No abstract

No abstract

This article describes an experimental determination of the correlated, longitudinal phase-space electron distribution produced by a radio frequency photoinjector. Measurements of the electron beam energy spectra and pulse shapes are analyzed to deduce the longitudinal phase space at the exit of the photoinjector rf cavity. Data were obtained for micro-pulse charges of 0.5, 1.0, 2.0, 3.0, 4.0, and 5.0 nC, and show different phenomena in the low-charge and high-charge regimes. At low beam charge, the uncorrelated energy spread increases with increasing charge density, while rf bunching appears to cancel any pulse-length elongation due to the space-charge forces. At high beam charge, the data show that the micro-pulse separates into three distinct sub-pulses of nearly equal charge, and with a temporal separation proportional to the relativistic plasma frequency. These effects are compared with the space-charge generated instabilities and virtual-cathode phenomena observed in lower voltage devices. The implications that these results have upon the fundamental limits of beam brightness and magnetic pulse compression limitations are discussed.

No abstract

Measurements of elastic and inelastic scattering cross sections have been performed for 2.5 and 4.1 MeV neutrons incident on 155,156,157,158,160 Gd. Angular distributions have been measured at both energies for the 0 ϩ , 2 ϩ , and 4 ϩ members of the ground-state ͑gs͒ band of the even-even isotopes and for the 3/2 Ϫ , 5/2 Ϫ , and 7/2 Ϫ levels of the gs band of the even-odd isotopes. Angular distributions for inelastic scattering from the 9/2 Ϫ level of the gs band of 155 Gd and 157 Gd have also been measured at 4.1 MeV. These results together with previously measured s-and p-wave strength functions, potential scattering radii, and elemental total cross sections have been combined in an analysis based on coupled-channel semimicroscopic optical model potential ͑OMP͒ and statistical model calculations. The deformed OMP, an extension of our earlier work ͓E. Bauge, J.P. Delaroche, and M. Girod, Phys. Rev. C 48, 1118 ͑1998͔͒, is built using a complex density-dependent effective interaction and deformed matter densities deduced from unconstrained, axially symmetric Hartree-Fock-Bogoliubov ͑HFB͒ calculations based on the Gogny force. The HFB calculations which describe quite nicely a wealth of results from electron scattering and Coulomb excitations measurements, lead to semimicroscopic OMP predictions in good agreement with the neutron scattering and reaction measurements. A phenomenological OMP analysis is also performed to compare the global properties of both potentials.