Results of the joint experiment between ILE Japan and NLHPLP/IAPCM China are reported. New optics for improved line focusing, a cylindrical lens array and a deformable mirror, were used in irradiation of x-ray laser targets. Double-pass amplification at 7.9 nm has been demonstrated. Strong lasing at 7.9 nm with approximately 100 (mu) J output energy has been obtained in Ni-like Nd ions by quasi-traveling wave pumping of double targets.

This work has consisted in demonstrating that high gain can be achieved by pumping x-ray lasers (XRL) with a combination of a high intensity and short duration driving pulses (approximately 100 ps). Short pulses are very well suited for pumping collisional XRL since a high lasant ion density, electron density and temperature can be achieved simultaneously. We have successfully tested this pumping scheme on the 4d-4p (J equals 0 - 1) transition of Ni-like tin (lambda approximately 11.93 nm) and silver (lambda approximately 13.89 nm) as well as on the 3p-3s (J equals 0 - 1) Ne-like iron (lambda approximately 25.5 nm) at an intensity of approximately 2 X 10¹³ Wcm^-2 (130 ps in duration). The driving laser (lambda equals 1.06 micrometer) was composed of three pulses (a prepulse and two main pulses). Large amplifications were demonstrated in tin and silver (respectively GL approximately 12 and GL approximately 16). Finally, the saturation of the 3p-3s (J equals 0 - 1) transition of Ne-like iron at 25.5 nm was achieved on both pumping pulses, using a prepulse of 10⁹ Wcm^-2. A gain coefficient of 15 plus or minus 3 cm^-1 (GL approximately 26 plus or minus 5) on the first main pulse and 12 plus or minus cm^-1 (GL approximately 23 plus or minus 2) on the second one was measured.

Recent studies of soft-x-ray and XUV lasers in Ne- and Ni-like ions using the Asterix IV iodine laser as a pump are reviewed. Progress achieved includes the observation of new laser lines in a number of low to medium-Z Ne-like ions at wavelengths from 20 to 87 nm, the reduction of the driver energy for neon- like S to a value of 20 J and lasing in Ni-like Sn at 12 nm. We also present recent results in characterizing near- and far-field patterns and compare them with predictions of simulations, using a 2D hydrodynamic code combined with a ray tracing code.

The use of multi-pulse irradiation of neon-like ions has been shown to produce orders-of-magnitude enhancement of x-ray laser output. Recent results obtained at the Rutherford Appleton Laboratory are reviewed with an emphasis on understanding the reasons for the enhancement. Simulations with the fluid and atomic physics code EHYBRID are used to show that enhancement occurs because of a spatial enlargement of the gain region and consequent better propagation of the x- ray laser beam along the gain region.

The aim of this paper is to identify ways in which current designs can be modified to improve the output performances of the collisional x-ray lasers. The effectiveness -- for slab systems -- of some ideas are examined from a theoretical standpoint. They all involve the temporal shaping of the driver pulse and judiciously combine low and high intensity, long and short irradiations. Simulations of Ne-like Fe and Ni- like Ag XRLs experiments are also presented to support the study.

We report the first demonstration of saturation in nickel-like x-ray lasers, specifically nickel-like Ag, In, Sn, and Sm x- ray lasers at wavelengths of 14, 12.6, 12.0 and 7.3 nm respectively. These x-ray lasers were found to be very monochromatic x-ray sources with the laser lines completely dominating the output spectra. Using high-resolution spatial imaging and angularly resolved streaking techniques, the output source sizes as well as the time histories, divergences, energies and spatial profiles of these x-ray lasers have been fully characterized. The output intensities of these x-ray lasers were measured to be in the range of 0.7 - 2 X 10¹¹ W (DOT) cm^-2 in approximately 40 ps. The high monochromaticity, narrow divergence, short pulse duration, high efficiency and high brightness of these x-ray lasers make them ideal candidates for many applications.

