A New Regime for Studying the High Bootstrap Current FractionPlasma

A new experimental regime has recently been studied for achieving high fraction of the bootstrap current in the JT-60U hydrogen discharges. The high poloidal beta (β_p ～ 3.61) plasma was obtained by high-power neutral beam injection heating at very high edge safety factor (I_p = 0.3 MA, B_t = 3.65 T, q_eff = 25 - 35) region, and the bootstrap current fraction (f_BS) was about 40% using the ACCOME code calculation. It was observed that there were no magnetohydrodynamics instabilities to retard the increase of β_p and f_BS parameters in the new regime.