Designing A Buildable Optimized Stellarator to Confine an Electron-Positron Plasma

We present the integrated design of the Electrons and Positrons in an Optimized Stellarator (EPOS) experiment, from plasma equilibrium to buildable superconducting coils. By leveraging novel optimization tools, such as single-stage, stochastic methods and direct minimization of strain in High-Temperature Superconducting (HTS) tapes, we have identified configurations that satisfy key physics and engineering metrics. The configurations converged to a quasi-axisymmetric plasma, closely resembling a tokamak with low rotational transform, small volume to reach the desired positron densities and convex cross sections. The designs, resulting from active interaction with an engineering team, achieve precise quasi-symmetry, enabling predicted positron confinement times of up to 2 seconds. We have developed a new setup that uses E×B drifts to inject positrons into a stellarator's magnetic field. This is accomplished by guiding the particles along stray magnetic field lines that originate from large 'weave-lane' superconducting coils. Monte-Carlo simulations allowed to estimate tolerances of 1 mm on the coil shapes using Gaussian Processes to simulate manufacturing and assembly deviations while preserving physics aspects. We will discuss a feasibility study comparing candidates across different major radii and coil currents with different coil shapes concluding with the presentation of the optimal EPOS design to date.