Experimental Double-differential Cross Sections Research Articles

Spectral energy and angular distributions of bremsstrahlung radiation produced by 3.5 keV electrons in scattering with a free SF6 molecule

Absolute double differential cross sections (DDCS) of bremsstrahlung (BS) radiation produced by 3.5 keV electrons in scattering with a free SF6 molecule were measured by using a Si-PIN photodiode detector in the angular detection range of 45°−110° relative to the direction of incident electrons. Angular distributions of the BS photons are found to be anisotropic. The experimental DDCS spectra are compared with the theoretical calculations obtained from atomic-field BS formulations of Kissel–Quarles–Pratt (KQP) using the “additivity hypothesis”. A fair agreement is observed between the measured results and those obtained from the KQP calculations for both the energy and the angular spectral distributions of BS radiation. The measured anisotropy of bremsstrahlung radiation is reproduced reasonably well by a modified Sommerfeld formula, if the relative velocity β is chosen to be half of the incident electron velocity β0. The measured anisotropy may be described by a parameter P, which is compared with the degree of polarisation obtained from theoretical calculations. Further, it is noted that the molecular weight, geometry and the number of constituent atoms present in the considered molecule do not seem to influence the usefulness of “additivity hypothesis”. In conclusion, the present results have once again corroborated the validity of “additivity hypothesis” for predicting the spectral distributions of molecular bremsstrahlung produced by keV-electrons.

DWBA double differential ionization cross sections for positron and electron impact on argon

The ionization of the 3p orbital of argon by 100 eV incident electrons and positrons is studied with the DWBA-WM approximation. The variation of our double differential ionization cross sections with the angles of the ejected electrons is found to be in reasonable agreement with the experiment. We found that the inclusion of the post-collision interaction in the theoretical model is necessary to obtain the size of the difference between the experimental double differential cross sections for electron and positron impact ionization.

Development of a code system DEURACS for theoretical analysis and prediction of deuteron-induced reactions

We have developed an integrated code system dedicated for theoretical analysis and prediction of deuteron-induced reactions, which is called DEUteron-induced Reaction Analysis Code System (DEURACS). DEURACS consists of several calculation codes based on theoretical models to describe respective reaction mechanisms and it was successfully applied to (d ,xp ) and (d ,xn ) reactions. In the present work, the analysis of (d ,xn ) reactions is extended to higher incident energy up to nearly 100 MeV and also DEURACS is applied to (d ,xd ) reactions at 80 and 100 MeV. The DEURACS calculations reproduce the experimental double-differential cross sections for the (d ,xn ) and (d ,xd ) reactions well.

Experimental and theoretical double differential cross sections for electron impact ionization of methane

Experimental and theoretical double differential cross sections (DDCSs) for electron-induced ionization of methane (CH4) are here reported for primary energies ranging from 50 eV to 350 eV and ejection angles between 25° and 130°. Experimental DDCSs are compared with theoretical predictions performed within the first Born approximation Coulomb wave. In this model, the initial molecular state is described by using single center wave functions, the incident (scattered) electron being described by a plane wave, while a Coulomb wave function is used for modeling the secondary ejected electron. A fairly good agreement may be observed between theory and experiment with nevertheless an expected systematic overestimation of the theory at low-ejection energies (<50 eV).

Development of a Calculation Code System for Evaluation of Deuteron Nuclear Data

Abstract A calculation code system for evaluation of deuteron nuclear data is extended so that the stripping reaction to bound states in the residual nucleus can be taken into account properly using a conventional zero-range DWBA approach. The code system is applied to deuteron induced-reactions on 27 Al for incident energies up to 100 MeV. It is found that the spectroscopic factors derived from the present DWBA analysis have incident energy dependence. The calculation using the extended code system reproduces experimental double-differential cross sections for the 27 Al(d,xp) reaction at 25.5, 56, and 100 MeV, and production cross sections of 28 Al in the incident energy range from the threshold to 20 MeV.

