Prepulse dependence of X-ray emission from plasmas created by IR femtosecond laser pulses on solids

Abstract

We report a strong prepulse dependence of the emission of X-rays from plasmas created by 150 fs Ti:sapphire laser pulses on solids. The laser pulses were focused onto plane samples of aluminium and vanadium with a main pulse power density of about . By splitting off a portion of the main pulse we were able to generate a prepulse whose delay and intensity were variable relative to the main pulse. With no prepulse, very weak X-ray radiation from and was observed, whereas a prepulse to main pulse ratio of more than 0.1% and the prepulse preceding the main pulse by more than 2 ns produced up to 50 times stronger X-ray output.

A broadband laser plasma x-ray source for application in ultrafast chemical structure dynamics

“…A specific consequence of these ongoing developments is that the present studies have enjoyed unusually low levels of prepulses and ASE pedestals ͑Ͻ10 −8 contrast ratio͒, both of which critically affect x-ray production in laser plasma sources. 26,27 Key matters related to these aspects of the temporal quality of the laser beam are the temporal structure of the x-ray generation, optimal target interaction geometry, and the production of energetic electron beams. Associated maximum energies available to our experiments have varied from ϳ40 to ϳ 300 mJ/pulse, while shot to shot stability is obtained by gain depletion in the final multipass amplifier stage.…”

Spatial distribution of soft x-ray line emissions from aluminum plasma excited by a pair of femtosecond-laser pulses

“…1,2 Of these sources, a thermal plasma source emits continuum x rays as a result of plasma recombination and bremsstrahlung radiation along with line emissions caused by the transitions of excited ions. [6][7][8][9][10][11][12] Preformed plasma is created as an absorber of the main pulse, and the plasma density and the density gradient are changed by controlling the pulse-separation time. 3-5 These x-ray sources have been extensively studied and particular attention has been paid to their pulse duration and enhancement of their emission with a view to using them as diagnostic tools for material dynamics.…”