Monitoring the leakage of 3.0 and 14.7 MeV protons from a fusion plasma

An experiment to study, separately, the leakage of protons of 3.0 and 14.7 MeV in the JET Tokamak, is presented. The activity of the activation products induced by the plasma in different samples that were placed inside the Tokamak was measured using ultra low-level gamma-ray spectrometry (ULGS). Stacking of some of the samples during activation allowed differentiating between the protons of 3.0 and 14.7 MeV that originated in two different reactions in the plasma. For the B4C sample the ratio of the 3.0 and 14.7 MeV proton flux could be determined as 0.17(10) assuming normal incidence and 0.31(16) assuming 45° incidence. For LiF the result obtained was that, within the uncertainty, there was no contribution from the 3.0 MeV protons.