Anomalous Beam-Ion Loss in TFTR Reversed Magnetic Shear Plasmas

Anomalous beam-ion loss has been observed in an experiment with short tritium beam pulses injected into deuterium-beam-heated Tokamak Fusion Test Reactor plasmas ( $P_{\mathrm{NBI}}=15\mathrm{}$ MW) with reversed magnetic shear (RS). Comparisons of the measured total 14 MeV neutron emission, the neutron flux along eight radial locations, and the perpendicular plasma stored energy with predictions from an extensive set of TRANSP simulations suggest that about $40\%$ beam power is lost on a time scale much shorter than the tritium beam pulse length $\Delta t=70\mathrm{}$ ms. In contrast with recent results [K. Tobita et al., Nucl. Fusion 37, 1583 (1997)] from RS experiments at JT-60U, we were not able to show conclusively that magnetic field ripple is responsible for this anomaly.