[en] Wear of ultra-high-molecular-weight-polyethylene (UHMWPE) is usually measured by gravimetric methods making laboratory wear tests a time consuming exercise. Methods for the determination of polyethylene wear with a higher sensitivity would reduce test times and costs. One of these alternative methods is ultra-thin-layer-activation (UTLA), which relies on recoil implantation of heavy radioactive nuclei, such as ⁷Be, by using light mass particle beams. However, the possibility of damages within the polyethylene surface, which would have consequences on its wear behavior, cannot be excluded. In this work the effect of an implantation of ⁷Be on wear of a medical grade UHMWPE was studied using a block-on-cylinder screening wear tester. The results show that the implantation of UHMWPE with ⁷Be recoils under the implantation conditions chosen does not alter the tribological behavior of medical grade UHMWPE

No abstract available

[en] Longitudinal momentum distributions of ⁷Be fragments following the dissociation of ⁸B on heavy, highly charged target nuclei show forward-aft asymmetries, the result of interference of electric quadrupole (E2) transitions with the dominant E1 excitation process. These asymmetries can therefore be used to gain insight into the E2 contributions to the breakup process. To assess the sensitivity of these E2 interference terms to the assumed reaction mechanism, in particular, the role of higher-order coupling effects at medium energies, coupled discretized continuum channels (CDCC) calculations are carried out for ⁸B breakup at 44 and 81 MeV/nucleon on heavy targets. The effects of higher-order processes due to both Coulomb and nuclear breakup mechanisms can be estimated. In line with earlier work we find that the asymmetries produced by the calculations are reduced when including the higher-order couplings, reflecting an effective quenching of the E2 contributions. The full CDCC calculations show less asymmetry than the available experimental data, suggesting that the structure or reaction model now contains insufficient E2 strength. This contrasts with the results of lowest-order reaction theories that conclude that the ⁸B model E2 amplitudes are too large

No abstract available

[en] Several modifications and additions have been made to improve the radioactive beam facility at Livermore with the main aim of measuring the cross section for ⁷Be(p,γ)⁸B (which is important in determining the solar neutrino flux) and other reactions of astrophysical interest. The quadrupole sextuplet spectrometer has been upgraded by inserting an electrostatic deflection element near the midpoint and by installing a movable beam stop near the ⁷Be production target. These changes have allowed an improvement in the purity, and a large increase in the intensity, of the ⁷Be beam. Six large NaI(Tl) detectors and the gas cell from the OSU system along with its active and passive shielding have been incorporated into the Lawrence Livermore facility. True events are to be identified by a multiple coincidence. The first requirement is the detection of a γ-ray from the proton capture ⁷Be(p,γ)⁸B. After the candidate capture gamma is observed the ⁸B decay signature is required. This signature is a positron (from ⁸B → ⁸Be* + e⁺ + ν) along with the two α's from ⁸Be → α + α observed in a CaF₂ detector into which the ⁸B have implanted. Also a detector telescope inside the gas cell monitors the incoming ⁷Be beam. The current status of the ⁷Be(p,γ)⁸B measurement is discussed

[en] For many years, the cosmological "7Li problem has been tackled from various aspects. The nuclear reaction data have also been improved, but still there remains some ambiguities. We review our experimental plans to measure the cross sections of three key reactions which act to destroy "7Be during the Big-Bang Nucleosynthesis (BBN). These experiments are all based on "7Be beams produced at Center-for-Nuclear-Study Radioactive Ion Beam separator (CRIB) in collaborations mainly with research groups from INFN-LNS and RCNP. The preliminary result of the previous experiment and the future plan are discussed

[en] The Borexino experiment has recently celebrated the 10 years of data taking. Among the most relevant results already published, we remind the first direct measurement of ⁷Be and pep neutrinos and the best upper limit on CNO. In 2010-11 six purification were very successful in further reducing the already low backgrounds: a new high-purity Phase II data taking was started in October 2011, aimed to perform high precision measurements and to try to aggress the weakest components of the solar neutrino flux. In this contribution the first results based on the new Phase II data are reviewed. (paper)

No abstract available

[en] As part of a wider programme of investigations being carried out in N. Wales, a study of the radioactivity of sheep droppings has been undertaken, some preliminary results from which are presented in this note. (author)

[en] In this paper the impact of the Solar magnetic field on ⁷Be activity concentration in aerosols was investigated. The changes in the ⁷Be activity in aerosols in the period from the second part of 22nd to the second part of 24th Solar cycle were mathematically processed using the Fourier analysis and the 22 years period was pointed out. It corresponds to the most intense period of the Solar polar field strength for the same observed period. The Pearson's linear coefficient between the average annual value of ⁷Be activity in aerosols and the Solar polar field strength was 0.58. - Highlights: • Influence of the Solar magnetic field on the ⁷Be activity. • The Fourier analysis of the ⁷Be activity and the Solar magnetic field. • Correlation between the ⁷Be activity and the Solar magnetic field.