A method for measuring light ion reaction cross-sections (original) (raw)
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Absolute measurements of photoionization cross-sections for ions
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005
A merged-beam setup for absolute measurements of photoionization cross-sections of ions is described. The facility is capable of recording cross-sections as low as 10 À19 cm 2 and has been used to study a large number of singly-and multiply-charged, atomic and molecular, positive and negative ions. It is based on a synchrotron radiation beam line fitted with an undulator at the storage ring ASTRID and a low-energy ($2 keV) ion beam line. Photons in the energy range 15-200 eV are merged co-linearly with the target ions over a distance of 50 cm, and the absolute photoionization cross-section is determined from the resulting photoion yield with a typical accuracy of 10%. Different types of ion sources are available, thus permitting a large number of positive and negative, atomic and molecular, singly-and multiply-charged ions to be investigated. Emphasis is put on accurate determination of the absolute cross-sections, requiring calibration of photodiode and particle detectors together with measurements of the photon-ion overlap.
Total cross sections of reactions induced by neutron-rich light nuclei
Zeitschrift f�r Physik A Atomic Nuclei, 1989
Total nuclear reaction cross-sections are determined by means of a 4 re-7 method. The results cover a wide span of targets for various stable beams. The validity of the method is shown in a combined systematics including also the results of transmission-type experiments. The data are very well described by the formula developed by Kox et al. The same method is applied to secondary fragment beams produced from a 44 MeV/u 22Ne beam on a 332 mg/cm 2 181Ta target. Using the LISE spectrometer the fragments 4'6He, are analyzed and transported to interact with a 199.4 mg/cm 2 Cu target surrounded by a 4rc-7 counter. The measured total reaction cross-sections oR are discussed in terms of the reduced strong absorption radius ro and compared with other experimental results.
Nucl Instrum Meth Phys Res a, 2005
A new technique for the spectrometry of (n,a) reactions on light elements at MeV energies has been developed and successfully used for the measurement of the 10 B(n,a) 7 Li reaction at the 7 MV Van de Graaff accelerator of IRMM. The basic elements of the new technique are a gridded ionisation chamber, a fast waveform digitizer and advanced off-line analysis. The powerful data visualisation allowed the discovery of the effect of particle leaking. Particle leaking arises from the simultaneous emission of more than one reaction products in forward angles and the inability of the detector to resolve multiple particles. It is an inherent property of all GIC spectrometers used for the study of (n, charged particle) reactions on light-element solid targets. The measurement of the cross section strongly benefits from it, but the determination of other measurables is negatively affected. Cross sections at seven energies between 1.5 and 3.8 MeV have been obtained by using the new technique. Compared to evaluations the IRMM cross sections are close to the JENDL-3.2 data for energies from 1.5 to 2.15 MeV and above 2.5 MeV they have values between those of JENDL-3.2 and JEF-2.2, but strongly deviate from the ENDF/B-VI data with the exception of very good agreement at 2.5 MeV. Forward angular distributions are truncated at large emission angles by the effect of particle leaking and appears depleted of reaction products between a kinematically determined angle y 0 and 901. It is shown that all values of the branching ratio a 0 /a 1 of the 10 B(n,a) 7 Li reaction published up to now in refereed journals and obtained by using ionisation chambers and face-to-face surface-barrier detectors contain inaccuracies caused by particle leaking which was not considered.
Nuclear Instruments Methods in Physics Research Section a Accelerators Spectrometers Detectors and Associated Equipment, 2005
A new technique for the spectrometry of (n,a) reactions on light elements at MeV energies has been developed and successfully used for the measurement of the 10 B(n,a) 7 Li reaction at the 7 MV Van de Graaff accelerator of IRMM. The basic elements of the new technique are a gridded ionisation chamber, a fast waveform digitizer and advanced off-line analysis. The powerful data visualisation allowed the discovery of the effect of particle leaking. Particle leaking arises from the simultaneous emission of more than one reaction products in forward angles and the inability of the detector to resolve multiple particles. It is an inherent property of all GIC spectrometers used for the study of (n, charged particle) reactions on light-element solid targets. The measurement of the cross section strongly benefits from it, but the determination of other measurables is negatively affected. Cross sections at seven energies between 1.5 and 3.8 MeV have been obtained by using the new technique. Compared to evaluations the IRMM cross sections are close to the JENDL-3.2 data for energies from 1.5 to 2.15 MeV and above 2.5 MeV they have values between those of JENDL-3.2 and JEF-2.2, but strongly deviate from the ENDF/B-VI data with the exception of very good agreement at 2.5 MeV. Forward angular distributions are truncated at large emission angles by the effect of particle leaking and appears depleted of reaction products between a kinematically determined angle y 0 and 901. It is shown that all values of the branching ratio a 0 /a 1 of the 10 B(n,a) 7 Li reaction published up to now in refereed journals and obtained by using ionisation chambers and face-to-face surface-barrier detectors contain inaccuracies caused by particle leaking which was not considered.
Chimera: a project of a 4π detector for heavy ion reactions studies at intermediate energy
Nuclear Physics A, 1995
One of the most interesting goals of the intermediate energy heavy ion research is to probe the properties of the nuclei under extreme conditions of density and temperature. The hot and compressed system formed in the early stage of the collision can deexcite leading to multifragment final states. This multifragmentation is predicted to be the major decay mode for a nuclear system produced at high density and temperature [1].
