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Description
Compact torus (CT) injection is a promising technique for core fueling in large magnetic confinement fusion devices, where the achievable injection velocity is determined by the CT acceleration dynamics. In this work, the acceleration behavior of CT plasma in the Compact torus injector on KTX device (KTX-CTI) is investigated experimentally and theoretically.
Time-resolved magnetic probe and fiber-optic interferometer measurements are analyzed using instantaneous frequency analysis (IFA) and equivalent circuit modeling to characterize the CT motion during acceleration. The results show that the CT acceleration process cannot be adequately described by conventional model that treat the CT as a dimensionless current sheet. Instead, the CT occupies the acceleration channel and exhibits a continuously increasing effective mass as it propagates downstream.
To capture this behavior, a variable-mass point model is introduced and applied to the KTX-CTI system. The model successfully reproduces the measured acceleration history and final CT velocity, demonstrating significantly improved agreement with experimental observations compared to simplified single-mass formulations. The results indicate that plasma entrainment and magnetic structure evolution play essential roles in governing the CT acceleration process.
These findings provide new insight into the physical mechanisms underlying CT acceleration and establish a more realistic modeling framework for compact torus injectors. The results are directly relevant to the optimization of high-velocity CT injection systems for core fueling applications in future fusion devices.
[1]. Chen Chen, Tao Lan et al Plasma Sci. Technol. 24, 045102 (2022).
[2]. Tao Lan et al Plasma Sci. Technol. 26, 105102 (2024).
[3]. Qilong Dong, Tao Lan et al Plasma Phys. Control. Fusion 67, 085004 (2025).
| Keyword-1 | Compact torus |
|---|---|
| Keyword-2 | variable-mass point model |