Research Group Laser-Electron Acceleration

In laser wakefield acceleration (LWFA), extremely high accelerating fields exceeding hundreds GV/m are generated in the wake of an ultra-intense laser pulse propagating through transparent plasmas, stimulating innovative research fields spreading from the development of compact and lower-cost high-energy particle accelerators, advanced radiation sources to the TeV energy frontier accelerators. Our group explores the physics of high-intensity laser-plasma interactions aiming for better control on the injection and acceleration process at the same time improving the primary electron beam parameters, namely beam energy and energy spread, beam emittance and shot-to-shot stability. State-of-the-art ultrafast diagnostics are being developed to probe subtle details of the relativistic plasma and electron beam dynamics on micrometer-size at femtosecond-time scale. Furthermore potential applications of such electron beams particularly as drivers for secondary radiation sources are investigated. Recently, together with groups from France: Synchroron SOLEIL, LOA-Ecole Polytechnique and PhLAM- Univ. Lille, we demonstrated for the first time a laboratory scale free-electron laser in the so-called seeding configuration driven by our plasma accelerator. As our long term mission, improved understanding of the underlying interaction processes will advance the field forward moving from basic research on novel acceleration concepts towards user-readiness, from “acceleration to accelerators”. 

We are permanently seeking ambitious students to join us for internship, bachelor-, diploma- or doctoral-thesis.

If you are interested or have any questions please do not hesitate to contact us.

Potential projects are listed → here ←

 

Projects:

• High quality nanocoulomb-class plasma accelerator

Investigation of various injection methods aiming for the generation of high quality electron beam from plasma acceleration mechanism is being persued. Particularly we explore schemes to enhance the trapped charge within the quasi-monoenergetic peak which can lead to ultra-high peak current electron beam (> 100 kA). In view of applications, the overall performance of plasma accelerators is being investigated aiming for reliable and stable operation over many hours and days. We investigate the correlation between laser and plasma parameters on the beam quality. Such high quality beams will pave the way for the next generation of radiation sources ranging from high-fields THz, high-brightness x-ray to gamma-ray sources, compact FELs and laboratory beam-driven laser-plasma accelerators.  

 Reference: 
"Improved performance of laser wakefield acceleration by tailored self-trucated ionization injection", A. Irman, et.al., Plasma Physics and Controlled Fusion 60, 044014 (2018)

 "Demonstration of a beam loaded nanocoulomb-class laser wakefield accelerator", J.P. Couperus, et.al., Nature Communications 8, 487 (2017)

• "In-situ" diagnostics for ultrafast plasma and beam dynamics at micron-scale

"You can only improve it if you can measure first!". We develop an optical probing technique for time-resolved study of ultrafast plasma wave evolutions. An extremely high spatio-temporal resolution, i.e femtosecond in time and micrometer in space, is required since the plasma structure is only tens of microns and moving with a velocity close to the speed of light in vacuum. Understanding of plasma wave excitation and evolution is essential for controlled and stable generation of high quality electron beams. In order to assess the generated electron beam quality, we aim to characterize the full phase-space distribution of a laser wakefield accelerated electron beam. Because the duration of such bunches is the femtosecond range, the most challenging task is to extract the longitudinal phase-space information. For this a powerful tool based on the measurement of the spectral intensity of Coherent Transition Radiation (CTR)  is being developed to infer the temporal distribution with sub-femtosecond time resolution.

Reference:

"Multioctave high-dynamic range optical spectrometer for single-pulse, longitudinal characterization of ultrashort electron bunches", O. Zarini,  et.al. Physical Review Accelerators and Beams 25, 012801(2022)

"Coherent optical signatures of electron microbunching in laser-driven plasma accelerators", A. Lumpkin, et.al., Physical Review Letters 125, 014801(2020)

• LWFA-driven advanced radiation sources: Free-electron lasers, Thomson backscattering and betratron radiation

We have demonstrated the generation of ultrashort and tunable X-ray pulses by colliding the ELBE electron beam and the DRACO laser beam. By using laser wakefield accelerated electron beams this energy range can be easily extended to the γ-ray range. Ultrashort X-ray pulses can also be generated by relativistic electrons undergoing oscillatory motion during acceleration inside plasma waves. Our goal is the increase of the peak brightness of such X-ray beams which is required for future X-ray pump-probe spectroscopy experiments. This project is closely connected to The Helmholtz International Beamline for Extreme Fields (HIBEF) at the European XFEL in Hamburg. We recently demonstrated seeded free-electron lasing in the ultraviolet wavelength range driven by our laser wakefield accelerator. Future work, we aim to go to shorter wavelengths with higher energy per pulse. 

References:

"Seeded free-electron laser driven by a compact laser plasma accelerator", M. Labat, et.al Nature Photonics (2022) - in press

"Compact spectroscopy of keV to MeV X-rays from a laser wakefield accelerator", A. Hannasch, et.al. Scientific Reports 11, 14368(2021)

"Making spectral shape measurements in inverse Compton scattering a tool for advanced diagnostic applications", J. Krämer, et.al, Scientific Reports 8, 1398 (2018)

• Hybrid LWFA-driven PWFA

We utilize high peak-current electron beams generated from a laser wakefield accelerator (LWFA), replacing the km-scale conventional accelerator, as the driver for an electron beam-driven plasma accelerator (PWFA). This hybrid plasma accelerator allows for harnessing key advantages of  beam-driven plasma accelerators for the generation of high brightness beam at dephasing-free acceleration in university-scale laser labs. We study the physics of PWFA like cold-injection, driver-witness energy transfer in an easy-access scale model and explore high-gradient acceleration of ultralow emittance bunches.

References:

"Effect of driver charge on wakefield characteristics in a plasma accelerator", S. Schöbel, et.al. New Journal of Physics 24, 083034(2022)

"Gas-dynamic density downramp injection in a beam-driven plasma wakefield accelerator", J. Couperus Cabadag, et.al, Physical Review Research 3, L042005(2021)

"Demonstration of a compact plasma accelerator powered by laser-accelerated electron beams", T. Kurz, et.al. Nature Communications 12, 2895(2021)

• Plasma target development and characterization

We develop a variety of plasma targets which later will be used as media for electron acceleration. These targets will provide a large range of plasma densities, i.e., from low plasma densities (provided by gas cells and pre-discharge plasma channels) to high plasma densities (provided by supersonic gas jets). Precise characterization of these targets is a key ingredient for the study of electron injection and acceleration mechanisms.

References:

"Tomographic characterisation of gas-jet targets for Laser Wakefield Acceleration", J.P. Couperus, et.al., Nuclear Instruments and Methods in Phyiscs Research Section A 830, 504 (2016)