Path-integrated electrostatic energization in laser-driven collisionless cylindrical convergence

Abstract

Collisionless converging ion flows can sustain particle energization over an extended path, but the field channel responsible for the energy gain is not always identifiable. In laser-driven bladed microtube implosion, energetic carbon ions were previously observed alongside a self-generated gigagauss-class axial magnetic field [D. Pan and M. Murakami, Phys. Plasmas 32, 072107 (2025)], leaving the origin of their energization unresolved. Using two-dimensional particle-in-cell simulations, field-particle power decomposition and trajectory-resolved work accounting show that radial electrostatic work accumulated along the converging path supplies more than 98% of the net in-plane electric work, whereas the azimuthal channel associated with the time-varying magnetic field remains subdominant. The peak local mean ion energy factorizes, to good approximation, into an incident-flow contribution controlled by laser intensity and a geometric enhancement that grows approximately linearly with the inner radius because ions accumulate electrostatic work over a longer convergence path. The path-averaged radial electric field $\langle E_r\rangle$ scales with the peak laser intensity $I_L$ as $\langle E_r\rangle \propto I_L^{0.47}$, favoring a geometry-pinned, comoving charge-separation structure over Debye-limited scaling. The peak local mean carbon-ion energy reaches 0.89 GeV. A smooth-cylinder control exhibits comparable peak energization, showing that blade modulation mainly affects poststagnation ion residence rather than the energy source.