Abstract The D2O-moderated 252Cf is a non-point neutron source used as a calibration facility for measuring devices. The Bonner spheres spectrometer (BSS) is one of the common instruments for neutron spectrometry. Due to having a non-point source, the neutron spectrum depends on distance. On the other hand, because of the detector and source size, there is a deviation in BSS reading from that expected according to the inverse square law. In the present study, the Monte Carlo simulations were applied to investigate the effect of beam divergence on the response of BSS. The average energy of neutrons reaching the surface of the BSS was dependent on distance, and its value increases with increasing distance. Subsequently, the response of the BSS under plane-parallel beams was also dependent on the distance. Thus, for 2", 3", and 5" spheres, with increasing distance, the response decreased, and for larger spheres, it was the opposite. The calculated geometry correction factors for 12", 15" and 18" spheres were less than one at all distances; however, for other spheres, at closer distances they were higher than one, and gradually reduced to below the one by increasing the distance.

中文翻译：

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D2O 调节的 252Cf 光谱的距离相关性和对校准因子的影响

摘要 D2O 慢化 252Cf 是一种非点中子源，用作测量设备的校准设施。邦纳球能谱仪（BSS）是中子能谱测定的常用仪器之一。由于具有非点源，中子谱取决于距离。另一方面，由于探测器和源尺寸的原因，BSS 读数与根据平方反比定律预期的读数存在偏差。在本研究中，蒙特卡罗模拟被应用于研究光束发散对 BSS 响应的影响。中子到达 BSS 表面的平均能量取决于距离，其值随着距离的增加而增加。随后，BSS 在平面平行光束下的响应也取决于距离。因此，对于 2"、3" 和 5" 球体，随着距离的增加，响应降低，而对于更大的球体，则相反。12"、15" 和 18" 球体的计算几何校正系数在所有距离处都小于 1；但是，对于其他球体，在较近的距离处它们大于 1，并通过增加距离逐渐减小到小于 1。