ASTM E496-14
Standard Test Method for Measuring Neutron Fluence and Average Energy from?³H40;d,n41; ⁴He Neutron Generators by Radioactivation Techniques

Standard No.

ASTM E496-14

Release Date

2014

Published By

American Society for Testing and Materials (ASTM)

Status

Be replaced

Replace By

ASTM E496-14e1

Latest

ASTM E496-14(2022)

Scope

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 ......

ASTM E496-14 Referenced Document

• ASTM E170 Standard Terminology Relating to Radiation Measurements and Dosimetry
• ASTM E181 Standard Test Methods for Detector Calibration and Analysis of Radionuclides
• ASTM E261 Standard Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques
• ASTM E265 Standard Test Method for Measuring Reaction Rates and Fast-Neutron Fluences by Radioactivation of Sulfur-32
• ASTM E720 Standard Guide for Selection and Use of Neutron-Activation Foils for Determining Neutron Spectra Employed in Radiation-Hardness Testing of Electronics

ASTM E496-14 history

• 2022 ASTM E496-14(2022) Standard Test Method for Measuring Neutron Fluence and Average Energy from ³H(d,n)⁴He Neutron Generators by Radioactivation Techniques
• 2014 ASTM E496-14e1 Standard Test Method for Measuring Neutron Fluence and Average Energy from?³H40;d,n41; ⁴He Neutron Generators by Radioactivation Techniques
• 2014 ASTM E496-14 Standard Test Method for Measuring Neutron Fluence and Average Energy from?³H40;d,n41; ⁴He Neutron Generators by Radioactivation Techniques
• 2009 ASTM E496-09 Standard Test Method for Measuring Neutron Fluence and Average Energy from ³H(d,n)⁴He Neutron Generators by Radioactivation Techniques ¹
• 2002 ASTM E496-02 Standard Test Method for Measuring Neutron Fluence and Average Energy from ³H(d,n)⁴He Neutron Generators by Radioactivation Techniques ¹
• 1996 ASTM E496-96 Standard Test Method for Measuring Neutron Fluence Rate and Average Energy From Neutron Generators by Radioactivation Techniques