Papers by Hartwig Freiesleben
Neutronics experiments with a LiAlPb assembly for HCLL-TBM mockup experiments planned by EU
Neutronics experiments with a LiAlPb assembly for HCLL-TBM mockup experiments planned by EU
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Systematic study of the pp [FORMULA] pp[FORMULA] reaction
European Physical Journal A, 2010
A systematic study of the production of [FORMULA] -mesons in proton-proton collisions was carried... more A systematic study of the production of [FORMULA] -mesons in proton-proton collisions was carried out in a kinematically complete experiment at three excess energies ( [FORMULA] = 92, 128, 173 MeV). Both protons were detected using the large-acceptance COSY-TOF spectrometer at an external beam line at the Cooler Synchrotron COSY at Forschungszentrum Julich. The total cross-section, angular distributions of both [FORMULA] -mesons and protons were measured and presented in various reference frames such as the overall CMS, helicity and Jackson frame. In addition, the orientation of the [FORMULA] -spin and invariant-mass spectra were determined. We observe [FORMULA] -production to take place dominantly in Ss and Sp final states at [FORMULA] = 92, 128 MeV and, additionally, in Sd at [FORMULA] = 173 MeV. No obvious indication of resonant [FORMULA] -production via N * -resonances was found, as proton angular distributions are almost isotropic and invariant-mass spectra are compatible with ...
Production of [FORMULA] and [FORMULA] hyperons in proton-proton collisions
This paper reports results on simultaneous measurements of the reaction channels pp[FORMULA]pK + ... more This paper reports results on simultaneous measurements of the reaction channels pp[FORMULA]pK + [FORMULA] and pp[FORMULA]pK + [FORMULA] at excess energies of 204, 239, and 284MeV ([FORMULA] and 127, 162, and 207MeV ([FORMULA] . Total and differential cross-sections are given for both reactions. It is concluded from the measured total cross-sections that the high-energy limit of the cross-section ratio is almost reached at an excess energy of only about 200MeV. From the differential distributions observed in the overall CMS as well as in the Jackson and helicity frames, a significant contribution of interfering nucleon resonances to the [FORMULA] production mechanism is concluded while resonant [FORMULA] production seems to be of lesser importance and takes place only through specific partial waves of the entrance channel. The data also indicate that kaon exchange plays a minor role in the case of [FORMULA] but an important role for [FORMULA] production. Thus the peculiar energy dep...
AIP Conference Proceedings, 2005
In order to reduce the deviation of calculated-to-experimental activity (C/E) following benchmark... more In order to reduce the deviation of calculated-to-experimental activity (C/E) following benchmark experiments with pure W irradiated by 14-MeV neutrons, of interest for safety aspects and waste management of power plants, a detailed analysis of the activation cross sections was carried out using the computer codes EMPIRE-II and TALYS as well as local parameter sets within the STAPRE-H code. The sensitivity of the calculated cross sections to various model parameters is derived and discussed in connection with improving the C/E of the benchmark experiment.
Electric flux lines representing device, has opaque work plate with open section, in which basin is inserted, and electrode form immersed in basin filled with oil and suspended particles
Nuclear bremsstrahlung near the one- and two-pion thresholds
AIP Conference Proceedings, 1991
The experiment on pp-bremsstrahlung presented here aims at a detailed study of off-shell effects ... more The experiment on pp-bremsstrahlung presented here aims at a detailed study of off-shell effects in the strong interaction. A detector set-up will be developed which allows measurements at maximum kinematically allowed photon energies, where the strongest deviations from the soft-photon approximation (which incorporates only on-shell information) are to be expected. The detector mainly consists of a large time-of-flight spectrometer covering
Nuclear data benchmarking for lead by LiAI/Pb Fusion blanket mock-up experiment
Export Date: 13 September 2013, Source: Scopus
On determining the cross section of the supposed pentaquark $ \Theta^{+}_{}$ in the reaction pp $ \rightarrow$ $ \Theta^{+}_{}$ $ \Sigma^{+}_{}$ $ \rightarrow$ pK0 $ \Sigma^{+}_{}$
The European Physical Journal A, 2014
ABSTRACT This paper addresses the problem of how to extract an upper limit on the cross section f... more ABSTRACT This paper addresses the problem of how to extract an upper limit on the cross section for θ+ production via the reaction pp →θ+Σ+, where the θ+ is assumed to decay into the pK0 subsystem. Recent data of the COSY-TOF Collaboration, namely the angular distribution of protons in the Σ+K0 helicity frame and the invariant mass spectrum of the pK0 system, were scrutinized with regard to a resonance by applying the profile likelihood method. It is found that the former distribution is best suited for setting an upper limit on the θ+ production, which varies between 90 nb for an assumed θ+ mass of 1500 MeV/c² and 56 nb for 1540 MeV/c².
