Reconstructing Cross Sections in the Enge Focal Plane

Particle transfer and elastic scattering cross sections can be used to probe single-particle excitations in nuclei. The Enge Split-pole Spectrograph at the Triangle Universities Nuclear Laboratory (TUNL), is focused on understanding excited states important for astrophysical reactions. Key information about these excited states are excitation energies, spin-parities, and spectroscopic factors, all of which are essential in determining the cross sections of interest. To extract spin-parities and spectroscopic factors, theoretical differential cross sections are typically fitted to experimental data collected at a range of angles. Here we present a new method to determine the cross section in finer detail. By using a wide spectrograph entrance aperture, a method was developed to reconstruct these cross sections on a fine scale by performing ray-tracing through the focal-plane detector of the Enge Split-pole Spectrograph. This is achieved by including two position-sensitive sections in the detector package. The method was tested with well-known cross sections. To investigate the effects of detector response on this ray-tracing procedure, the Geant4 Monte Carlo simulation toolkit was used. The results of this reconstruction are finer, more detailed cross section calculations.