At the Institute for Applied Physics (FB Physik, TU Darmstadt), a position is open in the research unit „Relativistic laser-plasma interactions'' and available now for a:
Research Assistant (all genders) – 65 %
The position has a limited duration of three years from the start date.
The research topic is the control of laser-plasma instabilities (LPI) in experiment and simulation. LPI appear during the interaction of a highly energetic laser pulse with matter. Because LPIs can be detrimental to laser-plasma interaction, their control and prediction is important for many applications. Here, in the context of this project, the influence of the plasma and laser parameters on the onset of LPI should be studied experimentally with the goal to develop LPI control methods. The PHELIX facility at GSI Helmholtzzentrum für Schwerionenforschunng GmbH will play a central role in the experimental part of the work, with an emphasis on tests with the newly-developed laser frontend that delivers incoherent broadband laser pulses. The experimental results will be illustrated with 2-to-3 dimensional particle-in-cell simulations, using the EPOCH simulation code.
Your tasks:
The tasks of the candidate include the design and planning of the experiment and its realization. A first experiment in planned for 2024 at PHELIX. Other experiments in an international context are also envisioned. In addition, the analysis of the experimental data and the comparison with simulation should be part of the project.
In addition, an active participation of the candidate to teaching activities is expected.
Your profile:
- A successfully completed university degree (Master/Diplom) in physics is required.
- In addition, a knowledge and preliminary experience in laser and plasma physics is required.
- A direct experience in the field of high-intensity lasers will be particularly appreciated.
- The candidate should be proficient with one of the following scientific programming languages: Matlab or Python, in order to perform the analysis of data produced by simulation and experiment.
- We expect an interest for interdisciplinary work to foster the collaboration with colleagues from connected topics.
Opportunity for further qualification (doctoral dissertation) is given. The fulfillment of the duties likewise enables the scientific qualifications of the candidate.
The Technische Universität Darmstadt intends to increase the number of female employees and encourages female candidates to apply. In case of equal qualifications applicants with a degree of disability of at least 50 or equal will be given preference. Wages and salaries are according to the collective agreements on salary scales, which apply to the Technische Universität Darmstadt (TV-TU Darmstadt).
Applications should be sent electronically as a PDF file with the usual documents, quoting the identification number, to: vincent.bagnoud@physik.tu-darmstadt.de.
Masterthesis
Motivation:
The current front end of the PHELIX laser at GSI uses an amplifier module based on titanium-sapphire (Ti:Sa) for pre-amplification in order to bring the pulses to energies in the range of 20 mJ before coupling them into the high-energy amplifier chain. Although Ti:Sa has the necessary amplification bandwidth, its use at the PHELIX wavelength (1054 nm) is far from the Ti:Sa optimum and therefore less efficient. Furthermore, the use of Ti:Sa requires a pump laser that produces energetic pulses in a short time at a wavelength of around 532 nm, which makes it difficult to use efficient pump systems such as laser diodes. Switching to a newer laser material, such as Ytterbium:CALGO, with longer lifetime, broad emission around 1050 nm, and absorption in a range covered by laser diodes, increases efficiency. The use of laser diodes is also expected to increase energy stability.
Tasks:
- Design of the system (analytical estimates, technical drawings)
- Simulation of the system / estimation of the performance in relation to the amplification bandwidth and output energy
- Setup of the system in the laboratory and commissioning
Goals:
- Design and Setup of an amplifier module based on Yb:CALGO
- Setup and characterization of the system
Useful prior knowledge / prerequisites:
- Optics
- Basics of Lasers / optical cavities
- Programming skills for modeling and analysis of generate data (e.g. Python, Matlab…)
Literature (max 3):
- https://link.springer.com/book/10.1007/b106789
- https://opg.optica.org/oe/fulltext.cfm?uri=oe-30-12-22153
- www.politesi.polimi.it/bitstream/10589/209879/1/Master_Thesis_Freddi.pdf
If you are interested in this work, please write a mail to:
Bachelor or Master Thesis
Motivation
To better understand the interaction of an intense laser beam with matter it is necessary to know the parameters of the laser system. In particular, this this includes a measurement of the temporal laser pulse profile. The method of "Frequency Resolved Optical Gating" (FROG) has proven itself as a possible way for such characterizations, which is able to reconstruct both the temporal envelope of the pulse and the corresponding temporal phase from a measured "FROG trace". After the measurement, the temporal pulse shape can be optimized with the aid of an "Acousto-Optic Programmable Dispersive Filter" (AOPDF). The aim of the first part of this work is therefore to plan a FROG, set it up at the PHELIX system and use it to measure and optimize the temporal laser pulse.
These measurements are complicated by beam aberrations and the coupling between spatio-temporal effects, which typically occur in large laser systems. Therefore, the aim of the second part of this work is to consider and potentially optimise precisely such effects in the existing reconstruction algorithm.
Tasks B.Sc.:
- Planning and design of the FROG system
- Calibration of the system by image analysis
- Commissioning and testing on at PHELIX system.
