Speaker
Description
Laser wakefield acceleration (LWFA) is the most compact technique to produce GeV electron beams as short as few fs. To achieve optimal LWFA conditions, the laser pulse energy, time duration and focal spot size must be properly set. Limiting factors to the maximum attainable energy are the depletion of the pump laser and the dephasing of the electrons with the accelerating field, since the laser propagates slower than the electrons inside the plasma. The generation of a pre-ionized plasma channel enables a longer acceleration length, maximizing the electron beam energy.
ELBA at ELI Beamlines is a laser-electron collider, based on the Ti:Sa L3-HAPLS laser, designed to deliver up to 30 J, 30 fs pulses at a 10 Hz repetition rate. Once the square 230 mm x 230 mm laser pulses arrive in ELBA, they are 50:50 wavefront split by a full-size dielectric mirror with a 150 mm hole. The round laser pulses are sent to an off-axis parabola that focuses them down to 55 um FWHM focal spot 10 meters downstream. The square hollow laser pulses propagate through a delay line before reaching a 375 mm focal length off axis parabola that focuses them onto the counterpropagating electron beam. ELBA is designed to collide 2 GeV electron beam with 1021 W/cm2 laser pulses. At the moment, ELBA has been commissioned with up to 15 J at 0.2 Hz and up to 8 J at 3.3 Hz, achieving up to 5 GeV electron beams. Six user experimental campaigns have been completed, and the user proposal acceptance rate is around 50%.
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