共查询到20条相似文献,搜索用时 15 毫秒
1.
J. Arnold B. van den Brandt M. Daum M. Finger M. Finger Jr. J. Franz N. Goujon-Naef P. Hautle R. Hess A. Janata J.A. Konter H. Lacker C. Lechanoine-Leluc F. Lehar S. Mango D. Rapin E. Rössle R. Schirmaier P.A. Schmelzbach M. Schmidt H. Schmitt P. Sereni M. Slunecka A. Teglia B. Vuaridel 《The European Physical Journal A - Hadrons and Nuclei》1998,2(4):411-415
Abstact: The kinetic energy spectrum and the polarization of the PSI neutron beam produced in the reaction 12C(p,n)X at 0° with 590 MeV polarized protons were investigated. A strong energy dependence of the neutron beam polarization is
observed which was not expected at the time the neutron beam was built.
Received: 3 April 1998 相似文献
2.
B. Krusche J. Ahrens R. Beck M. Fuchs S.J. Hall F. Härter J.D. Kellie V. Metag M. Röbig-Landau H. Ströher 《The European Physical Journal A - Hadrons and Nuclei》1999,6(3):309-324
Photoproduction of neutral pions from the deuteron has been studied for incident photon energies from 200 MeV to 792 MeV
with the TAPS detector at the Mainz MAMI accelerator. Total and differential cross sections covering the full angular range
have been obtained for coherent and incoherent single πo-photoproduction. Good agreement between model predictions and the data was found for the coherent process. The incoherent
cross section in the energy region of the Δ(1232)-resonance is overestimated by existing models. A comparison to model predictions
indicates that final state interaction effects are much more important than for the coherent reaction. However, the angular
dependence of the data in the Δ-peak region follows the pattern expected from the dominant excitation of the M1+-multipole on the free nucleon. The energy and angular dependence of single πo-photoproduction in the second resonance region is remarkably different from the reaction on the free proton, indicating a
strong nuclear effect. Finally the total cross section for double πo-photoproduction from the deuteron has been measured for the first time and was used to estimate the cross section for double
πo-photoproduction from the neutron.
Received: 24 June 1999 / Revised version: 30 August 1999 相似文献
3.
Low energy single nucleon transfer reactions are proposed as a tool to investigate the structure of nuclei far off stability.
Experimental concepts and conditions are discussed, in particular high resolution γ-ray spectroscopy after single nucleon
pickup reactions. Nuclear structure is described by Skyrme Hartree-Fock calculations including pairing. As representative
examples, binding energies, radii and wave functions for Mg and Sn isotopes are calculated. In the neutron deficient Mg isotopes
a proton skin is found. At the neutron driplines the Mg and Sn isotopes develop extended neutron skins. The nuclear structure
results are used in DWBA and EFR-DWBA transfer calculations. Single nucleon transfer reactions of 32,36Mg and exotic Sn beams on targets ranging from 2H to 24Mg in inverse kinematics are explored. The one-nucleon transfer cross sections decrease strongly for high-Z targets. An impact
parameter analysis shows that the transfer process is selective on the tails of the wave functions. The largest cross sections
are obtained for 2H and 9Be targets at incident energies of E
lab
= 2-5 MeV/u. The energy-momentum dependence is closely related to the special properties of wave functions of weakly bound
states. Two-neutron (p,t) stripping reactions are studied for a 6He projectile. A strong competition of sequential and direct processes is found at low energies.
Received: 1 October 1997 / Revised version: 25 November 1997 相似文献
4.
R. Crespo A. M. Moro I. J. Thompson M. Rodríguez-Gallardo J. Gómez-Camacho J. M. Arias 《The European physical journal. Special topics》2007,150(1):13-14
The p-6He inelastic scattering at 700 MeV u-1 is studied
using Multiple Scattering expansion
of the total Transition amplitude (MST)
framework with a pseudo-state representation of 6He continuum.
