Laser Plasma Accelerators (LPAs) rely on the non-linear interaction of ultra-intense laser pulses (intensity >1018 W/cm2) and underdense gas targets. Following ionization, the laser generates a strong co-propagating plasma wave in which background electrons can be self-injected in accelerating field gradients in excess of 100 GV/m. Over recent years, efforts have focused both on extending the beam energy well past multi-GeV, and on characterizing and optimizing the beam quality (i.e. beam brightness). At few-fs duration, multi-kA current, and sub-micron emittance, the LPA beam quality supports several high-profile applications, including driving a compact free electron laser (FEL).
At LBNL's BELLA Center we are currently pursuing an LPA FEL at soft X-ray energies (100-300 MeV electrons, producing 45-400 nm photons), capitalizing on the LPA system compactness and laser-synchronization. In my talk, recent experiments on high-quality LPA performance will be discussed, including a tunable shock-injected LPA configuration*, and single-shot emittance measurements for two LPA injection schemes**. The proposed lay-out for the LPA FEL transport and beam-manipulation line will be presented, including critical e-beam focusing optics such as the active plasma lens***, the strong-focusing VISA undulator, and a chicane to mitigate the percent-level LPA energy spread. Extensive front-to-end modeling was performed to optimize the LPA FEL line, validating the possibility of coherent FEL gain of several orders of magnitude for realistic LPA parameters. The presentation will finish with the current status of our new LPA FEL facility, including the new FEL-dedicated 100TW laser system, the transport line assembly, and undulator characterization.
This work is supported by the US DOE under Contract No. DE-AC02-05CH11231, the National Science Foundation under Grant No. PHY-1632796, and the Gordon and Betty Moore Foundation under Grant ID GBMF4898.
[*] K. Swanson et al. Phys. Rev. Accel. Beams 20, 051301 (2017)
[**] S. Barber et al. Phys. Rev. Lett. 119, 104801 (2017)
[***] J. van Tilborg et al. Phys. Rev. Lett. 115, 148802 (2015), J. van Tilborg et al. Phys. Rev. Accel. Beams 115, 032803 (2017)
Argonne Physics Division Colloquium Schedule