Vega-Carrillo H R, Martínez-Ovalle S A, Lallena A M, Mercado G A, Benites-Rengifo J L
Unidad Academica de Estudios Nucleares, Universidad Autónoma de Zacatecas, C Cipres 10, Fracc La Peñuela, 98060 Zacatecas, Zac, Mexico.
Appl Radiat Isot. 2012 Dec;71 Suppl:75-80. doi: 10.1016/j.apradiso.2012.03.034. Epub 2012 Mar 29.
A Monte Carlo calculation, using the MCNPX code, was carried out in order to estimate the photon and neutron spectra in two locations of two linacs operating at 15 and 18 MV. Detailed models of both linac heads were used in the calculations. Spectra were estimated below the flattening filter and at the isocenter. Neutron spectra show two components due to evaporation and knock-on neutrons. Lethargy spectra under the filter were compared to the spectra calculated from the function quoted by Tosi et al. that describes reasonably well neutron spectra beyond 1 MeV, though tends to underestimate the energy region between 10(-6) and 1 MeV. Neutron and the Bremsstrahlung spectra show the same features regardless of the linac voltage.
为了估算在15和18兆伏运行的两台直线加速器两个位置处的光子和中子能谱，使用MCNPX代码进行了蒙特卡罗计算。计算中使用了两台直线加速器机头的详细模型。在均整过滤器下方和等中心处估算能谱。由于蒸发中子和撞出中子，中子能谱显示出两个成分。将过滤器下方的勒让德能谱与由托西等人引用的函数计算出的能谱进行了比较，该函数对1兆电子伏以上的中子能谱描述得相当好，不过往往低估了10^(-6)到1兆电子伏之间的能量区域。无论直线加速器电压如何，中子和轫致辐射能谱都显示出相同的特征。
