Recent experiments carried out at the Central Laser Facility clearly show amplification of spontaneous emission at 182Å with a g1-4 in a recombining carbon plasma. Thin 7µm diam. carbon fibres were irradiated with the VULCAN Nd.glass laser system. This scheme was extended to shorter wavelengths by using LiF-coated carbon fibre targets. Initial analysis of the experimental data indicates gain of the Balmer a transition of fluorine at 81Å.

Attempts have been made for using a multilayer interferential mirror in normal incidence to enhance X-UV Amplification of Spontaneous Emission (A.S.E) from an aluminum plasma column in the range of 100 A. Two series of experiments have been performed successively, one dealing with time integrated, the other with time resolved measurements using on line detectors for both series. Detailed description is made of experimental set-ups and a discussion is presented about further improvement.

We present the soft X-ray laser experiments performed at Greco "Interaction Laser-Matiere" (Palaiseau). They are mainly concerned with Lithium-like ions of aluminum in plasmas produced by 1.06μ Nd-laser. We describe the experimental set-up which performs time-dependent gain measurements. We report results showing a gain-length product of 2 - 2.5 for the 3d - 5f line at 105.7 A . The gain appears during plasma recombination. Comparison is made between experiment and computational model. The possible limiting role of radiation trapping for long plasma columns is discussed. We present the future projects regarding larger gains and new wavelengths.

Data are presented from three different x-ray laser inversion schemes tested on the Novette laser facility at LLNL: collisional excitation of neon-like selenium (λ = 206, 209, 220Å); resonant photoexcitation of hydrogen-like fluorine (λ = 81Å); and recombination of hydrogen-like magnesium (λ = 130Å). The data illustrate the measurement capabilities of a new, time resolved imaging spectrometer (TGSS-EM), and provide insight to the dynamics and emission characteristicts of a new class of laser produced plasmas.

Since the successful demonstration of gain in neon-like selenium using an exploding foil amplifier, the x-ray laser group at Lawrence Livermore National Laboratory has investigated further the exploding foil amplifier concept for use in XUV lasers. Results are reported of the characteristics of selenium amplifiers up to 50 mm in length. Observation of at least 16 gain lengths for the 206 Å line of selenium is reported. Output powers in excess of 1 MW have been measured in pulses of approximately 200 picoseconds. The effects of refraction on the performance of long amplifiers have been studied. The occurrence time of the x-ray laser output relative to the input heating pulse has been measured and found to be in disagreement with a recent model that suggests three-body recombination driven by rapid radiative cooling as the inversion process in the selenium plasma.

We report progress toward the development of multipass, soft x-ray laser cavities operating in a spectral range around 200 Å. Experimental results on the characterization of normal incidence multilayer mirrors, the survival of multilayer mirrors in the hostile x-ray laser environment, and the performance of double pass cavities at 206 Å to 209 Å are presented.

Measurements on a proposed short wavelength laser system at 108.9 nm in doubly ionized Xenon are reported. Previous electron spectroscopy data indicate that a population inversion should be created between the Xe III states 5s0 5p6 1S0 and 5s0 5p6 1P1 due to selective Auger decay following photoionization of a 4d electron from the neutral atom. Using a high repetition rate laser produced plasma x-ray source and time correlated photon counting, we measured the lifetime of the 1S0 upper state to be 4.75 ±0.15 nsec with a collisional quenching rate of 2.8±0.2x107 (torr-sec)-1. We also determined the Auger branching ratio into the upper and lower states by measuring fluorescence intensities. Implementation of this laser scheme is discussed including limitations in photopumping short wavelength lasers due to amplified spontaneous emission.

In experiments performed during the past two years on Proto II (a 10-TW pulsed-power accelerator), we imploded annular plasmas onto thin-walled annular x-ray laser targets in order to create both a radiation pump source and an x-ray laser medium. For x-ray lasing the Z-pinch must be axially uniform, must efficiently produce the pump radiation, yet not destroy the laser medium on the cylindrical axis of symmetry until after the x-ray laser pulse. To characterize the pump source x-rays and lasant conditions, we regularly field a large number of x-ray diagnostics. In recent experiments, we produced over 15 kJ of >1-keV pump radiation with an imploding neon gas-puff load, recorded spectra from the pump source and lasant, and measured the axial pump source asymmetry. We are considering both recombination and resonance-pumped x-ray laser schemes.

Our present goal is to design, demonstrate and utilize a sub 44 Å, single transverse mode number, saturated output (GL ≥ 16-20), 1 GW x-ray laser. In this talk I summarize our progress to date, critique the various successful amplification techniques and describe some new ones which may make it possible to achieve our goal.

A reflectometer has been set up at the radiometric laboratory of PTB at the Berlin electron storage ring BESSY. Special attention has been paid to optimize the instrumentation for the characterization of multilayer structures suitable for laboratory soft x-ray laser research. The instrumentation is described and its performance demonstrated showing examples of optical component characterization.

