The Doppler broadening of gamma rays occurs in the fast neutron analysis with photons emitted in inelastic scattering reactions on certain nuclei, such as ¹²C and ¹⁴N. In this paper, we developed an algorithm based on the Monte Carlo method to calculate the Doppler broadened gamma peak shape of the 4.438 MeV gamma ray emitted by ¹²C in graphite when exposed to fast neutrons of different energies. The SAND-II unfolding iterative method is applied to obtain the spectrum of the incident neutron beam by using the Doppler broadened gamma spectra. In the calculation example, the unfolded neutron spectrum shows reasonable agreements with the original incident neutron spectrum.

伽马射线的多普勒展宽发生在快速中子分析中，光子在某些核上的非弹性散射反应中发射，例如¹² C 和¹⁴ N。在本文中，我们开发了一种基于蒙特卡罗方法的算法来计算多普勒展宽当暴露于不同能量的快中子时，石墨中¹² C发出的 4.438 MeV 伽马射线的伽马峰形状。应用SAND-II展开迭代法，利用多普勒加宽的伽马谱获得入射中子束的谱。在计算示例中，展开的中子谱与原始入射中子谱显示出合理的一致性。