Characterization of thin-foil preformed plasmas for high-intensity laser plasma interactions

Complete test of publication follows. High-intensity laser and thin foil interactions produce collimated particles, hard x-ray and high-order harmonics. In these cases, the preformed plasma plays an important role for interaction with the high-density thin-foil plasma. Therefore, it is necessary to characterize the preformed plasmas for generating the high-energy particles and x-ray radiations. In this experiment, we characterize the preformed plasmas produced by a high-intensity Ti:sapphire laser with a metal foil target and optimize the proton signals by changing the size of preformed plasma. We use a Ti:sapphire laser (JLITE-X) at the pulse duration of 250 fs. A p-polarized laser beam is transported into a target chamber. The incident beam is divided into pump and probe beams by a beam splitter. The pump beam is focused by an off-axis parabolic mirror with an F number of 13. The estimated peak intensity is up to ∼2 x 1017 W/cm2 with an energy of 220 mJ. The probe beam is frequency-doubled in a KDP crystal. The second harmonic probe beam passed through the target surface. A preformed plasma of 3 μm thick Ti foil target is observed by an interferometer. We simultaneously observe the proton signal with time of flight (TOF) proton measurement. The protons with the maximum energy of ∼900 keV is produced by controlling the size of preformed plasma. The characterization of preformed plasmas will significantly contribute to describe the relativistic-intensity laser thin-foil interactions for generation of high-energy particles as well as high-order harmonics.