GLORIA: A compact detector system for studying heavy ion reactions using radioactive beams
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2014
The GLObal ReactIon Array (GLORIA) has been designed in order to study direct nuclear reactions induced by exotic nuclei at energies close to the Coulomb barrier. The detector array consists of six silicon particle-telescopes arranged in a very close geometry around a 30 • rotated-target system, allowing the measurement of reaction fragments in a continuous angular range from 15 • to 165 • (Lab.). GLORIA has been used for the first time at the SPIRAL/GANIL facility at Caen (France) to study the scattering of the system 8 He+ 208 Pb at the collision energies of 16 and 22 MeV.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2005
A new technique for the spectrometry of (n,a) reactions on light elements at MeV energies has been developed and successfully used for the measurement of the 10 B(n,a) 7 Li reaction at the 7 MV Van de Graaff accelerator of IRMM. The basic elements of the new technique are a gridded ionisation chamber, a fast waveform digitizer and advanced off-line analysis. The powerful data visualisation allowed the discovery of the effect of particle leaking. Particle leaking arises from the simultaneous emission of more than one reaction products in forward angles and the inability of the detector to resolve multiple particles. It is an inherent property of all GIC spectrometers used for the study of (n, charged particle) reactions on light-element solid targets. The measurement of the cross section strongly benefits from it, but the determination of other measurables is negatively affected. Cross sections at seven energies between 1.5 and 3.8 MeV have been obtained by using the new technique. Compared to evaluations the IRMM cross sections are close to the JENDL-3.2 data for energies from 1.5 to 2.15 MeV and above 2.5 MeV they have values between those of JENDL-3.2 and JEF-2.2, but strongly deviate from the ENDF/B-VI data with the exception of very good agreement at 2.5 MeV. Forward angular distributions are truncated at large emission angles by the effect of particle leaking and appears depleted of reaction products between a kinematically determined angle y 0 and 901. It is shown that all values of the branching ratio a 0 /a 1 of the 10 B(n,a) 7 Li reaction published up to now in refereed journals and obtained by using ionisation chambers and face-to-face surface-barrier detectors contain inaccuracies caused by particle leaking which was not considered.
Recent results in reactions using radioactive ion beams
After more than two and a half decades of radioactive beam physics, the existence of nuclear halos remains as probably the most outstanding discovery in the field. Many measurements have been performed with light halo systems, especially with a 6 He projectile, which has a two-neutron halo. The total reaction cross sections that can be extracted from these measurements follow a system-atic trend that can be compared to the behavior of the respective core, in this case 4 He. By using an appropriate scaling for energies and cross sections, such comparison clearly shows the effects of the halo, which can be separated into static and dynamic effects. For a few systems, where the reactions of the halo have been explicitly measured, application of the same scaling criteria leads to the conclusion of a core-halo decoupling. The behavior of the proton-halo projectile 8 B is similar to that of 6 He insofar as total reaction cross sections are concerned. The measured fusion data for 8 B + 58 ...
Physical Review C
Photodisintegration reaction rates involving charged particles are relevant to the p-process nucleosynthesis that aims at explaining the production of stable neutron-deficient nuclides heavier than iron. In this study, considering the compound and pre-equilibrium reaction mechanisms, the cross sections and astrophysical rates of (γ, p) and (γ, α) reactions for about 3000 target nuclei with 10 Z 100 ranging from stable to proton dripline nuclei are computed. To study the sensitivity of the calculations to the optical model potentials (OMPs), both the phenomenological Woods-Saxon and the microscopic folding OMPs are taken into account. The systematic comparisons show that the reaction rates, especially for the (γ, α) reaction, are dramatically influenced by the OMPs. Thus, better determination of the OMP is crucial to reduce the uncertainties of the photodisintegration reaction rates involving charged particles. Meanwhile, a γ-beam facility at Extreme Light Infrastructure-Nuclear Physics (ELI-NP) is being developed which will open new opportunities to experimentally study the photodisintegration reactions of astrophysical interest. Considering both the important reactions identified by the nucleosynthesis studies and the purpose of complementing the experimental results for the reactions involving p nuclei, the measurements of six (γ, p) and eight (γ, α) reactions based on the γ-beam facility and the Extreme Light Infrastructure Silicon Strip Array (ELISSA) for the detection of charged particles at ELI-NP are proposed. Furthermore, the GEANT4 simulations on these (γ, p) and (γ, α) reactions are performed using the calculated cross sections and the features of the γ-beam facility and the ELISSA detector at ELI-NP. Simultaneously satisfying the minimum detectable limit of the experimental yield and the particle identification of protons and α particles, the minimum required energies of the γ beam to measure the six (γ, p) and eight (γ, α) reactions are estimated. It is shown that the direct measurements of these photonuclear reactions based on the γ-beam facility at ELI-NP within the Gamow windows at the typical temperature of T 9 = 2.5 for the p-process are fairly feasible and promising. We believe that this pivotal work will guide the future photodisintegration experiments at ELI-NP. Furthermore, the expected experimental results will be used to constrain the OMPs of the charged particles, which can eventually reduce the uncertainties of the reaction rates for the p-process nucleosynthesis.