University of California, San Diego La Jolla United States
The project State-of-the-art high-flux mono-energetic ion sources driven by ultra-intense laser pulses has made significant progress in the completion of project goals outlined in the original proposal. First, the effects of the laser parameters were examined using both the Hercules and T-cubed lasers at the University of Michigan. This information was crucial to understand how the laser energy is coupled to thin targets, which this project utilizes for the production of ion beams, when ultra-short pulses at high intensity with ultrahigh contrast conditions are used. This work showed that relatively high reflectivities of laser light are achievable at the typically used laser intensities, which is important when plasma mirrors are used to enhance the laser pulse contrast. The effects of surface limited targets on electron dynamics were also examined. This portion of the work also found that smaller surface areas can limit the sheath field development to a localized area, and therefore increase the strength of this accelerating field. Stronger sheath fields then enhance the acceleration of ions. Second, a weak departure from the TNSA ion acceleration mechanism, attributed to contributions by the RPA mechanism, was observed in experiments utilizing the Hercules laser. These experiments showed the production of high-charge-state ion beams with high energy per nucleon, high maximum energy, and narrow energy band concentration when thin sub-micron thickness foil targets were used. This work demonstrated the predictive capabilities of the collaboration through the use of the particle-in-cell PIC codes EPOCH, while also providing important information for the benchmarking of the codes.