The demonstration of amplified spontaneous emission at soft x-ray wavelengths has highlighted the need for normal incidence optics for soft x-rays. Specifically, x-ray laser cavity components will be needed to further advances in x-ray laser research. In this paper, we present the fabrication, characterization and analysis of two possible cavity components, an x-ray beamsplitter and a highly dispersive multilayer mirror. Each of these can be used as x-ray laser cavity output couplers.

Recent advances in the development of lasers at soft x-ray wavelengths has spurred increasing interest in the production of cavity components using multilayer technology. We have established a comprehensive capability to design, fabricate, and characterize multilayer x-ray optics directed towards the goal of building the first x-ray laser cavity. High quality multilayer structures have been fabricated using magnetron sputtering. In addition, we have applied microfabrication technology to create freestanding beamsplitters and three-dimensional diffracting structures, as is discussed in another paper at this conference. The x-ray reflectivity and transmission of the multilayer components have been measured using synchrotron radiation. We have also characterized the microstructure of these devices using high-resolution transmission electron microscopy (TEM). This information provides structural parameters that are incorporated into computer codes to calculate the theoretical performance of the multilayer components. Comparison of the calculated reflectivity and transmission with the measured performance of the multilayer optics provides insight into the physics of these devices. In addition, a successful modeling capability allows us to iterate the fabrication cycle, modifying the design of the multilayer components to optimize their performance.

Mo-Si multilayers were fabricated by means of ion-beam sputtering. The reflectances of Mo-Si multilayers, single layers of Mo and Si, and a glass substrate were measured for s-polarization with synchrotron radiation. The peak reflectance of the best Mo-Si multilayer was 17.5% at 13.7 nm. The optical constants of Mo, Si and BK7 glass obtained from the reflectance data are given at a wavelength region of 12nm (104eV) to 20nm (62.3eV).

Silicon/tungsten multilayer normal-incidence mirrors with maximum reflectance at 212 Å have been designed and studied. Details of the fabrication and characterization techniques are given. Preliminary results of synchrotron measurements show agreement with calculations based on microscopic structure of these multilayers. The Si/W combination has desirable characteristics for use in X-UV or soft x-ray devices.

Described here is a new magnetron sputtering device which will produce high reflectivity mirrors in the X-UV spectral range. The system is designed to produce automatically each bilayer with great accuracy and with a high degree of reproducibility. The mode of operation is explained. One of the important parameters is the roughness of each interfaces which can cause significant losses in the reflectivity of such mirrors. We describe here how these defects may be reduced by changing some of the initial parameters in our sputtering coating plant. A theoretical study and experimental determination of the homogeneity of the deposition system are presented. Several methods of characterization of our samples are used. Our choice of such a modified device is discussed with respect to our objective which is to obtain a well defined interface between the two hlaterials and high reflectivity mirrors used in the X-UV range.

The use of multilayer structures for soft x-ray spectroscopy requires an accurate knowledge of their reflection properties. In this paper, measurements and calculations will be presented for the single crystal integral reflection coefficients of several multilayer structures. Experimental results will be presented for wavelengths from about 0.8 to 1.4 nm. The measured integral reflection coefficients were smaller than those calculated for a perfect multilayer structure, in agreement with previous results. This reduction of diffraction efficiency is due to imperfections in the multilayer structure. Introduction of appropriate defect structure into the computational methods will be discussed. Evidence will be presented that the effect of substrate roughness is dominant.

Diode RF sputtering technique has been used to produce carbon tungsten ultra thin layers stacks for application in the soft X-ray donain as optical system. In situ kinetic ellipsometry has been chooser to control the multilayers growth with a great accuracy. Grazing X-ray reflection (1.54 Å), absolute soft X-ray reflectivity (44.7 Å) and electron microscopy results confirm a posteriori the ellipsometry capabili-ties. The stacks have low roughness (2 Å) and low periodicity errors (2 %), 13 % experimental reflectivity instead of 20 % theoretical (2 d = 90 Å) and 7 % instead of 12 % (2 d = 60 Å) have been obtained.

In a previous paper on Si-SiO2 multilayered mirrors (1), we have shown that metal-oxyde systems can be an interesting alternative to metal-metal multilayered coatings for XUV optics in the range from 10 nm to 60 nm. In this paper, we report experimental results of studies made on : a) an Si-Si02 Fabry-Perot etalon b) an Al-Si02 multilayered mirror c) an Al-A1203 multilayered mirror

Development of laboratory X-ray lasers will require cavity components (mirrors, etc) able to survive intense pulses of soft x-rays. In this paper we examine physical processes which are likely to limit the performance of layered synthetic microstructures and establish a theoretical damage limit ~ .1 Joule/cm2 for Mo-Si composites. We also examine the suitability of our general computational tools (XSN, QEOS, TKN, LASNEX) for this unusual low-temperature application.

Many promising applications of multilayer x-ray optical elements subject them to intense radiation. This paper discusses the selection of optimal pairs of materials to resist heat damage and presents simulations of multilayer performance under extreme heat loadings.

