1. 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
D. Hilscher for the NESSI collaboration

2. Nuclear data for the target station of a spallation neutron source
GeV p
60 cm W, Hg, Pb
20 cm
25 n/p GeV
Window Fe .. Ta
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
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 = MeV/c Ekin= 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. Two step spallation reaction: INC+PE plus evaporation
()  n p E*
GeV p ER
2.5 GeV p + Au FF

8. preliminary INC protons
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. Hadron induced neutron production in thick Pb-targets
35 cm
15cm
thick target
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 > 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

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. Window lifetime at different proton energies
He production in window materials per neutron produced in a thick Pb spallation target
Average n-multiplicity per GeV
60 cm,  20cm
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?
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. preliminary preliminary
Fission probability Pf as a function of excitation energy E* for 2.5GeV p+U
inclusive
preliminary
preliminary
fission probability
excitation energy
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. preliminary preliminary
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. Pfiss preliminary preliminary
Fission probability Pf as a function of light neutron multiplicity Mn for 2.5GeV p+U
Pfiss
preliminary
preliminary

36. excitation energy distributions sensitive test of INC models
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*
D. Hilscher for the NESSI collaboration