Group of Hans-Werner Becker: Projects

Diffusion of H bearing species in silicate glasses at low temperatures - development of a new experimental technique

The transport of H in glasses at relatively low temperatures (below 200 °C) is relevant for a number of applications such as obisidian dating of archaeological artefacts, palaeoclimate studies, storage of high level nuclear waste and many more. We have developed several new experimental aspects, and in particular (a) the ability to produce H-bearing amorphous thin films to act as a source of H without the presence of free H2O, and (b) the ability to measure low concentrations of H, independent of the speciation, with a high spatial resolution on the nanometer scale. In this project it is intended to use these developments to explore the diffusion of H-bearing species at conditions that have been inaccessible so far. A specific goal is to characterize the compositional dependence of H-diffusion at these conditions and understand the change of diffusion mechanism that leads to a different behaviour from those observed at higher temperatures.

Production of a 12C Target for Nuclear Astrophysics

A 12C Target for Nuclear Astrophysics purposes will be produced by implantation with energies between 30 and 50 keV at the 100 keV implanter

He4 implantation ino thin aluminum foils

For experiments at the superconducting cyclotron at the Laboratory Nazionali del Sud of the INFN in Catania He4 targets are prepared by He implantation into thin aluminum foils. The goal is to have a high He concentration in foils as thin as possible. The foils will be characterized by RBS with protons.

NRRA analysis of hydrogen in natural garnet samples as a calibration for FTIR spectroscopy (University Bern, Group Jörg Hermann)

Fourier Transform Infrared (FTIR) Spectroscopy is a frequently used technique for measuring water species in geological materials. However, the method has to be calibrated for each type of mineral or glass. We use the "standard-free" NRRA technique to analyse hydrogen depth profiles, which can then be used to calibrate methods such as FTIR or SIMS. This project is a collaboration with Prof. Jörg Hermann and Julien Reynes of the Geological Department of the University Bern.

Implantation of hydrogen in olivine (Yale University, Group Shun-ichiro Karato)

Space weathering involves solar wind implantation of elements, such as hydrogen, in planetary materials. Thus, it is crucial to study this process in order to evaluate its impact on the hydrogen budget of planetary bodies. We implant different amounts of hydrogen (fluences) in olivine at different energies to study at which fluence hydrogen saturation in this mineral is attained. This project is a collaboration with Shun-ichiro Karato, Jiang Zhenting, and Qinting Jiang of the Yale University.

Burried layers in diamond (Group Lorke, University Duisburg-Essen)

A burried graphite layer to serve as a gate for a FET should be produced by the implantation of carbon in diamond with an energy of 100 keV to open the possibility to stabilize and manipulate single NV centres.

Diffusion of hyrogen in nominally anhydrous minerals

The continuous improvement of analytical techniques led to the finding that minerals, which were once thought to be water-free (nominally anhydrous minerals), can indeed incorporate substantial amounts of water in their atomic structure. This observation changed fundamental aspects of our geodynamic models. The detection of water in minerals that are part of mantle xenoliths is one example. This information is interpreted to be evidence for a "wet mantle". To better understand the entity of the geologic water cycle in our earth it is necessary to quantify the transport rates of hydrogen in various phases in dependence of intensive variable (e.g. temperature). In this project we study the diffusion of hydrogen in minerals specifically at low temperatures using hydrogen implantation and NRRA.