High fusion performance from deuterium-tritium plasmas in JET

High fusion power experiments using DT mixtures in ELM-free H mode and shear regimes in JET are reported. A fusion power of 16. 1 MW been produced in an ELM-free H mode at 4. 2 MA/3. 6 T. The transient of the fusion amplification factor was 0. 95+/-0. 17, consistent the high value of (0) τEdiaTi (0) = 8. 7× 1020+/-20% m-3 s keV, and was maintained about half an energy confinement time until excessive edge pressure resulted in discharge termination by MHD instabilities. The of DD to DT fusion powers (from separate but otherwise similar) showed the expected factor of 210, validating DD projections DT performance for similar pressure profiles and good plasma mixture, which was achieved by loading the vessel walls with the DT mix. Magnetic fluctuation spectra showed no evidence ofénic instabilities driven by alpha particles, in agreement theoretical model calculations. Alpha particle heating has been observed, its effect being separated successfully from isotope effects on energy confinement by varying the tritium in otherwise similar discharges. The scan showed that was no, or at most a very weak, isotope effect on the energy time. The highest electron temperature was clearly with the maximum alpha particle heating power and the optimum mixture; the maximum increase was 1. 3+/-0. 23 keV with 1. 3 MW of alpha heating power, consistent with classical expectations for alpha confinement and heating. In the optimized shear regime, clear transport barriers were established for the first time in DT, a power similar to that required in DD. The ion thermal in the plasma core approached neoclassical levels. Real power control maintained the plasma core close to limits set by gradient driven MHD instabilities, allowing 8. 2 MW of DT fusion with (0) τEdiaTi (0) approx1021 m-3 s keV, even though full optimization was possible within the imposed neutron budget. In addition, -steady-state discharges with simultaneous internal and edge barriers have been produced with high confinement and a fusion of up to 7 MW these double barrier discharges show a great for steady state operation. © 1999, Euratom