We have developed an ion cyclotron resonance of frequencies (ICRF) heating system for the Ring Trap 1 magnetospheric device. We excite slow waves from the polar region of the dipole magnetic field. The target helium plasma is produced by electron cyclotron heating. The electrons comprise high-temperature (>10 keV) and low-temperature (<100 eV) components with both typically exhibiting the densities of same order of magnitude. The ICRF heating causes an increase in the ion temperatures and toroidal flow velocities in the core plasma region.We observe appreciable temperature differences between the different ion species (main He + and impurity C 2+ ), suggesting a strong influence of the charge-exchange loss due to which the bulk ions remain relatively cold (~20 eV) compared to the impurity ions (~40 eV). By EX/P3-47 2 developing an electro-optical measurement system, we have measured the local wave electric field in the plasma.
Ion cyclotron range of frequencies (ICRF) heating with a frequency of a few MHz and an input power of 10 kW was applied for the first time, to the best of our knowledge, in a magnetosphere plasma device. An antenna was installed near the pole of a dipole field for slow-wave excitation. Further, a ∩-shaped antenna was implemented and characterized for efficient ion heating. Electron cyclotron heating with an input power of 8 kW sustained helium plasmas with a fill gas pressure of 3 mPa. ICRF heating was then superimposed onto the target plasma (H, D, and He). While the ICRF power was turned on, the increase in ion temperatures was observed for low-pressure helium plasmas. However, the temperature increase was not clearly observed for hydrogen and deuterium plasmas. We discuss the experimental results in terms of power absorption based on result calculated with the TASK/WF2 code.
The direct measurements of high-frequency electric fields in a plasma bring about significant advances in the physics and engineering of various waves. We have developed an electro-optic sensor system based on the Pockels effect. Since the signal is transmitted through an optical fiber, the system has high tolerance for electromagnetic noises. To demonstrate its applicability to plasma experiments, we report the first result of measurement of the ion-cyclotron wave excited in the RT-1 magnetosphere device. This study compares the results of experimental field measurements with simulation results of electric fields in plasmas.
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