J. Rahighi

A compilation of charged-particle induced thermonuclear reaction rates

Low-energy cross section data for 86 charged-particle induced reactions involving light (1 less than or equal to Z less than or equal to 14), mostly stable, nuclei are compiled. The corresponding Maxwellian-averaged thermonuclear reaction rates of relevance in astrophysical plasmas at temperatures in the range from 10(6) K to 10(10) K are calculated. These evaluations assume either that the target nuclei are in their ground state, or that the target states are thermally populated following a Maxwell-Boltzmann distribution, except in some cases involving isomeric states. Adopted values complemented with lower and upper limits of the rates are presented in tabular form. Analytical approximations to the adopted rates, as well as to the inverse/direct rate ratios, are provided

Long range absorption in the scattering of 6He on 208Pb and 197Au at 27 MeV

Quasi-elastic scattering of 6He at E_lab=27 MeV from 197Au has been measured in the angular range of 6-72 degrees in the laboratory system employing LEDA and LAMP detection systems. These data, along with previously analysed data of 6He + 208Pb at the same energy, are analyzed using Optical Model calculations. The role of Coulomb dipole polarizability has been investigated. Large imaginary diffuseness parameters are required to fit the data. This result is an evidence for long range absorption mechanisms in 6He induced reactions. Comment: 10 pages, 10 figures, minor corrections. To appear in Nucl. Phys. A

Kinematically complete study of the Li7(p, )8Be*2± reaction at Ep=25 MeV

A kinematically complete study of the {sup 7}Li({ital p},{gamma}){sup 8}Be{sup *}{r arrow}2{alpha} reaction at {ital E}{sub {ital p}}=25 MeV is described. An upper limit of {ital d}{sigma}/{ital d}{Omega}{lt}0.04 {mu}b sr{sup {minus}1} is reported for the {theta}{sub {gamma}}=90{degree} capture cross section to the 2{sup +} states at 16.62 and 16.93 MeV, which is five times smaller than published results. This new datum is shown to be more consistent with a semidirect reaction mechanism involving the giant dipole resonance built on the {sup 8}Be{sup *} 2.94-MeV state than the previously proposed direct reaction mechanism.

The Coulomb break-up of 9Be

Abstract Kinematically complete data is presented on the break-up reaction 120Sn(9Be, 8Beg.s. + n) 120Sng.s. at Ebeam = 90 MeV for several scattering angles inside the grazing angle. These data are compared with the predictions of a Coulomb break-up model. It is shown that the data can be understood in terms of the Coulomb model provided some account is taken of the interactions of the break-up fragments with the target. Analysis of the 90Be(γ, n) cross-section, indicates that for this photo-disintegration reaction there is probably a significant direct components to the threshold cross-section, in addition to a threshold resonance at 1.69 MeV.

Monte Carlo and analytical calculations for characterization of gas bremsstrahlung in ILSF insertion devices

Gas bremsstrahlung is generated in high energy electron storage rings through interaction of the electron beam with the residual gas molecules in vacuum chamber. In this paper, Monte Carlo calculation has been performed to evaluate radiation hazard due to gas bremsstrahlung in the Iranian Light Source Facility (ILSF) insertion devices. Shutter/stopper dimensions is determined and dose rate from the photoneutrons via the giant resonance photonuclear reaction which takes place inside the shutter/stopper is also obtained. Some other characteristics of gas bremsstrahlung such as photon fluence, energy spectrum, angular distribution and equivalent dose in tissue equivalent phantom have also been investigated by FLUKA Monte Carlo code.

IOPscience - Scattering of 6He at energies around the Coulomb barrier

We have measured elastic cross sections of the scattering of 6 He at E Lab = 14, 16, 17,18 and 22 MeV on 208 Pb in the angular ranges of 20°-64° and 135°-170°. A significant amount of 4 He events is found at energies well below the Coulomb barrier, that becomes dominant above it. Optical model calculations have been performed including a dynamic polarization potential. Very large imaginary diffuseness parameter is needed in order to describe the experimental distributions.

Scattering of6He at energies around the Coulomb barrier

We have measured elastic cross sections of the scattering of 6 He at E Lab = 14, 16, 17,18 and 22 MeV on 208 Pb in the angular ranges of 20°-64° and 135°-170°. A significant amount of 4 He events is found at energies well below the Coulomb barrier, that becomes dominant above it. Optical model calculations have been performed including a dynamic polarization potential. Very large imaginary diffuseness parameter is needed in order to describe the experimental distributions.

Kinematically complete study of the sup 7 Li( p ,. gamma. ) sup 8 Be sup * r arrow 2. alpha. reaction at E sub p =25 MeV

A kinematically complete study of the {sup 7}Li({ital p},{gamma}){sup 8}Be{sup *}{r arrow}2{alpha} reaction at {ital E}{sub {ital p}}=25 MeV is described. An upper limit of {ital d}{sigma}/{ital d}{Omega}{lt}0.04 {mu}b sr{sup {minus}1} is reported for the {theta}{sub {gamma}}=90{degree} capture cross section to the 2{sup +} states at 16.62 and 16.93 MeV, which is five times smaller than published results. This new datum is shown to be more consistent with a semidirect reaction mechanism involving the giant dipole resonance built on the {sup 8}Be{sup *} 2.94-MeV state than the previously proposed direct reaction mechanism.

Kinematically complete study of theLi7(p,γ)8Be*→2α reaction atEp=25 MeV

A kinematically complete study of the {sup 7}Li({ital p},{gamma}){sup 8}Be{sup *}{r arrow}2{alpha} reaction at {ital E}{sub {ital p}}=25 MeV is described. An upper limit of {ital d}{sigma}/{ital d}{Omega}{lt}0.04 {mu}b sr{sup {minus}1} is reported for the {theta}{sub {gamma}}=90{degree} capture cross section to the 2{sup +} states at 16.62 and 16.93 MeV, which is five times smaller than published results. This new datum is shown to be more consistent with a semidirect reaction mechanism involving the giant dipole resonance built on the {sup 8}Be{sup *} 2.94-MeV state than the previously proposed direct reaction mechanism.