Studies of inelastic scattering of fast heavy ions

In the present experiment 250A MeV O-17 ions were melastically scattered front xenon and argon in the cluster-jet target of the CELSIUS storage ring. The magnetic lattice of the ring is such that the quadrant following the target can be used as a magnetic spectrometer with an acceptance cone of +/-0.6degrees, centred at 0degrees. A focal plane telescope, placed in the injection straight section. determined the excitation energy of the residual target nuclei. Data were taken for excitation energies between 15 and 35 MeV. The neutron decay was studied by the EDEN detector array positioned around the target, covering an angular range of 7-110degrees.

In order to investigate a previously observed forward peaked fast neutron component. significant improvements were made in measurements of neutron energy, angular resolution and coverage. as well as in the design of the focal plane telescope. Preliminary comparisons between data and statistical model calculations show an excess of fast neutrons. The forward peaking of the angular distribution for argon is. however. weaker than was indicated in a previous experiment on xenon.