Betatron resonance electron acceleration and generation of quasi-monoenergetic electron beams using 200fs Ti:Sapphire laser pulses

摘要

Generation of collimated, quasi-monoenergetic electron beams (peak energy~17-22MeV, divergence ~10mrad, energy spread ~20%) by interaction ofTi:sapphire laser pulse of 200fs duration, focussed to an intensity of ~2.1x10^18 W/cm^2,with an under-dense (density~3.6x10^19 to ~1.1x10^20 cm-3) Hegas-jet plasma was observed. Two stages of self-focusing of the laser pulse inthe plasma were observed. Two groups of accelerated electrons were alsoobserved associated with these stages of the channeling and is attributed tothe betatron resonance acceleration mechanism. This is supported by 2D PICsimulations performed using code EPOCH and a detailed theoretical analysiswhich shows that present experimental conditions are more favorable forbetatron resonance acceleration and generation of collimated,quasi-thermal/quasi-monoenergetic electron beams.