English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The Target Normal Sheath Acceleration (TNSA) regime for proton accelerationby laser pulses is experimentally consolidated and fairly well understood.However, uncertainties remain in the analysis of particle-in-cell (PIC)simulation results.  The energy spectrum is exponential with a cut-off, but the maximum energydepends on the simulation time, following different laws in two and threedimensional (2D, 3D) PIC simulations, so that the determination of anasymptotic value has some arbitrariness.  We propose two empirical laws for rise time of the cut-off energy in 2D and3D PIC simulations, suggested by a model in which the proton acceleration isdue to a surface charge distribution on the target rear side. The kineticenergy of the protons that we obtain follows two distinct laws, which appear tobe nicely satisfied by PIC simulations. The laws depend on two parameters: thescaling time, at which the energy starts to rise, and the asymptotic cut-offenergy.  The values of the cut-off energy, obtained by fitting the 2D and 3Dsimulations for the same target and laser pulse, are comparable. This suggeststhat parametric scans can be performed with 2D simulations, since 3D ones arecomputationally very expensive. In this paper, the simulations are carried outfor $a_0=3$ with the PIC code ALaDyn by changing the target thickness $L$ andthe incidence angle $\alpha$. A monotonic dependence, on $L$ for normalincidence and on $\alpha$ for fixed $L$, is found, as in the experimentalresults for high temporal contrast pulses.

Rise time of proton cut-off energy in 2D and 3D PIC simulations