1. Neutron production study with the thick lead target and uranium blanket irradiated by 1.5 GeV protons Filip Křížek, ÚJF AV ČR

2. The experiment on JINR Dubna accelerator Nuclotron The experiment was carried out in December 2001. A thick lead target and an uranium rod blanket were irradiated with 1.5 GeV proton beam. The weight of uranium blanket was about 200 kg. The set-up was irradiated approximately 12 hours. Total proton flux during the period of irradiation was Electrical current was approximately 40 pA. The aims of the experiment were: - the study of neutron field in the set-up, - transmutation of radioactive samples, - heat production in the set-up.

3. Lead target with the natural uranium rod blanket

4. View on the experimental set-up

5. The Activation Detector Method 209 Bi(n,5n) 205 Bi Fredholm equation: Reactions induced on activation detector (n,  ), (n,2n), (n,3n),...

6. Positions of activation detectors in the set-up Sandwiches contained Al, Au, Co and Bi foils. Foils had square shape 2 cm × 2 cm.

7. Activation reactions

8. Processing of gamma spectra with programme DEIMOS HPGe spectrometer Ortec The graphical environment of programme DEIMOS

9. The yield (N yield ) is the number of produced nuclei of certain isotope in activation detector during the whole period of irradiation divided by mass of the activation detector and total proton flux. The determination of the yield N det (E) - area of transition peak with energy E given by DEIMOS I  (E) - transition absolute intensity  p (E) - peak efficiency of the detector COI - correction on the cascade coincident effects t real / t live - correction on the detector dead time m I(p + ) - product of foil mass and total proton flux - decay constant t 0 - interval from the end of irradiation until the begin of measurement t irr - irradiation time

12. Ratios of the yields from the front and from the back of the target

13. Simulation of the neutron field at different places in the target

14. Comparison of experimental data with simulation made by the MCNPX code

15. Comparison of experimental data with simulation made by the MCNPX code

16. Conclusion The neutron production was measured in the set-up which consisted of a thick lead target and an uranium rod blanket. The Activation Detector Method was used to determine the shape of neutron energetic distribution in different places of set-up. The comparison was made between the simulations calculated by the MCNPX code and experimental data. Simulations are in good qualitative agreement with our measurement. They underestimate production of isotopes in the blanket and at the end of the target. In 2003 was carried out another experiment on the same set-up. Energy of the proton beam was 1 GeV. Next experiment will be in the JINR Dubna in summer 2004 (2.5 GeV proton beam).