ASTM E496-14
采用放射性技术测量3 H40;d,n41; 4 He中子发生器所产生的中子通量率和平均能量的标准试验方法

Standard Test Method for Measuring Neutron Fluence and Average Energy from?³H40;d,n41; ⁴He Neutron Generators by Radioactivation Techniques

被代替

标准号

ASTM E496-14

发布

2014年

发布单位

美国材料与试验协会

替代标准

ASTM E496-14e1

当前最新

ASTM E496-14(2022)

 

 

引用标准

ASTM E170 ASTM E181 ASTM E261 ASTM E265 ASTM E720

适用范围

5.1 Refer to Practice E261 for a general discussion of the measurement of fast-neutron fluence rates with threshold detectors.

FIG. 1 Variation of 0 Degree8201;³H(d,n)⁴He Differential Cross Section with Incident Deuteron Energy (1)

FIG. 2 Variation of 0 Degree8201;³H(d,n)⁴He Differential Cross Section with Incident Deuteron Energy (1)

5.2 Refer to Test Method E265 for a general discussion of the measurement of fast-neutron fluence rates by radioactivation of sulfur-32.

5.3 Reactions used for the activity measurements can be chosen to provide a convenient means for determining the absolute fluence rates of 14-MeV neutrons obtained with8201;³H(d,n)⁴He neutron generators over a range of irradiation times from seconds to approximately 100 days. High purity threshold sensors referenced in this test method are readily available.

5.4 The neutron-energy spectrum must be known in order to measure fast-neutron fluence using a single threshold detector. Neutrons produced by bombarding a tritiated target with deuterons are commonly referred to as 14-MeV neutrons; however, they can have a range of energies depending on: (1) the angle of neutron emission with respect to the deuteron beam, (2) the kinetic energy of the deuterons, and (3) the target thickness. In most available neutron generators of the Cockroft-Walton type, a thick target is used to obtain high-neutron yields. As deuterons penetrate through the surface and move into the bulk of the thick target, they lose energy, and interactions occurring deeper within the target produce neutrons with correspondingly lower energy.

5.5 Wide variations in neutron energy are not generally encountered in commercially available neutron generators of the Cockroft-Walton type. Figs. 1 and 2 (1)⁶ show the variation of the zero degree8201;³H(d,n)⁴He neutron production cross section with energy, and clearly indicate that maximum neutron yield is obtained with deuterons having energies near the 107 keV resonance. Since most generators are designed for high yield, the deuteron energy is typically about 200 keV, giving a range of neutron energies from approximately 14 to 15 MeV. The differential center-of-mass cross section is typically parameterized as a summation of Legendre polynomials. Figs. 3 and 4 (1,2) show how the neutron yield varies with the emission angle ......

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