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Capillary discharge extreme ultraviolet lasers. [Colorado State Univ. , Ft. Collins]

Description: The project objective is to explore the generation of soft X-ray laser radiation in a plasma column created by a fast capillary discharge. The proposed capillary lasing scheme offers the potential for compact, simple and efficient soft X-ray laser sources. For this purpose a compact, fast pulse generator which produces 100 kA current pulses with a risetime of 11 ns was constructed. Initial experiments were conducted in evacuated capillaries, in which the plasma is produced by ablation of the capillary walls. The soft X-ray emission from discharges in polyethylene capillary channels was studied to investigate the possibility of amplification in the 3-2 transition of C VI, at {lambda} = 18.2 nm. Time-resolved spectra in which this transition appears anomalously intense with respect to the 4--2 transition of the same ion were obtained. To date, however, this phenomenoa could not be confirmed as gain, as the intensity of the 18.2 nm line has not been observed to increase exponentially as a function of the capillary length. Encouraging results were obtained by fast pulse discharge excitation of capillaries filled with preionized gas. High temperature (Te > 150 eV), small diameter ({approximately}200 {mu}m) plasma columns were efficiently generated. Fast current pulse excitation of a selected low mass density of uniformly preionized material Mag the capillary was observed to detach rapidly the plasma from the capillary walls, and form a plasma channel of a diameter much smaller and significantly hotter than those produced by a similar current pulse in evacuated capillaries of the same size. Discharges in argon-filled capillaries at currents between 20 and 60 kA produced plasmas with ArX-Ar{sub XIV} line emission, and with spectra that are similar to those of plasmas generated by > I MA current implosions in large pulsed power machines. The characteristic of these plasmas approach those necessary for ...
Date: August 1, 1992
Creator: Rocca, J.J.
Partner: UNT Libraries Government Documents Department

Ion Beam Deposition of (NbTa)2O5/SiO2 Multilayers for High-Efficiency Dielectric Gratings for High Average Power Laser Systems Operating at 800 nm Central Wavelength

Description: The ion beam deposition of (NbTa)2O5 has been investigated for realizing high reflectance multilayer stacks of high damage threshold for applications in the engineering of dielectric gratings for use at 800 nm. Deposition conditions were optimized to yield fully oxidized films as determined from x-ray photoelectron spectroscopy (XPS). The film properties were also investigated using spectroscopic ellipsometry, and spectrophotometry to determine their refractive index and thickness respectively. Damage threshold testing was performed on single films using an amplified Ti:Sapphire laser producing a train of 170 ps pulses at a wavelength of 800 nm with an average energy of 100 mJ. The laser output was focused at the surface of the samples via a 0.5 m focal length lens to generate fluences ranging from 0 to 9 J/cm{sup 2}. At the optimum deposition conditions for highest optical quality and damage threshold, high reflector stacks of (NbTa){sub 2}O{sub 5}/SiO2 were fabricated. These stacks were employed to fabricate dielectric gratings with 1740 l/mm for use with 800 nm light. At an input angle of 8{sup o} from Littrow and a wavelength from 770 to 830 nm, >90% diffraction efficiency is achieved, with peak diffraction efficiency of >97%. The demonstration of dielectric gratings at 800 nm is opening the pathway to significantly increase the power handling capabilities of grating compressors for picosecond and femtosecond chirped pulse amplifications systems.
Date: June 2, 2006
Creator: Menoni, C S; Patel, D; Brizuela, F; Rocca, J J; Nguyen, H T & Britten, J A
Partner: UNT Libraries Government Documents Department

High-Efficiency 800 nm Multi-Layer Dielectric Gratings for High Average Power Laser Systems

Description: We report on the design, fabrication, and performance of a 1740 l/mm multilayer dielectric diffraction grating for use with 800 nm light. At an input angle of 8{sup o} from Littrow and a wavelength from 770 to 830 nm, >90% diffraction efficiency is achieved, with peak diffraction efficiency of >97% at 800nm. We will also comment on laser damage threshold and power-handling properties.
Date: June 15, 2006
Creator: Nguyen, H T; Britten, J A; Patel, D; Brizuela, F; Rocca, J J & Menoni, C S
Partner: UNT Libraries Government Documents Department

