Future prospects for secondary-beam production Schmidt, K.-H.; Benlliure, J.; Enqvist, T. ...
Nuclear Physics A,
04/2002, Letnik:
701, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
This contribution discusses the characteristics of different types of nuclear reactions and the influence of the beam energy in view of future prospects for secondary-beam production. First, ...electronic interactions in the target are considered because they define the usable target thickness. Rather high beam energies are advantageous. Secondly, the nuclear-reaction aspects are discussed. Three reaction mechanisms provide the most promising prospects for the production of secondary beams. Fusion is best suited for the production of nuclei near the proton drip line and for the heaviest elements. Fission specifically populates mid-mass neutron-rich isotopes. Fragmentation and spallation reactions represent rather universal production mechanisms for both neutron-deficient and neutron-rich exotic nuclei, since the fluctuations in the
N-over-
Z ratio are very important. Due to these large fluctuations, this is the most promising reaction mechanism to reach extremely exotic nuclei over the whole mass range, if sufficiently high primary-beam intensities are available. In particular, it seems to be a unique process for the production of extremely neutron-rich isotopes of elements above the region of fission fragments. These considerations are verified with experimental data. In particular, a systematic overview on the production of residual nuclei in reactions at relativistic energies has been obtained in several experiments recently performed at GSI in inverse kinematics. They allow to give a rather realistic estimate on the prospects for secondary-beam production in next-generation facilities.
In this paper, we describe a biomimetic-fabric-based sensing glove that can be used to monitor hand posture and gesture. Our device is made of a distributed sensor network of piezoresistive ...conductive elastomers integrated into an elastic fabric. This solution does not affect natural movement and hand gestures, and can be worn for a long time with no discomfort. The glove could be fruitfully employed in behavioral and functional studies with functional MRI (fMRI) during specific tactile or motor tasks. To assess MR compatibility of the system, a statistical test on phantoms is introduced. This test can also be used for testing the compatibility of mechatronic devices designed to produce different stimuli inside the MR environment. We propose a statistical test to evaluate changes in SNR and time-domain standard deviations between image sequences acquired under different experimental conditions. fMRI experiments on subjects wearing the glove are reported. The reproducibility of fMRI results obtained with and without the glove was estimated. A good similarity between the activated regions was found in the two conditions.
Spallation reactions are generally considered to proceed in two stages: a cascade stage followed by an evaporation stage. Light charged particle (lcp) spectra indicate that such particles are ...produced by both stages. The mechanism of production in the cascade stage is still not fully understood. Using the improved versions of the Liège Intra-Nuclear Cascade model and of the ABLA evaporation model, we have recently shown that lcp's are presumably produced by some kind of dynamical coalescence process, by which a fast particle of the cascade drags a few other nucleons. In the very recent years, precise measurements of the production of heavier clusters have been performed. We improved and generalized our production models for the heavier clusters, up to A=10 and we reached good agreement with experiment. These results strongly suggest that the dynamical coalescence mechanism applies to heavy clusters. The importance of these data for spallation neutron sources and accelerator-driven systems is underlined.
Total fission cross sections and charge distributions of the final fission fragments have been measured at GSI in inverse kinematics for the reactions super(208)Pb + p,d at 500 A MeV and super(182)Ta ...+ p at 300, 500, 700 and 1000 A MeV. These data are used to investigate dissipative and transient effects at low deformation and its possible dependences with temperature and fissility.
The very neutron-rich oxygen isotopes O-25 and O-26 are investigated experimentally and theoretically. The unbound states are populated in an experiment performed at the R3B-LAND setup at GSI via ...proton-knockout reactions from F-26 and F-27 at relativistic energies around 442 and 414 MeV/nucleon, respectively. From the kinematically complete measurement of the decay into O-24 plus one or two neutrons, the O-25 ground-state energy and width are determined, and upper limits for the O-26 ground-state energy and lifetime are extracted. In addition, the results provide indications for an excited state in O-26 at around 4 MeV. The experimental findings are compared to theoretical shell-model calculations based on chiral two- and three-nucleon (3N) forces, including for the first time residual 3N forces, which are shown to be amplified as valence neutrons are added.
The residual nuclei produced in the spallation reaction of Xe-136 nuclei at 200A MeV on protons have been studied by measuring the isotopic distributions for the elements from cadmium (Z = 48) to ...cesium (Z = 55) by using the fragment separator (FRS) spectrometer at GSI and the inverse kinematics technique. This is one of the few measurements performed at such a low projectile energy, close to the validity limit for intranuclear cascade models such as INCL or ISABEL. The experimental results have been compared to these intranuclear cascade codes coupled to the evaporation code ABLA. Both code combinations reproduce qualitatively the measured isotopic distributions; however, both underestimate the production of residues with mass numbers between 126 and 134. The measured cross sections are of interest for the planning of future radioactive beam or neutron source facilities.
The construction of two new-generation complementary RIB facilities in Europe, one based on the in-flight fragmentation or fission (IFF) method (FAIR) and the other on the isotope separation on-line ...(ISOL) method (EURISOL) is expected in the next 10-15 years. The reaction mechanisms, responsible for the production of the secondary nuclei, along with the technical constrains, have to be considered for the designs of the facilities. In this work, we study which reaction mechanisms can be exploited at best for the production of the secondary beams in the two facilities.
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