Analysis with neutrons

Prompt gamma activation analysis (PGAA) of the Universities of Cologne and Berne at the FRM II. (Photo: Andreas Heddergott / TUM)

The high neutron flux also allows analytical applications, such as neutron activation analysis (NAA). This is currently the most sensitive method for determining the presence of trace elements in a wide range of materials and plays an indispensable role in the analysis. Small traces of impurity atoms become radioactive themselves by absorbing neutrons and then emit characteristic gamma radiation, which can be measured. On comparison with an irradiated standard with accurately known element concentrations, the elemental content of the sample can then be calculated from the gamma spectra. For example, at the FRM II, it is possible to identify 21 different elements (Na, Ca, K, Sc, Mn, Fe, Co, Rb, Sb, Ba, Cs, La, Ce, Nd, Eu, Tb, Yb, Lu, Hf, Ta, Pa).

A variant of NAA is prompt gamma neutron activation analysis (PGAA), which simultaneously measures the gamma radiation released by the neutron irradiation. This method is primarily used at the FRM II.

The areas of application of neutron activation analysis are extremely diverse and range from the study of prehistoric pottery to geological and petrochemical samples and experiments on fundamental physics as well as the exploration of the universe.

For NAA and PGAA, the following equipment is in place at the FRM II: