Browsing Conference Proceedings (Physics) by Title
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- ItemAlpha-cluster structure in the ground state of 40Ca displayed in a (p,pa) knockout reaction(IOP Publishing, 2013) Cowley, A. A.The analyzing power is very sensitive to details of the reaction mechanism of (p, pα) knockout reactions in the incident energy range of approximately 100 MeV and higher. Whereas distorted wave impulse approximation calculations in the past proved to give an excellent reproduction of analyzing power angular distributions for quasifree (p, pα) reactions on light targets such as 6Li, 9Be and 12C, the situation for 40Ca was not as simple. It is now shown that the theory also offers good agreement with the experimental distribution of the heaviest target nucleus if care is taken to use proper distorted waves which treat α−36Ar properly as a system for which α–elastic scattering is anomalous. Thus it is shown that 40Ca reveals its ground state α–cluster structure in an unambiguous way similar to the light target nuclei.
- ItemDistorted-wave Born approximation study of the 11Li(p,t) 9Li reaction(IOP Publishing, 2016) Cowley, A. A.The reaction 11Li(p,t) 9Li(gs) at an incident energy of 4 MeV is treated in terms of a simplistic distorted-wave Born approximation transfer. The halo neutrons involved in the reaction are treated as a di-neutron cluster transferred in a simultaneous process. This appears to be a good approximation of the mechanism. The dominant contribution to the reaction comes from the known (1s1/2) 2 structure component of the ground state of 11Li, and the cross section angular distribution seems to be relatively insensitive to the fact that 11Li has an anomalously large radius due to its Borromean halo properties. Significantly this simple treatment of the reaction is in much better agreement with the experimental angular distribution than a more sophisticated calculation.
- ItemEffectiveness of using a magnetic spectrograph with the Trojan Horse method(IOP Publishing, 2018) Manwell, S.; Parikh, A.; Chen, A. A.; De Sereville, N.; Adsley, P.; Irvine, D.; Hammache, F.; Stefan, I.; Longland, R. F.; Tomlinson, J.; Morfuace, P.; Le Crom, B.The Trojan Horse method relies on performing reactions in a specific kinematic phase space that maximizes contributions of a quasi-free reaction mechanism. The hallmark of this method is that the incident particle can be accelerated to high enough energies to overcome the Coulomb barrier of the target, but once inside the target nucleus the relative motion of the clustered nuclei allows the reaction of interest to proceed at energies below this Coulomb Barrier. This method allows the experimentalist to probe reactions that have significance in astrophysics at low reaction energies that would otherwise be impossible due to the vanishing cross section. Traditionally the Trojan Horse method has been applied with the use of silicon detectors to observe the reaction products. In this study we apply the Trojan Horse method to a well studied reaction to examine the potential benefits of using a splitpole magnetic spectrograph to detect one of the reaction products. We have measure the three body 7Li(d,αn)α reaction to constrain the energy 7Li(d,α)α cross section. Measurements were first made using two silicon detectors, and then by replacing one detector with the magnetic spectrograph. The experimental design, limitations, and early results are discussed.
- ItemEfficiency of Tm3+ -doped silica triple clad fiber laser(Optical Society of America, 2011) Ndebeka, Wilfrid Innocent; Heidt, A.; Schwoerer, Heinrich; Rohwer, Erich G.We present measurements of the slope efficiency and the pump power at threshold of a Tm3+ -doped silica triple clad fiber laser emitting at 2.02 μm using different cooling techniques. The slope efficiency of 53.6 % was obtained at a temperature of 25oC with a maximum output power of 5 W for 19 W of absorbed power at the pump wavelength of 800 nm and 9.9 W threshold. In a slightly different setup, the output power could be increased to 10 W for an absorbed pump power of 32 W.
- ItemFrom chi^2 to Bayesian model comparison : the example of Levy-based fits to e+e- correlations(Proceedings of Science, 2012) De Kock, Michiel B.; Eggers, Hans C.; Csorgo, TamasThe usual χ2 method of fit quality assessment is a special case of the more general method of Bayesian model comparison which involves integrals of the likelihood and prior over all possible values of all parameters. We introduce new parametrisations based on systematic expansions around the stretched exponential or Fourier-transformed Lévy source distribution, and utilise the increased discriminating power of the Bayesian approach to evaluate the relative probability of these models to be true representations of a recently measured Bose-Einstein correlation data in e +e− annihilations at LEP.
- ItemSpectroscopy of low lying states in 136Cs(IOP Publishing, 2016) Rebeiro, B.; Triambak, S.; Lindsay, R.; Adsley, P.; Burbadge, C.; Ball, G.; Bildstein, V.; Faestermann, T.; Garrett, P. E.; Hertenberger, R.; Radich, A.; Rand, E.; Varela, A.; Wirth, H.-F.The low-lying excited states in 136Cs relevant to the double beta decay of 136Xe were studied via a 138Ba(d, α)136Cs transfer reaction with a high resolution magnetic spectrometer. Preliminary results from the experiment are presented.
- ItemTowards the improvement of spin-isospin properties in nuclear energy density functionals(IOP Publishing, 2016) Roca-Maza, X.; Colo, G.; Liang, H. Z.; Meng, Jie; Ring, P.; Sagawa, H.; Zhao, P. W.We address the problem of improving existing nuclear Energy Density Functionals (EDFs) in the spin-isospin channel. For that, we propose two different ways. The first one is to carefully take into account in the fitting protocol some of the key ground state properties for an accurate description of the most studied spin-isospin resonances: the Gamow-Teller Resonance (GTR) . The second consists in providing a strategy to build local covariant EDF keeping the main features from their non-local counterparts . The RHF model based on a Lagrangian where heavy mesons carry the nuclear effective interaction have been shown to be successful in the description of spin-isospin resonances .