U. Hager

Scattering of the Halo Nucleus Be 11 on Au 197 at Energies around the Coulomb Barrier

Angular distributions of the elastic, inelastic, and breakup cross sections of the halo nucleus ^{11}Be on ^{197}Au were measured at energies below (E_{lab}=31.9u2009u2009MeV) and around (39.6xa0MeV) the Coulomb barrier. These three channels were unambiguously separated for the first time for reactions of ^{11}Be on a high-Z target at low energies. The experiment was performed at TRIUMF (Vancouver, Canada). The differential cross sections were compared with three different calculations: semiclassical, inert-core continuum-coupled-channels and continuum-coupled-channels ones with including core deformation. These results show conclusively that the elastic and inelastic differential cross sections can only be accounted for if core-excited admixtures are taken into account. The cross sections for these channels strongly depend on the B(E1) distribution in ^{11}Be, and the reaction mechanism is sensitive to the entanglement of core and halo degrees of freedom in ^{11}Be.

TACTIC: A new detector for Nuclear Astrophysics Experiments

Directly measuring nuclear astrophysics reactions presents unique challenges. Low energy reaction products and small reaction cross sections are just two of the issues that the TACTIC detector addresses. TACTIC is the TRIUMF Annular Chamber for Tracking and Identification of Charged-particles detector being developed by TRIUMF and the University of York, UK. TACTIC is a cylindrical, active-target TPC providing high detection efficiency; a shielding cathode traps the ionization created by the beam and allows for higher intensities than typical TPCs. The 480 anode signals are collected through custom preamplifiers, digital electronics and acquisition systems. Acquisition and analysis software is also undergoing extensive development. Amplification of the small signals is accomplished using a Gas Electron Multiplier (GEM). The fill gas, He-CO2, provides both particle detection and a homogeneous, variable-thickness target for studying reactions on αs, such as 8Li(α,n)11B. A preliminary study of this flagship reaction was carried out in June 2009 and the results are providing feedback into the development of the final detector and infrastructure.

Cross section measurements of the 3He(α, γ)7Be reaction using DRAGON at TRIUMF

We present our initial efforts with the DRAGON separator at TRIUMF facility towards obtaining the energy dependence of the astrophysical S-factor for 3He(?, ?)7Be reaction in the energy range of Ecm = 2 to 3 MeV that was recommended by the recent evaluations. A comparison between the existing data and our new complementary Madrid data, together with the recent theoretical calculations, is also given in the context of our ongoing work.

Scattering of the Halo Nucleus Be11 on Au197 at Energies around the Coulomb Barrier

Angular distributions of the elastic, inelastic, and breakup cross sections of the halo nucleus ^{11}Be on ^{197}Au were measured at energies below (E_{lab}=31.9u2009u2009MeV) and around (39.6xa0MeV) the Coulomb barrier. These three channels were unambiguously separated for the first time for reactions of ^{11}Be on a high-Z target at low energies. The experiment was performed at TRIUMF (Vancouver, Canada). The differential cross sections were compared with three different calculations: semiclassical, inert-core continuum-coupled-channels and continuum-coupled-channels ones with including core deformation. These results show conclusively that the elastic and inelastic differential cross sections can only be accounted for if core-excited admixtures are taken into account. The cross sections for these channels strongly depend on the B(E1) distribution in ^{11}Be, and the reaction mechanism is sensitive to the entanglement of core and halo degrees of freedom in ^{11}Be.

12C+16O: Properties of sub-barrier resonance γ-decay

In a recent experiment performed at Triumf using the Dragon 0° spectrometer and its associated BGO array, the complete γ-decay of the radiative capture channel below the Coulomb barrier has been measured for the first time. This measurement has been performed at two energies Ec.m. = 6.6 and 7.2 MeV. A selective contribution of the entrance spins 2+ and 3− has been evidenced which is consistent with existing results above the barrier.

TACTIC: A new detector for tracking in low energy nuclear astrophysics

K.A. Chipps∗a,1, P.A. Amaudruz2, L. Buchmann2, P. Bruskiewich2, S.P. Fox1, B.R. Fulton1, U. Hager2, A.M. Laird1, P. Machule2, L. Martin2, R. Openshaw2, G. Ruprecht2, A.C. Shotter2,3, P. Walden2, M. Walter2 aE-mail: kc612@york.ac.uk 1Department of Physics, University of York, Heslington, York, UK 2TRIUMF Laboratory, Vancouver, BC, Canada 3School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK

TACTIC – Ion tracking in nuclear physics

Ion tracking is still an unusual detection method in nuclear physics. TACTIC (TRIUMF annular chamber for tracking and identification of charged particles) is suitable for tracking low-energy ejectiles. The cylindrical design allows for an electrical separation of target and drift region without hindering the ejectiles to enter the drift region. The first experiment with radioactive beam – the reaction 8Li(α,n)11B which is important for the α-process in neutrino-driven supernova winds – took place in June 09. Since no off-the-shelf analysis tools and methods are available for this kind of tracking, TRIUMFs TACTIC group developed graphical tool for analysing data that can also be used for other modern nuclear physics detectors.