Follow the power—pathways to steady-state tokamak reactors

[摘要] Diagramming pathways of dimensionless power is a potent method for extrapolating between operating points on present-day tokamaks and future burning plasma devices. The heat transport power, current drive power, H-mode threshold power and other 'plasma physics' powers can be expressed in dimensionally correct (or normalized) form asPa ^3/4, wherePis the power andais the plasma minor radius, with the relative gyroradius ( ρ _*) dependence ranging from gyro-Bohm-like for transport (P{a}^{3/4}propto {rho }_{{ast}}^{-3/2} ), Bohm-like for current drive (P{a}^{3/4}propto {rho }_{{ast}}^{-5/2} ) and worse than Bohm-like for H-mode threshold (P{a}^{3/4}propto {rho }_{{ast}}^{-3} ). The D–T fusion power cannot be normalized in the same fashion since it is governed by nuclear physics, but at fixedB _T it scales like P{a}^{3/4}propto {rho }_{{ast}}^{-9/2} . Other 'mixed physics' powers can be incorporated into the dimensionless power framework by holdingB _T fixed in the same manner. Diagramming these dimensionless powers vsρ _* shows how the pathway to a steady-state reactor can be optimized relative to various operational boundaries. Using a steady-state hybrid discharge withβ _N = 3.2 from DIII-D as the starting point, a multi-parameter optimization finds an attractive pathway to steady-state operation on ITER using 76 MW of current drive power (fusion gain ofQ _fus = 8), along with a pathway toQ _fus = 20 in a JET-sized steady-state reactor withB _T = 10 T.

[关键词] dimensionally similar;steady-state;tokamak