Richard Bindel1, Lei Cao1,2, and Rick Paul1


1 Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA


2 Current Address: Nuclear Engineering Program, The Ohio State University,

Columbus, OH 43210, USA


Prompt gamma-ray activation analysis (PGAA) provides a non-destructive means of simultaneously determining the presence and amount of various elements in a sample.  The chemical and physical form of the sample is relatively unimportant, and no special preparation, e.g. dissolving, atomization, etc., is required.  PGAA involves irradiating a sample with a collimated beam of neutrons while concurrently observing production of gamma rays, which, in turn, have energies characteristic of the elements from which they originated.  PGAA is particularly useful for measuring light elements such as hydrogen and boron.

At the NIST PGAA facilities, collimated neutron beams typically ranging from 10 to 20 mm in diameter are used to irradiate samples.  Recently, a neutron optic has been used at the cold neutron PGAA station to produce a spot roughly a millimeter diameter (FWHM).  The neutron flux density averaged over the FWHM is roughly an order of magnitude greater than that of the unfocused beam.  Using motorized stages to translate samples relative to the focal spot, a prototype for a scanning PGAA facility has been built.  Detailed characterization of the focused beam and a scan map of a hydrogenous sample will be presented.