Charged Fusion Product Loss Measurements Using Nuclear Activation Analysis

In ITER, alpha particle loss measurements will be required in order to understand the physics of the high energy alpha particle population. Techniques capable of operating in the ITER harsh environment need further development and testing. Recent experimental studies on JET have demonstrated the potential of nuclear activation to measure the flux of escaping MeV ions. New results from MeV ion induced activation of several metallic, ceramic and crystal samples placed near the plasma edge are reported in this paper. The position of the samples allowed for the distribution of activation products to be measured as a function of the orientation with respect to the toroidal magnetic field as well as function of the distance to the plasma. The activity in these samples was measured using an ultra low level background gamma ray spectrometry technique. Results show distribution of fusion proton induced activation products is strongly anisotropic due to the magnetic field and falls off rapidly with increasing distance to the plasma while fusion neutron induced activation products are rather uniformly distributed on the samples. The 14.7MeV fusion proton fluence was measured to within 4% accuracy. Finally, prospects for using this technique in ITER are discussed.
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