Rickard Holmberg | Searcharxiv

arXiv2025

Novatron: Equilibrium and Stability

The Novatron is a fusion concept characterized by its axisymmetric mirror-cusp magnetic topology. The magnetic field exhibits good curvature and a high mirror ratio. Plasma equilibrium profiles for the Novatron are obtained by solving an axisymmetric guiding-center anisotropic boundary-value problem. These profiles are then analyzed with respect to several MHD stability criteria, including the mirror, firehose, and interchange conditions. A generalized Rosenbluth and Longmire MHD interchange criterion, where anisotropic pressure variations along flux tubes are allowed for, is subsequently employed for determining stable MHD equilibria. Additionally, a corresponding CGL double adiabatic interchange criterion is investigated for obtaining stable equilibria in the collisionless limit, both theoretically and numerically using the large scale Hybrid Particle-In-Cell code WarpX.

physics.plasm-ph↗

arXiv2023

Introducing the Novatron, a novel mirror fusion concept

A new magnetic mirror-cusp concept is described - the Novatron - with the potential to confine compact and stable fusion plasmas. Traditionally, the major challenges for open field line designs include MHD interchange modes, drift cyclotron loss-cone (DCLC) modes, neoclassical transport, and axial losses of particles and energy. The novel magnetic field configuration features favorable curvature throughout the plasma region, suppressing interchange modes. Moreover, the Novatron is designed to be self-stabilized against DCLC modes by allowing for a large plasma to Larmor radius ratio. The vacuum magnetic field geometry is axisymmetric, mitigating neoclassical transport. The Novatron features a high mirror ratio, providing strong magnetic confinement and suppressed axial losses. This paper describes the fundamental magnetic field topology and outlines the design of the magnet system. MHD interchange stability of anisotropic low-\b{eta} equilibria is demonstrated by derivation of two novel criteria, based on anisotropic ideal MHD and the Chew-Goldberger-Low model, and numerical computation in Novatron geometry. The Novatron design is also placed into a historic context by summarizing challenges faced by both previous and more current mirror/cusp concepts.

physics.plasm-ph↗