On the measurement of toroidal rotation for the impurity and the main ion species on the Joint European Torus

The neoclassical moment approach of Hirshman and Sigmar [Nucl. Fusion 21, 1079 (1981)] has been used for the first time on the Joint European Torus [J. Wesson, Tokamaks, 2nd ed. (Oxford Science Publication, Oxford, 1997), p. 581] to deduce the toroidal rotation frequency of the main ion species from that measured for the impurity ions. A significant differential rotation between these two species is found where the second radial derivative of the ion temperature is large. The position of radially localized magnetohydrodynamic instabilities is then deduced from the Doppler shift in the frequency and verified using the cross-correlation between the magnetic and the electron cyclotron emission measurements. Accurate agreement between these estimates of the mode location is only found when using the toroidal rotation frequency of the main ion species. This result fully verifies the neoclassical approach and can be used directly as a diagnostic tool to localize magnetohydrodynamic instabilities. (C) 2002 American Institute of Physics.