Progress on High β_N Steady State Scenario in KSTAR

The low q_min≈1, high β_N scenario at a relatively high value of the internal inductance, ??_i is one of the promising candidates for the ITER steady-state scenario. The high ??_i scenario on KSTAR has achieved β_N≈3, G=β_NH₈₉/q₉₅²>0.3, f_NI≈0.9 at q₉₅=5, approaching the normalized performance required for the fully non-inductive, Q=5 goal for ITER. The dRsep>0 (upper single null) operation achieved an “optimized” ??_i≈1 by considering trade-off between the edge pedestal and high ??_i at lower density to maximize the current drive efficiency for the fully non-inductive operation. The no-wall β_N limit calculated by DCON, β_N,limit≈3.9, indicates that higher β_N operation is possible even without wall stabilization. The higher current drive efficiency for the central electron cyclotron current drive (ECCD) compensates for the relatively low bootstrap current fraction for the fully non-inductive operation. No obvious sign of performance degradation has been observed for the pulse length of ~10 sec at β_N≈3. We will report recent progress to achieve higher β_N>3 and longer pulse > 15 sec, guided by the integrated scenario modeling IPS-FASTRAN.