Zero-degree measurements ofC12fragmentation at 95 MeV/nucleon on thin targets

During therapeutic treatments using ions such as carbon, nuclear interactions between the incident ions and nuclei present in organic tissues may occur, leading to the attenuation of the incident beam intensity and to the production of secondary light charged particles. As the biological dose deposited in the tumor and the surrounding healthy tissues depends on the beam composition, an accurate knowledge of the fragmentation processes is thus essential. In particular, the nuclear interaction models have to be validated using experimental double differential cross sections which are still very scarce. An experiment was realized in 2011 at GANIL to obtain these cross sections for a 95-MeV/nucleon carbon beam on different thin targets for angles raging from 4${}^{\ensuremath{\circ}}$ to 43${}^{\ensuremath{\circ}}$. To complete these data, a new experiment was performed in September 2013 at GANIL to measure the fragmentation cross section at zero degree for a 95-MeV/nucleon carbon beam on thin targets. In this work, the experimental setup will be described, the analysis method detailed, and the results presented.

New Approach for Nuclear Reaction Model in the Combination of Intra-nuclear Cascade and DWBA

We applied a new nuclear reaction model that is a combination of the intra nuclear cascade model and the distorted wave Born approximation (DWBA) calculation to estimate neutron spectra in reactions induced by protons incident on 7Li and 9Be targets at incident energies below 50 MeV, using the particle and heavy ion transport code system (PHITS). The results obtained by PHITS with the new model reproduce the sharp peaks observed in the experimental double-differential cross sections as a result of taking into account transitions between discrete nuclear states in the DWBA. An excellent agreement was observed between the calculated results obtained using the combination model and experimental data on neutron yields from thick targets in the inclusive (p, xn) reaction.

Impact ionization of molecular oxygen by 3.5-MeV/u bare carbon ions

We have measured the absolute double-differential cross sections (DDCSs) for electron emission in ionization of O${}_{2}$ molecules under the impact of 3.5-MeV/u C${}^{6+}$ ions. The data were collected between 10 and 600 eV, in an angular range of ${30}^{\ensuremath{\circ}}$ to ${150}^{\ensuremath{\circ}}$. The single-differential cross sections (SDCSs) in emission angle and electron energy are deduced from the electron DDCS spectra. Also, the total cross section has been obtained from the SDCS spectra. The DDCS spectra as well as the SDCS spectra are compared with continuum distorted-wave eikonal initial-state calculations which employ molecular wave functions built as linear combinations of atomic orbitals. The DDCS ratio i.e. $\ensuremath{\sigma}{{}_{\mathrm{O}}}_{2}/2{\ensuremath{\sigma}}_{\mathrm{O}}$, derived by dividing the experimental DDCS for molecular oxygen with the theoretical DDCS for atomic oxygen, does not show any primary or secondary oscillations arising from Young-type interference, which is apparently in contrast to what has been observed earlier for H${}_{2}$ and in agreement with the model calculation. Similarly, the forward-backward angular asymmetry increases monotonically with the velocity of the emitted electrons. However, the results on the DDCSs, SDCSs, the asymmetry parameter, and the nonexistence of oscillations are in qualitative agreement with the predictions of the model used.

Mechanism of the93Nb(p⃗,3He) inclusive reaction at an incident energy of 160 MeV

The inclusive ${}^{93}$Nb($\stackrel{P\vec}{p}{,}^{3}$He) reaction to the continuum was investigated at an incident energy of 160 MeV. Emission-energy distributions for cross sections as well as analyzing powers were explored. A range of scattering angles from 15${}^{\ensuremath{\circ}}$ to 60${}^{\ensuremath{\circ}}$ (lab.) was covered and ${}^{3}$He emission energies from $\ensuremath{\approx}\phantom{\rule{-0.16em}{0ex}}30$ MeV to the kinematic limit were measured. As in our earlier work, the experimental distributions were compared with a multistep direct theory in which a reaction mechanism based on two-nucleon pickup is employed. Reasonable agreement between experimental double-differential cross sections and analyzing powers and the theoretical expectation was obtained. This work, together with published results for the same reaction at a lower projectile energy, allows the incident-energy dependence of the cross section and analyzing power distributions to be explored.

