Will it scale? Designing and testing the axial confinement of the Novatron fusion concept

A new mirror cusp magnetic field configuration for confining fusion plasma has been developed by the Novatron Fusion Group. The central cell being MHD stable by design shifts the primary challenge to achieve effective axial confinement. Current investigations focus on a combination of electrostatic ambipolar fields and ponderomotive forces generated by RF fields. These confinement strategies are slated for experimental validation in the upcoming Novatron 2 device, with the objective of demonstrating scalability toward reactor-relevant conditions.

Optimizing the axial confinement approach for a reactor scale device includes choosing a magnetic topology. Starting from a set of magnetic field topologies, a target confinement time will be optimized. The topologies all build on a Novatron central cell and one or several appended tandem cells. We optimize the parameters required to build up and maintain a confining ambipolar field as well as an efficient ponderomotive plugging. These parameters include plasma density and temperature distributions as well as magnitude and frequencies of the ponderomotive field. Having established the optimal parameter ranges for each topology, fine tuning of the topologies, heating and fueling strategy as well as ponderomotive electrode systems will be carried out. Once an optimal reactor design has been found, experimental validation is devised to be carried out by the minimal (in terms of size, complexity and cost) experimental setup capable of testing the reactor design.

Evaluations of the plugging efficiency for different parameter ranges and topologies will thus have to be carried out both at reactor scale and the experimental platform scale. Particle-in-cell simulations will be used both for explicit evaluation for a specific design but also for inferring analytical scaling laws which will be used to speed up the design optimization procedure where explicit particle-in-cell simulations are costly, for instance for large densities and volumes. We present the current status of this design process.