VERDI detector benchmark experiment at the ENEA 14 MeV Frascati Neutron Generator

For future fusion plants, there is a great need for detectors capable to accurately monitor neutrons under the harsh fusion environment. In particular, detectors required in Test Blanket Modules must be capable to accurately measure neutron fluence under high and variable neutron fluxes, high gamma background, high temperature, high and variable magnetic fields. The noVEl neutRon Detector for fusIon (VERDI) project aims to develop a detector which will provide a robust approach for neutron detection in fusion plants. The detector comprises a low activation capsule containing a defined concentration of added metallic elements. The neutron fluence and energy spectrum will be derived by the analysis of the multiple gamma lines produced by the metallic elements activation. In this work, the candidate metallic elements for the VERDI detector are defined. A benchmark experiment with a number of prototype detectors was performed at the ENEA Frascati Neutron Generator under DT operation to demonstrate the feasibility of VERDI detectors to measure neutron fluence under a reference fusion relevant field. The results of product isotopes measurements are compared to respective calculated data using the FISPACT-II code and very good agreement is observed. Preliminary unfolding of the neutron spectrum was also performed.