Thermal Neutron PGAA
Figure 1. Schematic Representation of PGAA experiment
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| Basic Experimental Design: |
| In PGAA samples are placed in a neutron beam and "prompt" gamma rays are collected
using a high purity germanium detector (HPGe) during sample irradiation. As the elements in the sample undergo
neutron capture compound nuclei are formed and de-excitation of the compound nucleus occurs via emission of gamma
rays, in less than a nanosecond. PGAA can be performed using either a cold or thermal beam of neutrons. The NMG
maintains both a thermal and a cold PGAA instrument at the NIST Center for Neutron Research. |
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| Analysis of Hydrogenous Materials: |
| In most materials that contain percent levels of hydrogen, neutron scattering
by hydrogen decreases sensitivities for CNPGAA but increases those for TNPGAA. Therefore, thermal neutron PGAA is
used in the analysis of materials containing percent levels of hydrogen such as most biological materials, and the
CNPGAA facility is usually used for most other materials. |
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| Recent TNPGAA Applications: |
| Used by NIST scientists to determine element composition of SRM 1632c Coal, SRM 1566b Oyster Tissue,
and SRM 1848 Lubricant Additive Package. Used by FDA scientists to determine element composition of foods and
nutritional supplements.
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| References: |
"Prompt Gamma-Ray Activation Analysis: Fundamentals and Applications" R. M. Lindstrom and R. L. Paul., J. Radioanal. Nucl. Chem 243, 2000, pp. 181-189.
"Facility for Nondestructive Analysis for Major and Trace Elements Using Neutron-Capture Gamma-Ray Spectrometry", D. L. Anderson, M. P Failey, W. H. Zoller, W. B. Walters, G. E. Gordon, R. M. Lindstrom, J. Radioanal. Chem 63, 1981, pp. 97-119. |
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| Contacts: |
| Elizabeth A. Mackey, 301-975-5149, Lmackey@nist.gov |
| Richard Lindstrom, 301-975-6281, Richard.Lindstrom@nist.gov |
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| NCNR Thermal Neutron Instruments |
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Last modified 20-November-2002 by website owner: NCNR (attn: Bill Kamitakahara) |
