| In the last years several experiments demonstrated the possibility of accelerating ions through the interaction of an ultraintense sub picosecond laser pulse with a solid target. Ion sources development is interesting for its innovative applications in medicine, such as hadrontherapy and technology, as diagnostic for plasma radiography. We present here experimental measurements of backward accelerated proton emission, when a ultrashort kHz laser pulse (5 fs), with high temporal contrast (108), interacts with a thick solid target. Under this conditions proton spectra dependence from laser parameters, such as pulse energy and polarization, is studied. Afterwards also proton behavior with laser pulse length is investigated, stretching the pulse from 5 to 500 fs. 2D PIC simulations performed with the code CALDER, supporting experimental data, indicate that proton acceleration is driven by Brunel electrons, oscillating in the laser field. The investigation permits to understand better the dynamics of laser plasma interaction and, specifically, acceleration with ultrashort laser pulses. |
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