Simulation Study of Driving Pulse Properties on the Performance of Sub-Terawatt Laser Wakefield Acceleration

Chia-Ying Hsieh^1*, Ming-Wei Lin², Shih-Hung Chen¹

¹Department of Physics, National Central University, Jhongli, Taiwan
²Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Chia-Ying Hsieh, email:101222011@cc.ncu.edu.tw

A particle-in-cell model has been developed to study the scheme of laser wakefield acceleration (LWFA) in which sub-terawatt (sub-TW) 1030-nm pulses produced from a diode-pumped laser system are introduced into a gas cell containing hydrogen atoms of a flat-top density profile. Because these 1030-nm lasers are typically produced with a long duration > 200 fs, a spectral broadening technique can be applied to reduce the pulse duration such that a greater ponderomotive force is acquired to drive LWFA. To understand the dependence of LWFA performance on the driving pulse duration, selected durations are assigned for 0.5-TW, 1030-nm pulses in a series of simulations. Results show that a duration around 50 fs can provide the optimal LWFA results, as a compromise between the weak ponderomotive force available from a long pulse >100 fs and the depletion effect which can rapidly diminish a short pulse < 25 fs in a dense plasma. When a low laser peak power of 0.25 TW is available, the pulse depletion can be significant at a high target density and render LWFA ineffective. Using a laser pulse with a longer wavelength >2 μm represents a viable route to realize an efficient LWFA process driven by a 0.25-TW pulse.

Keywords: Laser Wakefield Accelerator, Self-Focusing Effect, Self-Modulation Effect, Particle-In-Cell Simulations