Abstract
We have developed an ion cyclotron resonance frequency (ICRF) heating system for the Ring Trap 1 (RT-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 densities of the 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 C2+), suggesting a strong influence of the charge-exchange loss, which caused the bulk ions to remain relatively cold (~20 eV) compared to the impurity ions (~40 eV). By developing an electro-optical measurement system, we have measured the local wave electric field in the plasma.
Highlights
The Ring Trap 1 (RT-1) device is a laboratory magnetosphere generated by a levitated superconducting ring magnet
We considered to observe the signature of the ion heating by the ion cyclotron resonance of frequencies (ICRF) heating in the RT-1 plasmas
[7,8,9,10,11] is applicable to the magnetospheric plasma, we have developed an ICRF heating system for active ion heating in the RT-1
Summary
The Ring Trap 1 (RT-1) device is a laboratory magnetosphere generated by a levitated superconducting ring magnet. The stable high-beta (~1) confinement in magnetospheric plasmas was successfully demonstrated with high-temperature electrons (Te >10 keV), the heating of the ions has been challenging. Because the beach heating scheme exciting a left-hand polarized slow wave [7,8,9,10,11] is applicable to the magnetospheric plasma, we have developed an ICRF heating system for active ion heating in the RT-1. The dipole-field system has unique properties; i.e., the magnetic field only has the poloidal component with the field strength varying strongly along the field lines, and the curvature of the magnetic fields is opposite to that found in the usual toroidal systems These features require a novel approach for the ion heating in a magnetospheric plasma device. This paper describes the ICRF heating experiments using the double-loop antenna and their detailed results obtained for the magnetospheric plasmas
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