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Studentische Aushilfskraft (d/m/w) PHELIX

 

 

Job vacancies and topics for Bachelor / Master Theses

PhD Positions

At the Institute LP2IB, 19 Chemin du Solarium, F-33170 Gradignan, France a position is open in the research unit "Sciences Physiques et de l'Ingénieur (SPI)"and available now for a:

Research Assistant (all genders)

The position has a limited duration of three years from the start date.

Laser plasma acceleration of ions and electrons attracts remarkable attention to drive novel types of applications thanks to the unique properties of the accelerated particle beams. The arrival of high-power, high-repetition rate lasers will unlock a multitude of applications (radioisotope production, new generation of radiography, material analysis …) so far limited by the low rate of one shot per hour. This is why efforts must continue to develop particle sources so that they can be used at a higher repetition rate, particularly using gaseous targets.  Fundamental research into innovative mechanisms for accelerating electrons and ions from gaseous targets must be carried out in order to increase the average current delivered by these sources. This PhD work will include experimental studies on resources in Bordeaux and on PHELIX high-intensity laser facility at GSI in Darmstadt, as well as numerical modelling (hydrodynamic and Particle-in-cell simulations) and the development of on-line diagnostics to produce and characterize these promising sources.

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.

The main objective of the PhD student will be to complete the analysis and interpretation of the previous experiment on the LPA of ions carried out in 2022 by the Bordeaux team and to prepare, run, analyze and interpret the future experimental campaigns of LPA of electrons on the PHELIX/GSI laser facility. Study of particle beam diagnostics working at HHR and compatible with high intensity laser environments will also be part of the PhD work. Finally, in order to interpret the experimental results, the PhD student will run and analyses Hydrodynamics and PIC simulations with the expert plasma physicists from CELIA lab at Bordeaux and GSI at Darmstadt.

Candidates must be interested in experimental physics, instrumentation and simulations (GEANT4, SRIM, SMILEI, etc.) to design, carry out and interpret experiments in national and international laser facilities and particle accelerators. The candidate will spend part of the thesis in Darmstadt and the other part in Bordeaux. The thesis will lead to a double diploma from the University of Bordeaux and the TU-Darmstadt.

Applications should be sent electronically as a PDF file with the usual documents to: medhi.tarisien(at)u-bordeaux.fr.

Topics for Bachelor / Master Theses

Master’s thesis

Motivation:

For experiments in the field of matter with high energy density, an x-ray or gamma radiation source is often used to detect the state of matter. This radiation, preferably of short duration and high intensity, can be generated using high-energy electrons. One mechanism for accelerating electrons using a high-intensity laser is the so-called "Self-Modulated Laser Wakefield Acceleration" (SM-LWFA), which requires targets with a relatively low electron density in the range of 1018 - 1019 cm-3, but with a large spatial expansion in the range of several millimeters. In order to realize such a target with a controllable density profile, a so-called gas jet is suitable, which is generated via a pulsed nozzle at a relatively high pressure of up to 100 bar. The aim of this work is the construction, characterization and commissioning of such a gas jet for a planned experiment at the PHELIX high-energy laser.

Tasks:

  • Construction of a gas jet for laser plasma acceleration experiments
  • Construction of a test stand to characterise the properties of the gas jet
  • Characterisation of the gas system parameters by means of interferometry
  • Analysing the data and determining the system parameters to achieve certain properties of the gas jet
  • Commissioning of the gas jet during an experiment period at PHELIX

Goals:

  • Charakterisierung des Gas-Jets
  • Inbetriebnahme während einer Strahlzeit im März 2025

Useful prior knowledge / prerequisites:

  • Knowledge on optics
  • Experience in programming (e.g. Python, Matlab…)
  • Knowledge with gas systems

Literature:

  • J. Nejdl et al., Rev. Sci. Instrum. 1 June 2019; 90 (6): 065107. doi.org/10.1063/1.5098084
  • N Lemos et al.,Plasma Phys. Control. Fusion58 034018, DOI 10.1088/0741-3335/58/3/034018

If you are interested in this work, please write a mail to:

v.bagnoud(at)gsi.de and j.hornung(at)gsi.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):

If you are interested in this work, please write a mail to:

v.bagnoud(at)gsi.de und y.zobus(at)gsi.de

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:

If you are interested in this work, please write a mail to::

v.bagnoud(at)gsi.de und y.zobus(at)gsi.de

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:

If you are interested in this work, please write a mail to:

v.bagnoud(at)gsi.de und y.zobus(at)gsi.de

Internships

Internships for master students and PhD student positions are offered regularly in the department.

For the latest offers please send your resumes and a short motivation email to Prof. V. Bagnoud.


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