X-ray and particle generation from relativistic interaction of ultra-intense and ultra-short laser pulses with Titanium foils

In this report, we present the experimental results on the generation of X-ray emission and particle acceleration using high temporal contrast (∼10−9), ultra-short (∼30 fs), ultra-relativistic near-IR laser pulses interacting with Titanium thin foils for normal and 45º incidence angle geometry. Energy spectra of electrons and protons were measured from both the front and rear sides of the target together with the angular distribution of electron density behind the target. We observed ∼2× increase in the effective temperature of hot electrons for normal focusing condition in comparison to the 45∘ focusing on both the front and rear sides of the target. The measured spectra of protons ejected from the front and back sides of the target for different focusing conditions show a similar temperature (∼ 0.16 MeV), whereas the back-side protons are much hotter (∼ 0.5 MeV) and show a clear cut-off at ∼ 1.2 MeV. Additionally, measured X-ray spectra show that the line emissions from highly charged states like He-like and Li-like Titanium ions are much more intense for the case of normal focusing than for 45∘. These high charge states are clear evidence of having relatively hot and dense plasma. Our results are very promising in the advancement of laser nano-target interaction research field with a fundamental wavelength of Ti:Sapphire laser systems without frequency doubling temporal contrast enhancement in order to reach the ultra-relativistic and ultra-intense regime of interaction using terawatt-class lasers of only a few hundred milli-joules./span>