DEUTERIUM-TRITIUM RESULTS OF TFTRS-ALPHA COLLECTOR

An escaping alpha collector probe has been developed for the deuterium -tritium (DT) phase of the Tokamak. Fusion Test Reactor (TFTR) to comp lement the results of the lost alpha scintillator detectors, which hav e been operating on TFTR since 1988. Measurements of the energy distri bution of escaping alphas have been made by measuring the range of alp has implanted into nickel foils located within the alpha collector. Ex posed samples have been analysed for four DT plasma discharges at plas ma currents of 1.0 and 1.8 MA. The results at 1.0 MA are in good agree ment with predictions for first orbit alpha loss at 3.5 MeV. The 1.8 M A results, however, indicate a large anomalous loss of partially therm alized alphas at an energy similar to 30% below the birth energy and a t a total fluence nearly an order of magnitude above the expected firs t orbit loss. This anomalous loss is not observed with the lost alpha scintillator detectors in DT plasmas but does resemble the anomalous ' delayed' loss seen in DD plasmas. Several potential. explanations for this loss process are examined. None of the candidate explanations pro posed thus far are fully consistent with the anomalous loss observatio ns.