Session CO2 - Laser Accelerators; Ultraintense Laser Applications.
ORAL session, Monday afternoon, November 15
Room 203, SCC
Laser-plasma electron acceleration experiments have previously produced relativistic electrons in large energy spread, quasi-thermal beams. Here we report the observation of mono-energetic features in the electron spectrum in a non-linear or forced laser wakefield experiment. The 340~mJ, 45~fs pulses were focused to a 25~\mum focal spot onto a gas jet. At high density the energy spectrum has a quasi-thermal distribution. At lower density multiple spikes appear in the spectrum with narrow energy spreads. With an increase in laser energy to 640~mJ it is possible to produce single energy beams of E \sim 60 - 80~MeV with spreads of < 5%. Simulations also produce such features and show that these beams are injected into the non-linear plasma wave when it breaks transversely. If the plasma density is high, such that the bunch has time to dephase from the plasma wave before it reaches the end of the interaction then quasi-thermal spectra are produced. If the density is lower these mono-energetic features can be propagated out of the plasma before they have dephased.