Publications (24)63.23 Total impact
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ABSTRACT: Data on elastic scattering of 96 MeV neutrons from 56Fe, 89Y, and 208Pb in the angular interval 1070° are reported. The previously published data on 208Pb have been extended, as a new method has been developed to obtain more information from data, namely to increase the number of angular bins at the most forward angles. A study of the deviation of the zerodegree cross section from Wick's limit has been performed. It was shown that the data on 208Pb are in agreement with Wick's limit while those on the lighter nuclei overshoot the limit significantly. The results are compared with modern optical model predictions, based on phenomenology and microscopic nuclear theory. The data on 56Fe, 89Y, and 208Pb are in general in good agreement with the model predictions.  [Show abstract] [Hide abstract]
ABSTRACT: Three neutrondeuteron scattering experiments at 95 MeV have been performed recently at The Svedberg Laboratory in Uppsala. Subsets of the results of these experiments have been reported in two short articles, showing clear evidence for threenucleon force effects. In this paper, we present further discussion of the results. We obtained excellent precision in the angular range of the nd cross section minimum. The data are in good agreement with Faddeev calculations using modern NN potentials and including 3N forces from a 2πexchange model, while the calculations without 3N forces fail to describe the data. CHPT calculations at nexttonexttoleading order represent an improvement compared to calculations with NN forces only, but still underestimate the data in the minimum region. In addition to neutrondeuteron scattering data, neutronproton and 12C(n,n) elastic scattering data have been measured for normalization purposes, and 16O(n,n) data have been obtained for the first time at this energy. It was possible to extract 12C(n,n') and 16O(n,n') inelastic scattering cross sections to excited states below 12 MeV excitation energy. These data are shown to have a significant impact on the determination of nuclear recoil kerma coefficients.  [Show abstract] [Hide abstract]
ABSTRACT: In the present experiment 250A MeV 17O ions were inelastically scattered from xenon and argon in the clusterjet target of the CELSIUS storage ring. The magnetic lattice of the ring is such that the quadrant following the target can be used as a magnetic spectrometer with an acceptance cone of ±0.6°, centred at 0°. A focal plane telescope, placed in the injection straight section, determined the excitation energy of the residual target nuclei. Data were taken for excitation energies between 15 and 35 MeV. The neutron decay was studied by the EDEN detector array positioned around the target, covering an angular range of 7–110°. In order to investigate a previously observed forward peaked fast neutron component, significant improvements were made in measurements of neutron energy, angular resolution and coverage, as well as in the design of the focal plane telescope. Preliminary comparisons between data and statistical model calculations show an excess of fast neutrons. The forward peaking of the angular distribution for argon is, however, weaker than was indicated in a previous experiment on xenon. 

Article: Measurement of the Absolute Differential Cross Section for np Elastic Scattering at 194 MeV
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ABSTRACT: A tagged mediumenergy neutron beam has been used in a precise measurement of the absolute differential cross section for np backscattering. The results resolve significant discrepancies within the np database concerning the angular dependence in this regime. The experiment has determined the absolute normalization with 1.5% uncertainty, suitable to verify constraints of supposedly comparable precision that arise from the rest of the database in partial wave analyses. The analysis procedures, especially those associated with evaluation of systematic errors in the experiment, are described in detail so that systematic uncertainties may be included in a reasonable way in subsequent partial wave analysis fits incorporating the present results. Comment: 22 pages, 21 figures, submitted for publication in Physical Review C  [Show abstract] [Hide abstract]
ABSTRACT: We have measured the neutrondeuteron (nd) elasticscattering differential cross section at 95 MeV incident neutron energy, using both the Medley and the SCANDAL setups at TSL in Uppsala. The full angular distribution was covered by detecting recoil deuterons from thin CD2 targets, and the result was normalized to the neutronproton (np) cross section. Recent theories predict that threenucleon (3N) force effects, if present, would affect the cross section in the minimum region by about 30%. The results are compared with theoretical calculations and are well described if 3N forces are included.  [Show abstract] [Hide abstract]
ABSTRACT: A new facility is constructed for measurements of neutron‐induced fission cross sections in the 20–180 MeV energy region versus the np scattering cross section, which is adopted as the primary neutron standard. The advantage of the experiment compared to earlier studies is that the fission‐fragment detection and the neutron‐flux measurement via np scattering are performed simultaneously and at the same position in the beam, and, therefore, many sources of systematic errors cancel out. Further reduction of systematic errors is achieved due to “embedded” determination of effective solid angle of particle detectors using α‐particles from the radioactive decay of the target nuclei. The performance of the facility is illustrated by first data obtained for angular distributions of fission fragments in the 238U(n,f) reaction.  [Show abstract] [Hide abstract]
