Suppression of complete fusion due to breakup in the reactions 10,11^{10,11}B + 209^{209}Bi

Above-barrier cross sections of $\alpha$-active heavy reaction products, as well as fission, were measured for the reactions of $^{10,11}$B with $^{209}$Bi. Detailed analysis showed that the heavy products include components from incomplete fusion as well as complete fusion (CF), but fission originates almost exclusively from CF. Compared with fusion calculations without breakup, the CF cross sections are suppressed by 15% for $^{10}$B and 7% for $^{11}$B. A consistent and systematic variation of the suppression of CF for reactions of the weakly bound nuclei $^{6,7}$Li, $^{9}$Be, $^{10,11}$B on targets of $^{208}$Pb and $^{209}$Bi is found as a function of the breakup threshold energy

Influence of entrance-channel magicity and isospin on quasi-fission

The role of spherical quantum shells in the competition between fusion and quasi-fission is studied for reactions forming heavy elements. Measurements of fission fragment mass distributions for different reactions leading to similar compound nuclei have been made near the fusion barrier. In general, more quasi-fission is observed for reactions with non-magic nuclei. However, the $^{40}$Ca+$^{208}$Pb reaction is an exception, showing strong evidence for quasi-fission, though both nuclei are doubly magic. Time-dependent Hartree-Fock calculations predict fast equilibration of $N/Z$ in the two fragments early in the collision. This transfer of nucleons breaks the shell effect, causing this reaction to behave more like a non-magic one in the competition between fusion and quasi-fission. Future measurements of fission in reactions with exotic beams should be able to test this idea with larger $N/Z$ asymmetries.Comment: accepted for publication in Physics Letters

Disentangling effects of nuclear structure in heavy element formation

Forming the same heavy compound nucleus with different isotopes of the projectile and target elements allows nuclear structure effects in the entrance channel (resulting in static deformation) and in the dinuclear system to be disentangled. Using three isotopes of Ti and W, forming 232Cm, with measurement spanning the capture barrier energies, alignment of the heavy prolate deformed nucleus is shown to be the main reason for the broadening of the mass distribution of the quasifission fragments as the beam energy is reduced. The complex, consistently evolving mass-angle correlations that are observed carry more information than the integrated mass or angular distributions, and should severely test models of quasifission

Predominant Time Scales in Fission Processes in Reactions of S, Ti and Ni with W: Zeptosecond versus Attosecond

The inhibition of fusion by quasifission is crucial in limiting the formation of superheavy elements in collisions of heavy nuclei. Time scales of ∼10⊃-18s inferred for fissionlike events from recent crystal blocking measurements were interpreted to

Recent developments of SOLEROO: Australia's first high energy radioactive Ion Beam capability

The first measurements of the Australian National University's new radioactive ion beam capability were carried out using elastic scattering of a 8Li radioactive beam from a 197Au target. The purpose of this experiment was to test the radioactive ion beam capability as a complete system, which uses a pair of twin position-sensitive parallel plate avalanche counters as tracking detectors along with a highly pixelated double sided Si detector array. The tracking detector system allows us to have extremely high purity secondary radioactive ion beams by electronically tagging the reaction products of interest, thus allowing complete separation from the unwanted contaminant beam species of similar mass and charge. Here, some recent developments and characteristics of this system are presented

THE ECONOMIC BENEFITS OF KNOWLEDGE VALIDATION OF ERP TO LOW TECH SMES

Abstract: Knowledge Validation is a challenge in Small to Medium Sized Enterprises (SMEs), as most of the available information is held in people's minds as tacit knowledge, or saved on each employees PC without sharing or common validation. This case study is based on a company in Leicester who installed an enterprise resource planning (ERP) system after two previous failed trials with different type of software. The underlying reasons for the problems were due to the distributed and tacitly held knowledge where the assumptions in one part of the company were inconsistent with other parts. The research goes through three years of ERP implementation and analyses the main problem of validating knowledge in more detail and identifies the consequences of failing to do this. It also describes the potential economic benefits for installing enterprise resource planning system in SMEs and investigates the claim of ERP vendors that their ERP solutions increase the performance of their customers, increase profitability and efficiency of work processes. It discusses the effects of ER