A high-resolution x-ray imager (HRXI) devoted to laser-plasma experiments combines two state-of-the-art technologies developed in France: a high-resolution x-ray microscope and a high-speed x-ray streak camera. The resulting streaked imager achieves spatial and temporal resolutions of approximately 5 microm and approximately 10 ps, respectively. The HXRI has recorded enhanced spatial and temporal resolution radiographs of indirectly driven targets on OMEGA. This paper describes the main features of the instrument and details the activation process on OMEGA (particularly the alignment). Recent results obtained on joint CEA/LLE radiographic OMEGA experiments will also be presented.

The design of efficient lamellar multilayer amplitude grating (LMAG) monochromators in terms of bandwidth and peak reflectivity for the soft-X-ray domain, covering the K emission of low atomic-number elements: B to Si, is considered. A Mo/B4C LMAG suited for spectrometry in this spectral domain has been designed, fabricated using electron beam lithography together with reactive ion etching and tested with success.

Metrology of XUV beams (X-ray lasers, high-harmonic generation and VUV free-electron lasers) is of crucial importance for the development of applications. We have thus developed several new optical systems enabling us to measure the optical properties of XUV beams. By use of a Michelson interferometer working as a Fourier-transform spectrometer, the line shapes of different X-ray lasers have been measured with a very high accuracy (Δλ/λ∼10 -6 ). Achievement of the first XUV wavefront sensor has enabled us to measure the beam quality of laser-pumped as well as discharge-pumped X-ray lasers. A capillary discharge X-ray laser has demonstrated a very good wavefront allowing us to achieve an intensity as high as 3×10 14 W cm -2 by focusing with a f=5 cm mirror. The sensor accuracy has been measured using a calibrated spherical wave generated by diffraction. The accuracy has been estimated to be as good as λ/120 at 13 nm. Commercial developments are underway. At Laboratoire d’Optique Appliquée, we are setting up a new beamline based on high-harmonic generation in order to start the femtosecond, coherent XUV optic .

The time resolved crystal x-ray spectrometers called SXDHR-lt of the Ligne d’Intégration laser is presented. It is necessary to calibrate all x-ray sensitive elements of diagnostics before using them in laser matter interaction experiments. In particular, crystals need to be calibrated. Measurements of the integrated coefficient of reflection of a beryl cylindrical crystal used in this spectrometer were performed with synchrotron radiation and with an x-ray tube and are presented. A test of the homogeneity of the reflection of the crystal was also performed. Aging or accidental pollution of x-ray diagnostics installed around target chambers is always possible. This happened to the DMX broadband spectrometer installed on the OMEGA Laser Facility at the University of Rochester (Laboratory for Laser Energetics) and this changed the spectral sensitivity of its channels. The evolution over time of the x-ray sensitivity needs to be critically assessed and if necessary x-ray sensitive elements will need to be recalibrated.

The first longitudinal coherence measurement of the transient inversion collisional x‐ray laser is presented. The scheme under study is the picosecond output of the Ni‐like Pd x‐ray laser at 14.68 nm generated by the COMET laser facility at LLNL. Interference fringes were generated using a Michelson interferometer setup in which a thin multilayer membrane was used as a beam splitter. Longitudinal coherence measurements were made for this transition by changing the length of one interferometer arm and measuring the resultant variation in fringe visibility. The nature of this dependence also allows for an estimation of the linewidth of the lasing transition to be made. Analysis indicates a linewidth of ∼0.3 pm which is a factor of four less than previous measurements on quasi‐steady state x‐ray laser schemes.

We present the longitudinal coherence measurement of the transient inversion collisional x-ray laser for the first time. The Ni-like Pd x-ray laser at 14.68 nm is generated by the LLNL COMET laser facility and is operating in the gain-saturated regime. Interference fringes are produced using a Michelson interferometer setup in which a thin multilayer-coated membrane is used as a beam splitter. The longitudinal coherence length for the picosecond duration 4d(1)S(0) --> 4p(1)P(1) lasing transition is determined to be similar to400 mum (1/e HW) by adjusting the length of one interferometer arm and measuring the resultant variation in fringe visibility. This is four times improved coherence than previous measurements on quasi-steady state schemes largely as a result of the narrower line profile in the lower temperature plasma. The inferred gain-narrowed linewidth of similar to0.29 pm is also substantially narrower than previous measurements on quasi-steady state x-ray laser schemes. This study shows that the coherence of the x-ray laser beam can be improved by changing the laser pumping conditions. The x-ray laser is operating at 4-5 times the transform-limited pulse.

Metrology of XUV beams and more specifically X-ray laser (XRL) beam is of crucial importance for development of applications. We have then developed several new optical systems enabling to measure the x-ray laser optical properties. By use of a Michelson interferometer working as a Fourier-Transform spectrometer, the line shapes of different x-ray lasers have been measured with an unprecedented accuracy (deltalambda/lambdasimilar to10(-6)). Achievement of the first XUV wavefront sensor has enable to measure the beam quality of laser-pumped as well as discharge pumped x-ray lasers. Capillary discharge XRL has demonstrated a very good wavefront allowing to achieve intensity as high 3*10(14) Wcm(-2) by focusing with a f = 5 cm mirror. The measured sensor accuracy is as good as lambda/120 at 13 nm. Commercial developments are under way.