We show that the differential cross sections calculated
with two different pseudo-state bases are in good agreement. 相似文献
5.
Studying the ω<Emphasis Type="Italic">N</Emphasis> elastic and inelastic cross section with nucleons
Ye.S. Golubeva W. Cassing L.A. Kondratyuk A. Sibirtsev M. Büscher 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):271-277
We explore the possibility to measure the elastic and inelastic ωN cross section in p+d→d+ω+p
sp and p+A reactions. Our studies indicate that the elastic scattering cross sections can be determined for ω momenta above 1 GeV/c
in p+d reactions by gating on high proton spectator momenta whereas the ωN absorption cross section down to low relative ω momenta is most effectively studied in p+A reactions at beam energies 2.0–2.7 GeV.
Received: 15 October 1999 相似文献
6.
Differential cross sections for neutrons scattered from natural Pb and 99.9 % isotopically pure 238U have been measured at 0.5°, 1.0°, and 1.5°. A neutron energy continuum was produced by bombarding a thick natural lithium target with a 4 MeV, nanosecond-pulsed proton beam. Neutron energies were determined by time-of-flight techniques. Flight paths from the neutron source to the scatterer and from the scatterer to the detector were each about 5 m. For the 0.5° measurements an annular detector geometry with an angular resolution of ± 0.1° was developed to maximize detection solid angle. Data were averaged over 100 keV intervals from 0.6 to 2.2 MeV and were corrected for backgrounds, multiple scattering and inelastic scattering. Measured cross sections were compared to optical-model calculations which included electromagnetic interactions of neutrons with the nuclear Coulomb field. Inclusion of an induced neutron electric dipole moment interaction was not warranted by the data. The angular dependence of the cross section was fitted with a function θ at each energy. Mean values of B for 238U are in agreement with theoretical predictions. Values of B for Pb are apparently 15 % too low. 相似文献
7.
L. Gialanella D. Rogalla F. Strieder S. Theis G. Gyürki C. Agodi R. Alba M. Aliotta L. Campajola A. Del Zoppo A. D'Onofrio P. Figuera U. Greife G. Imbriani A. Ordine V. Roca C. Rolfs M. Romano C. Sabbarese P. Sapienza F. Schümann E. Somorjai F. Terrasi H.P. Trautvetter 《The European Physical Journal A - Hadrons and Nuclei》2001,11(3):357-370
An excitation function of the ground-state γ0-ray capture transition in 12C (α,γ)16O at θγ = 90° was obtained in far geometry using six Ge detectors, where the study of the reaction was initiated in inverse kinematics
involving a windowless gas target. The detectors observed predominantly the E1 capture amplitude. The data at E = 1.32 to 2.99 MeV lead to an extrapolated astrophysical S factor S
E1(E
0) = 90±15 keV b at E
0 = 0.3 MeV (for the case of constructive interference between the two lowest E1 sources), in good agreement with previous works. However, a novel Monte Carlo approach in the data extrapolation reveals
systematic differences between the various data sets such that a combined analysis of all available data sets could produce
a biased estimate of the S
E1(E
0) value. As a consequence, the case of destructive interference between the two lowest E1 sources with S
E1(E
0) = 8±3 keV b cannot be ruled out rigorously.
Received: 6 June 2001 / Accepted: 26 July 2001 相似文献
8.
