Optimization of 4.7-keV X-ray titanium sources driven by 100-ps laser pulses

An experiment with thin titanium foils irradiated by two pulses delayed in time is conducted on the Shenguang-II laser facility. A prepulse induces an underdense plasma, 2-ns later a main pulse (lambda(L) = 0.35 mu m, E-L approximate to 120 J, tau(L) approximate to 100 ps) is injected into the underdense plasma and produces strong line emission from the titanium K shell (i.e., He-alpha at 4.7 keV). Data show that the intensity of 4.7-keV X-ray emission with the prepulse is approximately twice more than without the prepulse, and can be used as a backlighting source satisfying the diagnostic requirements for dense plasma probing. High-quality plasma images are obtained with the backlighting 4.7-keV X-rays in a Rayleigh-Taylor hydrodynamic instability experiment.