Analysis and sensitivity study of an HTS spherical tokamak pilot plant design using the PROCESS 0-D systems code

PPPL and CCFE are collaborating on the use of the PROCESS systems code to explore innovative pilot plant and Fusion Nuclear Science Facility (FNSF) designs. We have used PROCESS to benchmark a spherical tokamak pilot plant design published in Menard et. al. (2016). Previously, the copper-centerstack FNSF design in that paper was benchmarked by Muldrew et. al. (2020).

We benchmarked another design of Menard, a larger pilot plant design with a high-temperature superconducting (HTS) centerstack requiring less recirculating power. It has 3.0 meter major-radius, aspect ratio 2.0, 50 MW NBI power, Greenwald fraction 80%, and beta-normalized 4.2 %Tm/MA

We reproduced the plasma geometry, input and fusion power, plasma current, and bootstrap fraction, and Greenwald fraction to within 5%, but with beta-normalized (including alphas) 20% lower than the Menard value. This is similar to the earlier Muldrew benchmarking. We discuss this beta-N discrepancy. 

The many user-selectable models available in PROCESS allow sensitivity studies to be performed. This includes models for profile type, bootstrap fraction, current drive efficiency, geometric relationships, and confinement. We quantify the sensitivity of the performance and optimality of a given design on these chosen assumptions.