We report a systematic measurement of the (2p(1/2)(-1)3d(3/2))(J=1) and (2s(1/2)(-1)3p(1/2))(J=1) levels in 14 neonlike ions between Ba46+ and Pb72+ and document the effects of their avoided crossing near Z = 68. Strong mixing affects the oscillator strengths over a surprisingly wide range of atomic numbers and leads to the vanishing of one transition two atomic numbers below the crossing. The crossing voids the otherwise correct expectation that the (2p(1/2)(-1)3d(3/2))(J=1) level energy is only weakly affected by quantum electrodynamics (QED). For about 10 atomic numbers surrounding the crossing, its QED contributions are anomalously large, attaining almost equality to those affecting the (2s(1/2)(-1)3p(1/2))(J=1) level. As a result, the accuracy of energy level calculations appears compromised near the crossing.

It is almost a decade since the first tabletop x-ray laser experiments were implemented at the Lawrence Livermore National Laboratory (LLNL). The decision to pursue the picosecond-driven schemes at LLNL was largely based around the early demonstration of the tabletop Ne-like Ti x-ray laser at the Max Born Institute (MBI) as well as the established robustness of collisional excitation schemes. These picosecond x-ray lasers have been a strong growth area for x-ray laser research. Rapid progress in source development and characterization has achieved ultrahigh peak brightness rivaling the previous activities on the larger facilities. Various picosecond soft-x-ray based applications have benefited from the increased repetition rates. We will describe the activities at LLNL in this area.

Iron spectra have been recorded from plasmas created at three different laser plasma facilities: the Tor Vergata University laser in Rome ( Italy), the Hercules laser at ENEA in Frascati ( Italy), and the Compact Multipulse Terawatt ( COMET) laser at LLNL in California ( USA). The measurements provide a means of identifying dielectronic satellite lines from Fe XVI and Fe XV in the vicinity of the strong 2p --> 3d transitions of Fe XVII. About 80 Delta n >= 1 lines of Fe XV (Mg-like) to Fe XIX (O-like) were recorded between 13.8 and 17.1 angstrom with a high spectral resolution (lambda/Delta lambda approximate to 4000); about 30 of these lines are from Fe XVI and Fe XV. The laser-produced plasmas had electron temperatures between 100 and 500 eV and electron densities between 10(20) and 10(22) cm(-3). The Hebrew University Lawrence Livermore Atomic Code (HULLAC) was used to calculate the atomic structure and atomic rates for Fe XV - XIX. HULLAC was used to calculate synthetic line intensities at T-e = 200 eV and n(e) = 10(21) cm(-3) for three different conditions to illustrate the role of opacity: optically thin plasmas with no excitation-autoionization/dielectronic recombination (EA/DR) contributions to the line intensities, optically thin plasmas that included EA/DR contributions to the line intensities, and optically thick plasmas ( optical depth approximate to 200 mu m) that included EA/DR contributions to the line intensities. The optically thick simulation best reproduced the recorded spectrum from the Hercules laser. However, some discrepancies between the modeling and the recorded spectra remain.

The wavelength of the 3s(1/2)-3p(3/2) transition of Na-like U81+ was determined to be 9.499 85+/-0.000 15 Angstrom (1305.12+/-0.02 eV), using the EBIT-I electron beam ion trap. The measurement is many times more sensitive to the radiative contributions from quantum electrodynamics than earlier measurements for Pt67+ and Pb71+. Our result strongly deviates from various predictions employing scaled hydrogenic quantum electrodynamic corrections and establishes a benchmark for multielectron QED calculations that agrees well with the trend established by ab initio calculations.

An x-ray line diagnostic for use in magnetic field measurements in high-temperature plasmas has been identified. The intensity of the otherwise strictly forbidden 1s(2)2s(2)2p(1/2)2p(4)(3/2)3s(1/2) 3P0-->1s(2)2s(2)2p(6) 1S0 transition in neonlike ions is shown to depend on the magnetic field strength. The field dependence is illustrated between one and 3 T in the Ar8+ spectrum. The line is well resolved, bright, and close to reference lines, making it an experimentally simple to use diagnostic.

The wavelength of the 3s{sub 1/2}-3p{sub 3/2} transition of Na-like U{sup 81+} was determined to be 9.499 85{+-}0.000 15 Aa (1305.12{+-}0.02 eV), using the EBIT-I electron beam ion trap. The measurement is many times more sensitive to the radiative contributions from quantum electrodynamics than earlier measurements for Pt{sup 67+} and Pb{sup 71+}. Our result strongly deviates from various predictions employing scaled hydrogenic quantum electrodynamic corrections and establishes a benchmark for multielectron QED calculations that agrees well with the trend established by ab initio calculations.