Plasma Interactions in Laser Irradiated Semi-Cylindrical Cavities Studied with Soft X-Ray Interferometry Using a Capillary Discharge Laser

Description: Soft x-ray interferometry was used to measure the evolution of dense converging plasmas created by laser irradiation of 500 {micro}m diameter semi-cylindrical carbon targets. Optical laser pulses with an intensity of {approx} 1 x 10{sup 12} W cm{sup -2} and 120 ps duration were used to heat the surface of the cavities. The dense plasma formed expands from the walls converging slightly off the semi-cylinder's axis, giving rise to a bright localized high density plasma region. A sequence of electron density maps were measured using a 46.9 nm wavelength tabletop capillary discharge soft x-ray laser probe and a amplitude division interferometer based on diffraction gratings. The measured density profiles are compared with simulations conducted using the multi-dimensional hydrodynamic code HYDRA. The benchmarked model was then used to simulate particle trajectories which reveal that the increase in electron density near the axis is mainly the result of the convergence of plasma that originated at the bottom of the groove during laser irradiation.
Date: September 19, 2007
Creator: Purvis, M A; Grava, J; Filevich, J; Marconi, M; Rocca, J J; Moon, S J et al.
Partner: UNT Libraries Government Documents Department

Plasma conditions for improved energy coupling into the gain region of the Ni-like Pd transient collisional x-ray laser

Description: We have directly probed the plasma conditions in which the Ni-like Pd transient collisional x-ray laser is generated and propagates by measuring the near-field image and by utilizing picosecond resolution soft x-ray laser interferometry of the preformed Pd plasma gain medium. The electron density and gain region of the plasma have been determined experimentally and are found to be in good agreement with simulations. We observe a strong dependence of the laser pump-gain medium coupling on the laser pump parameters. The most efficient coupling of laser pump energy into the gain region occurs with the formation of lower density gradients in the pre-formed plasma and when the duration of the main heating pulse is comparable to the gain lifetime ({approx}10ps for mid-Z Ni-like schemes). This increases the output intensity by more than an order of magnitude relative to the commonly utilized case where the same pumping energy is delivered within a shorter heating pulse duration (< 3ps). In contrast, the higher intensity heating pulses are observed to be absorbed at higher electron densities and in regions where steep density gradients limit the effective length of the gain medium.
Date: October 4, 2004
Creator: Smith, R F; Dunn, J; Filevich, J; Moon, S; Nilsen, J; Keenan, R et al.
Partner: UNT Libraries Government Documents Department

Soft X-Ray Laser Interferometry of Colliding Laser-Created Plasmas in Semi-Cylindrical Cavities

Description: A table-top capillary discharge soft x-ray laser was used to acquire high contrast interferograms that map the evolution of dense aluminum plasmas created by laser irradiation of a 500 {micro}m diameter semi-cylindrical cavity with 120 ps optical laser pulses of {approx}1.1 x 10{sup 12} Wcm{sup -2} peak intensity. The measured electron density maps, that were compared with simulations, show that the plasma converges on axis, where it collides to form a localized region with density exceeding 1 x 10{sup 20} cm{sup -3}.
Date: December 10, 2007
Creator: Purvis, M. A.; Grava, J.; Filevich, J.; Marconi, M.; Dunn, J.; Moon, S. J. et al.
Partner: UNT Libraries Government Documents Department

Spatial coherence measurements of a 13.2 nm transient nickel-likecadmium soft x-ray laser pumped at grazing incidence

Description: We report the experimental confirmation of the production of element 110. In the bombardment of a {sup 208}Pb target with a 309 MeV {sup 64}Ni beam, we have observed two chains of time- and position-correlated events. Each chain consisted of the implantation of an evaporation residue followed by the emission of {alpha}-particles. We attribute these two chains to the decay of {sup 271}110 produced with a cross section of 8.3{sup +11}{sub -5.3} pb.
Date: September 27, 2006
Creator: Lui, Y.; Wang, Y.; Larotonda, M.A.; Luther, B.M.; Rocca, J.J. & Attwood, D.T.
Partner: UNT Libraries Government Documents Department

Dynamics of Converging Laser-Created Plasmas in Semi-Cylindrical Cavities Studied using Soft X-Ray Laser Interferometry

