D-HE-3 FUSION IN THE JOINT EUROPEAN TORUS TOKAMAK - RECENT EXPERIMENTAL RESULTS

A new series of D-He-3 fusion yield experiments has been performed in the Joint European Torus (JET) using ion cyclotron resonance heating (ICRH) to generate a high-energy He-3 tail reacting with a background deuterium plasma. Using recently installed antennas with beryllium screens, radio-frequency power reaching 15 MW can be coupled to the plasma at the fundamental cyclotron resonance of He-3 near the magnetic axis. Best results are obtained with 3.5-MA discharges in the double-null configuration with high recycling on the outboard limiters to stay in L mode and to control the plasma density and purity. A record fusion power level of P(fus) = 140 kW is obtained, corresponding to a reaction rate of 4.6 X 10(16) reaction/s. The amplification factor Q = P(fus)/P(ICRH) reaches a maximum of 1.25% at P(ICRH) = 10 MW. The previous best results were P(fus) = 100 kW and Q = 1%. Time-resolved measurements show a correlation between fusion power and energy stored in the fast He-3 ions in agreement with calculations based on classical slowing down of the He-3 ions driven by ICRH to an average energy in the mega-electron-volt range.