We present the first direct spatial measurement of the two dimensional gain profiles for a Ne-like ion using a slab target illuminated by the multiple pulse technique. To understand the spatial dependence of the gain in Ne-like Ge on the 19.6 nm laser line for plasmas driven by a series of 100 ps pulses 400 ps apart we did a series of Nova experiments backlighting short Ge amplifiers. Two-dimensional, high- resolution, spatial images of the 19.6 nm laser emission from the output aperture of the amplifiers were measured to determine the spatial position of the gain. The amplifier lengths were chosen to be short enough to avoid significant refraction of the beam. In previous imaging experiments which measured the near field output of the Ge laser, the position of the laser output was dominated by refraction effects. To assure good temporal overlap, we used the traveling wave geometry to illuminate both the amplifier and backlighter. The amplifier design included a wire fiducial which provided an absolute spatial reference and avoided the usual difficulty of determining the location of the target surface. We compare the measured gain with simulations done using LASNEX, which calculates the hydrodynamic evolution of the plasma, and XRASER, which uses the temperature and densities from LASNEX to do the gain and kinetics calculations.

We discuss high resolution two-dimensional near-field images of the neon-like nickel and germanium x-ray laser obtained using the Asterix laser at the Max-Planck-Institute and the Nova laser at Lawrence Livermore National Laboratory. Our imaging diagnostic consisted of a concave multilayer mirror that imaged the output end of the x-ray laser line onto a backside illuminated x-ray CCD detector. A 25 micrometer thick wire positioned at the end of the target provided a spatial fiducial. With the Asterix iodine laser, a prepulse 5.23 ns before the main pulse, was used to irradiate slab targets. A great deal of structure was observed in the near field images, particularly in the J equals 0 - 1 emission. We observed a large difference in the spatial dependence of the J equals 0 - 1 and J equals 2 - 1 lines of germanium, with the J equals 2 - 1 emission peaking farther away from the original target surface. A larger prepulse moved the peak emission farther away from the target surface. For the Nova experiments we used a series of 100 ps pulses spaced 400 ps apart to illuminate a germanium target. We obtained high resolution images of both the J equals 0 - 1 and J equals 2 - 1 lines of Ge. these measurements are compared to hydrodynamic simulations coupled with atomic kinetics and including refraction effects.

Low pump energy transient gain x-ray lasers in Ti at 32.6 nm, 30.15 nm, in V at 30.4 nm and Ge at 19.6 nm using picosecond pulse heating of a long pulse preformed plasma of neonlike ions has been realized for the first time. Gain saturation was demonstrated in Ti and Ge XRL. Results of pump consumption, x- ray divergence and output energy are given.

This paper models recent experiments in which a solid titanium target was illuminated by several joules of combined energy from a nsec laser pulse to create a preplasma followed by a psec laser pulse to drive the gain. Gains greater than 200 cm^-1 are predicted for the Ne-like Ti 3p ¹S₀ yields 3s ¹P₁ transition at 32.6 nm which is driven by the monopole collisional excitation. High gain is also predicted for the 3d ¹P₁ yields 3p ¹P₁ transition at 30.1 nm which is driven by a combination of collisional excitation and self photopumping. We also discuss the possibilities for driving a Ne-like Ge laser using this approach. For the Ni-like ions we model a solid molybdenum target under similar conditions used for Ti and predict gains greater than 300 cm^-1 for the Ni-like Mo 4d ¹S₀ yields 4p ¹P₁ transition at 18.9 nm which is driven by the monopole collisional excitation. High gain is also predicted for a self photopumped 4f ¹P₁ yields 4d ¹P₁ transition at 22.0 nm and several other transitions driven by inner shell collisional ionization.

We examine a scheme for a compact nickel-like tungsten soft x- ray laser operating on the 4d - 4p, J equals 0 - 1 transition at 43.2 angstrom. High gains are achieved by operating at high electron densities (n_e greater than 10²² cm^-3). In this regime, the gain during non-equilibrium ionization can greatly exceed that of the steady state. The duration of this transient gain is on the order of the ionization time which makes picosecond-pulsed optical pumps ideal. We predict gains of 220 cm^-1 for a 1 micrometer pump of intensity I equals 1 X 10¹⁷ W/cm².

