1.1 本试验方法定义了测量有效准直比的经验技术， 信用证 ，中子射线照相光束。该技术基于中子射线照相图像的分析，与基于准直系统物理尺寸的测量和计算无关。通过该技术得出的值应比基于物理测量的值更准确，尤其是对于定义较差的孔径。 1.2 本试验方法涵盖测量装置的制造和使用 信用证 比率。 1.3 该方法的中子图像可以使用指南中详述的适当转换屏在射线照相胶片上生成 E748 或带有适当中子转换器的CR屏。该方法尚未通过数字探测器阵列生成的图像进行验证。 1.4 本试验方法仅适用于具有冷中子谱或热中子谱的中子束线。 1.5 单位- 以国际单位制表示的数值应视为标准值。 1.6 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.7 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 中子射线照相图像的质量取决于许多因素。这个 信用证 比值是这些因素之一，构成了中子束几何形状的数值定义。这个 信用证 特定中子射线照相检查所需的比率取决于样本的厚度和特定感兴趣元素的物理特性。使用该测试方法允许射线照相师和用户确定并定期测量有效准直比。

1.1 This test method defines an empirical technique for the measurement of the effective collimation ratio, L/D , of neutron radiography beams. The technique is based upon analysis of a neutron radiographic image and is independent of measurements and calculations based on physical dimensions of the collimation system. The values derived by this technique should be more accurate than those based on physical measurements, particularly for poorly defined apertures. 1.2 This test method covers both the manufacture and use of the device to measure L/D ratios. 1.3 Neutron images for this method can be produced on radiographic film using an appropriate conversion screen as detailed in Guide E748 or a CR screen with appropriate neutron converter. The method has not been validated with images produced by digital detector arrays. 1.4 This test method only applies to neutron beam lines with cold or thermal neutron spectrums. 1.5 Units— The values stated in SI units are to be regarded as standard. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 4.1 The quality of a neutron radiographic image is dependent upon many factors. The L/D ratio is one of those factors and constitutes a numerical definition of the geometry of the neutron beam. The L/D ratio required for a specific neutron radiographic examination is dependent upon the thickness of the specimen and the physical characteristics of the particular element of interest. Use of this test method allows the radiographer and the user to determine and periodically measure the effective collimation ratio.