Recent experimental results from HELIOS


Alan Wuosmaa


Western Michigan University, USA


The renewed emphasis on nuclear structure far from stability, studied with nucleon-transfer reactions that utilize radioactive beams, has led to many new and exciting results.  Accompanying these developments are, however, several issues which make such measurements far more difficult than older studies done with light beams incident on heavy stable targets, because they must be carried out in inverse kinematics.  Among the problems are the identification of the reaction products, and the resolution of the states of interest in the residual nuclei.  A new device, HELIOS (the HELIcal Orbit Spectrometer) at the ATLAS facility at Argonne National Laboratory, has been built to solve many of the problems encountered with transfer reactions in inverse kinematics.  The device utilizes the uniform magnetic field of a large, superconducting solenoid to transport light reaction products from the target to a linear array of position-sensitive silicon detectors.  In operation since August 2008, HELIOS has been used primarily to study (d,p) reactions with stable and unstable beams with masses ranging from A=11 to 136.  The operating principles of HELIOS will be described, and selected results from measurements done with light radioactive beams produced at ATLAS will be presented.  This work is supported by the U. S. Department of Energy, Office of Nuclear Physics under contract numbers DE-FG02-04ER41320 (WMU) and DE-AC02-06CH11357 (ANL).