The numerical optimization of the temporal shape of the pump laser for the design of a 38.8 angstrom H-like x-ray laser is presented. Enhancement of local and integrated gains is obtained by smoothing the pulse rise, without drastic increase of the x-ray emission duration. Sensitivity of the results to the pulse intensity is also examined. High temporal resolution spectroscopy of aluminum targets performed in the keV range at the P102 facility in Limeil is finally presented.

Pumping of proposed inner-shell photo-ionized (ISPI) x-ray lasers places stringent requirements on the optical pump source. We investigate these requirements for an example x-ray laser (XRL) in Carbon lasing on the 2p - 1s transition at 45 angstrom. Competing with this lasing transition is the very fast auger decay rate out of the upper lasing state, such that the x-ray laser would self-terminate on a femto-second time scale. XRL gain may be demonstrated if pump energy is delivered in a time short when compared to the auger rate. The fast self-termination also demands that we sequentially pump the length of the x-ray laser at the group velocity of the x- ray laser. This is the classical traveling wave requirement. It imposes a condition on the pumping source that the phase angle of the pump laser be precisely de-coupled from the pulse front angle. At high light intensities, this must be performed with a vacuum grating delay line. We also include a discussion of issues related to pump energy delivery, i.e. pulse-front curvature, temporal blurring and pulse fidelity. An all- reflective optical system with low aberration is investigated to see if it fulfills the requirements. It is expected that these designs together with new high energy (greater than 1 J) ultra-short pulse (less than 40 fs) pump lasers now under construction, may fulfill our pump energy conditions and produce a tabletop x-ray laser.

We describe recent experiments at the Lawrence Livermore National Laboratory (LLNL) to produce a table-top x-ray laser. Using a combination of long 800 ps and short approximately 1 ps high power laser pulses with approximately 6 J in each beam, a transient collisionally excited Ne-like ion x-ray laser scheme has been investigated. We present results of high x-ray laser gain for the Ne-like Ti 3p - 3s J equals 0 - 1 transition at 326 angstrom and have achieved gL product of 15 for target lengths up to 1 cm. We have extended the transient collisional scheme to shorter wavelengths using the Ni-like analog, specifically the 4d - 4p J equals 0 - 1 of Ni-like Pd at 147 angstrom.

Collisional X-UV lasers are now currently produced world-wide. The LSAI team has developed at LULI an efficient, high brightness laser at 21.2 nm, using neonlike zinc. Beside the effort aimed at improvement of efficiency of the neonlike X-UV lasers, the LSAI recent activity has covered scaling the collisional scheme down to shorter wavelengths, as well as development of applications. In this paper we present results of applications of the 21.2 nm laser in atomic physics, solid state physics, and X-UV interferometry of surfaces. The emphasized message is that the characteristics of the existing X-UV lasers render possible applications in many research areas nowadays.

Collisionally pumped x-ray lasers are ideal for a wide variety of plasma diagnostics. They have been demonstrated over a wavelength range extending from 3.5 nm to 40 nm and have output energies as high as 10 mJ in 150 ps pulses. The beam divergence is less than 15 mrad and the linewidth (lambda) /(Delta) (lambda) approximately 10⁴ provides sufficient longitudinal coherence for interferometry. Using various arrangements constructed with multi-layer XUV reflective optics we have carried out a variety of experiments with the yttrium x-ray laser operating at 15.5 nm. Initial experiments involved x-ray laser backlighting and Moire deflectometry, while later work demonstrated interferometric determinations of plasma density profiles in various targets. We have also studied hydrodynamic imprinting of laser speckle patterns on directly driven thin foils with 1 - 2 micrometer spatial resolution. These detailed plasma diagnostic capabilities provide an important means to benchmark hydrodynamic calculations of dense plasma flows.