Model calculation of neutron kerma coefficient for n+ 56Fe below 20 MeV

Model calculations for the n+ 56Fe reaction have been performed by using extended UNF code, which is based on the unified Hauser–Feshbach and exciton model. Based on the excellent agreement with the experimental double-differential cross-sections of neutron, alpha and proton, the total kerma coefficients are derived naturally with the formula K Φ = ∑ i K Φ i = N ∑ ijk E ¯ ijk ( E n ) σ ijk ( E n ) ( Sun et al., 2008), which contains more comprehensive parameter information. The discrepancies of total kerma coefficients between the experimental data, evaluated data and the calculated results of this paper have been further analyzed, and one can have some confidence in predicting the kerma coefficients derived naturally by this model calculation.

Multistep direct mechanism in the (p→,He3) inclusive reaction onCo59andNb93at incident energies between 100 and 160 MeV

Emission-energy distributions for cross sections as well as analyzing powers were investigated for ($\stackrel{\ensuremath{\rightarrow}}{p},^{3}\mathrm{He}$) reactions on $^{59}\mathrm{Co}$ and $^{93}\mathrm{Nb}$ to the continuum from a threshold of $\ensuremath{\sim}$40 MeV up to the kinematic limit at incident energies of 130 and 160 MeV. A range of scattering angles from 15$\ifmmode^\circ\else\textdegree\fi{}$ to 140$\ifmmode^\circ\else\textdegree\fi{}$ (laboratory) was explored. The experimental distributions were compared with a multistep direct theory in which a reaction mechanism based on deuteron pickup is employed. Reasonable agreement between experimental double differential cross sections and analyzing powers and the theoretical expectation was obtained. This work, together with published results for the same reaction and targets at a lower projectile energy of 100 MeV, allowed the incident-energy dependence of the cross section and analyzing power distributions to be explored.

Light charged-particle production in 96 MeV neutron-induced reactions on carbon and oxygen

In recent years, an increasing number of applications involving fast neutrons have been developed or are under consideration, e.g. radiation treatment of cancer, neutron dosimetry at commercial aircraft altitudes, soft-error effects in computer memories, accelerator-driven transmutation of nuclear waste and energy production and determination of the response of neutron detectors. Data on light-ion production in light nuclei such as carbon, nitrogen and oxygen are particularly important in calculations of dose distributions in human tissue for radiation therapy at neutron beams, and for dosimetry of high-energy neutrons produced by high-energy cosmic radiation interacting with nuclei (nitrogen and oxygen) in the atmosphere. When studying neutron dose effects, it is especially important to consider carbon and oxygen, since they are, by weight, the most abundant elements in human tissue. Preliminary experimental double-differential cross sections of inclusive light-ion (p, d, t, (3)He and alpha) production in carbon induced by 96-MeV neutrons have been presented. Energy spectra were measured at eight laboratory angles: 20, 40, 60, 80, 100, 120, 140 and 160 degrees. Measurements were performed at The Svedberg Laboratory (TSL), Uppsala, using the dedicated MEDLEY experimental setup. The authors have earlier reported experimental double-differential cross sections of inclusive light-ion production in oxygen. In this paper, the deduced kerma coefficients for oxygen has been presented and compared with reaction model calculations.

Accelerating multiple scattering of the emitted electrons in collisions of ions with atoms and molecules

Double differential cross-sections for electron emission were measured in the collisions of N+ ions with N2, Ne and Ar targets in the 700–1500keV impact energy range. We studied the target atomic number dependence of the Fermi-shuttle type acceleration mechanism. The experimental double differential cross-sections are in good agreement with the theoretical values obtained from CTMC calculations for argon target. According to the calculations, multiple scattering contribution to the Ar spectra above 300eV is significant.

TheMo96(p⃗,d)Mo95reaction at50MeV

The $^{96}\mathrm{Mo}(p,d)^{95}\mathrm{Mo}$ reaction has been studied with a $50\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ polarized beam. Differential cross sections and analyzing powers have been measured for investigating the level structure in $^{95}\mathrm{Mo}$ up to the excitation energy of $5.8\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$. The standard distorted-wave Born approximation theory provides transfer angular momentum values and spectroscopic factors for the excited states. Furthermore, the theoretical analysis is extended also for the continuum region with a direct reaction model. Experimental double differential cross sections for continuum spectra are predicted well by adopting an asymmetric Lorentzian form for the response function in the distorted wave Born approximation based cross section calculations.

