Application of Prompt Gamma-Ray Activation Analysis (PGAA)
with a Portable Neutron Source

Richard B. Firestone, Ka-Ngo Leung, G.A. English, and D.L. Perry
Lawrence Berkeley National Laboratory
August 28, 2001

Abstract:
Prompt Gamma-ray Activation Analysis (PGAA) can be used to perform nondestructive, in situ, quantitative analysis on solid, liquid, and gaseous samples for all elements from hydrogen to plutonium except helium. The PGAA method takes advantage of the fact that the prompt g-ray spectrum produced by neutron capture on any isotope is unique. The spectra produced by neutrons bombarding unknown samples can be analyzed to determine the relative concentrations of each element with sensitivities ranging from 0.00001 to 1 mg per g. Since neutrons are highly penetrating, analyses can be performed on sealed samples. PGAA has been known for many years, but was difficult to apply until several recent advances. No adequate g-ray database was available until we recently measured the g-ray cross section yields for 80 elements to 2-3% accuracy at the Budapest Reactor. Advances in neutron beams and improved detector technology have made it possible analyze complex g-ray spectra ranging from 0-11 MeV recorded in low background counting areas. Finally, we are overcoming the limitation of PGAA to reactor facilities with the development of compact, high-flux neutron tubes at LBNL. We will discuss plans to develop a tabletop PGAA facility suitable for the analysis of legacy material. Sealed samples can be analyzed before handling to minimize possible contamination before opening. The neutron tube can be pulsed offering capabilities not possible with a reactor, and it can also be used for conventional Neutron Activation Analysis (NAA), isotope production, or to provide up to 14 MeV neutrons for Fast Neutron Activation Analysis (FNAA). Recent applications of PGAA to the analysis of geothermal vent samples, photometric materials, and archaeology will also be presented.