The GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt operates one of the world’s leading particle accelerator facilities for fundamental research. Together with international partners, GSI is currently building FAIR (Facility for Antiproton and Ion Research), one of the largest research projects worldwide. GSI and FAIR offer the opportunity to work in an international environment within a dedicated team committed to scientific excellence.

Within the framework of the research project LAser Simulation for Enhanced FUSion Efficiency (LASE-FUSE), we are seeking at the earliest possible date:

PhD Position (f/m/d) – Modeling and Experimental Evaluation of Focal Zooming in High-Energy Laser Systems for Fusion
Reference number: 26.78-1700

Project Context (LASE-FUSE)

Nuclear fusion has long been pursued as a sustainable and virtually inexhaustible energy source. Despite significant breakthroughs—such as the net energy gain achieved at the National Ignition Facility (NIF) through inertial confinement fusion (ICF)—the path toward an economically viable fusion power plant remains highly challenging.

A key limitation of current approaches, particularly those based on indirect laser drive of fusion fuel capsules (“indirect drive”), is the inefficient conversion of laser energy into fusion-relevant conditions.

Direct-drive concepts promise to overcome this limitation by eliminating the intermediate step of X-ray conversion. However, they place exceptionally high demands on existing and future laser technologies.

Focal zooming is a critical technique in direct-drive inertial confinement fusion for maintaining efficient energy coupling during the dynamic implosion of fusion targets. As the target capsule shrinks during compression, a fixed focal-spot size can lead to significant energy loss. Furthermore, overlapping laser pulses in plasma may trigger cross-beam energy transfer (CBET) instabilities, massively complicating controlled implosions.

The objective of this PhD project is to investigate, model, and experimentally evaluate methods for dynamically adjusting the focal spot during implosion to optimize energy coupling. This includes both numerical simulation and laboratory-based validation of focal zooming approaches for coherent as well as spectrally/temporally and spatially incoherent laser pulses.

In the broader context of LASE-FUSE, this position contributes to the development of a holistic digital twinof high-energy laser systems and focuses on the conceptual and technical integration of focal zooming with other smoothing techniques, ultimately aiming to enhance the efficiency and robustness of fusion-relevant laser systems.

Your Responsibilities:

• Development and extension of simulation codes for modeling focal zooming in the relevant range of target-compression within LASE-FUSE.
• Implement numerical models to investigate laser-parameter manipulation for focal zooming, including spatio-spectral phase and/or intensity modulation.
• Explore the integration of focal zooming with spatially and temporally incoherent pulses, analyzing the influence of incoherence on robustness, stability, and energy coupling efficiency.
• Conceptually design optical setups for implementing focal zooming in laboratory environments, compatible with both coherent and incoherent beams.
• Construct and operate experimental test setups for validation of focal zooming concepts and their combination with incoherent pulses and smoothing techniques.
• Perform experiments and analyze data to benchmark and validate optical simulation models.
• Close collaboration with internal project partners (postdocs, PhD students) as well as external partners from academia and industry.
• Documentation of developed models and software components, as well as publication of results in scientific journals and at international conferences.

Your Profile:

• Completed university degree (Master’s or equivalent) in physics, ideally with a focus on optics, photonics, or a related field.
• Solid knowledge in at least one of the following areas: laser physics, nonlinear optics, or wave optics.
• Basic programming skills (e.g. Python, Rust, C/C++ or similar) and interest in developing scientific software.
• Experience with numerical methods or simulation of physical systems is an advantage.
• Ideally, hands-on experience in optical laboratories, particularly in setting up and characterizing optical systems and amplifiers.
• Motivation to work on both theoretical/numerical and experimental topics.
• Independent and structured working style, as well as the ability to work in an interdisciplinary team.
• Good command of English (written and spoken); German language skills or willingness to acquire them are an advantage.

The duration of the position is limited for 3 years

GSI supports the vocational development of women. Therefore, women are especially encouraged to apply for this position.

Handicapped persons will preferentially be considered when equally qualified.

Further information about FAIR and GSI is available at www.gsi.de and www.fair-center.eu.

For questions, please contact Dr. Yannik Zobus (y.zobus@gsi.de, Tel. +49 6151-71-3381).

If you consider this position an exciting personal challenge and would like to work in an outstanding scientific environment, please submit your complete application documents, including your earliest possible starting date and the reference number 26.78-1700, by June 8^th  via our online application portal.

Online-Bewerbungsportal

GSI Helmholtzzentrum für Schwerionenforschung GmbH

Abteilung Personalmanagement

Planckstraße 1

64291 Darmstadt

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