Overdense microwave plasma heating in the CNT stellarator
| Autor: | Alf Köhn, R. R. Diaz-Pacheco, Kenneth Hammond, Francesco Volpe, Y. Wei |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Electron density
Materials science FOS: Physical sciences Plasma Condensed Matter Physics 01 natural sciences Electromagnetic radiation Physics - Plasma Physics Ion source 010305 fluids & plasmas law.invention Magnetic field Plasma Physics (physics.plasm-ph) Nuclear Energy and Engineering law Ionization 0103 physical sciences Atomic physics 010306 general physics Stellarator Microwave |
| Zdroj: | Plasma Physics and Controlled Fusion |
| Popis: | Overdense plasmas have been attained with 2.45 GHz microwave heating in the low-field, low-aspect-ratio CNT stellarator. Densities higher than four times the ordinary (O) mode cutoff density were measured with 8 kW of power injected in the O-mode and, alternatively, with 6.5 kW in the extraordinary (X) mode. The temperature profiles peak at the plasma edge. This was ascribed to collisional damping of the X-mode at the upper hybrid resonant layer. The X-mode reaches that location by tunneling, mode-conversions or after polarization-scrambling reflections off the wall and in-vessel coils, regardless of the initial launch being in O- or X-mode. This interpretation was confirmed by full-wave numerical simulations. Also, as the CNT plasma is not completely ionized at these low microwave power levels, electron density was shown to increase with power. A dependence on magnetic field strength was also observed (for O-mode launch) and discussed. 24 pages, 12 figures |
| Databáze: | OpenAIRE |
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