Soft X-ray: High harmonic generation from ions in a capillary discharge plasma waveguide

The production of higher photon flux at shorter soft X-ray wavelengths is an important goal in the development of high harmonic generation (HHG) as a light source. The highest energy photons are generated from target atoms that ionize at high laser intensities since HHG is the result of ionization of the nonlinear medium followed by rapid acceleration of the electron in the light field. A capillary discharge creates an ideal medium for HHG from ions by providing a preformed plasma waveguide with tunable density and ionization. The presence of the discharge reduces phase modulation of the driving laser and increases the laser intensity available for harmonic generation. Use of a capillary discharge plasma as a medium for high harmonic generation shows significant increase in harmonic flux and extends efficient harmonic generation to shorter wavelengths.