Experimental cross-sections for light charged particle emission induced by neutrons with energies between 25 and 65 MeV incident on natFe, 59Co, 209Bi, and natU

Experimental double-differential cross-sections ( d 2σ/ dΩ dE ) for fast neutron-induced proton, deuteron, triton, and α-particle emission on natFe, 59Co, 209Bi, and natU are reported at several incident neutron energies between 25 and 65 MeV for outgoing particle energies above the experimental energy detection thresholds. Angular distributions were measured at laboratory angles between 20° and 160°. Reliable extrapolated spectra were obtained at very forward (2.5° and 10°) and at very backward (170° and 177.5°) angles. Based on these experimental data, energy-differential (d σ/d E), angle differential ( dσ/ dΩ ), and total cross-sections ( σ T) are reported for each detected particle species.

Semiclassical Distorted Wave Model Analysis of Inclusive (N, N’x) Reactions for Incident Energies up to 400 MeV

The semiclassical distorted wave (SCDW) model with the Wigner transform of a one-body density matrix is applied to analyses of multistep direct processes in (p, p’x) reactions on 12C, 90Zr, and 197Au at incident energies near 150 MeV, and 392 MeV (p, p’x) and 346 MeV (p, nx) reactions on 40Ca. The calculations show good agreement with experimental double-differential cross sections over a wide mass range of target nuclei, except at backward angles.

Spallation neutron production by 0.8, 1.2, and 1.6 GeV protons on various targets

Spallation neutron production in proton induced reactions on Al, Fe, Zr, W, Pb and Th targets at 1.2 GeV and on Fe and Pb at 0.8, and 1.6 GeV measured at the SATURNE accelerator in Saclay is reported. The experimental double-differential cross-sections are compared with calculations performed with different intra-nuclear cascade models implemented in high energy transport codes. The broad angular coverage also allowed the determination of average neutron multiplicities above 2 MeV. Deficiencies in some of the models commonly used for applications are pointed out.

Experimental cross sections for light-charged particle production induced by neutrons with energies between 25 and 65 MeV incident on aluminum

Experimental double-differential cross sections (d2σ/dΩdE) for fast neutron-induced proton, deuteron, triton, and alpha-particle production on aluminum are reported, at several incident neutron energies between 25 and 65 MeV, for outgoing particle energies above the experimental energy thresholds. Angular distributions were measured at laboratory angles between 20° and 160°. Reliable extrapolated spectra are derived for very forward (2.5° and 10°) and very backward angles (170° and 177.5°). Based on these experimental data, energy-differential (dσ/dE), angle-differential (dσ/dΩ), and total production cross sections (σT) are reported for each outgoing particle.

Multistep direct mechanism in the(p→,3He)inclusive reactionon59Coand93Nb at an incident energy of 100 MeV

The inclusive $(\stackrel{\ensuremath{\rightarrow}}{p}{,}^{3}\mathrm{He})$ reactions on ${}^{59}\mathrm{Co}$ and ${}^{93}\mathrm{Nb}$ were investigated at an incident energy of 100 MeV. Emission-energy distributions for cross sections as well as analyzing powers, were measured from a threshold of $\ensuremath{\sim}35 \mathrm{MeV},$ determined by the detector configuration, up to the kinematic maximum. An angular range from 15\ifmmode^\circ\else\textdegree\fi{} to 140\ifmmode^\circ\else\textdegree\fi{} (lab) was covered. The experimental distributions were compared with a multistep direct theory in which a reaction mechanism based on deuteron pickup is employed. Reasonable agreement between experimental double differential cross sections and analyzing powers and the theoretical expectation is obtained.

EXPERIMENTAL CROSS SECTIONS FOR LIGHT CHARGED PARTICLE PRODUCTION INDUCED BY NEUTRONS WITH ENERGIES BETWEEN 25 AND 75 MeV INCIDENT ON CARBON

Experimental double-differential cross sections (d2σ/dΩdE) for fast neutron-induced production of proton, deuteron, triton, and alpha particle in carbon are reported at several incident neutron energies between 25 and 75 MeV. Angular distributions were measured in the laboratory angular range of 20° to 160°. Reliable extrapolated spectra are obtained at very forward (2.5° and 10°) and very backward (170° and 177.5°) angles. Based on these experimental data, energy differential (dσ/dE), angle differential (dσ/dΩ), and total cross sections (σT) are reported for each detected particle.