Extreme ultraviolet lasers and their interactions with matter

This work describes the generation and matter interactions of laser radiation with wavelengths between approximately 10 and 100 nanometres. The properties and dynamics of plasmas, created rapidly by photons of this wavelength range through the process of photoionization, are discussed here. A collisional-radiative model has been developed and used to simulate the ion populations in such plasmas and make comparisons with local thermodynamic equilibrium (LTE), which is frequently used to model dense plasmas. Despite the effects of rapid heating, due to the absorption of laser energy, and free electron degeneracy, due to the high densities, it is shown that LTE holds for such laser plasmas. Simulations predict that intense photoionizing radiation can cause a wavelike lowering of opacity to propagate through plasma. A number of experiments have been undertaken using a capillary discharge laser operating in neon-like argon, with a wavelength of 46.9 nanometres. Two focal geometries have been used to create plasmas at solid density: a Fresnel zone plate and a multilayer mirror. The focal intensity profiles in both cases have been modelled by a diffraction code, which closely matched micrographs produced in these experiments. The motion of laser-produced plasmas has been modelled by a 2-dimensional radiation-hydrodynamic code. These simulations were extended to 3 dimensions by a geometrical approach and compared to perforations made in thin targets. Laser experiments have allowed the viability of simultaneously generating and probing dense plasmas to be evaluated for both focusing geometries.