We measured laser channeling into an overdense plasma by using a 19.6 nm Ne-like Ge XUV laser. One micrometer/100 ps laser light at 10¹⁷ W/cm² interacted with a long scale length plasma preformed on a CH slab target. Grid image refractometry (GIR) with the x-ray laser was applied to obtain the deflection information in the plasma, which provided two dimensional density profiles (2-D) of the overdense plasmas.

Soft x-ray laser based Moire deflectometry has been shown to be a viable and useful diagnostic for probing dense plasmas relevant to inertial confinement fusion (ICF). Collisionally pumped soft x-ray lasers are thereby used as reliable radiation sources which provide unique intensity and coherence characteristics in the soft x-ray region in order to overcome the adverse effects of absorption and refraction of the probe beam in the plasma. We present results obtained from Moire deflectometry experiments carried out at the ILE Gekko XII laser facility where the neon-like germanium x-ray laser with line emission at 196 angstrom has been used to probe laser produced plasmas created from 100 micrometer thick CH targets. Besides a high brightness the x-ray laser exhibits small beam divergence (less than 4 mrad) and short pulse duration of about 80 ps. The results show that peak electron densities of 3 X 10²¹ cm^-3 at the initial target surface can be probed with this diagnostic technique, however, no convincing evidence was found for channel formation in the plasma caused by a 1 (omega) (1.053 micrometer) drill beam.

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.

A simple technique of the generation of high-density metal- vapor columns for x-ray capillary lasers is demonstrated. The method is based on vaporization of the electrode material in the low-pressure (P less than 1 torr) capillary microsecond- discharge. High-density (N_Al greater than 10¹⁷ cm^-3), small-diameter (1 divided by 6 mm), long (5 divided by 20 cm) Al-vapor columns have been produced. The Al- vapor density along the capillary and the time-resolved spectra from Al-vapor plasmas are presented. The Al-vapor density and profile were controlled by varying the discharge parameters.

We propose to enhance the gain of Ne-like ion capillary lasers by the utilization of two discharge pulses. A first pulse working in the pinch regime mode is designed to create the cold-plasma column with the required ionization degree, followed by a second fast high-voltage pulse to do the effective collision excitation. The second pulse, which heats the electrons to a kinetic temperature T_e greater than T_e^cold in times shorter than the ionization time, increases the laser gain. In the two stage pumping scheme, both the amplitude of each of the pulses and the delay between them can be adjusted for independent control of the ionization degree and excitation rate. Numerical estimations performed for the low-Z-ion (Na⁺¹, . . ., Ar⁺⁸) lasers with the double pulse pumping predict enhancement in gain by a factor of approximately 10. In addition, the extension of two-stage electrical pumping to the high-Z-ion collision and recombination laser schemes is discussed. Description of the experimental set-up constructed for such experiments and some related measurement data are also presented.

We have studied the dynamics of fast capillary Z-discharge to obtain prospects for laser operation in shorter wavelength range. The recent results of our studies indicate that, by preionized fast discharge, the column can implode stably in a wide initial pressure range of 200 - 1000 Pa of argon. These results also suggest that the final plasma parameters and their spatial distributions can be controlled in the stable implosion range. If we can avoid destructive magneto- hydrodynamic (MHD) instabilities over a wide range of implosion parameters, we can make Z-scaling to shorter wavelengths. In order to obtain accurate prospects for the operation in shorter wavelengths, the Z-scaling should be carried out based on a proper modeling including the Z- discharge dynamics and radiation transport.

Numerical modeling of transient inversion and capillary discharge x-ray lasers were performed for the purposes of understanding of recent experiments, improving the laser efficiency and planing their further development. The first demonstration of saturation of a low pump energy x-ray laser utilizing a transient inversion mechanism on the 3p - 3s transition at 32.63 nm in Ne-like Ti has been confirmed. A close to saturation amplification was simultaneously achieved for the 3d - 3p, J equals 1 - 1 transition at 30.15 nm. Small signal effective transient gain coefficients of g approximately equals 46 cm^-1 and approximately 35 cm^-1 and effective gain-length products of 16.7 and 16.9 for these lines were obtained. Experiments and calculations demonstrate that it is possible to achieve saturated laser action in a transient regime with Ne-like Ti for a pump energy as low as approximately 5 J. With such energies just recently the lasing on Ni-like Pd at 14.7 nm has been achieved. MHD simulations of capillary discharges were performed for several elements with shorter lasing wavelengths. A new approach which intends to combine advantages of electrical discharge plasma preparation with CPA-laser excitation was investigated. It will enable a kind of x-ray lasers to be built with ultrashort pulse duration and the high efficiency. In this case the well preformed cylindrical shell of discharge plasma and the transient population inversion combined with the traveling-wave excitation will enable to achieve lasing at much shorter wavelengths.