Description: The evolution of dense aluminum and carbon plasmas produced by laser irradiation of 500 {micro}m diameter semi-cylindrical targets was studied using soft x-ray laser interferometry. Plasmas created heating the cavity walls with 120 picosecond duration optical laser pulses of {approx} 1 x 10{sup 12} W cm{sup -2} peak intensity were observed to expand and converge on axis to form a localized high density plasma region. Electron density maps were measured using a 46.9 nm wavelength tabletop capillary discharge soft x-ray laser probe in combination with an amplitude division interferometer based on diffraction gratings. The measurements show that the plasma density on axis exceeds 1 x 10{sup 20} cm{sup -3}. The electron density profiles are compared with simulations conducted using the hydrodynamic code HYDRA, which show that the abrupt density increase near the axis is dominantly caused by the convergence of plasma generated at the bottom of the groove during laser irradiation.
Date: September 19, 2007
Creator: Purvis, M A; Grava, J; Filevich, J; Marconi, M; Dunn, J; Moon, S J et al.
Partner: UNT Libraries Government Documents Department

High repetition rate collisional soft x-ray lasers based on grazing incidence pumping

Description: We discuss the demonstration of gain-saturated high repetition rate table-top soft x-ray lasers producing microwatt average powers at wavelengths ranging from 13.9 to 33 nm. The results were obtained heating a pre-created plasma with a picosecond optical laser pulse impinging at grazing incidence onto a pre-created plasma. This pumping geometry increases the energy deposition efficiency of the pump beam into the gain region, making it possible to saturate soft x-ray lasers in this wavelength range with a short pulse pump energy of only 1 J at 800 nm wavelength. Results corresponding to 5 Hz repetition rate operation of gain-saturated 14.7 nm Ni-like Pd and 32.6 nm line Ne-like Ti lasers pumped by a table-top Ti:sapphire laser are reported. We also discuss results obtained using a 1 {omega} 1054 nm pre-pulse and 2{omega} 527 nm short pulse from a Nd:glass pump laser. This work demonstrates the feasibility of producing compact high average power soft x-ray lasers for applications.
Date: November 18, 2005
Creator: Luther, B M; Wang, Y; Larotonda, M A; Alessi, D; Berrill, M; Rocca, J J et al.
Partner: UNT Libraries Government Documents Department

Structural transformations in Sc/Si multilayers irradiated by EUVlasers

Description: Multilayer mirrors for the extreme ultraviolet (EUV) are keyelements for numerous applications of coherent EUV sources such as newtabletop lasers and free-electron lasers. However the field ofapplications is limited by the radiation and thermal stability of themultilayers. Taking into account the growing power of EUV sources thestability of the optics becomes crucial. To overcome this problem it isnecessary to study the degradation of multilayers and try to increasetheir temporal and thermal stability. In this paper we report the resultsof detailed study of structural changes in Sc/Simultilayers when exposedto intense EUV laser pulses. Various types of surface damage such asmelting, boiling, shockwave creation and ablation were observed asirradiation fluencies increase. Cross-sectional TEM study revealed thatthe layer structure was completely destroyed in the upper part ofmultilayer, but still survived below. The layers adjacent tothe substrateremained intact even through the multilayer surface melted down, thoughthe structure of the layers beneath the molten zone was noticeablychanged. The layer structure in this thermally affected zone is similarto that of isothermally annealed samples. All stages of scandium silicideformation such as interdiffusion, solid-state amorphization, silicidecrystallization, etc., are present in the thermally affected zone. Itindicates a thermal nature of the damage mechanism. The tungstendiffusion barriers were applied to the scandium/silicon interfaces. Itwas shown that the barriers inhibited interdiffusion and increased thethermal stability of Sc/Si mirrors.
Date: August 21, 2007
Creator: Voronov, D.L.; Zubarev, E.N.; Pershyn, Y.P.; Sevryukova, V.A.; Kondratenko, V.V.; Vinogradov, A.V. et al.
Partner: UNT Libraries Government Documents Department

Understanding the anomalous dispersion of doubly-ionized carbon plasmas near 47 nm

