Laser-Driven Plasma-Based Incoherent X-Ray Sources at PALS and ELI Beamlines

In this paper, we report on development of incoherent secondary X-ray sources at the PALS Research Center and discuss the plan for the ELI Beamlines project. One of the approaches, how to generate ultrashort pulses of incoherent X-ray radiation, is based on the interaction of femtosecond laser pulses with underdense plasma. This method, known as laser wakefield electron acceleration (LWFA), can produce up to GeV electron beams emitting radiation in the collimated beam with a femtosecond pulse duration. This approach was theoretically and experimentally examined at the PALS Center. The parameters of the PALS Ti:Sapphire laser interaction were studied by extensive particle-in-cell (PIC) simulations with radiation postprocessors in order to evaluate the capabilities of our system in this field. The compressed air, and a mixture of helium and argon were used as accelerating medium. The accelerator was operated in the bubble regime with forced self-injection and resulted in the generation of stable relativistic electron beams with the energy up to 80 meV, hence, the betatron X-ray radiation with critical energy in the keV range was generated. The extensions of this method to the ELI Beamlines facility will enable to generate much higher X-ray energies from 10 keV up to 1 meV with 10 Hz repetition rate. Such source is suitable for various applications like phase contrast imaging or X-ray absorption experiments in a single shot.