Burn condition for fusion plasmas, helium particle confinement and exhaust efficiency
The burn condition for D-T plasmas is derived in a form which accounts for the stationary helium concentration being selfconsistently determined by the coupling of the fusion power and helium production. The ratio of the global alpha-particle confinement time to the energy confinement time is taken as a quantity characterising the prevailing confinement and exhaust regime. It is shown that for an ignited and stationary burning D-T plasma this ratio needs to remain below 15 (or below 10 for typical impurity concentrations). This poses a lower limit to the required helium exhaust efficiency and indicates that operational regimes might be desirable where the internal particle confinement time is slightly in excess of the energy confinement time, and where the boundary layer - e.g. through high particle density and outward flow - acts as a sufficient shield against recycled alpha-particles. It is further demonstrated that for any given temperature (and for otherwise equal overall exhaust and recycling conditions) burning can either be achieved at two quite different values of the fusion parameter and ash concentrations or not at all. A similar evaluation applied to the He fusion reaction leads to even more stringent limits on the above ratio which must be smaller by a factor 3 to 4 compared to the D-T case.
Bibliographic Reference: Report: Jül-2342 EN (1990) 30 pp.
Availability: Available from Zentralbibliothek der Kernforschungsanlage Jülich GmbH, Postfach 1913, 5170 Jülich (DE)
Record Number: 199011415 / Last updated on: 1994-12-02
Original language: en
Available languages: en