Abstract
Nowadays, high-energy radiation particles are used in radiation therapy gradually. High-energy radiation particles always accompany with high-energy neutrons. To evaluate the distributions of neutron energies and fluences, the Bonner Sphere Spectrometer (BSS) is most commonly used to assess the neutron spectrum in international, but it is not good when particle energy exceed 10 MeV. High atomic number materials like lead, or copper is added to traditional BSS to increase (n, xn) cross-section, and then enhance the magnitude of the response functions in high energies. This new detection system is called Extended-Range Bonner Sphere Spectrometer (ERBSS). In this research, 7 different sizes BSS and self-made ERBSS including 2 lead sphere-shells and 2 polyethylene sphere-shells with gold foil were used to measure neutron spectra of standard neutron source Cf-252 and Tsing-Hua Open-pool Reactor (THOR). The neutron spectra of Cf-252 and THOR measured by means of traditional BSS and ERBSS were compared. The results showed that the neutron spectra of ERBSS and traditional BSS are similar in measuring standard Cf-252 source and THOR, and the ability of self-made ERBSS measuring neutron spectra was verified and proved. The results also showed that traditional BSS accompany with PbPE sphere-shell is more fit to real neutron spectrum. It can increase the calculation accuracy of program UMG 3.3, which calculate the neutron spectrum, when the sphere set is increased. The high-energy neutron facilities are going to be constructed and operated in the future, in Taiwan. By experimental verification of this study, the feasibility of using self-made ERBSS system to evaluate and analysis high-energy neutron spectrum is approved.