Because of the wide variety of materials being used in neutron-activation measurements, this guide is presented with the objective of bringing improved uniformity to the specific field of interest here: hardness testing of electronics primarily in critical assembly reactor environments.

Note 2—Some of the techniques discussed are useful for 14-MeV dosimetry. See Test Method E 496 for activation detector materials suitable for 14-MeV neutron effects testing.

Note 3—The materials recommended in this guide are suitable for ²⁵²Cf or other weak source effects testing provided the fluence is sufficient to generate countable activities.

This guide is organized into two overlapping subjects; the criteria used for sensor selection, and the procedures used to ensure the proper determination of activities for determination of neutron spectra. See Terminology E 170 and General Methods E 181. Determination of neutron spectra with activation sensor data is discussed in Guides E 721 and E 944.

1.1 This guide covers the selection and use ofneutron-activation detector materials to be employed in neutronspectra adjustment techniques used for radiation-hardness testingof electronic semiconductor devices. Sensors are described thathave been used at many radiation hardness-testing facilities, andcomments are offered in table footnotes concerning theappropriateness of each reaction as judged by its cross-sectionaccuracy, ease of use as a sensor, and by past successfulapplication. This guide also discusses the fluence-uniformity,neutron self-shielding, and fluence-depression corrections thatneed to be considered in choosing the sensor thickness, the sensorcovers, and the sensor locations. These considerations are relevantfor the determination of neutron spectra from assemblies such asTRIGA- and Godiva-type reactors and from Californium irradiators.This guide may also be applicable to other broad energydistribution sources up to 20 MeV.

Note 1—For definitions on terminology used in this guide, seeTerminology E 170.

1.2 This guide also covers the measurement of the gamma-ray orbeta-ray emission rates from the activation foils and other sensorsas well as the calculation of the absolute specific activities ofthese foils. The principal measurement technique is high-resolutiongamma-ray spectrometry. The activities are used in thedetermination of the energy-fluence spectrum of the neutron source.See Guide E 721.

1.3 Details of measurement and analysis are covered asfollows:

1.3.1 Corrections involved in measuring the sensor activitiesinclude those for finite sensor size and thickness in thecalibration of the gamma-ray detector, for pulse-height analyzerdeadtime and pulse-pileup losses, and for backgroundradioactivity.

1.3.2 The primary method for detector calibration that usessecondary standard gamma-ray emitting sources is considered in thisguide and in General Methods E 181. In addition, an alternativemethod in which the sensors are activated in the known spectrum ofa benchmark neutron field is discussed in Guide E 1018.

1.3.3 A data analysis method is presented which accounts for thefollowing: detector efficiency; background subtraction;irradiation, waiting, and counting times; fission yields andgamma-ray branching ratios; and self-absorption of gamma rays andneutrons in the sensors.

1.4 The values stated in SI units are to be regarded as thestandard.

1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulatory limitations prior to use.