M. Pfützner

Projectile fission at relativistic velocities: a novel and powerful source of neutron-rich isotopes well suited for in-flight isotopic separation

Abstract Projectile fission of 238U was investigated at a bombarding energy of 750 A·MeV using a Pb target. Forward emitted fragments from 80Zn up to 155Ce were analyzed with the Fragment Separator (FRS) and unambigously identified by their energy-loss and time-of-flight. The magnetic selection of the largest momenta acted as a trigger of the low-energy fission component. More than forty new nuclear species were identified. The related isotopic production cross-sections are presented.

Energy deposition by relativistic heavy ions in thin argon absorbers

Abstract Experimental data on energy deposition for argon, krypton and xenon ions in the energy range from 100 to 950 MeV/u passing through an ionization chamber filled with an Ar (90%) + CH 4 (10%) gas mixture of thickness equivalent to 60 mg/cm 2 of argon are reported. Measured values are compared with the proposed model of energy deposition and with the model of Badhwar and Adams et al. The observed data support the picture of the escape of high energy δ rays from the active detector volume.

Production and identification of heavy Ni isotopes: evidence for the doubly magic nucleus 28 78 Ni

We report the first observation of the doubly magic nucleus78Ni50 and the heavy isotopes77Ni,73,74,75Co,80Cu. The isotopes were produced by nuclear fission in collisions of 750 A·MeV projectiles of238U on Be target nuclei. The fully-stripped fission products were separated in-flight by the fragment separator FRS and identified event-by-event by measuring the magnetic rigidity, the trajectory, the energy deposit, and the time of flight. Production cross-sections and fission yields for the new Ni-isotopes are given.

Longitudinal momenta and production cross-sections of isotopes formed by fragmentation of a 500 A×MeV86Kr beam

Abstract At the projectile-fragment separator FRS at GSI, longitudinal momentum distributions and production cross-sections were investigated for reactions between a 500 A× MeV 86 Kr beam and beryllium, copper and tantalum targets. Fragments in a wide A Z range were studied. For fragments close to the projectile the measured longitudinal momentum distributions agree qualitatively with a semi-empirical parametrization. Deviations from this simple picture are found, however, for the momentum widths of light fragments and for the momentum transfer to those fragments that differ in their A Z ratio from the most probable value. The experimental data on production cross-sections are used for testing the predictions obtained from a semi-empirical parametrization, a geometrical abrasion model and an intranuclear-cascade model. The cross-section for the formation of the doubly magic nucleus 78Ni in 86Kr fragmentation is estimated to be 17 pb.

8He-6He: a comparative study of electromagnetic fragmentation reactions

Dissociation of a 227 MeV/u 8He beam in a lead target has been studied in a kinematically complete experiment. The results are compared with similar data from the well-known halo nucleus 6He. Coulomb–nuclear interference in the inelastic channel gives evidence for a Iπ=1− resonance in 8He at Ex=4.15 MeV. The deduced B(E1) value of 0.38±0.07 e2 fm2 indicates a uniform distribution of the four neutrons around the greek small letter alpha-particle core.

Low-energy fission investigated in reactions of 750 AMeV238U-ions with Pb and Be targets

Charge distributions of fragments from low energy nuclear fission are investigated in reactions of highly fissile238U projectiles at relativistic energies (750 A·MeV) with a heavy (Pb) and a light (Be) target. The fully stripped fission fragments are separated by the Fragment Separator (FRS). Their high kinetic energies in the laboratory system allow the identification of all atomic numbers by using Multiple-Sampling Ionization Chambers (MUSIC). The elemental distributions of fragments observed at larger magnetic rigidities than the238U projectiles show asymmetric break-up and odd-even effects. They indicate a low energy fission process, induced mainly by dissociation in the electro-magnetic field for the U/Pb-system, or by peripheral nuclear interactions for the U/Be-system.

Production of neutron rich nuclei by fragmentation of 760 A·MeV 136Xe

Abstract The fragmentation of 760 A·MeV 136 Xe projectiles impinging on a 27 Al target has been investigated at the fragment separator FRS at GSI Darmstadt. Production cross sections for neutron rich nuclei in the 116 ≤ A ≤ 134 mass region have been determined and are compared to an empirical parametrisation as well as to model calculations. For the double magic nucleus 132 Sn we extrapolate σ ≅ 0.4 ± 0.3 μ barn.

β decay of 71 , 73 Co: Probing single-particle states approaching doubly magic 78 Ni

Low-energy excited states in 71,73Ni populated via the decay of 71,73Co were investigated in an experiment performed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). Detailed analysis led to the construction of level schemes of 71,73Ni, which are interpreted using systematics and analyzed using shell-model calculations. The 5/2 states attributed to the the f5/2 orbital and positive-parity 5/2+ and 7/2+ states from the g9/2 orbital have been identified in both 71,73Ni. In 71Ni the location of a 1/2 -decaying isomer is proposed, and limits are suggested as to the location of the isomer in 73Ni. The location of positive-parity cluster states are also identified in 71,73Ni. Beta-delayed neutron branching ratios obtained from this data are given for both 71,73Co. DOI: 10.1103/PhysRevC.85.034326 PACS number(s): 23.40. s, 21.10.Pc, 21.60.Cs, 27.50.+

6,8He: a comparative study of fragmentation reactions

Dissociation of 227 MeV/u 8He in lead and carbon targets has been studied in kinematically complete experiments, the data are compared with corresponding results for 6He.

STRUCTURE OF THE EXOTIC NUCLEI NEAR 70Ni PROBED BY ADVANCED TIME-DELAYED COINCIDENCE METHODS: THE INTERPRETATION OF THE 1.76 µs ISOMER IN 72Cu

Structure of the exotic nuclei near 70Ni probed by advanced time delayed coincidence methods: the interpretation of the 1.76 μs isomer in 72Cu