Evaporation residues produced in spallation of 208Pb by protons at

Abstract

The production cross sections of fragmentation-evaporation residues in the reaction Pb+p at 500A MeV have been measured using the inverse-kinematics method and the FRS spectrometer (GSI). Fragments were identified in nuclear charge using ionisation chambers. The mass identification was performed event-by-event using the Bρ − T OF − ∆E technique. Although partially-unresolved ionic charge states induced an ambiguity on the mass of some heavy fragments, production rates could be obtained with a high accuracy by systematically accounting for the polluting ionic charge states. The contribution of multiple reactions in the target was subtracted using a new, partly self-consistent code. The isobaric distributions are found to have a shape very close to the one observed in experiments at higher energy. Kinematic properties of the fragments were also measured. The total and the isotopic cross sections, including charge-pickup cross sections, are in good agreement with previous measurements and models. The data are discussed in the light of previous spallation measurements, especially on lead at 1 GeV.

Dissipative effects in spallation-induced fission ofPb208at high excitation energies

“…7, we compare our partial fission cross sections with the charge distribution of spallation-evaporation residues obtained in Ref. [41] for the reaction 208 Pb + p at 500A MeV. The distribution of evaporation residues was normalized by a factor which corresponds to the ratio of the total evaporation cross sections (1.44 b) to the total fission cross section measured in the present work (149 mb).…”

“…Therefore we can use this observable to constraint model calculations describing the prefragment formation in spallation reactions. normalized cross sections of spallation-evaporation residues (triangles) for the reaction 208 Pb + p at 500A MeV [41]. The atomic number of the fissioning nucleus was determined by the sum Z 1 + Z 2 .…”

Improving the description of proton-induced one-nucleon removal in intranuclear-cascade models

“…It is clear that the model predictions are in the right ballpark for neutron removal, but they overestimate the proton-removal data by a factor that can be as large as 3-4 for heavy nuclei. Note that the experimental data are globally consistent, even though they have been collected in inverse-kinematics experiments [14][15][16][17][18][19][20][21] or by off-line gamma spectroscopy [3,[22][23][24].…”

Measurement of the complete nuclide production and kinetic energies of the systemXe136+hydrogen at 1 GeV per nucleon

“…This property makes neutron-rich nuclei an ideal spallation target for conceiving high-intensity neutron sources. Systems such as 197 Au (800A MeV) +p [4,5], 208 Pb (500A MeV) +p [6,7], 208 Pb (1A GeV) +p [8,9], 208 Pb (1A GeV) + d [10], 238 U (1A GeV) +p [11][12][13][14][15], and 238 U (1A GeV) + d [16,17] were measured to study sequential evaporation and its intricate competition with fission. The measurement of 56 Fe+p at various energies [18,19] focused the attention on systems below the BusinaroGallone point [20,21] in the fissility region where the saddle point becomes unstable toward asymmetric splits, and revived the discussion on the intermediate-mass-fragment formation in spallation.…”