D-³He Fusion in the Joint European Torus Tokamak — Recent Experimental Results

A new series of D-³He fusion yield experiment has been performed in the Joint European Torus (JET) using ion cyclotron resonance heating (ICRH) to generate a high-energy ³He 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 ³He 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 × 10¹⁶ reaction/s. The amplification factor Q = P_fus/P_ICRH reaches a maximum of 1.25% at P_ICRH = 10 MW. The previous best result were P_fus = 700 kW and Q = 1%. Time-resolved measurements show a correlation between fusion power and energy stored in the fast ³He ions in agreement with calculations based on classical slowing down of the ³He ions driven by ICRH to an average energy in the mega-electron-volt range.