F. Rejmund

Isotopic yields and kinetic energies of primary residues in 1 A GeV 208Pb+p reactions

Abstract The production of primary residual nuclei in the reaction 1xa0 A xa0GeV 208 Pb on proton has been studied by measuring isotopic distributions for all elements from titanium ( Z =22) to lead ( Z =82). Kinematical properties of the residues were also determined and used to disentangle the relevant reaction mechanisms, spallation (projectile fragmentation) and fission. The fragment separator FRS at GSI, Darmstadt, was used to separate and identify the reaction products. The measured production cross sections are highly relevant for the design of accelerator-driven subcritical reactors and for the planning of future radioactive-beam facilities.

Measurement of isotopic cross-sections of spallation residues in 800-A/MeV Au-197 + p collisions

Abstract The spallation of 197 Au by 800 MeV protons was investigated in inverse kinematics at GSI, Darmstadt, by use of a 197 Au beam bombarding a liquid-hydrogen target. The fragment separator (FRS) was used to select and identify the reaction products prior to β decay. The individual production cross sections and the kinematic properties of 380 isotopes for all elements between mercury ( Z=80 ) and neodymium ( Z=60 ) have been measured. A comparison with a Monte-Carlo calculation based on the two-step model of the spallation reaction is given. The isotopic cross-section distribution of iridium isotopes is compared to that resulting from the aluminium-induced fragmentation of 197 Au. The mean kinetic energies of the fragments are deduced from the experimental data. The importance of the new data to improve our understanding of the spallation mechanism is discussed.

Isotopic production cross sections of fission residues in 197Au-on-proton collisions at 800 A MeV

Abstract Interactions of 197Au projectiles at 800 A MeV with protons leading to fission are investigated. We measured the production cross sections and velocities of all fission residues which are fully identified in atomic and mass number by using the in-flight separator FRS at GSI. The new data are compared with earlier measurements of the characteristics of fission in similar reactions. Both the production cross sections and the recoil energies are relevant for a better understanding of spallation reactions.

Fission-residues produced in the spallation reaction 238U + p at 1 A GeV

Abstract Fission fragments from 1xa0 A xa0GeV 238 U projectiles irradiating a hydrogen target were investigated by using the fragment separator FRS for magnetic selection of reaction products including ray-tracing and Δ E –ToF techniques. The momentum spectra of 733 identified fragments were analysed to provide isotopic production cross sections, fission-fragment velocities and recoil momenta of the fissioning parent nuclei. Besides their general relevance, these quantities are also demanded for applications. Calculations and simulations with codes commonly used and recently developed or improved are compared to the data.

Evaporation residues produced in the spallation reaction 238U+p at 1 A GeV

The production of heavy nuclides from the spallation-evaporation reaction of 238U induced by 1 GeV protons was studied in inverse kinematics. The evaporation residues from tungsten to uranium were identified in-flight in mass and atomic number. Their production cross-sections and their momentum distributions were determined. The data are compared with empirical systematics. A comparison with previous results from the spallation of 208Pb and 197Au reveals the strong influence of fission in the spallation of 238U.

Measurement of nuclide cross-sections of spallation residues in 1-A-GeV U-238 + proton collisions

The production of heavy nuclides from the spallation-evaporation reaction of 238U induced by 1 GeV protons was studied in inverse kinematics. The evaporation residues from tungsten to uranium were identified in-flight in mass and atomic number. Their production cross-sections and their momentum distributions were determined. The data are compared with empirical systematics. A comparison with previous results from the spallation of 208Pb and 197Au reveals the strong influence of fission in the spallation of 238U.

Signatures of fission dynamics in highly excited nuclei produced in 197Au(800 A MeV) on proton collisions

Abstract 197 Au(800xa0 A xa0MeV)-on-proton collisions are used to investigate the fission dynamics at high excitation energy. The kinematic properties together with the isotopic identification of the fission fragments allow to determine the mass, charge and excitation energy of the fissioning nucleus at saddle. The comparison of these observables and the measured total fission cross section with model calculations evidences a clear hindrance of fission at high excitation energy that can be explained in terms of nuclear dissipation. Assuming a statistical evaporation for other de-excitation channels than fission, an estimated value of the transient time of fission of (3±1)×10 −21 xa0s is obtained.

Complex nuclear-structure phenomena revealed from the nuclide production in fragmentation reactions

Abstract Complex structural effects in the nuclide production from the projectile fragmentation of 1 A xa0GeV 238 U nuclei in a titanium target are reported. The structure seems to be insensitive to the excitation energy induced in the reaction. This is in contrast to the prominent structural features found in nuclear fission and in transfer reactions, which gradually disappear with increasing excitation energy. Using the statistical model of nuclear reactions, relations to structural effects in nuclear binding and in the nuclear level density are demonstrated.

Primary-residue production cross sections and kinetic energies in 1AGeV 208Pb on deuteron reactions

Abstract The production cross sections and the kinematical properties of primary residual nuclei have been studied in the reaction 208 Pb(1xa0 A xa0GeV)+d. Isotopic distributions were measured for all elements from titanium ( Z =22) to lead ( Z =82). The measured kinematical properties of the residues were also used to disentangle the relevant reaction mechanisms, spallation–evaporation and spallation–fission. The fragment separator FRS at GSI, Darmstadt, was used to separate and identify the reaction products. The measured quantities are important for the design and planning of future radioactive-beam facilities and accelerator-driven systems. The measured data of the present work are comprehensively compared with the experimental data from the reaction 208 Pb(1xa0 A xa0GeV)+p.

Production of new neutron-rich isotopes of heavy elements in fragmentation reactions of 238U projectiles at 1A GeV

The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of {sup 238}U projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify 40 new heavy neutron-rich nuclei: {sup 205}Pt, {sup 207-210}Au, {sup 211-216}Hg, {sup 214-217}Tl, {sup 215-220}Pb, {sup 219-224}Bi, {sup 223-227}Po, {sup 225-229}At, {sup 230,231}Rn, and {sup 233}Fr. The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.