Midplane measurements of charged fusion product diffusion in the Tokamak Fusion Test Reactor

A radially movable detector located just below the outer midplane of the Tokamak Fusion Test Reactor (TFTR) [in Plasma Physics and Controlled Nuclear Fusion Research, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 1, p. 27] has been used to study the confinement of charged fusion products (CFP’s). The scrape-off length of escaping CFP flux was measured using perturbative techniques based on shadowing the detector with different obstacles. Experimental results indicate the presence of a diffusive process for trapped particles. Derived diffusion step sizes were found to be in excellent agreement with those expected from toroidal magnetic field (TF) stochastic ripple diffusion.