D. Filges F. Goldenbaum M. Enke J. Galin C.-M. Herbach D. Hilscher U. Jahnke A. Letourneau B. Lott R.-D. Neef K. Nünighoff N. Paul A. Péghaire L. Pienkowski H. Schaal U. Schröder G. Sterzenbach A. Tietze V. Tishchenko J. Toke M. Wohlmuther 《The European Physical Journal A - Hadrons and Nuclei》2001,11(4):467-490
A recent renascent interest in energetic proton-induced production of neutrons originates largely from the inception of projects
for target stations of intense spallation neutron sources, like the planned European Spallation Source (ESS), accelerator-driven
nuclear reactors, nuclear waste transmutation, and also from the application for radioactive beams. In the framework of such
a neutron production, of major importance is the search for ways for the most efficient conversion of the primary beam energy
into neutron production. Although the issue has been quite successfully addressed experimentally by varying the incident proton
energy for various target materials and by covering a huge collection of different target geometries --providing an exhaustive
matrix of benchmark data-- the ultimate challenge is to increase the predictive power of transport codes currently on the
market. To scrutinize these codes, calculations of reaction cross-sections, hadronic interaction lengths, average neutron
multiplicities, neutron multiplicity and energy distributions, and the development of hadronic showers are confronted with
recent experimental data of the NESSI collaboration. Program packages like HERMES, LCS or MCNPX master the prevision of reaction
cross-sections, hadronic interaction lengths, averaged neutron multiplicities and neutron multiplicity distributions in thick
and thin targets for a wide spectrum of incident proton energies, geometrical shapes and materials of the target generally
within less than 10% deviation, while production cross-section measurements for light charged particles on thin targets point
out that appreciable distinctions exist within these models.
Received: 22 May 2001 / Accepted: 3 September 2001 相似文献
9.
H.W. Dannhausen E.J. Durwen H.M. Fischer M. Leneke W. Niehaus F. Takasaki 《The European Physical Journal A - Hadrons and Nuclei》2001,11(4):441-455
The differential cross-section for the reaction γp↦π +
n was measured using the bremsstrahlung beam of the Bonn 2.5 GeV electron synchrotron. The pions were detected and momentum
analysed in a multichannel magnet spectrometer. Data reduction resulted in 1278 measured cross-sections which are presented
as energy distributions at six laboratory angles between 180° and 95°. The range of laboratory photon energies extended from
0.3 to 2.1 GeV. The statistical accuracy is better than 3 percent, the systematic error is about 5 percent. The data are compared
with other experimental results and predictions of a phenomenological analysis. These cross-sections are the result of a measurement
program which was started in the seventies. Further results will be reported in forthcoming publications.
Received: 2 February 2000 / Accepted: 14 August 2001 相似文献
10.
M. Schumacher P. Rullhusen F. Smend W. Mückenheim H.G. Börner 《Nuclear Physics A》1980,346(3):418-430
Using neutron capture γ-rays from a 140CeO2 source installed in the Grenoble high-flux reactor, differential cross sections for the elastic scattering of photons by Ta, Pb and U through θ = 120° have been measured for E = 4.291 and 4.767 MeV. These data have been supplemented by measuring elastic differential cross sections for U, θ = 120° and energies ranging from 0.279 to 1.332 MeV, using radioactive sources. The experimental differential cross sections below 1 MeV confirm the predicted Rayleigh amplitudes based on the second-order S-matrix within 3%. An excellent agreement between experiment and lowest-order Delbrück theory is observed between 1.0 and 1.4 MeV, showing that Coulomb corrections are small close to the threshold for pair production. At 4.291 and 4.767 MeV experiment and lowest-order Delbrück theory agree within ~12% 相似文献
11.
J. F. Liang D. Shapira C. J. Gross R. L. Varner H. Amro J. R. Beene J. D. Bierman A. L. Caraley A. Galindo-Uribarri J. Gomez del Campo P. A. Hausladen K. L. Jones J. J. Kolata Y. Larochelle W. Loveland P. E. Mueller D. Peterson D. C. Radford D. W. Stracener 《The European physical journal. Special topics》2007,150(1):35-36
Evaporation residue and fission cross sections of radioactive
132Sn on 64Ni were measured. Statistical model calculations
using parameters simultaneously fitting stable Sn+64Ni data
reproduce the 132Sn induced reaction very well. A large
sub-barrier fusion
enhancement was observed. The enhancement can be accounted for by
coupled-channels calculations including inelastic excitation of the
projectile and target, and neutron transfer. 相似文献
12.
