Gamma ray prompt

Prompt activation analysis (Erdtmann and Petri, 1986 Alfassi, 1990) uses the prompt radiation accompanying a nuclear reaction for determining elemental or isotopic concentrations. The variety of prompt methods is large because a sample can be irradiated with various particles - neutrons, charged particles or gamma-rays. Prompt activation analysis permits the determination of several elements - about 17 elements in environmental matrices (Germani et al., 1980) - but most analysis are used for the determination of light elements (H, He, Li, B, C, N, Si, S, Cl) as well of Cd and Gd. 

This can result in a radioactive product from the A(n, t)A reaction where A is the stable element, n is a thermal neutron, A is the radioactive product of one atomic mass unit greater than A, and y is the prompt gamma ray resulting from the reaction. A is usually a beta and/or gamma emitter of reasonably long half-life. Where access to a nuclear reactor has been convenient, thermal neutron activation analysis has proven to be an extremely valuable nondestructive analytical tool and in many cases, the only method for performing specific analyses at high sensitivities... 

Glascock, M.D., Spalding, T. G., Biers, J. C., and Corman, M.F. (1984). Analysis of copper-based metallic artefacts by prompt gamma-ray neutron activation analysis. Archaeometry 26 96-103. 

Ouri, Y., Shirari, N. and Ebihara, M. (2003) Chemical composition of Yamato (Y)980459 and Y000749 Neutron-induced prompt gamma-ray analysis study. Antarctic Meteorite Research, 16, 80—93. 

The prompt gamma-rays emitted following neutron or charged particle interactions with the target nuclide may be used as a basis for non-destructive analyses. The important advantage of this technique is that the determination does not depend in any manner on the half-life of a product radionuclide. In fact, using this technique, the product nuclide need not even be radioactive. Many conventional activation determinations are limited in their sensitivities by short half-life product radionuclides, or the fact that the most abundant or highest cross section isotope of the element to be determined leads to a stable product on irradiation. 

R.B. Bouiton, G.T. Ewan, Simultaneous analysis of light elements using prompt nuclear reaction gamma rays, Anal. Chem. 49 (1977) 1297-1303. 

Place the sample at a position and geometry relative to the detector whereby the gamma rays may be quantitatively analyzed. Count the sample for a period of time that will produce enough counts in the gamma-ray peak ROI to provide a low counting error, i.e., collect at least 1,000 counts per ROE Promptly after each measurement, check that the expected energy peaks are observable, sufficient counts have been collected for statistical reliability, and that previously unidentified peaks are attributed to the radionuclides that emit them. For repeated counts, assure that the sample position on the detector is reproducibly identical. 

Molnar, G. L., and R. M. Lindstrom. 1998. Nuclear reaction prompt gamma-ray analysis. In Nuclear methods in mineralogy and geology Techniques and applications. Ed. A. Vertes, S. Nagy, and K. Stivegh. 145-164. New York Plenum. 

Search for GRB Neutrinos. The AMANDA GRB search for correlated v emission relies on temporal (typically less than 100 s in duration) and angular information provided by BATSE and other satellites in the IPN network (Hurley et al., 1998). Initial search strategies for data collected between 1997-2000 (Hardtke et al., 2003) and for individual GRBs (Stamatikos et al., 2004), have assumed nearly concurrent emission within the duration of prompt gamma-ray emission (Tgo). A new search (Kuehn et al., 2004) also scans for neutrino emission prior to the Tgo start time. No excess was observed for either search method above the expected background from atmospheric v and poorly reconstructed... 

Figure 1. Histogram of detection limits for neutron activation analysis (NAA) and neutron-capture prompt gamma-ray activation analysis (PGAA). Data from Reference 15.

Neutron-capture prompt-gamma ray activation analysis (PGAA) is a recent addition to the nuclear analytical arsenal. In this technique the instantaneous gamma ray emission from a sample is measured as it is irradiated in a flux of reactor neutrons (33,3, 35). Because the sample must be several meters from either the core of the reactor or (less commonly) from the detector, the sensitivity of this technique is generally poorer than in conventional NAA. However, it is possible to measure small quantities of many elements which do not give radioactive neutron-capture products, notably 0.01 mg of H, 50 ng B, and 1 mg P in an electronics context. 

Paul RL and Lindstrom RM (2000) Prompt gamma-ray activation analysis, fundamentals and applications. J Radioanal Nucl Chem 243 181-189. 

PGNAA Prompt gamma-ray measurements are used for elements producing either very short or very long lived radionuclides, commonly H, C, N, Si, P and S. Enhanced sensitivities are obtained by direct measurement of prompt gamma-rays emitted by the transient compound nucleus instead of the radioactive reaction product. 

Andeeson DL (2000) Neutron capture prompt gamma-ray activation of meat homogenates. J Radioanal Nud Chem 244 225 - 229. 

Neutron activation analysts (NAA) can be accomplished by measurement of the prompt gamma rays during irradiation or by measurement of the delayed... 

FIGURE 32-6 Overview of the neutron activation process. The incident neutron is captured by the target nucleus to produce an excited compound nucleus, which de-excites with emission of a prompt gamma ray. The radioactive nucleus formed decays by emitting a beta particle. If an excited product nucleus is formed, a delayed gamma ray can be emitted. If decay is directly to the ground state of the product nucleus, no gamma ray is emitted. 

The prompt gamma rays formed by capture reactions are of analytical interest in some cases, but the radionuclide produced ( Na) and its decay radiations are more often used in NAA. 

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