1.1 本试验方法涵盖了测量中子发生器产生的快中子注量率的一般程序 3. H( d、 n ) 4. 他做出了反应。这样产生的中子通常被称为14 MeV中子，但能量范围取决于许多因素。本试验方法未充分涵盖等离子体速度可能是重要考虑因素的熔合源。 1.2 该测试方法使用阈值活化反应来确定中子的平均能量和该能量下的中子注量。至少需要从一组适当的剂量测定反应中选择三种活动来表征平均能量和通量。所需放射性通常通过伽马射线光谱学测量。 1.3 以国际单位制表示的数值应视为标准值。 本标准不包括其他计量单位。 1.4 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。 1.5 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====== 5.1 参考实践 E261 关于用阈值探测器测量快中子注量率的一般性讨论。 5.5.1 图5 ( 2. ) 显示了当入射氘的能量为150 keV并且入射到厚和薄的氚靶上时，中子能量如何取决于实验室坐标系中的散射角。对于厚靶，入射氘在穿透靶时会损失能量，并产生能量较低的中子。厚靶是指厚度足以完全阻止氘核入射的靶。中的两条曲线 图5 对于厚目标和薄目标，来自不同的来源。虚线计算来自Ref ( 3. ) ; 实曲线计算来自Ref ( 4. ) ; 测量数据来自Ref ( 5. ) . 点划线曲线和右轴给出了薄靶和厚靶计算中子能量之间的差异。计算机代码可用于帮助计算各种入射氘能量的预期厚靶和薄靶产额和中子谱 ( 6. ) . 图5 的依赖性 3. H( d、 n ) 4. 氦中子角能量( 2. ) 5.6 一回路的Q值 3. H( d、 n ) 4. 他的反应是 +17.59兆电子伏。当入射氘核能量超过3.71 MeV和4.92 MeV时，破裂反应发生 3. H( d、 np ) 3. H和 3. H( d 2. n ) 3. 他分别变得精力充沛。因此，在高氘能量（>3.71 MeV）下，该反应不再是单能反应。该反应可以在实验室前角产生能量约为14.8至20.4MeV的单能中子束 ( 7. ) . 5.7 建议将剂量测定传感器部署在需要剂量测定结果的准确位置。有许多因素可以影响中子束的单色性或能量扩散 ( 7. , 8. ) . 这些因素包括入射氘能量的能量调节、使用气体靶时挡窗内的能量损失或使用固体氚靶时靶内的能量损失、辐照几何形状以及辐照室内墙壁和地板散射产生的背景中子。

1.1 This test method covers a general procedure for the measurement of the fast-neutron fluence rate produced by neutron generators utilizing the 3 H( d,n ) 4 He reaction. Neutrons so produced are usually referred to as 14-MeV neutrons, but range in energy depending on a number of factors. This test method does not adequately cover fusion sources where the velocity of the plasma may be an important consideration. 1.2 This test method uses threshold activation reactions to determine the average energy of the neutrons and the neutron fluence at that energy. At least three activities, chosen from an appropriate set of dosimetry reactions, are required to characterize the average energy and fluence. The required activities are typically measured by gamma-ray spectroscopy. 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 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. 1.5 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 ====== 5.1 Refer to Practice E261 for a general discussion of the measurement of fast-neutron fluence rates with threshold detectors. 5.5.1 Fig. 5 ( 2 ) shows how the neutron energy depends upon the angle of scattering in the laboratory coordinate system when the incident deuteron has an energy of 150 keV and is incident on a thick and a thin tritiated target. For thick targets, the incident deuteron loses energy as it penetrates the target and produces neutrons of lower energy. A thick target is defined as a target thick enough to completely stop the incident deuteron. The two curves in Fig. 5 , for both thick and thin targets, come from different sources. The dashed line calculations come from Ref ( 3 ) ; the solid curve calculations come from Ref ( 4 ) ; and the measured data come from Ref ( 5 ) . The dash-dot curve and the right-hand axis give the difference between the calculated neutron energies for thin and thick targets. Computer codes are available to assist in calculating the expected thick and thin target yield and neutron spectrum for various incident deuteron energies ( 6 ) . FIG. 5 Dependence of 3 H( d,n ) 4 He Neutron Energy on Angle ( 2 ) 5.6 The Q-value for the primary 3 H( d,n ) 4 He reaction is +17.59 MeV. When the incident deuteron energy exceeds 3.71 MeV and 4.92 MeV, the break-up reactions 3 H( d,np ) 3 H and 3 H( d ,2 n ) 3 He, respectively, become energetically possible. Thus, at high deuteron energies (>3.71 MeV) this reaction is no longer monoenergetic. Monoenergetic neutron beams with energies from about 14.8 to 20.4 MeV can be produced by this reaction at forward laboratory angles ( 7 ) . 5.7 It is recommended that the dosimetry sensors be fielded in the exact positions where the dosimetry results are wanted. There are a number of factors that can affect the monochromaticity or energy spread of the neutron beam ( 7 , 8 ) . These factors include the energy regulation of the incident deuteron energy, energy loss in retaining windows if a gas target is used or energy loss within the target if a solid tritiated target is used, the irradiation geometry, and background neutrons from scattering with the walls and floors within the irradiation chamber.