Extreme ultraviolet diagnostics of preformed plasma in laser-driven proton acceleration experiments

Ragozin, E. N.*; Pirozhkov, A. S.; Yogo, Akifumi; Ma, J.-L.; Ogura, Koichi; Orimo, Satoshi; Sagisaka, Akito; Mori, Michiaki; Li, Z.*; Nishiuchi, Mamiko; Daido, Hiroyuki

Proton acceleration experiments involving a 5m thick Ti foil target irradiation are carried out with the femtosecond Ti:Sapphire laser JLITE-X. The plasma emission at 13.5 nm is recorded employing concave multilayer mirrors, which image the front- and rear-side plasmas onto the sensitive surfaces of a fast X-ray photodiode and a backside-illuminated CCD. Online time-of-flight fast-particle measurements are performed simultaneously with the XUV measurements. A strong correlation is observed between the energetic proton signal and the spatio-temporal behavior of the XUV plasma emission. In particular, the longer duration of the prepulse-produced XUV plasma emission indicates a lowering of the maximum proton energy. This allows using the XUV emission for the diagnostics of the high-intensity laser-solid-target interaction.