Investigation of GeV proton-induced spallation reactions

1. D. Hilscher for the NESSI collaboration Investigation of GeV proton-induced spallation reactions D. Hilscher, C.-M. Herbach, U. Jahnke, V.G. Tishchenko, HMI-Berlin J. Galin, B. Lott, A. Letourneau, A. Péghaire, GANIL D. Filges, F. Goldenbaum, K. Nünighoff, H. Schaal, G. Sterzenbach, FZ-Jülich L. Pienkowski, U. of Warsaw W.U. Schröder, J. Tõke, U. of Rochester • Motivation • Experiment • PE cluster-emission • Neutron multiplicities • Inelastic reaction cross sections • Production cross sections of LCPs • Decay of hot nuclei as a function of excitation energy • Fission probability • Summary

2. 25 n/p GeV GeV p 20 cm Window Fe .. Ta 60 cm W, Hg, Pb Nuclear data for the target station of a spallation neutron source Reaction length 18 cm (Pb) Preac = 1-exp(-z/Lreac) Range  60 cm (1 GeV) nuclear stopping cooling: 30 MeV/n reactor: 200 MeV/n GeV proton induced neutron production, multiplicity distributions production cross sections of n, 1,2,3H, 3,4 He, 6,7 Li ... energy spectra in thin targets excitation energy distributions of post INC residues Validation of models/codes: LAHET, HERMES, INCL, FLUKA Beam-induced radiation damage in window materials (Fe,Ta) helium, hydrogen gas production displacements per atom

3. Experiment

4. N I @ COSY GeV p

5. Investigation of spallation reactions at COSY/FZJ NESSI Collaboration: HMI-Berlin, FZ-Jülich, GANIL, Univ. Warsaw, Univ. Rochester Cooler synchrotron and storage ring for protons p = 600 - 3400 MeV/c Ekin= 175 - 2600 MeV

6. NESSI detector Neutron multiplicity BSiB: 162 detectors, particle separation of H, He, IMF, FF via TOF-E U. Jahnke et al., Nucl. Instr. Meth. A 508 (2003) 295 C.-M. Herbach et al., Nucl. Instr. Meth. A 508 (2003) 315

7. n  p GeV p n E* n n p () Two step spallation reaction: INC+PE plus evaporation ER 2.5 GeV p + Au FF

8. INC protons preliminary Too many low energetic INC protons, cutoff should be at ~20 MeV

9. Pre-equilibrium cluster emission

10. Relative yield of pre-equilibrium composite particle emission preliminary

11. Production cross sections preliminary preliminary preliminary

12. Coalescence model 2.5 GeV p+Au 300 Improvement of PE composite particle spectra but at the expense of INC nucleon spectra A. Letourneau et al., Nucl. Phys. A 712 (2002) 133

13. Systematics of PE emission 1.2 GeV p + X preliminary d α The yield of PE deuterons seems to depend on the N/Z ratio only and not in addition also on the nuclear size R t 3He

14. Systematics of PE emission preliminary The yield of PE deuterons and tritons seems to depend on the N/Z ratio only and not in addition also on the nuclear size R

15. Neutron multiplicity distributions in thin and thick targets

16. Neutron multiplicity (Z): thin targets 1.2 GeV p + ZT

17. Neutron multiplicity in thin and thick targets thin targets Increase of Mn with target thickness due to inter nuclear cascade A. Letourneau et al., Nucl. Instr. Meth. B170 (2000) 299

18. Validation of HE-transport codes: Neutron multiplicity distributions 2.5 GeV p + Hg Preac probability to produce in BNB Mn neutrons/p in 5, 15, and 15 cm long Hg cylinders with a diameter of 15 cm While for 1.2 GeV protons Mn distributions are well described by MCNPX and HERMES considerable deviations are observed at 2.5 GeV in particular with the MCNPX code D. Filges et al., Eur. Phys. J. A 11 (2001) 467

19. thick target 15cm 35 cm Hadron induced neutron production in thick Pb-targets Available energy: Ep + 2mpc2 D. Hilscher et al., Nucl. Instr. Meth. A414 (1998) 100

20. Inelastic reaction cross section

21. BNB as a reaction detector inelasticity > 10-15 MeV preliminary Energy dependence of σinel smaller than expected from systematics preliminary H.P. Wellish, D. Axen PRC 54 (1996) 1329 R.E. Prael, M.B. Chadwick LA-UR-97-1745

22. Production cross sections

23. Helium production cross sections - well known? Discrepancies both for measured as well as for calculated production cross sections

24. Hydrogen and helium production cross sections Hydrogen with Ep<25 MeV Helium

25. Average n-multiplicity per GeV 60 cm,  20cm Window lifetime at different proton energies He production in window materials per neutron produced in a thick Pb spallation target He production per neutron produced decreases for Fe-like windows, for Ta only above 3 GeV D. Hilscher et al., J. of Nucl. Materials 296 (2001) 83

26. Decay of hot nuclei as a function of excitation energy Proton induced spallation reactions generate thermal excitation energy with a minimum of compression deformation spin

27. Event-wise reconstruction of excitation energy

28. Heating efficiency of nuclei with GeV protons? heating efficiency LAHET Code (INC) overestimates the deposited excitation energy E* INCL Code predicts E* relatively well 10-20%

29. Fission probability Pfiss(E*,Mn,Mlcp)

30. Fission identification with BSiB 10 < Ai 50 < (A1+A2) A1/(A1+A2) < 0.8

31. fission probability preliminary preliminary excitation energy Fission probability Pf as a function of excitation energy E* for 2.5GeV p+U inclusive fission

32. Probability of fission, IMF-emission, ... as a function of Mn and Mlcp

33. Pfiss, IMF(Mlcp,Mn) for 2.5 GeV p + Au preliminary preliminary

34. Fission probability Pf as a function of light charged particle (p-α) multiplicity Mlcp for 2.5 GeV p+U inclusive fission preliminary preliminary

35. Fission probability Pf as a function of light neutron multiplicity Mn for 2.5GeV p+U Pfiss preliminary preliminary

36. D. Hilscher for the NESSI collaboration Summary • detailed, exclusive, and systematic data needed for validation of models • excitation energy distributions sensitive test of INC models • no satisfactory description of pre-equilibrium cluster-emission • neutron production in thick targets reasonably well described by different models (compensation effect) • H, He production cross-sections large differences between different models • radiation damage of the window due to He production decreases with p-energy • preliminary results of p-induced fission of U as a function of Mlcp, Mn and E*