J. Benlliure P. Armbruster M. Bernas C. Böckstiegel S. Czajkowski C. Donzaud H. Geissel A. Heinz C. Kozhuharov P. Dessagne G. Münzenberg M. Pfützner C. Stéphan K.-H. Schmidt K. Sümmerer W. Schwab L. Tassan-Got B. Voss 《The European Physical Journal A - Hadrons and Nuclei》1998,2(2):193-198
Projectile fragmentation of 238U in a lead target was investigated at a bombarding energy of 750 A MeV. Isotopic production cross sections of about 250 different projectile fragments in the element range Z= 30–53 were measured with the FRagment Separator (FRS). The magnetic selection and the kinematical analysis of the measured
isotopes allowed to disentangle fission and fragmentation residues. The mass loss of these residues indicates a violent collision
where a large amount of energy is dissipated. The position of the fragmentation corridor defined by the measured residues
was used to determine an effective proton-evaporation barrier.
Received: 3 October 1997 / Revised version: 27 February 1998 相似文献
13.
D. T. Khoa 《The European physical journal. Special topics》2007,150(1):31-34
DWBA analysis of the inelastic 30-40S(p,p') and
18-22O(p,p') scattering data measured in the inverse kinematics has been
performed to determine the isoscalar (δ0) and isovector (δ1)
deformation lengths of the 2+1 excitations in the Sulfur and Oxygen isotopes
using a compact folding approach. A systematic N-dependence of δ0 and
δ1 has been established which shows a link between δ1 and the
neutron-shell closure. Strong isovector deformations were found in several
cases, e.g., the 2+1 state in 20O where δ1 is nearly three
times larger than δ0. These results confirm the relation
δ1>δ0 anticipated from the core polarization by the valence
neutrons in the open-shell (neutron rich) nuclei. The effect of neutron shell
closure at N=14 or 16 has been discussed based on the folding model analysis
of the inelastic 22O+p scattering data at 46.6 MeV/u measured recently at
GANIL. 相似文献
14.
The (p, t) reaction on the even isotopes of samarium has been investigated at a proton energy of 25.5 MeV. Angular distributions were obtained in the range 18° ≦ θ ≦ 148° with angular steps between 2° and 5°. The experimental energy resolution varied between 35 keV and 50 keV FWHM. Spin and parity assignments are performed by comparing the measured angular distributions to zero-range DWBA calculations. Some difficulties of DWBA calculations for (p, t) reactions are pointed out. The relative cross sections for transitions to different levels of the final nuclei are compared with other (p, t) and (t, p) measurements in the same region of the rare earth isotopes. The dependence of the (p, t) cross sections for different transitions on the neutron number of the final nuclei is discussed. Some 2+ states observed in (p, t) and (t, p) reactions are described in the quadrupole pairing vibrational picture. 相似文献
15.
M.N. Andronenko L.N. Andronenko W. Neubert D.M. Seliverstov 《The European Physical Journal A - Hadrons and Nuclei》2001,12(2):185-190
Nuclear temperatures were determined from yields of isotopes with 1 ?Z? 14 accompanying the spontaneous and neutron-induced fission of heavy elements. The mean temperature derived from the corresponding
temperature distributions amounts to 1.10±0.15 MeV.
Received: 10 August 2001 / Accepted: 5 October 2001 相似文献
16.
C. Muri R.M. Anjos R. Cabezas P.R.S. Gomes S.B. Moraes A.M.M. Maciel G.M. Santos J. Lubian M.M. Sant'Anna C. Tenreiro R. Liguori Neto J.C. Acquadro P.A.B. Freitas 《The European Physical Journal A - Hadrons and Nuclei》1998,1(2):143-149
Elastic and inelastic scattering differential cross sections were measured in the energy range 30 MeV ≤ E
lab
≤ 55 MeV, for the 14N +59Co system. Ambiguities of the optical potential derived from the analysis of the elastic scattering data were removed by performing
calculations at the radius of sensitivity and by comparison with the available fusion cross section data. A simultaneous analysis
of the three mechanisms was performed by coupled channel calculations, and a unique energy independent nuclear potential was
found to be able to fit the data. Discussions and comparisons concerning the optical model, the threshold anomaly, full and
approximated coupled channel calculations are presented.