The recent results of the demonstration of the lasing action at 13.5 nm in transition to ground state of LiIII at 2 Hz repetition rate using two lasers is being presented in this paper. A gain length of GL approximately equals 5.5 was measured in the 5 mm long, 0.3 mm diameter, LiF microcapillary using a 50 mJ, 250 fsec UV laser beam. The initial plasma was created in the microcapillary by a low power, relatively long pulse Nd/YAG laser. In order to shed light on observed unusually high efficiency of the ionization of the atoms in microcapillaries, the subpicosecond UV laser beam transmissions through the plasma in microcapillaries were measured. Strong dependence of the beam transmission on the delay time between inial plasma formation with the Nd/YAG laser and the sub-picosecond UV laser was recorded. The final part of the paper discusses some necessary conditions for an extension of the present results towards the shorter wavelength lasers with an emphasis on the presently conducted experiments at Princeton University for the generation gain at 4.8 nm in BV.

The aim of this work was to investigate the conditions for waveguiding of nanosecond laser pulses in plasmas in microcapillary and gas jet for the development of a compact soft x-ray laser (SXL). A detailed study of He- and H-like carbon and nitrogen ion spectra, as a function of gas (plasma) densities, and plasma length was performed. The majority of the presented data were obtained in plasmas created in nitrogen injected into the vacuum chamber by pulsed electromagnetic valve. The waveguide conditions for the pump laser pulse (1.054 micrometer, 2 - 7 J, 1.5 ns) were achieved by line optical breakdown (up to 6 mm long) produced in gas by focusing a pre-pulse laser beam with an axicon lens. Intensive strong lines of H- and He-like ions were observed and the possibilities of obtaining the lasing conditions for SXL are discussed.

Using the prepulse technique, soft-x-ray lasing is demonstrated on the J equals 0 - 1 transitions of neon-like titanium, chromium, and iron at 32.6, 28.5, and 25.5 nm, respectively, and on the J equals 2 - 1 transitions of copper, zinc, and germanium at 27.9/28.5, 26.2/26.7, and 23.2/23.6 nm, respectively, for pump energies below 100 J, corresponding to irradiances of less than 10 TW/cm². A gain coefficient g equals 2.2 cm^-1 was measured for the 28.5-nm line of Cr at a pump energy of 90 plus or minus 5 J and with a 0.7% prepulse preceding the main pulse by 5 ns, resulting in a gain-length product of approximately 5.5. Angle-resolved spectra indicate a beam divergence of 3 mrad and a beam deflection angle of approximately 6 mrad. The space-resolved spectra show that the J equals 0 - 1 lasing line is emitted from an approximately 60-micrometer wide plasma region, while the nearby continuum emission is produced in a considerably broader plasma region of approximately 230 micrometer. Lasing was observed at pump energies as low as 60 J (approximately 6 TW/cm²), however with considerable shot-to-shot scatter in the data.

Basic concepts involved in inversionless laser schemes are reviewed. We focus on the V scheme recently proposed by the Stanford group, which uses AC Stark coupling to develop overlapping spectral lines that show an interference minimum in absorption and a maximum in emission at line center. The He-like C 1s(superscript 2/ - 1s2p transition is examined as a possible candidate for developing an absorption minimum; Doppler broadening effects are found to be severe. The situation is improved with the choice of heavier ions and stronger resonance lines in closed shell sequences. New short wavelength laser schemes in these systems are proposed.

