Application Of Verdi Detectors For Neutron Fluence Measurements During The Jet 2019 Deuterium-Deuterium Campaign

The Novel Neutron Detector for Fusion (VERDI) project aims to develop a passive detector which will provide a robust approach for neutron detection in current and future fusion devices. The detector comprises a low activation capsule, capable to withstand the harsh fusion conditions, containing defined added metallic elements, the activation of which provides neutron fluence and energy spectrum information. In the present work, VERDI detectors were employed for the first time to determine neutron fluence and energy spectra at the Joint European Torus (JET) Long Term Irradiation Station (LTIS) during the 2019 Deuterium-Deuterium (DD) campaign. Two materials, graphite and carbon fibre reinforced silicon carbide composite, were used for the capsule fabrication containing disc-shaped activation foils (Ag, Mn, Nb, Ni, Rh, Ti, Y). Post-irradiation gamma-spectrometry measurements were performed in order to identify the product isotopes and derive the incident neutron fluence. The results were fed into the MAXED code to reconstruct the neutron spectrum. The derived spectrum was in very good agreement with the calculated one using the MCNP code. A difference of 8% was found between the derived and the experimentally determined total integrated neutron flux. This work demonstrates the feasibility of employing VERDI detectors for neutron measurements in real fusion environments.