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

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

Experiment

N I @ COSY GeV p

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

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

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

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

Pre-equilibrium cluster emission

Relative yield of pre-equilibrium composite particle emission preliminary

Production cross sections preliminary preliminary preliminary

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

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

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

Neutron multiplicity distributions in thin and thick targets

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

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

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

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

Inelastic reaction cross section

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

Production cross sections

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

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

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

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

Event-wise reconstruction of excitation energy

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

Fission probability Pfiss(E*,Mn,Mlcp)

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

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

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

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

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

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

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