Low-level gamma-ray spectrometry for analysing fusion plasma conditions

A new method, combining activation by neutrons and charged particles with ultra low-level gamma-ray spectrometry, aimed at obtaining a better understanding and more adequate measurements of MeV particle leaks in magnetic fusion devices was studied here. A total of 36 samples containing Ti, LiF, B4C and W were placed in a boron-nitride holder mounted on the ceiling of the JET Tokamak. The samples were activated by 63 pulses from a D–3He plasma and were later measured using underground gamma-ray spectrometry. The radionuclides 7Be, 46Sc, 54Mn, 56Co, 57Co, 58Co, 124Sb, 181Hf, 182Ta, 181W and 185W were detected in several of the samples, with very low levels of activity of 47Sc and 48V found in a few of the samples. The various production channels for the radionuclides in question are discussed.