Two-dimensional effects in laser-created plasmas measured with soft-x-ray laser interferometry

Dynamics characteristics of highly-charged ions in laser-produced SiC plasmas

The radiation and dynamic properties of C VI, C V, Si VI and Si V ions from laser-produced SiC plasmas in a vacuum are studied both experimentally and theoretically. The EUV emission spectra of SiC plasmas are measured using the spatio-temporally resolved laser-produced plasma spectroscopy technique. To explore the dynamic evolution of highly-charged ions in such plasmas, an extended radiation hydrodynamics model is developed. The comparison of theoretical and experimental time-space evolved spectral profiles provides the temporal evolution of plasma temperature and electron density, the distribution of various transient ions and their velocities. The results show that the present radiation hydrodynamics model for a multi-element target reflects the dynamic evolution processes of their laser-produced plasmas, which make it an effective tool for plasma diagnostics.

Design of a phase-shifting interferometer in the extreme ultraviolet for high-precision metrology

The design of a phase-shift interferometer in the extreme ultraviolet (EUV) is described. The interferometer is expected to achieve a significantly higher precision as compared with similar instruments that utilize lasers in the visible range. The interferometer's design is specifically adapted for its utilization with a table top pulsed capillary discharge EUV laser. The numerical model evaluates the errors in the interferograms and in the retrieved wavefront induced by the shot-to-shot fluctuations and pointing instabilities of the laser.

Prediction and observation of tin and silver plasmas with index of refraction greater than one in the soft x-ray range

We present the calculated prediction and the experimental confirmation that doubly ionized Ag and Sn plasmas can have an index of refraction greater than one for soft x-ray wavelengths. Interferometry experiments conducted using a capillary discharge soft x-ray laser operating at a wavelength of confirm that in few times ionized laser-created plasmas of these elements the anomalous dispersion from bound electrons can dominate the free electron contribution, making the index of refraction greater than one. The results confirm that bound electrons can strongly influence the index of refraction of numerous plasmas over a broad range of soft x-ray wavelengths confirming recent observations. The understanding of index of refraction at short wavelengths will become even more essential during the next decade as x-ray free electron lasers will become available to probe a wider variety of plasmas at higher densities and shorter wavelengths.

Observation of a multiply ionized plasma with index of refraction greater than one

We present clear experimental evidence showing that the contribution of bound electrons can dominate the index of refraction of laser-created plasmas at soft x-ray wavelengths. We report anomalous fringe shifts in soft x-ray laser interferograms of Al laser-created plasmas. The comparison of measured and simulated interferograms shows that this results from the dominant contribution of low charge ions to the index of refraction. This usually neglected bound electron contribution can affect the propagation of soft x-ray radiation in plasmas and the interferometric diagnostics of plasmas for many elements.

Picosecond-resolution soft-x-ray laser plasma interferometry

We describe a soft-x-ray laser interferometry technique that allows two-dimensional diagnosis of plasma electron density with picosecond time resolution. It consists of the combination of a robust high-throughput amplitude-division interferometer and a 14.7-nm transient-inversion soft-x-ray laser that produces approximately 5-ps pulses. Because of its picosecond resolution and short-wavelength scalability, this technique has the potential for extending the high inherent precision of soft-x-ray laser interferometry to the study of very dense plasmas of significant fundamental and practical interest, such as those investigated for inertial confinement fusion. Results of its use in the diagnostics of dense large-scale laser-created plasmas are presented.