Standard Article

Time-Sequenced Prompt γ Neutron Activation Analysis

Nuclear Methods

  1. Sudeep Mitra

Published Online: 15 DEC 2009

DOI: 10.1002/9780470027318.a9128

Encyclopedia of Analytical Chemistry

Encyclopedia of Analytical Chemistry

How to Cite

Mitra, S. 2009. Time-Sequenced Prompt γ Neutron Activation Analysis. Encyclopedia of Analytical Chemistry. .

Author Information

  1. Brookhaven National Laboratory, Environmental Sciences Department, Upton, NY, USA

Publication History

  1. Published Online: 15 DEC 2009

Abstract

Time-sequenced prompt- γ neutron activation analysis is a powerful nondestructive, elemental analysis tool that exploits the temporal characteristics of a nuclear reaction to enhance the capability for multielemental analyses. Usually, it encompasses a 14-MeV neutron generator (NG), pulsed at a suitable frequency, such that the fast-neutron-induced reactions that occur concurrently with the neutron pulse are separated in time from slow neutron-capture reactions that are delayed by the thermalization time of neutrons in the matrix of the interrogated sample. Time-sequenced data acquisition, operating synchronously with the pulsing of the NG, partitions the characteristic elemental prompt γ-rays according to the type of the reaction. In another approach, the so-called associated particle technique, a specialized NG with a built-in α particle detector exploits the deuterium–tritium fusion reaction that emits a 14-MeV neutron and an α particle back-to-back. The direction of the neutron is deduced from detecting the α particle. This tagged neutron interacts with the interrogated object's nuclei and generates element-specific prompt γ-rays that are delayed by the neutron's time of flight. Detecting these γ-rays concurrently with the α particles enables the investigator to identify the element with vastly improved signal-to-noise ratios compared to the pulsed technique, and helps to determine the site of origin of the particular γ-ray.

Keywords:

  • pulsed neutrons;
  • prompt-γ rays;
  • associated particle technique;
  • multielement analysis;
  • nondestructive