The evolution of current-driven thin single Al wire plasmas was studied with soft X-ray shadowgraphy and interferometry using a very compact capillary discharge-driven λ=46.9 nm laser probe. Wires of 25 μm diameter excited by current pulses with a 78 A/ns increase rate were observed to expand uniformly at a rate of 3.5 μm/ns. In contrast, an increase in the rate of energy deposited per unit mass was observed to give rise to significant early plasma instabilities. The results illustrate the use of table-top soft X-ray lasers as a new tool for the diagnostics of dense pulse power driven plasmas.

Soft-x-ray laser interferograms of laser-created plasmas generated at moderate irradiation intensities (1 x 10(11)-7 x 10(12) W cm(-2)) with lambda=1.06 microm light pulses of approximately 13-ns-FWHM (full width at half maximum) duration and narrow focus (approximately 30 microm) reveal the unexpected formation of an inverted density profile with a density minimum on axis and distinct plasma sidelobes. Model simulations show that this strong two-dimensional hydrodynamic behavior is essentially a universal phenomena that is the result of plasma radiation induced mass ablation and cooling in the areas surrounding the focal spot.

Spectra of Nickel-like Cadmium (Cd XXI) ions in the 12.7–18.4 nm wavelength region obtained with a high current capillary discharge have been analyzed. Fifty-three 3d94p–3d94d and 3d94d–3d94f Cd XXI lines were identified with the assistance of calculations performed using the Slater–Condon method with generalized least-squares fits of the energy parameters. The average deviation between the measured and theoretical wavelengths is ⟨λexp - λth⟩ = 0.0065 nm. The results demonstrate that fast capillary discharges can produce high quality spectra for the study of multiply charged ions with charges of up to at least Z = 20.

We summarize results of several successful dense plasma diagnostics experiments realized by combining two different kinds of table-top soft x-ray lasers with an amplitude division interferometer based on diffraction grating beam splitters. In the first set of experiments this robust high throughput diffraction grating interferometer (DGI) was used with a 46.9 nm portable capillary discharge laser to study the dynamics of line focus and point focus laser-created plasmas. The measured electron density profiles, which differ significantly from those expected from a classical expansion, unveil important two-dimensional effects of the dynamics of these plasmas. A second DGI customized to operate in combination with a 14.7 nm Ni-like I'd transient gain laser was used to perform interferometry of line focus laser-created plasmas with picosecond time resolution. These measurements provide valuable new benchmarks for complex hydrodynamic codes and help bring new understanding of the dynamics of dense plasmas. The instrumentation and methodology we describe is scalable to significantly shorter wavelengths, and constitutes a promising scheme for extending interferometry to the study of very dense plasmas such as those investigated for inertial confinement fusion.

Spectra of Nickel-like Cadmium (CdXXI) ions in the 12.7-18.4 nm wavelength region obtained with a high current capillary discharge have been analyzed. Fifty-three 3d 9 4p-3d 9 4d and 3d 9 4d-3d 9 4f CdXXI lines were identified with the assistance of calculations performed using the Slater-Condon method with generalized least-squares fits of the energy parameters. The average deviation between the measured and theoretical wavelengths is hl explth i¼ 0:0065 nm. The results demonstrate that fast capillary discharges can produce high quality spectra for the study of multiply charged ions with charges of up to at least Z ¼ 20.

Emission at 13.2 nm from the 4d S-1(0) -4p P-1(1) laser transition of Ni-like Cd was observed in a cadmium vapor plasma column excited by a high-current capillary discharge. The dynamics of the plasma were studied using time-resolved soft x-ray pinhole images and hydrodynamic simulations. The pinhole images show that the plasma column maintains a good symmetry up to the time of maximum compression. Fifty-five Cd-XXI lines were identified in the 12.7-18.4 nm region with the assistance of calculations performed using the Slater-Condon method with generalized least-squares fits of the energy parameters.

We give an overview of recent capillary discharge-driven soft x-ray laser development experiments and applications at Colorado State University. We report the demonstration of the first desktop size soft x-ray laser, a capillary discharge Ne-like Ar soft x-ray laser that was measured to emit laser pulses with energy up to 10 muJ at 46.9 nm. In relation to the development of capillary discharge lasers at shorter wavelengths, spectra of the highly ionized cadmium plasmas identified strong emission from the 4d(1)S(0)- 4p(1)P(1) laser transition of Ni-like Cd at 13.16 nm. We have also demonstrated optical guiding of intense laser pulses in the plasmas of an Ar capillary discharge, a result that is of interest for the development of efficient longitudinally pumped collisional soft x-ray lasers in a gaseous media. In term of applications, we summarize our continued progress in establishing capillary discharge lasers as a compact soft x-ray source of coherent radiation for dense plasma diagnostics. The combination of a tabletop 46.9 nm capillary discharge Ne-like Ar laser and a Mach-Zehnder interferometer based on diffraction gratings was used to study two-dimensional hydrodynamic effects in laser-created plasmas. The short wavelength and high brightness of the capillary discharge soft x-ray laser allowed us to map the density profile up to similar to10(21) cm(-3), close to the critical density. The interferometry of laser-created plasmas created at moderate irradiation intensity (0.1 -7 x 10(12) W cm(-2)) shows the development of a concave electron density profile that differ significantly from that expected for a classical expansion. Measurements involving line-focus and spot-focus laser created plasmas and hydrodynamic model simulations confirm this two dimensional effect is essentially a universal effect that exists over a wide space of plasma parameters. In a separate experiments we have used the same soft x-ray laser interferometry tools to study the initial phase of the current-driven explosion of thin Al wires which are of current interest for the generation of x-ray radiation at large pulse power facilities. These measurements demonstrate the use of portable soft x-ray laser interferometry as a high-resolution tool for the study of high-density plasmas and for the validation of hydrodynamic codes.

