Measurements of the Production and Transport of Helium Ash in the TFTR Tokamak

Abstract
Helium ash production and transport have been measured in TFTR deuterium-tritium plasmas using charge-exchange recombination spectroscopy. The helium ash confinement time, including recycling effects, is 6-10 times the energy confinement time and is compatible with sustained ignition in a reactor. The ash confinement time is dominated by edge pumping rates rather than core transport. The measured evolution of the local thermal ash density is consistent with modeling based on previously measured helium transport coefficients and classical slowing down of the alpha particles.