X-ray lasings of Li-like Al ion in the recombination scheme have been investigated using a tabletop pulse-train YAG laser system. Two types of cavity experiments have been carried out, one is an unstable resonator consisting of two flat Mo/Si multilayer mirrors and the other is that with a concave mirror. Clear enhancement in the Li-like Al transition lines at 15.47 nm has been observed for both types of cavities as a high peak in line intensity preceding the plasma emission. The observed feature of the preceding emission can be reproduced by the raytrace calculation.

There exist some overlapping areas of research in the development of x-ray-lasers and synchrotron radiation sources. In this report, we compare the characteristics and applications of the currently available x-ray lasers and the third-generation synchrotron radiation.

We analyze the effect of plasma density fluctuations on x-ray laser coherence and discuss the implications of our results for exploding-foil x-ray laser experiments. We treat propagation of coherence using a deterministic ray-tracing technique based on the radiation transfer equation, coupled with the phase approximation of Huygens-Kirchhoff method to treat the random fluctuations. First we develop the propagation technique for the zero-fluctuation case, and derive analytical solutions for the intensity distribution and coherence function in the output plane of an active medium with parabolic transverse profiles of dielectric constant and gain coefficient. We discuss under what conditions we may include only the contribution of spontaneous sources adjacent to the far face of the active medium, and show that in many practical cases it is necessary to take into account sources throughout the whole active medium. We then include density fluctuations, and obtain expressions for the coherence function for homogeneous fluctuations with both Gaussian and exponential correlation, as a function of fluctuation amplitude and correlation length. We apply our results to selenium and yttrium exploding foil x-ray lasers, where non- uniformity in the optical laser pump beams or hydrodynamic instabilities may lead to fluctuations. We show how fluctuations can cause the coherence to saturate with increasing laser length, and indicate how a moderate level of fluctuations can explain the observed coherence in experiments on selenium x-ray lasers. We also characterize the sensitivity of the coherence to fluctuations by defining critical amplitude level above which they dominate the coherence.

We have measured the variation of the spatial coherence with plasma column length in a saturated table-top 46.9 nm Ne-like Ar capillary discharge soft x-ray amplifier for lengths up to 16.4 cm. The measurements, which are in good agreement with time dependent wave-optics model computations, provide the first experimental evidence of a monotonic increase of the coherence with length in a soft x-ray amplifier. The variation of the coherence across the beam profile was also studied. Off-axis the coherence is larger in the tangential than in the radical direction.

We investigate the polarization state of x-ray beams in collisionally pumped lasers, and compare our results to experimental data on Ne-like Ge lines. The plasma polarization properties are studied in terms of the orientation and alignment, using irreducible tensors of the density matrix. It is shown that the elastic electron-ion collisions tend to equalize the quantum-states populations of each level, and then lessen or even eliminate the polarization of the medium, that is induced by the x-ray beam.

In view of potential applications to the normal incidence optics we calculated the optical constants of metals Sc, Ti, V, Cr and Fe in the interval $HBAR(omega) less than or equal to 70 eV. The calculation was carried out within frames of the band structure approach with the use of the linear muffin-tin orbitals (LMTO) method and taking into account electron excitation of the nearest core levels. Obtained dielectric function shows good agreement with experimental spectra of the absorption (mu) ((omega) ), the reflectivity R((omega) ) and the electron energy loss spectroscopy (EELS) L((omega) ). The trends in optical spectra of metals along the 3d- series and mutual correlation of features of (mu) ((omega) ), R((omega) ) and L((omega) ) are considered and discussed.

The formation of an elongated laser spark in a high density gas puff target has been studied experimentally using 10 J 1.5 ns Nd:glass laser pulses. The laser sparks were created by focusing the laser beam on the gas puff targets with a spherical lens or an axicon. The spark was characterized using an imaging system with CCD camera and a grazing incidence grating x-ray spectrometer. Propagation of the second laser pulse of 1.5 ns time duration along the spark plasma was also studied.

