Cross Sections of the 83Rb (p,γ)84Sr and 84Kr(p,γ)85Rb Reactions at Energies Characteristic of the Astrophysical γ Process

We have measured the cross section of the 83 Rb ( p , γ ) 84 Sr radiative capture reaction in inverse kinematics using a radioactive beam of 83 Rb at incident energies of 2.4 and 2.7 A MeV. Prior to the radioactive beam measurement, the 84 Kr ( p , γ ) 85 Rb radiative capture reaction was measured in inverse kinematics using a stable beam of 84 Kr at an incident energy of 2.7 A MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the γ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be 0.17 – 0.42 times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the p nucleus 84 Sr , caused by the reduced rate of the 84 Sr ( γ , p ) 83 Rb reaction derived from the present measurement

Experimental Test of an Online Ion-Optics Optimizer

A technique has been developed and tested to automatically adjust multiple electrostatic or magnetic multipoles on an ion optical beam line – according to a defined optimization algorithm – until an optimal tune is found. This approach simplifies the process of determining high-performance optical tunes, satisfying a given set of optical properties, for an ion optical system. The optimization approach is based on the particle swarm method and is entirely model independent, thus the success of the optimization does not depend on the accuracy of an extant ion optical model of the system to be optimized. Initial test runs of a first order optimization of a low-energy ( \u3c 60 keV) all-electrostatic beamline at the NSCL show reliable convergence of nine quadrupole degrees of freedom to well-performing tunes within a reasonable number of trial solutions, roughly 500, with full beam optimization run times of roughly two hours. Improved tunes were found both for quasi-local optimizations and for quasi-global optimizations, indicating a good ability of the optimizer to find a solution with or without a well defined set of initial multipole settings

Design of the High Rigidity Spectrometer at FRIB

A High Rigidity Spectrometer (HRS) has been designed for experiments at the Facility for Rare-Isotope Beams (FRIB) at Michigan State University (MSU). The HRS will allow experiments to be performed with the most exotic neutron-rich isotopes at high beam energies (≳ 100 MeV/u). The HRS consists of an analysis beamline called the High-Transmission Beamline (HTBL) and the spectrometer proper called the Spectrometer Section. The maximum magnetic rigidity of the HRS is 8 Tm, which corresponds to the rigidities at which rare-isotope beams are optimally produced at FRIB. The resolving power, angular acceptance, and momentum acceptance are set to match the anticipated scientific program. An ion-optical design developed for the HRS is described in detail, along with the specifications of the associated magnet and detector systems