Evaluation of the spectrum unfolding methodology for neutron activation system of fusion devices

摘要

A neutron activation system (NAS) is a highly useful and reliable tool for neutron flux and energy-spectrum measurements in fusion devices. We are evaluating a fast and efficient methodology for processing of fusion NAS data. Starting with the gamma spectra of irradiated activation materials, the method ultimately produces unfolded spectrum of the incident neutrons and uncertainty estimates. Here, we test the method using data from dedicated experiments at the Joint European Torus (JET) tokamak in Culham and the Nuclear Physics Institute (NPI) in Rez. These measurements utilize few, from three to five reaction channels as input to the unfolding process. Two spectral adjustment code-packages have been adapted for this purpose: MAXED from UMG 3.3 and STAYSL-PNNL. While the former is frequently applied, the latter is a new addition to the case of fusion device NAS. We present the post-analyses of NAS data, spectral adjustments and some discussion on the experiences with these tools, required developments and our planned future studies.