The PHASOTRON experiment: EXPERIMENTAL AND CALCULATION STUDIES

1. The PHASOTRON experiment:EXPERIMENTAL AND CALCULATION STUDIES M. Majerle, J. Adam, P. Čaloun, S. A. Gustov, V. Henzl, D. Henzlová, V. G. Kalinnikov, M.I. Krivopustov, Krasa, F. Křížek, A. Kugler, I.V. Mirokhin, A.A. Solnyshkin, V. M. Tsoupko-Sitnikov, V. Wagner

2. Introduction • Several experiments in the frame of JINR research on ADS: • Transmutation on primary beam • Phasotron experiment • Energy Plus Tranmsutation • Gamma-2, Gamma-MD • Main interest – neutron production • Activation analysis is used to probe the neutron spectrum Dubna seminary

3. Monte Carlo simulations • Simulations are performed on micro level – nuclear reactions such as spallation, fission, … are performed for each primary particle and in each atom it meets in the material • Macroscopic values are extracted (neutron fluences, residual nuclei) • Neutron fluence convoluted with cross section = Reaction rate = Experimental value Dubna seminary

4. Monte Carlo simulations 2 • Neutron/proton fluences were calculated with: • MCNPX 2.6.f • INCL4/ABLA (Cugnon cascade model) • CEM03 (Bertini cascade model) • FLUKA 2006.3b • PEANUT pre-equilibrium cascade model • LA150 and ENDF/B-VI libraries (not important) • For cross-sections : • TALYS 1.0 code Dubna seminary

5. Phasotron experiment • December 2003 • 10 minutes of 660 MeV beam with 1013 protons/s, and 1.6-1.9 cm diameter Dubna seminary

6. Lead target (r = 4.8 cm, l = 45.2 cm) • Activation detectors: • - Al and Cu in front for beam integral • - Au and Al in the gap for beam displacement • - Au, Al, Bi on top (every 2 cm) • - 4 iodine samples (9th and 21st cm) Dubna seminary

7. Dubna seminary

8. Proton beam Lead target • The integral measured with two activation foils (Al, Cu) : 1,58·1015, accuracy 6% • Beam displacement (Al, Au): • Cross of five foils • Beam center between the top and the central foil • Beam was shifted upwards (or the cross was shifted downwards ?) • Problem with replacement of detectors shortly before the experiment Dubna seminary

9. Neutron detectors Au foils along the target Al foils along the target Bi foils along the target Dubna seminary

10. Iodine samples Iodine samples at the 9th cm Iodine samples at the 21st cm Dubna seminary

11. Simulations • To better understand the influence of setup parts • Concrete walls • Iron parts (table, beam tubes) • To estimate the systematical uncertainty • Beam displacement • Detector displacement • Comparison with experiment – are codes any good ? Dubna seminary

12. Concrete walls - moderator Neutron spectrum with walls Neutron spectrum without walls Ratio in spectra no_walls/walls Reaction rates: - Threshold reaction: walls have no influence -n,g :mainly produced by neutrons from walls Dubna seminary

13. Iron parts, holders, … • Simulation with and without such parts were made • Reaction rates in detectors used at the experiments were calculated • Results were the same within the statistical errors Dubna seminary

14. Beam displacement and profile 3 different profiles, same displacement=1 cm up Dubna seminary

15. Beam displacement and profile • Only the beam displacement (direction up-down) has significant influence • Beam profile does not influence reaction rates (as long as it is in reasonable limits – FWHM was at experiment ca. 1 cm) • Uncertainty in beam position 3-4 mm = systematic uncertainty 15% (the same in iodine samples) Dubna seminary

16. Detector and sample displacement • Detectors: • 2 mm upwards = -5% in reaction rates up to 20th cm, after 0% • 3 mm along the target = reaction rates the same, exception 30th cm (next slide) • Iodine samples: • 5 mm upwards or 5 mm along the target = 30% difference in reaction rates Dubna seminary

17. Proton induced reaction • Protons have significant influence only around the 30th cm • due to Coulomb scattering the primary protons exit the target here • up to 50% of reaction rate produced with protons • Sensible to the displacement of detectors along the target (maximum moves to the next detector) • Pions, photons: ~0% Dubna seminary

18. Simulation of beam parameters • Wire chamber : centered beam • Cross of detectors : beam displaced 1 cm upwards • Simulation with 1 cm upwards beam shows ratio exp/sim=0.6 • Centered beam ? Was cross displaced downwards ? Beam displaced 1 cm upwards Dubna seminary

19. Simulation of B(A) in detectors – MCNPX CEM03 Simulations were performed with centered beam. Dubna seminary

20. Simulation of B(A) in detectors – MCNPX INCL4/ABLA Simulations were performed with centered beam. Dubna seminary

21. Simulation of B(A) in detectors – FLUKA Simulations were performed with centered beam. Dubna seminary

22. Comparison of codes Spectra in the foil at 10th cm Dubna seminary

23. Simulation of iodine samples 21st cm 9th cm • MCNPX INCL4/ABLA were used • Agreement exp/sim is not as good for iodine samples as for other detectors • The probable reason: 30% uncertainty (5 mm sample displacement) + ?% uncertainty (geometrical and material properties of samples) Dubna seminary

24. Conclusion • The experiment provided a good set of experimental data about produced neutrons with energies > 1 MeV • Results are mostly sensitive to beam displacement (carefully in next experiments) • Ratios exp/sim close to 1 • All models predict total production 11.7-12.6 neutrons per primary proton, but disagree about neutrons with energies > 30 MeV – Phasotron experiment provides this data Dubna seminary