Description: Over the last several years we have predicted and observed plasmas with an index of refraction greater than one in the soft X-ray regime. These plasmas are usually a few times ionized and have ranged from low-Z carbon plasmas to mid-Z tin plasmas. Our main calculational tool has been the average atom code. We have recently observed C{sup 2+} plasmas with an index of refraction greater than one at a wavelength of 46.9 nm (26.44 eV). In this paper we compare the average atom method, AVATOMKG, against two more detailed methods, OPAL and CAK, for calculating the index of refraction for the carbon plasmas and discuss the different approximations used. We present experimental measurements of carbon plasmas that display this anomalous dispersion phenomenon. It is shown that the average atom calculation is a good approximation when the strongest lines dominate the dispersion. However, when weaker lines make a significant contribution, the more detailed calculations such as OPAL and CAK are essential. During the next decade X-ray free electron lasers and other X-ray sources will be available to probe a wider variety of plasmas at higher densities and shorter wavelengths so understanding the index of refraction in plasmas will be even more essential. With the advent of tunable X-ray lasers the frequency dependent interferometer measurements of the index of refraction may enable us to determine the absorption coefficients and line-shapes and make detailed comparisons against our atomic physics codes.
Date: April 15, 2008
Creator: Nilsen, J; Castor, J I; Iglesias, C A; Cheng, K T; Dunn, J; Johnson, W R et al.
Partner: UNT Libraries Government Documents Department

Modeling of laser produced plasma and z-pinch x-ray lasers

Description: In this work we describe our theoretical activities in two directions of interest. First, we discuss progress in modeling laser produced plasmas mostly related to transient collisional excitation scheme experiments with Ne- and recently with Ni-like ions. Calculations related to the delay between laser pulses, transient gain duration and hybrid laser/capillary approach are described in more detail. Second, the capillary discharge plasma research, extended to wider range of currents and rise-times has been outlined. We have systematically evaluated the major plasma and atomic kinetic properties by comparing near- and far-field X-ray laser output with that for the capillary Argon X-ray laser operating under typical current values. Consistent with the experiment insight was obtained for the 469{angstrom} X-ray laser shadowgraphy experiments with very small kiloamp currents. At higher currents, as much as {approximately}200 kA we evaluated plasma temperature, density and compared x-ray source size and emitted spectra.
Date: February 7, 1999
Creator: Dunn, J; Frati, M; Gonzales, J J; Kalashnikov, M P; Marconi, M C; Moreno, C H et al.
Partner: UNT Libraries Government Documents Department

Advances in full field microscopy with table-top soft x-ray lasers

Description: We describe recent advances in the demonstration of table-top full field microscopes that use soft x-ray lasers for illumination. We have achieved wavelength resolution and single shot exposure operation with a very compact 46.9 nm microscope based on a desk-top size capillary discharge laser. This {lambda}-46.9 nm microscope has been used to capture full field images of a variety of nanostructure systems and surfaces. In a separate development we have demonstrated a zone plate microscope that uses {lambda}=13.2 nm laser illumination to image absorption defects in an extreme ultraviolet lithography (EUVL) mask in the same geometry used in a 4x demagnification EUVL stepper. Characterization of the microscope’s transfer function shows it can resolve 55 nm half period patterns. With these capabilities, the {lambda}-13.2 nm microscope is well suited for evaluation of pattern and defect printability of EUVL masks for the 22 nm node.
Date: May 18, 2009
Creator: Menoni, C. S.; Brizuela, F.; Wang, Y.; Brewer, C. A.; Luther, B. M.; Pedaci, F. et al.
Partner: UNT Libraries Government Documents Department

Inspection 13.2 nm table-top full-field microscope

Description: We present results on a table-top microscope that uses an EUV stepper geometry to capture full-field images with a halfpitch spatial resolution of 55 nm. This microscope uses a 13.2 nm wavelength table-top laser for illumination and acquires images of reflective masks with exposures of 20 seconds. These experiments open the path to the realization of high resolution table-top imaging systems for actinic defect characterization.
Date: February 23, 2009
Creator: Brizuela, F.; Wang, Y.; Brewer, C. A.; Pedaci, F.; Chao, W.; Anderson, E. H. et al.
Partner: UNT Libraries Government Documents Department