Experimental validation of a Tokamak neutron spectrometer based on Bonner spheres^*

In order to realize real-time fusion neutron spectrum diagnosis for the HL_2A Tokamak, a Bonner Sphere Spectrometer (BSS) array has been developed, consisting of eight polyethylene spheres (PS) with embedded ³He proportional counters. To validate its spectrometric capability, spectrum measurement of an ²⁴¹Am-Be neutron source was carried out and is described. The Monte Carlo code Geant4 was used to calculate the response functions, taking this interference into consideration. Finally, the neutron spectrum was unfolded in the energy range from 10⁻⁹ MeV to 20 MeV. The unfolded spectrum has remarkable consistency with the ISO 8529-1 standard ²⁴¹Am-Be neutron spectrum which is a preliminary demonstration that this BSS is reliable and practical.