1. The analysis of element and isotope composition by neutron spectroscopy method N.V. Bazhazhina, Yu. D. Mareev, L.B. Pikelner, P.V. Sedyshev, V.N. Shvetsov Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research

2. Excited states of compound nucleus

3. Neutron transmission measurement

4. Partial cross sections measurements

5. IREN parameters Peak current, A 3 Repetition rate, Hz 25 Electron pulse duration, ns 100 Electron energy, MeV 30 Neutron intensity, n/s 10 11

6. General view of the detector

7. Request of Central Geological Laboratory of Mongolia

8. Time-of-flight spectrum for sample from Mongolia 250 ns

9. Amount of the element is determined by an intensity of the resonance area - number of neutrons which crossed all area of the sample during measurement - detection efficiency - radiation width of the resonance - total width of the resonance - resonance area on the transmission curve, where is defined as function of the resonance parameters and the sample thickness (nuclei/cm 2 ).

10. Used curves for the analysis of neutron resonances

11. Results of analysis Element Weight of the element in sample, g Mass concentration of the element in sample, (g/kg) Pt2.7±0.3 180±20 Pd0.1±0.02 6.7±1.34 Ir5.2±0.6 347±40 Ru1.14±0.2 76±13 Os4.3±0.5 287±33

12. Boron enriched unfired phosphate ceramics

13. Determination of B content in composite material - the number of target nuclei per 1 cm 2, which do not have resonances and they have only the constant elastic cross section. - the number of target nuclei per 1 cm 2, which have the energy dependence of the cross section.

14. Determination of B content in composite material

15. Weight of sample, g., сm -2 Weight of in the sample, g Weight of B in the sample, g Weight% 4.881.7±0.20.22±0.031.08±0.1322.1±2.7

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