GSI-FAIR PhD Award for Dr. Johannes Hornung


Dr. Johannes Hornung receives the GSI-FAIR PhD Award 2022 for his doctoral thesis on the interaction of high-intensity laser pulses with solid targets. The award was recently presented in a special colloquium by Professor Paolo Giubellino, Scientific Managing Director of FAIR and GSI, and Daniel Sälzer, Managing Director of Pfeiffer Vacuum GmbH. The annual award is sponsored by Pfeiffer Vacuum and is endowed with 1000 euros.

One of the applications that comes with the advent of high-intensity lasers is the generation of bursts of hard x-rays, gamma rays and particle beams, obtained from the interaction of ultrashort light pulses with matter. Scientists have quickly recognized that such sources exhibit new properties that make them very attractive compared to other more traditional and established particle sources. In this rapidly evolving field, a definite challenge lies in the precise understanding of the underlying processes that explain the coupling of the laser to secondary beams of particles and radiation. Gaining such understanding is complex since the interaction of the laser with matter takes place on ultrashort time scales, typically femtoseconds (10-15 seconds), and in tiny volumes in the micrometer range, which makes it challenging to observe.

Dr. Johannes Hornung received his doctoral degree from the University of Jena for his experimental work done with the PHELIX laser at GSI/FAIR under the co-supervision of Professor Matt Zepf and Professor Vincent Bagnoud. In his thesis he focused on the interaction of high-intensity laser pulses with solid targets, a regime of interaction in reach of the most powerful laser system worldwide. In particular, Johannes Hornung used a non-invasive method, namely the spectroscopy of the light reflected off the target, to gain new insights on the laser-matter interaction and showed that quantitative information on the dynamics of such processes can be extracted from the collected data.

In a typical experiment, the ultrashort laser pulse is focused down to a few micrometers in a vacuum chamber onto a micrometer-thin foil. A particle burst emerges from this interaction. At the beginning of the interaction, the foil is quickly heated by the laser into a thin plasma slab that reflects a portion of the laser light, like a mirror. However, the plasma either expands into the vacuum or is being pushed by the radiation pressure of the laser in the opposite direction, or a combination of both happens sequentially. Under such conditions, the light reflected by the expanding or recessing plasma is Doppler shifted, carrying precious information of the exact interaction dynamics. The doctoral thesis of Johannes Hornung reports on the experimental study done at the PHELIX laser regarding this effect and proposes an improved model for the description of the laser-matter interaction. The model is backed by numerical simulations performed by Johannes Hornung using the resources of GSI/FAIR’s computing center Green IT cube.

The annual FAIR-GSI PhD Award honors an excellent PhD thesis completed during the previous year. Eligible for nominations are dissertations that were supported by GSI in the context of its strategic partnerships with the universities of Darmstadt, Frankfurt, Giessen, Heidelberg, Jena, and Mainz, or through the research and development program. In the framework of the Graduate School HGS-HIRe (Helmholtz Graduate School for Hadron and Ion Research), more than 300 PhD students currently perform research for their PhD theses on topics closely related to GSI and FAIR. GSI has a long-standing partnership with the award sponsor, Pfeiffer Vacuum GmbH, which offers vacuum technology and pumps. Vacuum solutions from Pfeiffer Vacuum have been successfully used in GSI's facilities for decades. (CP)