ZEFF MEASUREMENTS AND LOW-Z IMPURITY TRANSPORT FOR NBI AND ICRF HEATED PLASMAS IN JIPP T-IIU

A visible bremsstrahlung detector array system for Zeff measurements and a charge exchange recombination spectroscopy system for fully ionized impurity profile measurements have been installed on JIPP T-IIU to study impurity transport in neutral beam injection (NBI) and ion cyclotron resonance frequency (ICRF) heated plasmas. More impurities are sputtered during ICRF heating than during NBI and/or Ohmic heating. The contribution of carbon to Zeff is 80-90% for NBI heated plasmas and 60% for NBI + ICRF heated plasmas. With carbon coating of the vacuum vessel, the contribution of carbon to Zeff becomes 80-90% also for NBI + ICRF heated plasmas. From the radial profile and the time evolution of fully ionized carbon after the ICRF pulse is turned on, a diffusion coefficient Da of 1.0 m2·s−1 and a convective velocity va(a) of 13 m·s−1 for the carbon impurity at the plasma edge are obtained. © 1990 IOP Publishing Ltd.