Čerenkov radiation diagnostics of hot electrons generated by fs-laser interaction with solid targets

A new method of diagnostics of hot electrons from a laser-produced plasma is experimentally demonstrated. Titanium-sapphire laser pulses (1$\un{J}$/130$\un{fs}$) irradiate copper foils backed by a dielectric. The energy distribution and direction of the hot electrons generated is determined by recording visible Čerenkov radiation with spatial resolution. The results demonstrate a change in the electron generation mechanism at relativistic intensities