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

TL;DR

This study demonstrates the generation of collimated, quasi-monoenergetic electron beams using 200fs Ti:Sapphire laser pulses interacting with under-dense helium plasma, highlighting betatron resonance acceleration as the key mechanism.

Contribution

The paper provides experimental evidence and theoretical analysis showing that betatron resonance acceleration can produce high-quality electron beams with specific energy characteristics under given laser and plasma conditions.

Findings

Electron beams with 17-22 MeV energy and ~10 mrad divergence were generated.

Two stages of self-focusing observed in the laser pulse within plasma.

Betatron resonance acceleration identified as the primary mechanism.

Abstract

Generation of collimated, quasi-monoenergetic electron beams (peak energy ~17-22MeV, divergence ~10mrad, energy spread ~20%) by interaction of Ti: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) He gas-jet plasma was observed. Two stages of self-focusing of the laser pulse in the plasma were observed. Two groups of accelerated electrons were also observed associated with these stages of the channeling and is attributed to the betatron resonance acceleration mechanism. This is supported by 2D PIC simulations performed using code EPOCH and a detailed theoretical analysis which shows that present experimental conditions are more favorable for betatron resonance acceleration and generation of collimated, quasi-thermal/quasi-monoenergetic electron beams.