Project of a Next-generation ISOL Facility for Exotic Beams at LNL
In the framework of the European program to define a second generation Radioactive Ion Beam facility, LNL are proposing the construction in the next five-seven years of a specialized national facility for RIB originated by fission fragments produced by secondary neutrons. It consists on a two-accelerator ISOL-type facility to provide intense neutron-rich radioactive ion beams of highest quality, in the range of masses between 80 and 160. The conceptual design is based on a high intensity 50 MeV (100 kW) proton linac as driver and on the availability of the heavy-ion accelerator ALPI as post accelerator. The estimated neutron yield is 2 x 10 n/s at 0, high enough to satisfy the demand for an advanced RIB facility. An intense R\&D program on different items is actually in progress in collaboration with other Laboratories and University groups and is moving in a European context.
ABOUT CARBIDES-MADE NANOCERAMICS FISSION TARGET FOR RIB PRODUCTION
Intensities of RIBs can be increased with improvement of release efficiency of fission targets. One of factor, which limits release efficiency of targets, is efficiency of release of isotopes from target material. This paper presents investigation of dependence of release efficiency from ceramics target on its grain size and inter-grains pores, as well shows some efficiency limits and ways to improve it. Simulations were performed for uniform target material made from powder of uranium carbide. Inter-grain spaces are taken relative to grain sizes, as another parameter to optimize is high density of target material. Results show that optimal grain size is in the range of hundreds thousands nanometers, while recent target materials utilize one order more sizes of grains. In addition, key points of production of such ceramics are discussed. The beam technologies allow producing the nanopowders from carbides of different metals with controlled grain size. Exact methods also give to us possibilities to obtain ceramics with optimal ratio between grain and pores sizes. Possible problems and preliminary program of experiments and tests are discussed. Figure 1. Layout of the SPES target system. Left to right: protecting collimator, neutron converter inside the cooling panels, fission target, ion source.
Resonant Auger decay study of C1s -> pi* core-excited OCS
The present work aims at characterizing short-lived C1s((-1)) pi*((1)) core-excited states of the OCS molecule based on the analysis of the vibrational fine structure and lineshape profiles of the high-resolution resonant Auger decay spectra recorded at the excitation energies along the C1s -> pi* resonance in the binding energy region 15-19eV. Very different behavior in terms of lineshape and resonant enhancement is observed for the (A) over tilde, (B) over tilde and (C) over tilde final states. This is explained by (1) the variation in the C-O bond lengths for the states involved in the electronic relaxation and (2) different contributions in terms of Mulliken population to the molecular orbitals determining the electronic character of the corresponding states. Since the final-state geometries are known from a number of previous experiments and ab initio calculations, the geometry of the C1s((-1)) pi*((1)) intermediate states can be predicted in analogy with e.g. the N-2, CO2 and N2O molecules. (C) 2009 Elsevier B.V. All rights reserved. (Less)