Intense, subpicosecond KrF laser pulses were focused into a boron nitride plasma containing boron atom clusters. Strong soft-x-ray spectra observed suggest the production of the fully stripped boron ions with the focused laser intensity of 8 X 10¹⁶ W/cm². Time history of the Lyman-(alpha) emission (4.8 nm) indicates the production of a cold plasma with H-like B ions within tens of ps after the irradiation of the subpicosecond KrF laser pulse.

For realizing a table-top x-ray laser or a compact short wavelength x-ray laser, improvement of the pumping efficiency is one of the most important points. Thermal conduction into inside of the target should suppress rising up of electron temperature of a laser-produced plasma. Then, the plasma produced on a very thin membrane target gets rid of this energy loss, and the efficiency of the high temperature plasma production will be increased. Moreover, density of the plasma from a membrane decreases very rapidly because of the small amount of target limited by the membrane thickness. These features of membrane plasma are suitable in recombination x- ray laser. To confirm the advantages of this pumping scheme, we produced the plasma on a thin membrane and the heating and expansion was evaluated. Experimentally observed spectral lines of H-like and He-like Si ions show effective heating and ionization of the plasma for a membrane target. Electron density evaluations and plasma expansion velocity measurements confirm rapid plasma expansion from the membrane target. Theoretical hydrodynamic simulation also showed the effective heating and ionization of the plasma from the membrane target.

An investigation of the rapid rise time of incoherent x-ray emission from targets heated by an ultra-short pulse (USP) high-intensity optical laser was conducted for use as the x- ray source for inner-shell photo-ionized (ISPI) x-ray lasing. Previous studies considered front-side x-ray emission; however, ISPI x-ray lasing requires a filtered x-ray source. Modeling using the hydrodynamics/atomic kinetics code LASNEX of a 40 fs USP driving laser with an intensity of 10¹⁷ W/cm² incident on a flat target of thin Au layered on a Be filter is presented. The filter has a modest influence on the x-ray emission of the Au via conduction cooling but has a large effect on the backside spectrum by removing low energy x-rays as the Au emission passes through the filter. The use of such a filtered source is shown to provide the needed x rays to achieve high gain in C at 45 angstrom.

Along with ultrahigh-resolution narrow-band spectrometers, a demand exists for medium- and high-resolution stigmatic instruments of a survey type, covering a spectral range of more than a hundred angstroms. Here, we describe several stigmatic spectroscopic configurations intended for characterizing various soft x-ray radiation sources (laser- produced plasmas, XUV lasers, etc.) and optical components [multilayer mirrors (MMs), absorption filters, etc.] in a broad spectral range. The combination of a grazing-incidence toroidal mirror and a large-area transmission diffraction grating (TG) made up a broadband spectrograph with a medium dispersion, with a plate scale of 4-to-20 angstrom/mm, which has proven to be inherently suited for characterizing plane MMs and the laser-plasma source itself. Two versions of W- coated toroidal mirrors were used, which operated at grazing angles of 7.6 degrees and 4 degrees and had respective practical short-wave cutoffs at about 40 and 15 angstrom. Line spectra of low-Z targets and quasicontinuous spectra of a tungsten target were obtained with a resolution of about 800. The configuration of a TG spectrograph was used to characterize CoC MMs with a d-spacing of 38 angstroms fabricated on Si(111) substrates by e-beam deposition and Kr⁺ ion beam polishing of metal layers. The absolute reflectivities near 75 angstrom were measured at 10%. The combination of a large-area TG and a concave MM with a strong lateral gradient of the d-spacing made up a stigmatic spectrograph for the 110 - 300 angstrom range. When the gradient was parallel to the TG lines, the TG was placed in the converging beam. When the gradient was orthogonal to the grating lines, the TG dispersed, unlike the configurations used previously, the diverging beam incident on the focusing MM. Removing the entrance slit transforms the spectrograph into a spectroheliograph. The latter configuration is well suited for producing 2-D solar images in the radiation of spectral lines and far-field images of single- and many- frequency x-ray lasers.