Helical confinement system has a great advantage of sustaining current-disruption-free steady-state fusion plasmas by external magnetic field with built-in divertor. In the 3-dimentional (3-D) configurations, the strong magnetic ripple enhances the plasma transport. On the other hand, it is helpful to operate high-density lower-temperature regime without thermal instabilities.
For understanding fusion plasma dynamics, the radial profile distribution is important, and the 3-D equilibrium and 1-D transport should be coupled for reactor predictive simulation. Especially, neoclassical and anomalous transports, beta and density limits, neo-classical radial electric field and magnetic multi-helicity effects are crucial in the prediction of ignited helical reactor plasmas.
Related to the optimization of reactor plasmas, several 3-D helical confinement ideas are explored, such as modular heliotron(MH) with helical divertor [1], quasi-axisymmetric(QA) helical system with compactness [2] and quasi-poloidal(QP) symmetric helical system with good alpha confinement [3].
First, we explore three-dimensional equilibria with good confinement and high beta vale using optimization code, and then analyze steady-state equilibrium-transport properties using TOTAL simulation code [4] with neoclassical transport with ambiploar electric field and multi-helicity magnetic field effects in addition to semi-empirical anomalous loss and drift turbulent loss models. The typical start-up and burn-sustained operations are also analyzed by this code in addition to simplified zero-dimensional global plasma prediction coupled with system code analysis.
The analysis shows that the reduction of effective ripple (< 5%) in the LHD-type MH reactor (R=16.5m, B=5T) is crucial for high-temperature reactor operation in addition to the reduction of anomalous transport (confinement H factor >2). The comparisons between MH, QA and QP transport properties with neoclassical and anomalous transports are discussed in details in the conference.

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