- Optimisation of the laser pulse in a control loop with an AOPDF (Acousto-Opti Porgrammable Dispersive Filter)
Additional Tasks M.Sc:
- Extension of the existing reconstruction algorithm under consideration of spatial-spectral effects
- Test of the new algorithm with controlled spatial-spectral effects and comparison with the expected behavior
- Investigation the effect of beam aberrations on pulse measurement and pulse reconstruction
Goals:
- Design, setup and calibration of the a FROG
- Implementation of the device in the system
- Extension and test of the reconstruction algorithm
Useful prior knowledge / prerequisites:
- Knowledge on optics and nonlinear effects
- Programming skills (e.g. LabVIEW, MATLAB or Python are of advantage)
Literature:
- D. J. Kane and R. Trebino, "Characterization of arbitrary femtosecond pulses using frequency-resolved optical gating," in IEEE Journal of Quantum Electronics, vol. 29, no. 2, pp. 571-579, Feb (1993)
- S. Akturk, M. Kimmel, P. O’Shea, and R. Trebino, "Measuring spatial chirp in ultrashort pulses using single-shot Frequency-Resolved Optical Gating," Opt. Express 11, 68-78 (2003)
If you are interested in this work please send a mail to:
v.bagnoud(at)gsi.de und j.hornung(at)gsi.de
Masterarbeit
Motivation:
Flawless beam quality is required for the generation of ultra-intense laser pulses. However, optical defects or incorrect alignment can quickly introduce errors in the beam that cannot be corrected retrospectively - reliable measurement methods are therefore essential!
The measurement of frequency-dependent beam errors, so-called "chromatic aberrations", is still very time-consuming today. This project aims to change this: Here, established techniques for wavefront measurement and spectral imaging are to be combined to design a compact and robust "plug-and-play" measuring device for the first time.
Task description:
- Sensor characterization in the laboratory
- Programming of live image evaluations (LabVIEW)
- Design, simulation and construction of an optical test bench
- Laboratory work on the Apollon Laser System in France
Objectives:
- Calibration of a multispectral camera
- Construction of a spectral wavefront sensor
- Test of the sensor on the Apollon Laser System
Prerequisites:
- Bachelor thesis with reference to optics
- Experience in programming
- Attendance of the lecture "Spectroscopy"
- Fluent in English
Literature:
- QWLSI wavefront measurement: www.researchgate.net/publication/221725185
- Multispectral wavefront measurement: doi.org/10.1364/OE.26.033387
Bachelor-/Masterthesis
Motivation:
Although Gaussian beams have excellent properties for beam transport, it is common practice in high-energy laser systems to use a uniform spatial energy distribution, a so-called flat-top beam. This has the advantage that, for example, the damage thresholds of optics are only reached at higher energies and this parameter can therefore be maximised. Another application is the use of such a beam profile for the pump beam of an optical parametric amplifier. This allows a more homogeneous amplification factor to be achieved over the entire beam profile, which also leads to higher amplification efficiency.
Tasks:
- Design of a beam-forming telescope with the following criteria:
- Design of an optical system for converting Gaussian beams into Flattop beams and vice versa
- Simulation of the telescope: ray tracing, phase calculation, beam propagation
- Determination of the beam sizes and the permitted variation, with additional estimation of the susceptibility to adjustment
- Estimation of the image-free propagation of the generated beam
- Design of a beam-forming telescope and its characterization:
- Efficiency
- Stability
- Residual ripple in the flattop
- susceptibility to adjustment
Goals:
- Design and construction of a beam-forming telescope
- Characterization of the telescope
Useful prior knowledge / prerequisites:
- Optics and optical design
- Programming skills for modeling and analysis of generate data (e.g. Python, Matlab, Zemax…)
Literatur:
- https://www.spiedigitallibrary.org/conference-proceedings-of-spie/9626/96261W/Modular-optical-design-for-flexible-beam-shaping-of-a-top/10.1117/12.2191062.short
- iopscience.iop.org/article/10.1088/1742-6596/276/1/012171/pdf
If you are interested in this work, please write a mail to::
Bachelorthesis
Motivation:
With the achievement of ever higher intensities, the measurement and optimisation of the temporal contrast is one of the most important tasks of modern laser systems. In addition to "quasi"-constant background noise (amplified spontaneous emission) and a rapidly increasing rising edge, so-called prepulses also play a role. Since the aforementioned disturbances in the temporal pulse profile can already generate plasmas and thus render experiments unusable, it is essential to avoid them. The occurrence of prepulses in particular is a rather dynamic process, as even slight changes in the system can generate them.
Tasks:
- Analysis of existing contrast measurements
- Calculate the optical path length of existing pre- and post-pulses
- Estimate which optics / optical systems can cause these
Goals:
- Identification of pre- and post-pulses in the laser system
- Localization of the points of origin by measuring the contrast at different points in the system
Useful prior knowledge / prerequisites:
- Basics of optics
- Programming skills for data analysis (e.g. Python)
Literature:
- https://link.springer.com/article/10.1007/s00340-019-7172-5
- https://www.cambridge.org/core/journals/high-power-laser-science-and-engineering/article/enhancement-of-prepulse-and-picosecond-pedestal-contrast-of-the-petawatt-jkarenp-laser/FD2BF3EAEFA3AC0ED82D7E49C8B87CE8
If you are interested in this work, please write a mail to:
