The electric component distributions of microwave field at plasma are studied. Examination of the field distribution along discharge makes possible to determine a wavelength of propagated wave /spl lambda//sub p/=16 mm (wavelength in free space is /spl lambda//sub 0/=31 mm). Consequently wave in plasma is twice as slow as wave propagated in free space. This is due to the surface electromagnetic wave that propagates along the plasma and sustains of discharge.