Pulsed time-of-flight refractometry measurements of the electron density in the T-11M tokamak
A new method for measuring the plasma density in magnetic confinement systems—pulsed time-of-flight refractometry—is developed and tested experimentally in the T-11M tokamak. The method is based on the measurements of the time delay of short (with a duration of several nanoseconds) microwave pulses propagating through the plasma. When the probing frequency is much higher than the plasma frequency, the measured delay in the propagation time is proportional to the line-averaged electron density regardless of the density profile. A key problem in such measurements is the short time delay of the pulse in the plasma (∼1 ns or less for small devices) and, consequently, low accuracy of the measurements of the average density. Various methods for improving the accuracy of such measurements are proposed and implemented in the T-11M experiments. The measurements of the line-averaged density in the T-11M tokamak in the low-density plasma regime are performed. The results obtained agree satisfactorily with interferometric data. The measurement errors are analyzed, and the possibility of using this technique to measure the electron density profile and the position of the plasma column is discussed.
KeywordsMicrowave Time Delay Plasma Density Density Profile Plasma Frequency
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- 2.A. W. Morris for the MAST Team, in Advanced Diagnostics for Magnetic and Inertial Fusion, Varenna, 2001, Abstracts of Papers.Google Scholar
- 3.V. F. Shevchenko, A. A. Petrov, V. G. Petrov, and Yu. A. Chaplygin, Fiz. Plazmy 22, 32 (1996) [Plasma Phys. Rep. 22, 28 (1996)].Google Scholar
- 4.R. T. Snider, T. N. Carlstrom, C. H. Ma, and W. A. Peebles, in Diagnostics for Experimental Thermonuclear Fusion Reactors, Ed. by P. E. Stott et al. (Plenum, New York, 1996).Google Scholar
- 5.S. H. Heijnen, C. A. J. Hugenholtz, F. C. Schüler, et al., in Proceedings of the 22nd EPS Conference on Controlled Fusion and Plasma Physics, Bournemouth, 1995, p. IV–441.Google Scholar
- 6.V. F. Shevchenko, A. A. Petrov, V. G. Petrov, and Yu. A. Chaplygin, Fiz. Plazmy 22, 25 (1996) [Plasma Phys. Rep. 22, 21 (1996)].Google Scholar
- 7.V. F. Shevchenko, A. A. Petrov, V. G. Petrov, and Yu. A. Chaplygin, Fiz. Plazmy 20, 33 (1994) [Plasma Phys. Rep. 20, 27 (1994)].Google Scholar
- 8.V. L. Ginzburg, The Propagation of Electromagnetic Waves in Plasmas (Nauka, Moscow, 1960; Pergamon, Oxford, 1970).Google Scholar
- 10.V. E. Golant, in Handbook of Plasma Physics, Vol. 2: Basic Plasma Physics, Ed. by A. A. Galeev and R. N. Sudan (Énergoatomizdat, Moscow, 1984; North-Holland, Amsterdam, 1984).Google Scholar