Orbit-Averaged Drift Kinetic Equation for the Study of Alpha-Particle Transport in Tokamaks

Alpha Particles in Fusion Research (Report on the IAEA Technical Committee Meeting, Kiev, Union of Soviet Socialist Republics, 23-26 October 1989)

“…This distortion results in a net parallel friction force producing a radial alpha particle flux. Radial alpha fluxes of several times 10 15 cm" 2 -s"' are shown numerically to occur at an RF power of 5 W-cm" 3 . (This appears adequate for the ITER helium pumping requirements of 4 x 10 20 particles/s at a fusion power of 1 GW (see Paper [26]). )…”

“…Cheremnykh (INR, Kiev) [19] presented a comprehensive and powerful analytic treatment of the destabilization of ballooning modes by alpha particles (this was treated numerically by Spong and Leboeuf [18] and previously by Rewoldt, see Footnote 2). In earlier work, Spong et al 3 had originally demonstrated destabilization of trapped alphas only, whereas Rewoldt found strong destabilization due to untrapped alphas. In Ref.…”

“…G.T. Sager (General Atomics, San Diego) [3] reported work on the derivation of the kinetic equation for high energy alpha particles. This derivation is rather general; it holds even for a large banana width when p g /L ~ 1 (fi e is the poloidal gyroradius and L is a characteristic gradient scale length).…”

“…If necessary, one must find mechanisms to transport the slowed alphas out of the plasma centre and to obtain sufficient helium ash pumping in the SOL to keep the helium fraction below 10%. Major parts of the unknown fast alpha physics can be explored at present in alpha particle simulation experiments using 3 He minority heating, perhaps augmented by high energy neutral beam injection to ameliorate the major drawback of ICRH which produces pressures with p l f > p )f (where f stands for fast particles). Concerning burn control, initially subignited operation (Q = 30-50) is anticipated for ITER, with feedback controlled external heating power for a proper choice of the operating point.…”

“…It has no divertor or limiter. The expected plasma parameters are: n = 3.6 x 10 20 m" 3 , n(0) = 7.2 x 10 20 m" 3 , T = 6.5 keV, T o = 12 keV, 0, = 0.6%, Z eff = 1.5, T E = 0.54 s, noT E = 3.9 x 10 20 , Pfusion = 149 MW, neutron wall load = 3 MW-nr 2 . Thus, ignition would occur at very small values of jS/^Troyon-B 2 a* 2 = 500, of which 270 is required for Ohmic ignition.…”