ABSTRACT: We describe a doublescattering experiment with a novel tagged neutron beam to measure differential cross sections for np backscattering to better than +/2% absolute precision. The measurement focuses on angles and energies where the cross section magnitude and angle dependence constrain the charged pionnucleon coupling constant, but existing data show serious discrepancies among themselves and with energydependent partialwave analyses. The present results are in good accord with the partialwave analyses, but deviate systematically from other recent measurements.  [Show abstract] [Hide abstract]
ABSTRACT: The differential np scattering cross section has been measured at 96 MeV in the angular range θc.m.=20°–76°. Together with an earlier data set at the same energy, covering the angles θc.m.=74°–180°, a new data set has been formed in the angular range θc.m.=20°–180°. This extended data set has been normalized to the experimental total np cross section, resulting in a renormalization of the earlier data of 0.7%, which is well within the reported normalization uncertainty for that experiment. A novel normalization technique has been investigated. The results on forward np scattering are in reasonable agreement with theory models and partial wave analyses and have been compared with data from the literature.  [Show abstract] [Hide abstract]
ABSTRACT: Differential cross sections of charged particle production, i.e., p, d, t, 3Heions and αparticles, in 96 MeV neutron–carbon interactions have been measured at laboratory angles in the range 20° to 160° in steps of 20°. The experimental techniques are described as well as the procedures for acquisition, analysis, reduction and correction of the data.Results including double differential, energydifferential, angledifferential and total particle production cross sections are reported and constitute the first data set with five ejectiles at such a high neutron energy. Thanks to the lowenergy thresholds, 50% of the production cross section of αparticles, and 85% of the production cross sections of protons and deuterons, could be measured. For αparticles, the measured fraction is much higher than what has been achieved earlier at lower energies.The results on the hydrogen isotopes agree fairly well with a previous measurement at 95 MeV and with recent GNASH calculations. For the helium isotopes, however, there are important discrepancies in spectral shape and magnitude between the new results and the model calculations.  [Show abstract] [Hide abstract]
ABSTRACT: Doubledifferential cross sections for lightion (p, d, t, He3 and alpha) production in oxygen, induced by 96 MeV neutrons are reported. Energy spectra are measured at eight laboratory angles from 20 degrees to 160 degrees in steps of 20 degrees. Procedures for data taking and data reduction are presented. Deduced energydifferential and production cross sections are reported. Experimental cross sections are compared to theoretical reaction model calculations and experimental data at lower neutron energies in the literature. The measured proton data agree reasonably well with the results of the model calculations, whereas the agreement for the other particles is less convincing. The measured production cross sections for protons, deuterons, tritons and alpha particles support the trends suggested by data at lower energies. Comment: 21 pages, 13 figures, submitted to Phys. Rev. C  [Show abstract] [Hide abstract]
ABSTRACT: The doubledifferential cross sections for (n, px), (n, dx), (n, tx), (n, 3Hex) and (n, alphax) reactions in carbon have been measured at 96 MeV incident neutron energy. The various charged particles (inclusive spectra) were identified using deltaEE techniques. From the experimental data, energy and angledifferential as well as production cross sections were determined, and subsequently the partial and total kerma coefficients. The deduced partial and total kerma coefficients were compared to previous experimental results and theoretical calculations. The findings indicate that the deduced kerma coefficients for the hydrogen isotopes are in good agreement with those deduced from a previous measurement, and that the kerma coefficient values, in particular of the hydrogen isotopes, are systematically higher than values obtained from recent model calculations, which consequently resulted in a total kerma coefficient which is up to 30% higher than predicted by the calculations.  [Show abstract] [Hide abstract]
ABSTRACT: The neutron–deuteron (nd) elastic scattering differential cross section has been measured at 95 MeV incident neutron energy. The neutron–proton (np) differential cross section has also been measured for normalization purposes. An inclusion of threenucleon forces gives a considerable improvement in the theoretical description of the nd data in the angular region of the crosssection minimum.  [Show abstract] [Hide abstract]
ABSTRACT: A unique experimental facility has been developed to measure absolute neutron scattering crosssections through the use of tagged intermediateenergy neutrons. The neutrons are produced via the reaction p+d→n+2p with an electroncooled circulating proton beam of bombarding energy incident on a deuterium gas jet target. The “tagging” of the neutrons is accomplished by detection of the associated recoil protons in an array of silicon microstrip detectors located in vacuum. The detection of two protons in coincidence signals the production of a neutron, while energy and position measurements on the recoil protons allow for reconstruction of the fourmomentum of the neutron, and its impact position on a secondary target, on an eventbyevent basis. Performance characteristics of this facility are presented, and its future application to an absolute measurement of the np elastic scattering crosssection is described. 
