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Laser-based plasma accelerators (LPA) have successfully demonstrated their capability to generate high-energy electron beams with intrinsically short bunch lengths and high peak currents at a setup with a small footprint. These properties make them attractive drivers for a broad range of different applications including injectors for rf-driven, ring-based light sources. In close collaboration the Deutsches Elektronen-Synchrotron (DESY), the Karlsruhe Institute of Technology (KIT) and the Helmholtz Institute Jena aim to develop a 50 MeV plasma injector and demonstrate the injection into a compact storage ring. This storage ring will be built within the project cSTART at KIT. As part of the ATHENA (Accelerator Technology HElmholtz iNfrAstructure) project, DESY will design, setup and operate a 50 MeV plasma injector prototype for this endeavor. This contribution gives a status update of the 50 MeV LPA-based injector and presents a first layout of the prototype design at DESY in Hamburg., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

Optics express 30(3), 3404 - 3415 (2022). doi:10.1364/OE.448551, Ultrafast laser pulses featuring both high spatio-temporal beam quality and excellent energy stability are crucial for many applications. Here, we present a seed laser with high beam quality and energy stability, based on a collinear optical parametric chirped pulse amplification (OPCPA) stage, delivering 46 ��J pulses with a 25 fs Fourier limit at 1 kHz repetition rate. While saturation of the OPCPA stage is necessary for achieving the highest possible energy stability, it also leads to a degradation of the beam quality. Using simulations, we show that spectrally dependent, rotationally symmetric aberrations dominate the collinear OPCPA in saturation. We experimentally characterize these aberrations and then remove distinct spatial frequencies to greatly improve the spectral homogeneity of the beam quality, while keeping an excellent energy stability of 0.2 % rms measured over 70 hours., Published by Soc., Washington, DC

Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil The 12th International Particle Accelerator Conference, IPAC 2021, Campinas, Brazil, 24 May 2021 - 28 May 2021; JACoW Publishing, Geneva, Switzerland 4 pp. (2021). doi:10.18429/JACOW-IPAC2021-TUPAB163, The laser-driven generation of relativistic electron beams in plasma and their acceleration to high energies with GV/m-gradients has been successfully demonstrated. Now, it is time to focus on the application of laser-plasma accelerated (LPA) beams. The 'Accelerator Technology HElmholtz iNfrAstructure' (ATHENA) of the Helmholtz Association fosters innovative particle accelerators and high-power laser technology. As part of the ATHENAe pillar several different applications driven by LPAs are to be developed, such as a compact FEL, medical imaging and the first realization of LPA-beam injection into a storage ring. The latter endeavor is conducted in close collaboration between Deutsche Elektronen-Synchrotron (DESY), Karlsruhe Institute of Technology (KIT) and Helmholtz Institute Jena. In the cSTART project at KIT, a compact storage ring optimized for short bunches and suitable to accept LPA-based electron bunches is in preparation. In this conference contribution we will introduce the 50 MeV LPA-based injector and give an overview about the project goals. The key parameters of the plasma injector will be presented. Finally, the current status of the project will be summarized., Published by JACoW Publishing, Geneva, Switzerland

Physical review / X 10(3), 031039 (1-7) (2020). doi:10.1103/PhysRevX.10.031039, Laser-plasma acceleration promises compact sources of high-brightness relativistic electron beams. However, the limited stability often associated with laser-plasma acceleration has previously prevented a detailed mapping of drive laser and electron performance and represents a major obstacle towards advancing laser-plasma acceleration for applications. Here, we correlate drive laser and electron beam parameters with high statistics to identify and quantify sources of electron energy drift and jitter. Based on our findings, we provide a parametrization to predict the electron energy drift with sub-percent accuracy for many hours from measured laser parameters, which opens a path for performance improvements by active stabilization. Our results are enabled by the first stable 24-hour operation of a laser-plasma accelerator and the statistics from 100,000 consecutive electron beams, which, by itself, marks an important milestone., Published by APS, College Park, Md.

Nature Communications 10(1), 2591 (2019). doi:10.1038/s41467-019-10657-4, Highly-efficient optical generation of narrowband terahertz radiation enables unexplored technologies and sciences from compact electron acceleration to charge manipulation in solids. State-of-the-art conversion efficiencies are currently achieved using difference-frequency generation driven by temporal beating of chirped pulses but remain, however, far lower than desired or predicted. Here we show that high-order spectral phase fundamentally limits the efficiency of narrowband difference-frequency generation using chirped-pulse beating and resolve this limitation by introducing a novel technique based on tuning the relative spectral phase of the pulses. For optical terahertz generation, we demonstrate a 13-fold enhancement in conversion efficiency for 1%-bandwidth, 0.361 THz pulses, yielding a record energy of 0.6 mJ and exceeding previous optically-generated energies by over an order of magnitude. Our results prove the feasibility of millijoule-scale applications like terahertz-based electron accelerators and light sources and solve the long-standing problem of temporal irregularities in the pulse trains generated by interfering chirped pulses., Published by Nature Publishing Group UK, [London]