Modular single-coil design for stellarators

Stellarators are a promising type of fusion reactor, but their construction is challenging. The coils that generate the magnetic field of a stellarator are complex in shape. Additionally, a single set of coils for a stellarator may not offer enough flexibility to generate different stellarator configurations. Recently, new ideas have been proposed to simplify the design of coils for stellarators. Among these, a "modular" single coil design is highlighted as an alternative that may reduce the complexity of the coils. Furthermore, it is intended to enable the operation of different stellarator configurations with the same vacuum chamber and supports for the coil. The utilization of this concept would enable the rapid study of different plasmas and improve the flexibility for the design of future power plants. One method is to recreate the current required for a stellarator with a variable distribution of electrical conductivity/electric voltage. The second method is to apply current sources and sinks on the winding surface. In this work, we use a Python-based version of REGCOIL from the DESC code. The code is used to find sheet currents on a winding surface for a set of different plasma equilibria. Later, electrical conductivity and electric potential distributions on the winding surface are found to mimic the same sheet currents. Engineering constraints such as critical current density and heating are considered when searching for these conductivity/voltage distributions. The second method requires the use of optimization with COMSOL. We show results for a set of different plasma equilibria after applying these methods for a "modular" single-coil concept.