We present results from soft x-ray laser interferometry/shadowgraphy of current-driven thin wire plasmas using a capillary discharge pumped 46.9 nm laser and a diffraction grating interferometer. We have obtained series of soft x-ray images of exploding Al wires 15 μm or 25 μm in diameter. The high photo-ionization cross sections of atoms and low charge ions at this wavelength allow the soft x-ray laser probe to detect the early stages of formation of a coronal plasma surrounding the wire core. Wires of 25 μm diameter excited by current pulses with a 78 A/ns increase rate are observed to expand uniformly. However, an increase in the rate of energy deposited per unit of mass is observed to give rise to significant instabilities. The simultaneous analysis of the fringe shift and soft x-ray absorption data suggests the coronal plasma contains a significant concentration of low Z impurities. The results illustrate that table-top soft x-ray lasers are a powerful new tool for the diagnostics of dense plasmas.

The advantages of using of table top x-ray lasers (XRLs) for different applications have been described. Examples of the first successful use of XRLs, the current efforts in applying them and the potential applications where an XRL can be used in future have been discussed. Modeling results showing the possibility of 3-4 times shorter wavelength capillary discharge x-ray lasers and calculated spectrum of Xe capillary EUV source are presented.

We report soft X-ray interferograms that illustrate the use of a very compact table-top soft X-ray laser in mapping the electron density evolution of a dense plasma. The spatial density distribution of a point-focus laser-created plasma with /spl sim/300 /spl mu/m dimension was measured for densities up to /spl sim/6.5 /spl times/ 10/sup 20/ cm/sup -3/.

It is long ago recognized that Z-pinches represent very natural medium for x-ray lasers (XRL) due to its favorable geometry and achievable high densities and temperatures. They also are very efficient x-ray sources. One of their variants, the capillary discharges, attracted attention of plasma physics researchers for almost two decades. It has been used for hot dense plasma formation and x-ray lasers [1,2], for transportation of laser beams and XUV radiation generation in x-ray lithography[3,4], for basic Z-pinch research and some others. The combination of efficiency, simplicity and low cost of capillary electrical discharges allowed to scale capillary x-ray lasers to table-top dimensions. In this paper we show the modeling results for next, 3–4 times shorter wavelength x-ray lasers. As an efficient x-ray source of line and continuum radiation it can be used for many practically important application in science and technology. In particular, the capillary discharge can appear as powerful potential candidate for emerging XUV microlithography. We present here the results of numerical modeling of spectra and density of Xe EUV source which involved plasma heating and dynamics, detailed atomic kinetics and radiation transport and material ablation physics.

Soft x-ray laser interferogramis of laser-created plasmas generated at moderate irradiation intensities (1 x 10(11) - 7 x 10(12) W cm(-2)) with lambda = 1.06 mum light pulses of similar to13 ns FWHM duration and narrow. focus (similar to30 mum) reveal the unexpected formation of an inverted density profile with a density minimum on axis and distinct plasma sidelobes. Model simulations show that this strong 2-dimensional hydrodynamic behavior is essentially a universal phenomenon that is the result of plasma radiation induced mass ablation and cooling in the areas surrounding the focal spot. These measurements, which mapped plasma densities up to 0.9 x 10(21) cm(-3), demonstrate the use of a portable soft x-ray laser interferometer as a high resolution tool for the study of high density plasma phenomena and the validation of hydrodynamic codes.

We report progress in soft X-ray interferometry of dense plasmas using a very compact 46.9 nm discharge-pumped laser. Soft X-ray interferograms of /spl sim/300 /spl mu/m dimension plasmas generated by /spl sim/0.6 J pulses from a Nd:YAG laser focused into a <30 /spl mu/m diameter spot were recorded and analyzed. The spatial density distribution of the plasma was measured for densities up to /spl sim/6.5/spl times/10/sup 20/ cm/sup -3/.

We report an extension of previous table-top soft x-ray laser interferometry work to plasma densities approaching the critical density. The evolution of line-focus and spot-focus plasmas created with Nd-YAG laser intensities of 0.1 and 7.0 TW/cm(2) respectively were studied utilizing a 46.9nm capillary discharge laser with a diffraction grating interferometer. In the later case, the electron density was mapped to values Up to 0.9x10(21) cm(-3) ( 90% of the critical density for the lambda=1.06mum pump laser). The interferograms show the development of concave electron density profiles with a minimum on axis and pronounced side lobes. Hydrodynamic model simulations show that the concave profile is the result of the hydrodynamic and radiation effects that enlarge the ablated target area. The measurements exemplify how soft x-ray lasers can be used to probe high density plasmas for the validation of hydrodynamic codes.