Radiative Capture Cross-section Measurements Research Articles

Design status of KOBRA for rare isotope production and direct measurements of radiative capture cross sections

KOBRA (KOrea Broad acceptance Recoil spectrometer and Apparatus) facility being designed at Rare Isotope Science Project in Korea will be utilized to produce rare isotope beams by employing multi-nucleon transfer reactions at about 20MeV/nucleon for studies of nuclear structure. KOBRA will also provide high suppression of beam induced background for direct measurements of radiative-capture cross sections in the astrophysical energy range. The present design status of the KOBRA facility is reported along with a brief introduction to the facility. We have studied the feasibility of production of 44Ti based on the present design of KOBRA as an example, and calculated the intensity of 44Ti secondary beam, to be about 105 particles per second, for 1 pnA 46Ti primary beam with a carbon target for a beam energy of 25MeV/nucleon. A Monte Carlo simulation with a ray-tracing code has been performed to show that recoil products 66Se are well separated from a 65As beam by KOBRA for the 65As(p,γ)66Se reaction at a beam energy of 1MeV/nucleon.

Radiative capture cross section measurements for fast neutrons using a large Gd-loaded liquid scintillator

A 500 1 gadolinium-loaded liquid scintillator tank, previously employed for measuring neutron multiplicities in fission and (n, 2n) cross sections, has been used for fast neutron radiative capture cross section measurements of both fissionable and non-fissionable nuclei. Specifically measurements for 238U and 197Au around a neutron energy of 2 MeV are presented. The scheme for measurement, data reduction and various corrections is described. Limitations of the method above 10 MeV are pointed out.

A new detector for neutron capture cross section measurements

A new detector for neutron radiative capture cross section measurements is proposed, the efficiency of which is 4 times that of the conventional Moxon-Rae detector. Principally, it consists of 6 equally thick plastic scintillator sheets which are alternatively connected to 2 photomultipliers operating in coincidence. The efficiency of the detector is proved to have a linear dependence on γ-ray energy. Some preliminary data on radiative neutron capture in natural Mo obtained with this detector are presented.

The Radiative Capture Cross Section of232Th for Neutrons in the Energy Range 300 to 1200 keV

A redetermination of the (n, γ) cross section of 232Th in the energy region 300 to 1200 keV has been made by an activation method. A discrepancy existed between the level structure of this nucleus obtained directly from inelastic scattering measurements and the level structure deduced by Lane and Lynn in their interpretation of radiative capture cross section measurements. The energy dependence of the radiative capture cross section used by Lane and Lynn showed a plateau extending between the neutron energies of 250 and 650 keV followed by a sharp drop. The present measurements show that this plateau actually extends up to about 900 keV so that the (n, γ) cross section is no longer inconsistent with the level structure of 232Th deduced from inelastic scattering measurements.