Received: 6 February 1997 / Revised version: 1 August 1997 相似文献
17.
V. K. Lukyanov 《Physics of Atomic Nuclei》2006,69(6):1033-1044
Nucleus-nucleus scattering is considered in the high-energy approximation and on the basis of Glauber-Sitenko microscopic theory in the optical limit. Analytic expressions for eikonal phase shifts are given for the case of Fermi-type realistic potentials and nuclear-density distributions. The effect of taking into account the distortions of the trajectories of the nuclei involved and the nuclear-density dependence of nucleon-nucleon forces on the total reactions cross sections is illustrated. The sensitivity of the reaction cross sections to the choice of model for the 6He projectile nucleus, which involves a neutron halo, is explored. Semimicroscopic optical potentials are introduced in order to describe differential cross sections for elastic scattering. The results of the present calculations are compared with available experimental data. 相似文献
18.
Elastic scattering of 7, 9, 11, 20 and 26 MeV neutrons from 208Pb has been measured with the Ohio University Tandem Van de Graaff accelerator. Standard pulsed beam time-of-flight techniques were employed. Measurements of the incident flux at 0° were used to normalize the differential cross sections. The measured cross sections were corrected for dead time, detector efficiency, flux attenuation, multiple scattering, finite geometry, neutron source anisotropy and compound elastic contribution. Relative uncertainties are estimated to be between 5%–10% and the uncertainty in the normalization is estimated to be less than 5 %. The data were used to obtain neutron optical potential parameters. A comparison with proton optical parameters is presented, and the (p, n) quasi-elastic cross section is calculated and compared with available data. Deformation parameters for the 3? state (Q = ?2.615 MeV) and 5ā (Q = ?3.198 MeV) in 208Pb were obtained at incident energies of 11 and 26 MeV. 相似文献
19.
E.Ya. Paryev 《The European Physical Journal A - Hadrons and Nuclei》2000,7(1):127-137
The inclusive K+ meson production in photon–induced reactions in the near threshold and subthreshold energy regimes is analyzed with respect
to the one–step (γN→K
+
Y, Y=Λ,Σ) incoherent production processes on the basis of an appropriate new folding model, which takes properly into account
the struck target nucleon removal energy and internal momentum distribution (nucleon spectral function), extracted from recent
quasielastic electron scattering experiments and from many–body calculations with realistic models of the NN interaction.
Simple parametrizations for the total and differential cross sections of the K+ production in photon–nucleon collisions are presented. Comparison of the model calculations of the K+ differential cross sections for the reaction γ+C12 in the threshold region with the existing experimental data is given, that displays the contributions to the K+ production at considered incident energies coming from the use of the single–particle part as well as high momentum and high
removal energy part of the nucleon spectral function. Detailed predictions for the K+ total and differential cross sections from γH2, γC12 and γPb208 reactions at subthreshold and near threshold energies are provided. The influence of the uncertainties in the elementary
K+ production cross sections on the K+ yield is explored.
Received: 12 April 1999 / Revised version: 11 September 1999 相似文献
20.
V.D. Efros H. Oberhummer A. Pushkin I.J. Thompson 《The European Physical Journal A - Hadrons and Nuclei》1998,1(4):447-453
A semi–microscopic model for the low–energy photodisintegration of the 9Be nucleus is constructed, and the experimental data are analyzed with its help. The older radioactive isotope data are supported
by this analysis. The theoretical photodisintegration cross section is derived. The astrophysical rates for the reaction α+α+n→9Be+γ and the reverse photodisintegration of 9Be are calculated. The new reaction rate for α+α+n→9Be+γ is compared with previous estimations.
Received: 19 January 1998 相似文献