A time resolved, 14 channel spectrometer with an absolutely calibrated response, was developed to cover an x-ray photon energy spectrum from 70 to 650 eV. The spectrometer utilized a combination of thin film prefilters, layered synthetic microstructure (LSM) diffractors, metal coated plastic scintillators, and photomultiplier detector tubes. Calibration of the spectrometer was done piecemeal for each component with standard techniques and the component calibrations were convolved to get a complete spectrometer response function. The complete assembled system was also calibrated at a synchrotron beamline. The two calibration procedures were compared.

Simple analytic and semianlytic models have been developed to estimate the useful lifetime of multilayer X-ray optics in pulsed, high x-ray flux environments. Analytic models are used for the reflectivity and absorption for arbitrary angle of incidence to calculate the absorbed power. The absorbed x-ray flux is converted to a temperature rise via the material enthalpy. Estimates of the effects of energy transport within the multilayer and of various mechanisms, which can effect multilayer performance are discussed.

Anisotropic etching was used to fabricate diffraction gratings on silicon wafers for use as substrates for layered synthetic multilayers. We worked with (110) and (100) oriented wafers to achieve etched sidewall angles of 35.3°, 46.5°, 54.7°, and 90°. Contact lithography was used to print gratings with a 20p period in order to evaluated the quality of the etched sidewalls. Projection lithography was used to print gratings with a 2μ period. Blazed gratings were fabricated from (111) oriented wafers cut 6° off the normal to the growth direction. A crystal alignment technique is described that allowed us to align the gratings to better than 0.1° of the correct crystal direction. Measurements are reported on the smoothness of etched silicon surfaces using three different etches.

We present preliminary results on a study of spatially resolved preheat of the rear of thin foils irradiated by laser (0.26 μm, 600 μs, 10 J). The record is done with a schwarzschild microscope made of two spherical multilayered mirrors coated to have the maximum reflectivity at normal incidence for the wavelength of 304 A (40 eV). The large aperture (0.2) and the high spatial resolution (~ 3 μm) of the device allow to perform a very precise record of the emissivity at 40 eV of the rear side of a thin laser heated foil. Results for different Z materials are presented.

An X-UV polarimeter with a rotating 45° angle of incidence multilayer as polarizer has been built and used to measure the polarization rates of the 154A and 304A light after monochromators. Due to the good polarization of the synchrotron source, polarization rates around of 70% have been measured.

A new apparatus designed to measure the quality of X-ray and X-UV dispersive devices of synchrotron radiation in the range 5000-50 eV is described. It consists of a double mirror high-frequency rejector, a constant deviation double crystal monochromator and a spectrogoniometer θ-2θ. The monochromator and the spectrogoniometer can be equipped with natural and artificial crystals or with multilayer interferential mirrors (MIMs). Absolute measurements of transmission for thin screens can be made, as well as reflectance for mirrors or MIMs. So, it is possible to determine optical constants particularly in anomalous regions. In the same way XANES, EXAFS, ref EXAFS, surface roughness, .... measurements can be achieved. In this paper we present the first results obtained by using beryl crystals and MIMs near 1000 eV.

A multilayer with 99 bi-layers and a 2.5 nm period made of carbon and tungsten has been produced as a test sample for a diode sputtering apparatus and process. The process included Microcleavage Transmission Electron Microscopy as a rapid characterization method.

We describe a model which predicts the performance characteristics of Charge-Coupled Device (CCD) detectors being developed for use in X-ray imaging. The model accounts for the interactions of both X-rays and charged particles with the CCD, and simulates the transport and loss of charge in the detector. Predicted performance parameters include detective and net quantum efficiencies, split-event probability and a parameter characterizing the effective thickness presented by the detector to cosmic-ray protons. The predicted performance of two CCDs of different epitaxial layer thicknesses is compared. The model predicts that, in each device, incomplete recovery of the charge liberated by a photon of energy between 0.1 and 10 keV is very likely to be accompanied by charge splitting between adjacent pixels. The implications of the model predictions for CCD data processing algorithms are briefly discussed.

In general, attention to a multitude of details is essential when designing low noise CCD cameras. This paper describes some of the critical details of the MIT X-ray CCD camera design. Special attention is given to those portions of the system which are different from conventional practice in the design of CCD cameras. Furthermore, an attempt has been made to generalize the design so that both optical and X-ray requirements can be satisfied wherever possible. Currently, noise levels of <8 electrons RMS are routinely achieved with this design, and even lower levels (<5 electrons) should be realizable.

The use of charge-coupled devices (CCDs) as single photon X-ray detectors has been documented by several research groups. In this paper we describe the design and performance of a powerful laboratory instrument for imaging and non-dispersive spectroscopy of soft X-rays (200 eV to 10 keV) utilizing Texas Instruments TI-4849 virtual-phase CCDs. With this instrument we have achieved a spatial resolution of 22 microns (limited by pixel size) with an overall array area of 584x390 pixels.We have achieved an energy-resolution of -140 eV FWHM for single-pixel Fe55 X-ray events (5.9 keV) with the CCD operated at only -30°C. We have operated the CCD in photon-counting mode at room-temperature and have obtained X-ray spectra with an energy resolution of -450 eV at 5.9 keV. We also have demonstrated the low-energy X-ray sensitivity of the CCD by detecting Carbon K-alpha X-rays (277 eV).