Evaluating Angular Dependence of Stilbene Neutron Diagnostic System for KSTAR

The stilbene scintillator was proposed as a neutron-flux monitor in measuring the characteristics of neutron radiation at the Korea Superconducting Tokamak Advanced Research (KSTAR). Various neutron diagnostic tools are used in fusion reactors for measurement of plasma parameters such as fusion power, power density, ion temperature, fast ion energy, and their spatial distribution. In this study, to evaluate the properties of the stilbene neutron diagnostic system, the efficiency of the radiation shielding was tested experimentally by changing the orientation of the n, γ source. Polyethylene was used to keep neutrons out of the sight line and gamma-rays were blocked by lead. A neutron tagger module was used for a signal digitization, which consists of Flash-ADC and FPGA implemented with real-time n-γ separation processor by using a charge comparison method. As a result, the designed and fabricated stilbene neutron diagnostic system show a good performance measuring neutrons and it was proper as the collimator to measure neutrons from fusion reaction at KSTAR