Article: Nucleoninduced reactions at intermediate energies: New data at 96 MeV and theoretical status
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ABSTRACT: Doubledifferential cross sections for light charged particle production (up to A=4) were measured in 96 MeV neutroninduced reactions, at TSL laboratory cyclotron in Uppsala (Sweden). Measurements for three targets, Fe, Pb, and U, were performed using two independent devices, SCANDAL and MEDLEY. The data were recorded with low energy thresholds and for a wide angular range (20160 degrees). The normalization procedure used to extract the cross sections is based on the np elastic scattering reaction that we measured and for which we present experimental results. A good control of the systematic uncertainties affecting the results is achieved. Calculations using the exciton model are reported. Two different theoretical approches proposed to improve its predictive power regarding the complex particle emission are tested. The capabilities of each approach is illustrated by comparison with the 96 MeV data that we measured, and with other experimental results available in the literature. Comment: 21 pages, 28 figures  [Show abstract] [Hide abstract]
ABSTRACT: Doubledifferential cross sections for lightion (p, d, t, He3 and alpha) production in silicon, induced by 96 MeV neutrons are reported. Energy spectra are measured at eight laboratory angles, ranging from 20 degrees to 160 degrees in steps of 20 degrees. Procedures for data taking and data reduction are presented. Deduced energydifferential, angledifferential and production cross sections are reported. Experimental cross sections are compared to theoretical reaction model calculations and experimental data in the literature. Comment: 23 pages, 10 figures, added wraparound correction (see section 4.3) leading to changed crosssections and figures, accepted Phys. Rev. C 
Article: Elastic Neutron Scattering at 96 MeV
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ABSTRACT: A facility for detection of scattered neutrons in the energy interval 50–130 MeV, SCANDAL, has recently been installed at the 20–180 MeV neutron beam line of the The Svedberg Laboratory, Uppsala. Elastic neutron scattering from 12C and 208Pb has been studied at 96 MeV in the 10°–70° interval. The achieved energy resolution, 3.7 MeV, is about an order of magnitude better than for any previous experiment above 65 MeV incident energy. The present experiment represents the highest neutron energy where the ground state has been resolved from the first excited state in neutron scattering. A novel method for normalization of the absolute scale of the cross section has been used. The estimated normalization uncertainty, 3%, is unprecedented for a neutroninduced differential cross section measurement on a nuclear target. The results are compared with modern optical model predictions based on phenomenology or microscopic nuclear theory.  [Show abstract] [Hide abstract]
ABSTRACT: A facility for detection of scattered neutrons in the energy interval 50\char21{}130 MeV, scattered nucleon detection assembly, has recently been installed at the 20\char21{}180 MeV neutron beam line of The Svedberg Laboratory, Uppsala. First results on elastic neutron scattering from ${}^{12}\mathrm{C}$ and ${}^{208}\mathrm{Pb}$ at 96 MeV incident neutron energy are presented. This experiment represents the highest neutron energy where the ground state has been resolved from the first excited state in neutron scattering. The results are compared with modern optical model predictions. 
Publication Stats
342  Citations  
63.23  Total Impact Points  
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Institutions

20002006

Uppsala University
 Department of Radiology, Oncology and Radiation Science
Uppsala, Uppsala, Sweden
