Measurement of Temperature and Density Profiles of the Plasma at PR-2 Facility
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NEERING DESIGN OF NUCLEAR PHYSICS EQUIPMENT
Measurement of Temperature and Density Profiles of the Plasma at PR-2 Facility I. A. Sorokina,b*, K. M. Gutorova, and M. D. Bolotova aNational Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe sh. 31, Moscow, 115409 Russia b
Kotelnikov Institute of Radio Engineering and Electronics (Fryazino Branch), Russian Academy of Sciences, pl. Vvedenskogo 1, Fryazino, Moscow oblast, 141190 Russia *e-mail: [email protected] Received May 25, 2017
Abstract—A new system of probe diagnostics at linear plasma simulator PR-2 is described, allowing us to measure the profiles of plasma temperature and density in different cross sections of the plasma column. The Langmuir probe fixed to the movable part of the two-coordinate positioning system built into the PR-2 passes the region of the discharge area during the process of measuring plasma parameters. The overall dimensions of the positioning system make it possible to mount electrical probes (magnetic probes, optical fibers, and other diagnostic equipment) covering almost the entire volume of the vacuum chamber between the magnetic mirrors of the device. We present the measurement results of local plasma parameters of the beam-plasma discharge (BPD) for different values of the input power and working gas pressure. The boundaries of appearance of discharge of three types were determined: the diffusive BPD mode, the BPD mode, and the arc mode. Dependences of the plasma concentration and temperature on the input power for different values of pressure have been also determined. Keywords: Langmuir probe, beam-plasma discharge, discharge regimes DOI: 10.1134/S1063778817110175
INTRODUCTION Diagnostics of local plasma parameters is the most important problem to ensure a stable operating mode and conditions of technological processes in plasma devices. The most common method of plasma diagnostics is the use of Langmuir probes [1]. Usually we can determine such basic plasma parameters as density, electron temperature, local plasma potential, and electron distribution function via the current—voltage characteristics (CVC) of the probe. Examples of application of probe diagnostics and calculation of local plasma parameters under different conditions are presented in [2–13]. Particular modifications of probe diagnostics also provide the information about ion fluxes (Mach probe [14, 15]), ion temperature [15, 16], and oscillation of local parameters in magnetized plasma (magnetically isolated probes [17], Katsumata probe [16, 18], tunnel probes [19], and ballpin probes [20]). Owing to its compactness, the probe method often allows the spatial distribution of parameters in the volume of plasma device to be measured by means of movable vacuum inputs or integrated positioning systems. The paper describes a new system of probe measurements of BPD profiles developed for the linear plasma simulator PR-2 [21, 22] and based on a twocoordinate positioning system mounted directly inside
the vacuum chamber of the facility. The
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