Sensitivity of Activation Cross Sections of the Hafnium, Tantalum and Tungsten Stable Isotopes to Nuclear Reaction Mechanisms
Nuclear Data Needs for Generation IV Nuclear Energy Systems - Proceedings of the International Workshop, 2006
Influence of Shell Structure on Neutron and Proton Exchange in the Reactions of ^{144}Sm on ^{144}Sm and ^{154}Sm on ^{154}Sm
Physical Review Letters, 1981
The reactions of 144Sm on 144Sm and 154Sm on 154Sm have been studied at energies 30% in excess of... more The reactions of 144Sm on 144Sm and 154Sm on 154Sm have been studied at energies 30% in excess of the barrier. Whereas the number of exchanges nucleons is similar in both reactions, the number of exchanged protons is considerably larger at small energy losses in the 144Sm system. On the basis of the shell-corrected liquid-drop potential energy surface these observations are attributed to the closed N=82 neutron shell which, for 144Sm, hinders the neutron exchange and leads to a preferential transfer of protons.
Compound nucleus fission at high angular momentum studied in the reaction ^{132}Xe+^{30}Si
Physical Review C, 1980
Reaction products from the bombardment of ¹³²Xe onto ³°Si at energies between 5.4 MeV/u and ... more Reaction products from the bombardment of ¹³²Xe onto ³°Si at energies between 5.4 MeV/u and 8.2 MeV/u have been measured by a time-of-flight system combined with an ionization chamber. At all energies fission fragments are found to be well separated from deep inelastic reaction products. The rapidly increasing excitation function for fission shows an onset at 65--70 h-bar. This value and an l/sub crit/ of 98 h-bar at 8.2 MeV/u are compatible with the concept of a fissioning compound nucleus. However, at the highest bombarding energies the Z distributions indicate the emission of charged particles, which is difficult to reconcile with the idea of a fully equilibrated compound nucleus. Incomplete momentum transfer reactions (incomplete fusion) followed by fission are considered as an explanation for the strong increase of the width of the Z distribution with excitation energy. Consequences for the formation of compound nuclei at high angular momenta are discussed.
A detector system for hyperon production at the COSY time-of-flight spectrometer
Physica Scripta, 1993
In an experiment at the external COSY beam associated strangeness production will be investigated... more In an experiment at the external COSY beam associated strangeness production will be investigated [1] by measuring total and differential cross sections as well as the polarization of the produced hyperons by means of an almost 4pi time-of-flight spectrometer. In a first step we will concentrate on the reaction pp --> KLambdap. The apparatus will consist of an inner arrangement
Nuclear Physics A, 1991
The heavy-ion radiative-capture reactions 6Li(6Li, y)'2C and 7Li(6Li, Y)'3C have been studied. Ut... more The heavy-ion radiative-capture reactions 6Li(6Li, y)'2C and 7Li(6Li, Y)'3C have been studied. Utilizing a large-volume Nal(TI) y-spectrometer, the y-transitions to the ground state and the three lowest excited states of '-'C in the former case and the transitions yo, y, , y2®3, 74 and Ys/6®s in the latter case could be resolved. The evaluation of absolute cross sections which range from 0.3 to 210 nb/sr relies on the thoroughly investigated response function of the spectrometer. Excitation functions at 125°as well as three-point angular distributions at several energies were measured . The results are compared with statistical model calculations. The latter make use of a smooth angular momentum cutoff in the entrance channel, isospin mixing in the compound nucleus, and giant resonances built upon excited states for y-strength distributions. All data are described by these model calculations. In addition to these statistical features a broad resonance (I'--0.8 MeV) is observed for the y, -transition in 6Li(6Li, Y) 12 C at E,, --30.3 MeV. NUCLEAR REACTIONS 6Li(6Li, y) 12C, 7Li(6Li, Y)' 3C Ec_m_=1-8 MeV; measured o(E), Q(e); statistical model calculations including y-decay of giant resonances ; resonance observed in '-'C.
