Scaling laws for laser-driven ion acceleration from nanometer-scale ultrathin foils

Abstract

Laser-driven ion acceleration has attracted global interest for its potential towards the development of a new generation of compact, low-cost accelerators. Remarkable advances have been seen in recent years with a substantial proton energy increase in experiments, when nanometer-scale ultrathin foil targets and high-contrast intense lasers are applied. However, the exact acceleration dynamics and particularly the ion energy scaling laws in this novel regime are complex and still unclear. Here, we derive a scaling law for the attainable maximum ion energy from such laser-irradiated nanometer-scale foils based on analytical theory and multidimensional particle-in-cell simulations, and further show that this scaling law can be used to accurately describe experimental data over a large range of laser and target parameters on different facilities. This provides crucial references for parameter design and experimentation of the future laser devices towards various potential applications.

On the control of electron heating for optimal laser radiation pressure ion acceleration

“…2018; Shen et al. 2021). Other significant challenges include the mitigation of corrugations at the laser–target interaction surface arising due to instabilities (Palmer et al.…”

“…An important difficulty relies on the requirement of low electron heating for efficient momentum transfer from the laser to the ions, and to avoid other competing ion acceleration mechanisms, such as TNSA and CSA, to develop and dominate. Indeed, recent experiments producing nearly 100 MeV proton beams likely involved the combination of different acceleration schemes and the observed energy spectra were broad (Kim et al 2016;Wagner et al 2016;Higginson et al 2018;Shen et al 2021). Other significant challenges include the mitigation of corrugations at the laser-target interaction surface arising due to instabilities (Palmer et al 2012;Eliasson 2015;Sgattoni et al 2015;Wan et al 2020;Chou et al 2022) and finite laser spot effects (Klimo et al 2008;Dollar et al 2012) and the control of the preplasma level that is naturally formed from the preheating and expansion of the target by a laser prepulse, which poses significant constraints on the laser contrast (Varmazyar, Mirzanejhad & Mohsenpour 2018).…”

Proton acceleration from picosecond-laser interaction with a hydrocarbon target

“…In RPA, the radiation pressure of an intense laser pushes forward the affected electrons of a dense target, producing a local charge-separation field that drives forward the target ions. Under suitable conditions, in RPA very energetic fast electrons can also propagate through the target and form behind it a chargeseparation field for TNSA of the backside ions [19][20][21][22][23][24][25][26][27][28]. That is, ions can be multiply accelerated by the dual-peaked charge-separation field: RPA at the target front and TNSA at the target back.…”

On the control of electron heating for optimal laser radiation pressure ion acceleration

“…An important difficulty relies on the requirement of low electron heating for efficient momentum transfer from the laser to the ions, and to avoid other competing ion acceleration mechanisms, such as TNSA and CSA, to develop and dominate. Indeed, recent experiments producing nearly 100 MeV proton beams likely involved the combination of different acceleration schemes and the observed energy spectra were broad Wagner 2016;Higginson 2018;Shen et al 2021). Other significant challenges include the mitigation of corrugations at the laser-target interaction surface arising due to instabilities (Palmer 2012;Eliasson 2015;Sgattoni et al 2015;Wan et al 2020;Chou et al 2022) and finite laser spot effects (Klimo et al 2008;Dollar 2012)and the control of the pre-plasma level that is naturally formed from the pre-heating and expansion of the target by a laser pre-pulse, which poses significant constraints on the laser contrast (Varmazyar et al 2018).…”