Parameters of radiation processes in the microwave resonant plasma
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IED PHYSICS
Parameters of Radiation Processes in the Microwave Resonant Plasma V. V. Andreev*, I. A. Voldiner, and M. A. Korneeva RUDN University, Moscow, 117198 Russia *e-mail: [email protected] Received March 14, 2016
Abstract—This work presents results of experimental studies of the spectral and photometric characteristics of optical radiation generated by a pulse-periodic microwave discharge close to ECR (2.45 GHz, average power of up to 200 W, argon pressure of 10–4–10–1 Torr). Under these conditions, dense (ne = 1010–4 × 1011 cm–3) low-temperature (Те = 3–5 eV) plasma is produced in the working volume at an ionization rate of 10–3–5 × 10–5. It is shown that the increase in the electron density near the upper boundary of the pressure range at a constant level of the input power leads to a drastic change in the type and spectral composition of plasma radiation and a jumplike increase in the light flux. The results of probe and optical measurements made it possible to determine the range of the operating parameters defining the character and parameters of the radiation processes under study. DOI: 10.1134/S1063780X17110022
INTRODUCTION The physical processes accompanying resonance interaction of the microwave electromagnetic field with magnetoactive plasma are extremely diverse and very sensitive to variations in the operating conditions. Resonant microwave discharges are widely used in various vacuum–plasma technologies [1]. If the microwave frequency is close to the electron cyclotron frequency, the discharge develops under conditions of the electron cyclotron resonance (ECR). Resonant generation of plasma confined by an external magnetic field with a mirror configuration makes it unnecessary to apply strong electric fields and substantially reduces the energy expenditure required to achieve the high degree of ionization. In addition, plasma parameters in this type of discharge can easily be controlled. Studies of the radiation processes and the possibility to control the spectral composition and intensity of radiation generated by such a discharge are of practical interest for applied studies in the field of plasma radiation technologies. The goal of the present work was to study the spectral and photometric characteristics of radiation generated by argon plasma produced under conditions close to ECR at gas pressures close to the upper boundary of the pressure range under study. EXPERIMENTAL SETUP The discharge in a magnetic field with a mirror configuration was excited in a quartz bulb located in a
cylindrical TE111 cavity with an operating frequency of 2.45 GHz. Gas breakdown was produced by supplying microwave power, and the ECR surface was within the working region of the cavity. The magnetic field was created by SmCo5 permanent magnets with a system of magnetic closure. The possibility was provided of varying the minimum value of the magnetic field and its gradient by using micrometric displacement of the pole magnets. The cavity was excited by means of diffraction coupling with a waveguide equipped wit
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