Dr. Felix Gaertner Profile

Dr. Felix Gaertner

at GSI Helmholtzzentrum für Schwerionenforschung GmbH

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Publications (2)

Proceedings Article | 18 April 2021 Presentation

Enhanced scattering from a locally produced transient plasma grating in a plasma-based amplifier

Gregory Vieux, Silvia Cipiccia, Gregor Welsh, Sam Yoffe, Felix Gaertner, Matthew Tooley, Bernhard Ersfeld, Enrico Brunetti, Bengt Eliasson, MinSup Hur, Joao Dias, Thomas Kuehl, Dino Jaroszynski

Proceedings Volume 11778, 117780L (2021) https://doi.org/10.1117/12.2595297

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The increasing demand for high laser powers is placing huge demands on current laser technology. This is now reaching a limit, and to realise new areas of research promised at high intensities, new cost-effective and technically feasible ways of scaling up the laser power and controlling its optical characteristics are required. It is likely that ultra-compact, time-dependent, plasma-based amplifiers and optical elements (such as mirrors, polarisers, waveplates, etc.) will be required to reach powers exceeding tens of petawatts and possibly exawatts, and to manipulate the laser beams. Plasma is a robust optical medium as it is broken-down and can sustain extremely high electric fields. Plasma-based optical elements will most likely require the production of transient plasma gratings (TPGs), which take advantage of the ponderomotive force of the beat of at least two laser pulses. To create an amplifier, the TPG is formed through the action of the beat wave of a pump and seed pulse, which has a phase velocity satisfying the conditions for energy and momentum conservation of the three waves, where the third wave is a Langmuir or ion acoustic wave. Other optical elements will normally require static TPGs produced by degenerate driver pulses. Here we present the results of an experimental campaign conducted at the Central Laser Facility, where we have studied chirped pulse Raman amplification at high intensities. We have used a relatively long duration, frequency chirped, pump pulse to limit the growth of noise amplification, while ensuring amplification of the short seed pulse. We show that by changing the sign of the frequency chirp of the pump, the measured back-scattered and amplified seed energies change significantly. A negative chirp leads to a strong reduction in scattering from thermal density fluctuations, but seed amplification saturates. In contrast, for a positive frequency chirp, scattered energy continues to increase with increasing plasma density, without showing any sign of saturation, for the range of densities studied. From simulations we attribute this observation to the production of a local, long-lived, static TPG that continues to scatter the pump pulse long after it has passed. We will discuss the specific conditions that should be satisfied to produce such a grating. The ability to produce and maintain robust TPGs may provide a breakthrough in technologies for manipulating, reflecting and compressing ultra-intense laser pulses.

Proceedings Article | 14 May 2019 Presentation

Chirped pulse Raman amplification in plasma (Conference Presentation)

Gregory Vieux, Silvia Cipiccia, Gregor Welsh, Sam Yoffe, Matthew Tooley, Craig Picken, Graeme McKendrick, Felix Gaertner, Enrico Brunetti, Bengt Eliasson, Bernhard Ersfeld, MinSup Hur, John Farmer, Joao Dias, Thomas Kuehl, Alexander Pukhov, Dino Jaroszynski

Proceedings Volume 11036, 1103604 (2019) https://doi.org/10.1117/12.2522976

KEYWORDS: Plasma, Raman spectroscopy, Laser applications, Laser amplifiers, Backscatter, Raman scattering, Scattering, Capillaries, Picosecond phenomena

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