Latest JET experimental results on the sawtooth

Sawtooth parameters play an important role in determining the ignition criteria of proposed fusion reactors. Of existing experiments, JET is most able to produce plasmas which approach thermonuclear conditions and hence the scaling of sawtooth data from JET is of particular interest. Further, a new technique has been developed for the analysis of the inversion radius which gives a more precise measurement than previously attained. If, as is commonly assumed, the inversion radius is identified with the q=1 radius, then not only can scaling laws be derived which include the q=1 radius, but the inversion surface may be used as a powerful diagnostic of the q-profile in the plasma core. A study of the ohmic sawtooth period dependence will be presented in this paper, based upon a large sample of data. Results from a study of the sawtooth inversion radius dependence in the ohmic, H-mode and 'monster' sawtooth regimes will then be discussed. (author) 4 refs., 4 figs