Laser-plasma accelerators (LPAs) are compact accelerators with field gradients that are approximately 3 orders of magnitude higher than RF-based machines, which allows for very compact accelerators. LPAs have matured from proof-of principle experiments to accelerators that can reproducibly generate ultrashort high-brightness electron bunches. Here we will discuss a first combination of LPAs with an electron storage ring, namely an LPA-based injector for the cSTART ring at the Karlsruher Institute of Technology (KIT). The cSTART ring is currently in the final design phase. It will accept electron bunches with an energy of 50 MeV and will have a large energy acceptance to accommodate the comparably large energy spread of LPA-generated electron beams. The LPA will be required to reproducibly and reliably generate 50 MeV electron bunches with few percent energy spread. To that end, different controlled electron injection methods into the plasma accelerating structure, tailored plasma densities are explored and beam transfer lines to tailor the beam properties are designed.

Most current laser-plasma accelerators (LPAs) require driver lasers with relativistic intensities and pulse durations that are significantly shorter than the plasma wavelengths. This severely limits the laser technology that can be used to drive LPAs and with that their wide spread and the currently achievable LPA parameters, such as repetition rate and accelerating gradient. Here, we report a widely unexplored regime of laser-plasma electron acceleration that is based on the direct parametric excitation of plasma waves. This method markedly relaxes the driver laser requirements in terms of peak power and pulse duration. We show experimental data that demonstrates the generation of high-charge mildly relativistic electron bunches with laser-to-electron conversion efficiency that is unprecedented in gas-phase targets. The accelerating field gradient in this regime reach 3 TV/m. The experimental results demonstrate a novel regime that opens LPA electron acceleration for a wide range of driver laser technologies and holds the promise for a path to ultracompact high-repetition rate LPAs with extreme field gradients for future compact particle accelerators and secondary sources.

Ultrafast high-brightness X-ray pulses have proven invaluable for a broad range of research. Such pulses are typically generated via synchrotron emission from relativistic electron bunches. Recently, compact X-ray sources based on laser-wakefield accelerated (LWFA) electron beams have been demonstrated, where the radiation is generated by transverse betatron oscillations of electrons within the plasma accelerator structure. Here, we present a novel method for enhancement of and control over the parameters of LWFA-driven betatron X-ray emission. We realize this through specific manipulation of the electron bunch phase-space using our novel Transverse Oscillating Bubble Enhanced Betatron Radiation (TOBER) scheme. The phase space is controlled through the orchestrated evolution of the temporal laser pulse shape and the accelerating plasma structure, which leads to off-axis electron injection and large-amplitude transverse betatron oscillation, resulting in enhanced X-ray emission. TOBER holds the promise of compact sources that can generate X-rays with optimized parameters for specific applications using the same setup beams with even higher peak and average brilliance.