Multi-MeV Ion Production from High-Intensity Laser Interactions with Underdense Plasmas

Experiments were performed using high-power laser pulses (greater than 50 TW) focused into underdense helium, neon, or deuterium plasmas $({n}_{e}\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{19}{\mathrm{cm}}^{\ensuremath{-}3})$. Ions having energies greater than 300 keV were measured to be produced primarily at 90\ifmmode^\circ\else\textdegree\fi{} to the axis of laser propagation. Ion energies greater than 6 MeV were recorded from interactions with neon. Images of the ion emission were also obtained, and it is possible that spatially resolved measurements of the ion energy spectrum can provide a method to estimate the intensity of the focused radiation in the interaction region.