1. NSTX S. A. Sabbagh XP615: Active Stabilization of the Resistive Wall Mode at Low Aspect Ratio  Goals (Part I):  Operate new RWM feedback system on 0.9–1.0 MA DND target All aspects of RWM control system / RWM sensors worked well. Good target plasmas with wide n=1 free window; high  N up to 6. Both locked/rotating RFA/RWM were observed/tracked by feedback.  Vary RWM feedback phase/gain to show control system influence I p = 1.0 MA target showed “best” phase <~ 270 o I p = 0.9 MA target more conclusive / finer scan; best phase = 225 o “Best” phase depends on whether mode is rotating or not  Reduce plasma rotation with n = 3 braking to excite RWM if needed RFA observed / RWM excited without braking in most cases I p = 0.9 MA target with phase = 250 o, 225 o required braking to excite mode

2. NSTX S. A. Sabbagh Setting RWM feedback relative phase in the range ~ 250 o superior for longer pulse, higher  N vs. ~ 0 o  Phase scan  Varied through 360 o, finer scan in 270 o range; 225 o appears to be “best”  n = 3 braking required to generate RWM when phase set to most favorable settings Feedback on  B p (n=1) (T)  collapse (250 o )  N = 6  collapse (290 o )  N = 4.9  collapse (0 o )  N = 4.7

3. NSTX S. A. Sabbagh Generated relatively low rotation plasmas at high  N ~ 5.7 n=3 DC (0.8kA) applied field   (kHz) 10 20 30 0 t = 0.5 – 0.65s 119674 40 n=1 feedback (270 o phase)  N = 5.7 1.01.21.41.6 R(m)   (kHz) 10 20 0 No n=1 rotating mode n=1 rotating mode onset 119758