Observation of ``Anomalous'' Energetic Ion Spectra by the E$\vert \vert $B Neutral Particle Analyzer on NSTX

An ``anomalous'' increase in E$\vert \vert $B NPA charge exchange neutral flux ($\sim $4x) localized at the neutral beam (NB) injection full energy, E$_{b}$ = 90 keV, is observed in NSTX. This so-called ``High-Energy Feature (HEF)'' appears in discharges only when kink-type modes (f $<$ 10 kHz) are absent, TAE activity ( f $\sim $ 10-150 kHz) is weak ($\delta $B$_{rms} <$ 75 mGauss) and CAE activity (f $\sim $ 400 -- 1200 kHz) is robust. The HEF exhibits a growth time of $\sim $ 20-80 ms and develops a slowing down distribution that evolves over 100-400 ms, a time scale long compared with the $\sim$ 50 ms equilibration time of the NB injected particles. Increases of $\sim$ 10-30{\%} in the measured neutron yield and total stored energy are observed to coincide with the HEF along with broadening of the CHERS T$_{i}$(r) profile. The HEF is observed only in H-mode (not L-mode) discharges with injected NB power above 4 MW and is suppressed by vessel conditioning using lithium deposition at rates $\sim$ 100 mg/shot sufficient to suppress ELM activity. Though a definitive mechanism has yet to be develop, the HEF appears to be driven by a form of CAE resonance.