The principle of a multilayer monochromator with a narrow bandwidth and a low specular background is recalled. The elaboration of such a monochromator obtained from a Mo/Si multilau-yer mirror is briefly described. The performance of the device measured at 1500 and 98 eV is presented. Le principe d'un monochromateur multicouche a bande passante etroite et presentant un faible fond continu est rappele. Nous decrivons brievement la fabrication d'un tel monochromateur obtenu a partir d'un miroir multicouche Mo/Si. Les performances de ce dispositif mesurees a 1500 et 98 eV sont presentees.

An x-ray multilayer monochromator with improved resolution and a low specular background is presented. The monochromator consists of a lamellar multilayer amplitude grating with appropriate parameters used at the zeroth diffraction order. The device is fabricated by means of combining deposition of thin films on a nanometer scale, UV lithography, and reactive ion etching. The performance of this new monochromator at photon energies near 1500 eV is shown.

The double Kirkpatrick–Baez (DBA) microscope is derived from the grazing x-ray Kirkpatrick–Baez (KB) microscope. The KB is compound of two concave spherical mirrors working at grazing incidence and in an energy range about 100 eV–10 keV. The combination of two similar mirrors in the DKB increases the useful field. This device only requires spherical mirrors, more easy to manufacture (precision and roughness) than aspherical ones. In order to image a laser plasma source in a large field of view and within a bandpass of 0.6 keV around 3.4 keV, a KB optic covered with multilayers is developed. In fact, a compromise has to be found between the resolution of the optic (better with a less grazing angle), and the reflectivity (better with more grazing angle). We have chosen to keep the average grazing incidence on the four mirrors around 2°–3° just as for a first uncoated DKB made in our laboratory. This allows us to keep the same radius of curvature for the mirrors. At this energy multilayers are needed, due to the required reflectivity of better than 7% for each mirror. A difficulty appears concerning the energy and angular acceptance of multilayers. It is shown that a nonperiodic multilayer structure can be calculated to solve this problem, in spite of the absorption of the layers at the low energy of our application. The variation of periods is not continuous as in known classical supermirrors, and all the experimental parameters such as complex index of refraction and roughness have to be known. Thicknesses can then be optimized individually. The multilayers were deposited, tested, and the defects identified and corrected. Final experimental results of such stacks are given.

Photoionization of multiply charged ions of the Ba isonuclear sequence up to Ba6+ has been studied in a beam-beam experiment. A very strong increase in the resonance structures was observed when moving from Ba2+ to Ba6+. Absolute values of the photoionization cross sections were measured for Ba2+ and Ba3+ ions. The interpretation of the results is provided using theoretical multiconfiguration Dirac-Fock and relativistic random phase approximation calculations, showing that the collapse of the nf orbitals occurs for Ba4+.

A new soft-x-ray multilayer monochromator with an improved resolution and a low specular background is presented. The principles of the device, based on the use of a lamellar multilayer amplitude grating (LMAG), are summarized. The techniques of fabrication of the monochromator (multilayer deposition, UV lithography and reactive ion etching) are given. The performance of this new monochromator at photon energies around 1500 eV is demonstrated. Copyright © 2001 John Wiley & Sons, Ltd.

Dans le cadre du projet Simulation du CEA/DAM, l'acces experimental aux hautes densites d'energie et au domaine de la fusion thermonucleaire en Laboratoire se fera par le Laser Megajoules (LMJ) dont le prototype LIL est en cours de construction au CEA/CESTA pres de Bordeaux. Les programmes experimentaux correspondants ont necessite des performances elevees et le developpement d'une instrumentation de premier plan. C'est notamment le cas des diagnostics plasma qui ont evolue avec le developpement des lasers de puissance et celui des technologies adaptees pour etudier leur comportement. Le Service Diagnostics Experimentaux du CEA/Bruyeres-Le-Chatel developpe des diagnostics et integre la metrologie associee dans la conception de diagnostics. Nous presentons les moyens dont on dispose aupres du rayonnement synchrotron pour la metrologie des diagnostics et l'interet de cette metrologie pour l'etude des plasmas-laser.

We present new results obtained on photoionization processes in Xe3+ to Xe7+ ions, using ion spectrometry. The experiment combines for the first time a beam of multiply-charged ions produced in an electron cyclotron resonance (ECR) ion source and a beam of synchrotron radiation emitted from an undulator. These results provide a complete picture of the behavior of resonant and continuum photoionization processes along the Xe isonuclear sequence, following the complete stripping, electron by electron, of the 5p subshell.

Photoionization of Xe4+ to Xe7+ ions was studied by combining an electron cyclotron resonance ion source with synchrotron radiation. Multiconfiguration Dirac-Fock calculations were performed to interpret the data. Many autoionization lines were measured and identified, resulting from excitation of a 4d electron into nf and np orbitals followed by Auger decay of the excited states. Continuum photoionization is negligible for the higher members of the isonuclear series.

In order for brominated plastic (CHBr) to be used in future large lasers, such as the National Ignition Facility, capsule design, and equation of state (EOS) data are needed to address uncertainties in modeling. We have performed CHBr EOS measurements using the impedance matching technique. Laser beams spatially smoothed, and giving a spot size of 400 μm and intensities ⩽5×1013 W/cm2, produced high-quality shock waves allowing the simultaneous measurements of the shock velocities in two materials, one used as reference. Results are compared to other experiments and to EOS calculations. We obtained very good agreement with the theoretical curve for pressures ranging from 1 to 3 Mbar.