Particle cross-field transport caused by magnetic fluctuations

Electrostatic and magnetic fluctuations generally cause cross-field particle transport in confined plasmas. In magnetic fusion, core localized magnetic turbulence must be sufficiently low to obtain required energy confinement. It is shown as an example that growth rates of electromagnetic modes in a fusion relevant plasma should fall below about 10-3 inverse Alfven times at a density fluctuation level of 1%. Magnetic fluctuation induced diffusion is thus a serious concern for most magnetic confinement schemes. The scaling of particle confinement is such that the loss mechanism is weak in most current experiments. However, observed short energy confinement times, a few μs or Alfven times, in the Extrap T1 z-pinch experiments are shown to be consistent with the model. 6 refs