Laser-driven acceleration of quasi-monoenergetic, near-collimated titanium ions via a transparency-enhanced acceleration scheme

Abstract

Laser-driven ion acceleration has been an active research area in the past two decades with the prospects of designing novel and compact ion accelerators. Many potential applications in science and industry require high-quality, energetic ion beams with low divergence and narrow energy spread. Intense laser ion acceleration research strives to meet these challenges and may provide high charge state beams, with some successes for carbon and lighter ions. Here we demonstrate the generation of well collimated, quasi-monoenergetic titanium ions with energies ∼145 and 180MeV in experiments using the high-contrast (<10 −9 ) and high-intensity (6 10 W cm 20 2 -) Trident laser and ultra-thin (∼100 nm) titanium foil targets. Numerical simulations show that the foils become transparent to the laser pulses, undergoing relativistically induced transparency (RIT), resulting in a two-stage acceleration process which lasts until ∼2 ps after the onset of RIT. Such long acceleration time in the self-generated electric fields in the expanding plasma enables the formation of the quasimonoenergetic peaks. This work contributes to the better understanding of the acceleration of heavier ions in the RIT regime, towards the development of next generation laser-based ion accelerators for various applications.

The effects of laser pulse length and collisional ionization on the acceleration of titanium ions

“…This study is of particular relevance to the previous work of Li et al [67], which studied titanium foils irradiated by a 650 fs laser pulse length. The authors used nearidentical parameters to our longer pulse case studied here (a 0 = 20.82, τ FWHM = 650 fs), and assumed field ionization was the sole ionization mechanism.…”

Modeling and simulations of ultra-intense laser-driven bremsstrahlung with double-layer targets

“…However, thin (e.g. micrometric) converters usually undergo strong ionization [98]; hence, PIC simulations should more aptly simulate such scenarios. A complete model should adaptively comprise the effect of screening in the cross-section according to the charge state of ions.…”

Quasi mono-energetic heavy ion acceleration from layered targets

“…Another important point to be noted here is that majority of the reported studies are mainly focussed on lighter ions and, in comparison, studies of heavy-ion acceleration are rare. It is important to note here that recent experimental reports [18,19] suggest heavy ion acceleration using high-contrast, ultra-high intensity laser pulses with ultra-thin (10 -250 nm) metal foils. These results are explained on the basis of coulombic interactions during the expansion phase.…”