Shock shell formation in the Coulomb explosion of hollow nanospheres

Abstract

Techniques in ion acceleration to generate relativistic high-energy ions have been developed with applications in proton therapy and laboratory astrophysics. Laser-driven Coulomb explosion (CE) is a method of ion acceleration that involves the expulsion of electrons due to the transfer of excess energies. During the CE of ion mixtures, fast ions conglomerate at the outermost layer of the expanding sphere, generating a shock. In this paper, we explore the shock dynamics of the CE of hollow targets with varying cavity size and number density ratios of slow and fast ions. By decomposing the sphere into thin shells, and utilizing the leapfrog algorithm, we simulated the CE dynamics and analyzed the resulting ion density profiles and ion energy spectra. Our results revealed that introducing a cavity in the spherical targets lessens the maximum energy acquired by the fast ions. Additionally, no shocks form at sufficiently low slow-to-fast ion ratios.