“…Ion cyclotron resonance heating is planned at a
rather modest level of 1–2 MW, thus playing a relatively minor role in the energy balance
for the ions, but is expected to play an important role in the generation of fast ions
(order 50 keV) on the inner magnetic surfaces, to verify their confinement. Experimental
verification of good confinement of 50 keV deuterium ions is a major goal of W7-X since they
are a good proxy for fusion
α particle confinement in a stellarator reactor: For 50 keV
deuterium ions at 2.5 T, the Larmor radius is cm, i.e., , whereas the fusion
α particles at 3.5 MeV in, e.g., the HELIAS 5-B reactor
design 38 at B = 5.5 T have cm, i.e., , slightly lower. Therefore, the confinement of 50 keV
deuterium ions in W7-X is a more than adequate proxy for α -particles in a stellarator
fusion reactor.…”