Progress towards laser plasma electron based free electron laser on coxinel

Laser plasma acceleration (LPA) [1] with up to several GeV beam in very short distance appears very promising. The Free Electron Laser (FEL), though very challenging, can be viewed as a qualifying application of these new emerging LPAs. The energy spread and divergence, larger than from conventional accelerators used for FEL, have to be manipulated to answer the FEL requirements. On the test COXINEL experiment [2–4] line, "QUAPEVA" permanent magnet quadrupoles of variable strength [5, 6] handle the emittance growth and a decompression chicane reduces the slice energy spread, enabling FEL amplification for baseline reference parameters [2]. A beam pointing alignment compensation method enables to properly transport the electrons along the line, with independent adjustments of position and dispersion [7]. The measured undulator spontaneous emission radiated exhibits the typical undulator radiation pattern, and usual features (a tunabilit small linewidth).