Characteristics of a Sub-Picosecond Titanium Kα Source Using Relativistically Intense Lasers

In this chapter, the microscopic characteristics of a bright, short-pulsed source of Ti Kα radiation are studied. This x-ray emission is generated from fast electrons that are generated when a relativistically intense laser pulse interacts with a solid metal surface. The electrons have average energies significantly exceeding the ionization threshold of the K-shell (5 keV) and give rise to K-radiation when the K-shell recombines with a lifetime of a few femtoseconds only. Hence the duration of the Kα emission is dominantly determined by the time these fast electrons are present. But at the same time, the electrons also generate a solid-density plasma state at several tens of electronvolts temperature (e.g., several 100 000 K). This alters the emission probabilities of the Kα source, potentially effecting the brightness of the x-ray source. These mechanisms and possible optimizations are subject of this chapter.