The wavelength of the ${3s}_{1/2}\ensuremath{-}{3p}_{3/2}$ transition of Na-like ${\mathrm{U}}^{81+}$ was determined to be $9.49985\ifmmode\pm\else\textpm\fi{}0.00015\mathrm{\AA{}}$ $(1305.12\ifmmode\pm\else\textpm\fi{}0.02\mathrm{eV}),$ using the EBIT-I electron beam ion trap. The measurement is many times more sensitive to the radiative contributions from quantum electrodynamics than earlier measurements for ${\mathrm{Pt}}^{67+}$ and ${\mathrm{Pb}}^{71+}.$ Our result strongly deviates from various predictions employing scaled hydrogenic quantum electrodynamic corrections and establishes a benchmark for multielectron QED calculations that agrees well with the trend established by ab initio calculations.

During recent months we have continued investigations of many different aspects of x-ray lasers to characterize and improve the source and applications. This work has included temporal characterization of existing laser-heated x-ray lasers under a wide range of pumping conditions. We have also looked into more details at different applications of x-ray lasers among which was the interferometry of laser-produced and capillary discharge plasmas in several irradiation conditions for different target Z materials. The reduction of pump energy remains the most important for the generation of new compact x-ray lasers. Numerical studies show that there are some ways to improve several of the key parameters of x-ray lasers specifically repetition rates and efficiency.

The wavelength of the 3s{sub 1/2}-3p{sub 3/2} transition of Na-like U{sup 81+} was determined to be 9.499 85{+-}0.000 15 Aa (1305.12{+-}0.02 eV), using the EBIT-I electron beam ion trap. The measurement is many times more sensitive to the radiative contributions from quantum electrodynamics than earlier measurements for Pt{sup 67+} and Pb{sup 71+}. Our result strongly deviates from various predictions employing scaled hydrogenic quantum electrodynamic corrections and establishes a benchmark for multielectron QED calculations that agrees well with the trend established by ab initio calculations.

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.

Recent measurements of the K-shell and L-shell x-ray spectra of highly charged heliumlike and neonlike ions are presented that were performed on the Livermore electron beam ion traps and the Princeton tokamaks. These measurements provide new insights into collisional and indirect line formation processes, identifications of forbidden lines, and a new plasma line diagnostic of magnetic field strength.

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.

Summary form only given, as follows. Tabletop X-ray lasers have been used in applications to diagnose high-density plasmas using their coherent properties. Recently, these lasers have demonstrated their usefulness by providing interferometry data on laser-produced plasmas reaching to near critical densities. Several initial experiments have obtained valuable and surprising results. Obtained density profiles show the generation of a density depression along the laser focus. Though axial jets and filaments in plasma were reported earlier in numerous experimental works, the formation of inhomogeneities in the density profile of such large magnitude at such relatively small laser fluxes has never been seen before. Density profiles reaching near-critical for a plasma heated by small-energy Nd-glass lasers, show both plasma blow-off from an increased effective spot and the creation of side lobes. This description seems in contradiction with the classical description of steady-state spherical plasma expansion under the influence of laser radiation. We used available numerical codes LASNEX and RADEX to evaluate the obtained plasma parameters and present our results.

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.

We report new results using the LLNL COMET laser to evaluate the effectiveness of different target architectures to improve the output and characteristics of the transient x‐ray laser scheme. Surprising observations were found when the laser line focus irradiating a single slab Cr or Fe target was divided into two or three distinct plasma column sections with millimeter scale gaps between each plasma. The Ne‐like 3p 1S0 → 3s 1P1 28.5 nm and 25.5 nm x‐ray laser lines, for Cr and Fe, respectively, were improved in beam divergence, by 2 – 3 times, and peak intensity, by up to one order of magnitude, when compared with a single plasma column of the same length or longer. This was contrary to expectations since these large‐scale inhomogeneities introduced along the plasma, as well as attenuation from the cold plasma at the end of each section, would be detrimental to the x‐ray propagation and amplification. Instead an injector‐amplifier (IA) type process appears to be at work where the plasma gaps may be beneficially modifying the ray propagation and coupling through the high Ne‐like ion gain regions. We present results showing the output of the amplifier stage with increasing length for the IA targets together with beam deflection and divergence measurements.

We report the generation of plasma columns in gas-filled capillary channels using discharge excitation powers that exceed those of previous studies by one to two orders of magnitude. Current pulses up to 200 kA and 10-90 % rise time of about 10 ns (current increase rate equivalent to 1.5 x 10(13) A/s) were utilized to excite plasmas in 3.3 and 4 mm diameter channels. Time resolved soft-x-ray spectra and pinhole images of the plasma were obtained. The experimental data and its comparison with model computations suggest that dense argon plasma columns 300 mum in diameter with electron temperatures >250 eV have been obtained. These characteristics make these plasmas of interest for extending discharge-pumped lasers to shorter wavelengths.