Abstract
With the high-intensity cold neutron flux available at the Prompt Gamma Activation Analysis (PGAA) instrument of the research reactor FRM II at the Heinz Maier-Leibnitz Zentrum (MLZ), samples with a weight of 1 mg or even less can be investigated for their elemental compositions using the (n,γ) capture reaction. In such cases, the typical sample packing material for PGAA experiments made of 25 μm thick PTFE foil (ca. 80 mg) can be orders of magnitude more massive than the sample weight itself. Proper choice of the packing material and measuring conditions are then of the highest importance [1].
Highlights
The Prompt Gamma Activation Analysis (PGAA) instrument started its user operation in 2008
To reduce the specific background in the PGAA spectra, elements intended for lining the sample chamber and sample holder are properly chosen: For neutron shielding (6Li and 10B-based) as well as for supporting the sample in the neutron beam, matrices are chosen from materials with very low neutron capture cross section like C, F-containing polymers
The samples were irradiated for 5 – 12 h and - together with prompt the decay gamma spectra taken in a low-background counting chamber next to the PGAA instrument were used for the precise data evaluation
Summary
The PGAA instrument started its user operation in 2008. Since the user group grows steadily, and more and more challenging proposals have been chosen by the referees for PGAA measurements. To reduce the specific background in the PGAA spectra, elements intended for lining the sample chamber and sample holder are properly chosen: For neutron shielding (6Li and 10B-based) as well as for supporting the sample in the neutron beam, matrices are chosen from materials with very low neutron capture cross section like C, F-containing polymers (called Teflon, FEP or PTFE). This way, hydrogen with relatively high capture as well as scattering cross-section (333 mb and 82 b, resp.) is exchanged by fluorine (10 mb and 4 b, resp.)
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