Nuclear Physics A, 1997
Angular distributions of 6Li+6Li elastic scattering were measured for Elab = 5-40 MeV. An optical... more Angular distributions of 6Li+6Li elastic scattering were measured for Elab = 5-40 MeV. An optical model analysis of these data together with older data of 7Li+7Li elastic scattering taken at El,b = 8-17 MeV was performed with the aim to search for a "global" OM potential which describes elastic scattering in both Li-Li systems in a broad energy range. Both surface and volume absorbing potentials can be found which fulfill this requirement if a linear energy dependence is assumed of the depths of the real as well as the imaginary potential. These depths, if fitted to individual angular distributions, are found to vary in a correlated manner with the beam energy. This is taken as indication of strong coupling between elastic, inelastic, and reaction channels. This is corroborated by the existence of resonances in reaction channels at these energies where the potential depths are most pronouncedly changing.
Potential interaction and transfer in elastic 7Li(6Li,6Li)7Li and inelastic 7Li(6Li,6Li)7Li0.48 scattering at Elab = 9–40 MeV
Nuclear Physics A, 1998
Angular distributions of 7Li(6Li,6Li)7Li and 7Li(6Li,6Li)7Li0.48 were measured for the first time... more Angular distributions of 7Li(6Li,6Li)7Li and 7Li(6Li,6Li)7Li0.48 were measured for the first time in the energy range Elab = 9–40 MeV. A theoretical analysis was performed taking into account potential scattering as well as one-step and two-step transfer processes which were treated in DWBA. Potential scattering was found to dominate at forward scattering angles, single-step neutron transfer to be most influential
Pre-equilibrium reactions on the stable tungsten isotopes at low energy
Nuclear Physics A, 2006
Excitation functions were measured for the 180W(n,2n)179mW, 182W(n,p)182Ta, 182W(n,p)182m2Ta, 182... more Excitation functions were measured for the 180W(n,2n)179mW, 182W(n,p)182Ta, 182W(n,p)182m2Ta, 182W(n,α)179m2Hf, 183W(n,p)183Ta, 183W(n,α)180mHf, 184W(n,p)184Ta, 184W(n,α)181Hf, 186W(n,p)186Ta, 186W(n,α)183Hf, 186W(n,n′α)182mHf, and 186W(n,2n)185W reactions from 13.4 to 14.9 MeV. The data of these reactions that are dominant for neutron-induced activation in tungsten were in most cases either defective or incomplete. The experimental results are compared with the results of calculations including all activation channels
The measurement of neutron and neutron induced photon spectra in fusion reactor related assemblies
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2002
The spectral neutron and photon fluence (or flux) measured outside and inside of assemblies relat... more The spectral neutron and photon fluence (or flux) measured outside and inside of assemblies related to fusion reactor constructions are basic quantities of fusion neutronics. The comparison of measured spectra with the results of MCNP neutron and photon transport calculations allows a crucial test of evaluated nuclear data as generally used in fusion applications to be carried out.The experiments concern
A parameter-free self-organizing map for the analysis of pp-reactions at COSY
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1997
... Thus, one may try to develop a parameterfree algorithm with a self-controlling SOM to avoid p... more ... Thus, one may try to develop a parameterfree algorithm with a self-controlling SOM to avoid parameter optimization ... The evaluation of the network status is performed via the validation function 'wal(r) = fynode(r) - .~Iinpot(r)]norm' (6) [~Oval(r), which is normalized to a range - 1 <_ ...
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Papers by Hartwig Freiesleben