Cesar H. Moreno

Operation and output pulse characteristics of an extremely compact capillary-discharge tabletop soft-x-ray laser

We report on the operating parameters and laser output pulse characteristics of an extremely compact discharge-pumped 46.9-nm laser of a size comparable with that of many widely utilized visible and ultraviolet gas lasers. This capillary-discharge laser generated subnanosecond laser pulses with energies of as much as 25microJ by single-pass amplification in an 18.6-cm-long argon-plasma column. Measurements of the laser output energy, pulse width, far-field beam profile, and beam divergence are reported.

Soft-x-ray laser interferometry of a plasma with a tabletop laser and a Lloyd's mirror.

We report what is believed to be the first demonstration of soft-x-ray interferometry of a plasma with a tabletop soft-x-ray laser. A Lloyds mirror interferometer was used in combination with a very compact lambda = 46.9 nm capillary-discharge-pumped laser to map the electron density in the cathode region of a pinch plasma.

Lasing in Ne-like S and other new developments in capillary discharge ultrashort wavelength lasers

We report our most recent progress in the development of capillary discharge soft x-ray lasers. This includes the first observation of discharge-pumped ultrashort wavelength lasing in a material that is solid at room temperature (S), and preliminary results of discharges in Ca. Excitation by a capillary discharge of S vapor generated by discharge ablation of a solid target resulted in amplification in Ne-like S at 60.8 nm with a gain-length product of 7.5. Overheating of the electron temperature respect to steady-state ionization conditions and transient population effects significantly increased the gain above the steady state-value. The results of two-dimensional near-field and far-field imaging of a saturated table-top Ne-like Ar laser and the measurement of its spatial coherence as a function of amplifier length are also reported and compared with model calculations. The generation of a capillary discharge plasma waveguide is to be used in combination with ultrashort pulse laser excitation for the generation of a new kind of efficient collisional soft x- ray laser is discussed.

Shadowgrams of a dense micro-capillary plasma obtained with a table-top soft X-ray laser

A sequence of high resolution shadowgrams that map the evolution of the plasma of a 380 /spl mu/m diameter microcapillary discharge was obtained using a very compact 46.9 nm laser. These images are the first plasma diagnostics data obtained using a table-top soft X-ray laser.

Plasma diagnostics with a tabletop soft x-ray laser

We discuss the first demonstrations of plasma diagnostics using a tabletop soft x-ray laser. A very compact capillary discharge pumped Ne-like Ar laser operating 46.9 nm was used to perform shadowgraphy and interferometry experiments in discharge-created discharge plasma waveguide. In a second set of experiments we took advantage of the good spatial coherence of the capillary discharge laser to perform soft x-ray interferometry measurements. In a first experiment the laser was used in combination with a simple wavefront division interferometer based on Lloyds mirror to map the electron density distribution in the cathode region of a pinch discharge. In our most recent experiment we used an amplitude division interferometer, which utilizes diffraction grating as beam splitters, to probe a large scale laser-created plasma. Both interferometer schemes can be adapted to operate at the wavelength corresponding to any of the presently available saturated soft x-ray lasers.

Demonstration of a 1 mW average power, 7 Hz table-top soft X-ray laser

Summary form only given. Important motivations for the development of high average power table-top sources of coherent soft X-ray radiation can be found in applications belonging to several disciplines of science and technology. To date, the leading sources of high average power coherent soft X-ray radiation have been undulators in modern storage rings, so-called third generation synchrotrons. High average power beams of soft X-ray coherent radiation can in principle also be generated with much more compact devices using either nonlinear optical techniques for frequency up-conversion of optical laser radiation, or the direct amplification of spontaneous emission in a plasma (an X-ray laser). Soft X-ray lasers have the advantage of a high energy per pulse and therefore the potential to produce very high average power. Soft X-ray lasers pumped by large optical lasers of the type used in fusion research have generated output pulse energies of up to several mJ but are limited to a repetition frequency of only a few pulses per hour at best. We report a 2 to 3 orders of magnitude increase in the average power of table-top soft X-ray lasers.

Plasma probing with a table-top soft X-ray laser

Summary form only given. Due to their short wavelength, high brightness, and good spatial coherence soft X-ray lasers are excellent sources for the diagnostics of dense plasmas. We report the demonstration of plasma imaging and interferometry using a very compact table-top soft X-ray laser. A capillary discharge pumped 46.9 nm laser was used to obtain a sequence of high resolution shadowgrams of the plasma of a microcapillary discharge (380 /spl mu/m diameter, 8 mm long evacuated channel in polyacetal excited by a /spl sim/1.5 kA peak amplitude current pulse of 155 ns duration). The plasma was illuminated on-axis with the soft X-ray laser, and was imaged with 24/spl times/ magnification into an MCP/CCD detector using a 60 cm radius of curvature concave mirror coated with an iridium film. The plasma is observed to rapidly evolve from a nonuniform plasma into a remarkably uniform plasma column with minimum density on axis. These measured plasma characteristics confirm the excellent properties of these discharges as waveguides for laser radiation.

Plasma diagnostics using a tabletop soft x-ray laser: demonstration of shadowgraphy and interferometry using a Lloyd's mirror

We report the first demonstration of plasma imaging and interferometry using a tabletop soft x-ray laser. A very compact capillary discharge Ne-like Ar laser operating at 46.9 nm was used as a backlighter to study the evolution of the plasma of a micro-capillary discharge. The resulting series of shadowgrams show the plasma created by ablation of the walls of the evacuated micro-capillary rapidly evolves from a non-uniform initial state into a symmetric column with minimum density on axis. In a second experiment we took advantage of the good spatial coherence of the capillary discharge laser to perform interferometry measurements in the plasma of a pinch discharge. In this experiment the laser was used in combination with a wavefront division interferometer based on Lloyds mirror to map the electron density distribution in the cathode region of the discharge.

Tabletop soft x-ray lasers by fast discharge excitation

We review the progress in the development of ultrashort- wavelength lasers based on discharge excitation. The observation of large soft x-ray amplification in Ne-like Ar at 46.9 nm in a capillary discharge created plasma [Phys. Rev. Lett. 77, 1476, (1996)] have opened a new path for the development of compact and practical soft x-ray lasers. These results have shattered the earlier perception that discharge- created plasmas are insufficiently stable and uniform for soft x-ray lasing. We report results of a detailed characterization of the capillary discharge Ne-like Ar laser, that include near-field and far-field images of the laser output and the measurement of its spatial coherence. The recent demonstration of lasing in Ne-like S at 60.8 nm in material ablated from a solid target by a discharge is also discussed.

Two-dimensional near-field and far-field imaging of a Ne-like Ar capillary discharge table-top soft X-ray laser

We have performed systematic measurements and numerical modeling of the divergence and exit beam size of a 46.9 nm Ne-like Ar capillary discharge pumped soft-x-ray amplifier. Two-dimensional near-field and far-field measurements were obtained over a wide range of discharge parameters. The spot size and divergence of the laser beam were observed to increase significantly with decreasing discharge pressure. Simultaneously, the beam intensity distribution changed from a single peak pattern to an annular profile. These effects are shown to be the result of increased refraction of the soft-x-ray beam, caused by larger density gradients in the plasma columns of the lower pressure discharges. The spatial images are nearly cylindrically symmetric, and have less structure than those reported in the literature for laser-driven soft-x-ray lasers. Beam profiles synthesized by model calculations are found to be in good agreement with the recorded images. The obtained images in combination with the model computations clarify the origin of the different beam patterns that are observed in capillary discharge soft-x-ray laser experiments. @S1050-2947 ~98!09208-7#