I am Mirko from Berlin, Germany. My PhD project is the ”Development of Vector Tomography Algorithms for 3D Imaging of Local Crystallographic Structures“. I am registered as a part-time external PhD student at the Open University working at the Hahn-Meitner-Institut (HMI) in Berlin.
My diploma thesis:
Before I started this PhD project I finished my diploma thesis in computer science in close cooperation with the HMI and the Berufsakademie which is part of the Berlin School of Economics (similar to a university of applied science). This Faculty of Company-Linked Programmes combines full-time classroom study with regular practical on-the-job trainings for a standard studying time of three years.
During my diploma thesis I was working for the tomography group of the materials science department at HMI. This group investigates lots of problems using computer tomography, especially engineering material applications using synchrotron radiation from the BESSY facility in Berlin-Adlershof. My work was the development of artefact compensation methods in tomographic images.
My philosophiæ doctor:
My current project is the development of methods measuring and analysing crystallographic properties of engineering materials using neutron transmission. This approach takes advantage of the so-called Bragg edge phenomenon appearing in the neutron transmission spectrum of crystallographic materials. These Bragg transmission edges, i.e. steep increases of the transmitted neutron intensity at certain wavelength positions, are directly related to the crystallographic lattice of the investigated sample. The following image shows a calculated version of a neutron transmission spectrum displaying sharp Bragg edges for a polycrystalline iron sample.
Calculated neutron transmission spectrum of Fe with Bragg edges
This work concentrates on the determination of local lattice strains and crystallographic orientation distributions, i.e. texture, within a specimen. By rotating the sample, as it is the case for tomography setups such as the CONRAD imaging instrument at HMI, one should be able to identify the above-mentioned properties by analysing the edge position, its width and its height. A feasibility study of this Bragg edge tomography method is part of this project.
In parallel, a simulation tool using the McStas neutron ray-tracing simulation environment will be developed in order to realise ideal experiments with well defined instrument parameters and well known sample properties. Together with real measurements these simulations should help to develop tomographic reconstruction methods for the determination of crystallographic properties. The overall goal of this project is a new generation of tomographic imaging that enables the visualisation of local stress and texture distributions provided with high spatial resolutions.
My supervisors are Dr Jon James and Prof Lyndon Edwards from the Open University as well as Dr Javier Santisteban and Dr Astrid Haibel - and of course a lot more people are involved in this project.
My web links:
Compensation of Ring Artefacts in Synchrotron Tomographic Images
McStas - Neutron ray-tracing simulation
My personal HMI webpage
Berufsakademie Berlin, part of the Berlin School of Economics
My HMI address:
Department of Methods & Instruments (SF1)
Glienicker Str. 100
14109 Berlin, GERMANY
Telephone: +49 (0)30 8062 3180