Energy Loss and Microturbulence under Multipulse ECR Plasma Heating at the L-2M Stellarator
- PDF / 1,012,503 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 78 Downloads / 174 Views
LARATORS
Energy Loss and Microturbulence under Multipulse ECR Plasma Heating at the L-2M Stellarator G. M. Batanova,*, V. D. Borzosekova,**, D. G. Vasilkova, b, S. E. Grebenshchikova, L. V. Kolika, E. M. Konchekova, A. A. Letunova, A. E. Petrova, V. D. Stepakhina, N. K. Kharcheva, and A. A. Kharchevskiia a Prokhorov
General Physics Institute of the Russian Academy of Sciences, Moscow, 119991 Russia b Bauman Moscow State Technical University, Moscow, 105005 Russia *e-mail: [email protected] **e-mail: [email protected] Received January 14, 2019; revised March 13, 2019; accepted March 25, 2019
Abstract―In experiments on multipulse on-axis electron cyclotron resonance heating (ECRH) of plasma by a series of microwave pulses at the L-2M stellarator, several phases of plasma energy loss were observed: the short stage of low-energy loss, the stage of rapid increase in energy loss, the quasi-steady stage, and the relaxation stage between the heating pulses. In the stage of rapid increase in energy loss, the energy loss power is two or more times higher than that in the relaxation stage at the same energy of the plasma column. Shortwavelength plasma density fluctuations were measured using both the ordinary and extraordinary microwave collective scattering technique. It is found that, in the quasi-steady stage, the amplitude of density fluctuations is much lower than that in the preceding heating stages. The fluctuation amplitude lowers just after the restructuring of the density profile and establishment of a steady-state hollow density profile due to the density pump-out effect. The amplitude of large-scale density fluctuations at the plasma periphery recorded by a Doppler reflectometer remains unchanged during the ECRH pulses and in the time intervals between them. However, when the stage of rapid increase in energy loss begins, the shape of the density fluctuation spectrum changes significantly. The initially narrow spectrum with one peak near the zero frequency broadens, the amplitude of the central peak decreases, and two additional peaks at frequencies of 0.7 and −0.7 MHz appear. DOI: 10.1134/S1063780X19080014
1. INTRODUCTION The multipulse mode of electron cyclotron resonance heating (ECRH) of plasma by a train of microwave pulses is of interest because it allows one to study various transport processes and their effect on the time evolution of the plasma parameters, such as the temperature and density profiles of charged particles and the characteristics of microturbulences of different scales and nature. In the experiments carried our at the L-2M stellarator [1], it was shown that, after the beginning of the ECRH pulse, there is a time interval during which the energy loss power varies only slightly. At the end of this time interval, the loss power begins to rapidly increase up to the value at which the loss power becomes equal to the ECRH power. If the ECRH power PECRH increases twice (from 0.2 to 0.4 MW), then the time interval in which the loss power varies weakly nearly halves. The goal of this work was
Data Loading...
