Core plasma physics basis and its impacts on the FNSF

Abstract

The FNSF core plasma physics is examined with detailed analysis to establish the basis for the reference configuration, R=4.8m, a=1.2m, Ip=7.87 MA, and BT=7.5T, q95=6, fBS=0.52, βN<2.7 established in Ref. [1]. Central solenoid (CS) and poloidal field (PF) coils are far from the plasma as in a power plant, and acceptable coil currents are determined for the rampup and flattop fiducial states. Time-dependent free-boundary plasma evolution simulations show that the FNSF plasma can be established, ramped up, and relaxed into flattop, including vertical stabilizers, internal feedback coils and feedback control on plasma current, position, and shape. A range of density (no/=1.3–1.5) and temperature (To/<T>=2.2–2.7) profiles are examined, indicating that energy confinement of H98=1.1–1.2 is required to provide 100% non-inductive plasma current in the FNSF. GLF23 theory based transport model predicted lower energy confinement of H98 ∼0.6–0.85. The EPED analysis shows that the pedestal temperature ranges from 4.0–4.7keV for pedestal densities of 1.7–1.0×1020/m3. The n=1 kink stability shows no-wall beta limits, using the pressure and current profiles associated with the transport and current drive sources, ranging from βN ∼2.25–2.55 depending on li. A conducting wall can extend these limits by 10–40% depending on li and wall location. At the lower beta’s of the reference plasma, a combination of 50MW of NB, 30MW of LH, 20MW of ICRF, 20MW of EC, and bootstrap current, are found to provide 100% of the plasma current with a stable current profile. Impacts on the FNSF of plasma physics are discussed and R&D challenges are highlighted.