Simultaneous imaging of K-α radiation and coherent transition radiation from relativistic-intensity laser-irradiated solid target plasmas

摘要

Laser acceleration of hot electrons and their transport through 12-32 μm thick Ti foils was explored experimentally using two complementary diagnostics, a bent crystal imaging the Ti K _α emission and optical imaging of the coherent transition radiation (CTR) produced by the exit of the hot electrons from the foil. The spatial extent of the hot electron production measured by these two diagnostics is dramatically different. Electrons producing CTR emerge in a spot of less than 7 μm and appear to maintain a high degree of collimation during transport through the foil while electrons that produce K _α emission appear to diverge to sizes of 50-100 μm as viewed from the back surface of the foil. These results indicate that there is a large difference in the transport of the highest energy electrons contributing to CTR signal as compared with the bulk of the hot electron population generating K _α signal.