41 research outputs found
Potassium self-diffusion in a K-rich single-crystal alkali feldspar
The paper reports potassium diffusion measurements performed on gem-quality
single-crystal alkali feldspar in the temperature range from to 1021 \,
\mbox{K}. Natural sanidine from Volkesfeld, Germany was implanted with
\mbox{}^{43}\mbox{K} at the ISOLDE/CERN radioactive ion-beam facility normal
to the (001) crystallographic plane. Diffusion coefficients are well described
by the Arrhenius equation with an activation energy of 2.4 \, \mbox{eV} and a
pre-exponential factor of 5\times10^{-6} \, \mbox{m}^{2}/\mbox{s}, which is
more than three orders of magnitude lower than the \mbox{}^{22}\mbox{Na}
diffusivity in the same feldspar and the same crystallographic direction.
State-of-the-art considerations including ionic conductivity data on the same
crystal and Monte Carlo simulations of diffusion in random binary alloy
structures point to a correlated motion of K and Na through the interstitialcy
mechanism
Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
Simulation results for future measurements of electromagnetic proton form
factors at \PANDA (FAIR) within the PandaRoot software framework are reported.
The statistical precision with which the proton form factors can be determined
is estimated. The signal channel is studied on the basis
of two different but consistent procedures. The suppression of the main
background channel, , is studied.
Furthermore, the background versus signal efficiency, statistical and
systematical uncertainties on the extracted proton form factors are evaluated
using two different procedures. The results are consistent with those of a
previous simulation study using an older, simplified framework. However, a
slightly better precision is achieved in the PandaRoot study in a large range
of momentum transfer, assuming the nominal beam conditions and detector
performance
Study of doubly strange systems using stored antiprotons
Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the P‾ANDA experiment at FAIR. For the first time, high resolution γ-spectroscopy of doubly strange ΛΛ-hypernuclei will be performed, thus complementing measurements of ground state decays of ΛΛ-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Ξ−-atoms will be feasible and even the production of Ω−-atoms will be within reach. The latter might open the door to the |S|=3 world in strangeness nuclear physics, by the study of the hadronic Ω−-nucleus interaction. For the first time it will be possible to study the behavior of Ξ‾+ in nuclear systems under well controlled conditions