G. Soullie

Soft-x-ray polarimeter with multilayer optics: complete analysis of the polarization state of light

The design of a versatile high-precision eight-axis ultrahigh-vacuum-compatible polarimeter is presented. This multipurpose instrument can be used as a self-calibrating polarization detector for linearly and circularly polarized UV and soft-x-ray light. It can also be used for the characterization of reflection or transmission properties (reflectometer) or polarizing and phase-retarding properties (ellipsometer) of any optical element. The polarization properties of Mo/Si, Cr/C, Cr/Sc, and Ni/Ti multilayers used in this polarimeter as polarizers in transmission and as analyzers in reflection have been investigated theoretically and experimentally. In the soft-x-ray range, close to the p edges of Sc, Ti, and Cr, resonantly enhanced phase retardation of the transmission polarizers of as much as 18 degrees has been measured. With these newly developed optical elements the complete polarization analysis of soft-x-ray synchrotron radiation can be extended to the water-window range from 300 to 600 eV.

Phase contrast hard x-ray microscopy with submicron resolution

In this letter we present a hard x-ray phase contrast microscope based on the divergent and coherent beam exiting an x-ray waveguide. It uses lensless geometrical projection to magnify spatial variations in optical path length more than 700 times. Images of a nylon fiber and a gold test pattern were obtained with a resolution of 0.14 μm in one direction. Exposure times as short as 0.1 s gave already visible contrast, opening the way to high resolution, real time studies.

Laser Integration Line target diagnostics first results (invited)

The Laser Integration Line (LIL) is part of the Laser Megajoule (LMJ) project. The LMJ installation, which is of the National Ignition Facility (NIF) class, will deliver 1.8MJ at 0.35μm wavelength on target with 60 quadruplets of elementary beams. The energy on target of LIL is 30kJ corresponding to one quadruplet, it is housed in a separate building and has its own experimental setup. Target diagnostics have been progressively installed in the LIL target area. Energy and imaging diagnostics as well as the broadband and high resolution spectrometers have been fabricated in the frame of a unique industrial contract. Optical pointers are used to align the diagnostics to the target. The supervisory system controlling the diagnostics configuration and data acquisition is now able to manage cooperative and Commissariat a l’ Energie Atomique (CEA) shots. The calibration data base is accessible from the processing network and will very soon include the characterization of all the streaked, gated, and charge coup...

Sub-micrometre coherent beams from x-ray waveguides: principles and applications

The operating principle and some applications of the x-ray waveguides are revised. Significant improvements in waveguide fabrication with respect to the first ones yielded gain of about a factor six with respect to the incident intensity. The high degree of coherence and the divergence of the beam exiting the waveguide allowed phase contrast experiments with unprecedented spatial resolution of 140 nm. An innovative geometry for microdiffraction experiments is proposed which can open the way to very high spatial resolution measurements. The results of a very recent test experiment on a patterned silicon crystal are presented.

X-ray multilayer monochromator with enhanced performance

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 x-ray calibration facility of the laser integration line in the 0.9–10 keV range: The high energy x-ray source and some applications

The laser integration line (LIL) located at CEA-CESTA is equipped with x-ray plasma diagnostics using different kinds of x-ray components such as filters, mirrors, crystals, detectors, and cameras. The CEA-DAM of Arpajon is currently developing x-ray calibration methods and carrying out absolute calibration of LIL x-ray photodetectors. To guarantee LIL measurements, detectors such as x-ray cameras must be regularly calibrated close to the facility. A new x-ray facility is currently available to perform these absolute x-ray calibrations. This paper presents the x-ray tube based high energy x-ray source delivering x-ray energies ranging from 0.9 to 10 keV by means of an anode barrel. The purpose of this source is mainly to calibrate LIL x-ray cameras but it can also be used to measure x-ray filter transmission of plasma diagnostics. Different x-ray absolute calibrations such as x-ray streak and framing camera yields, x-ray charge-coupled device quantum efficiencies, and x-ray filter transmissions are presented in this paper. A x-ray flat photocathode detector sensitivity calibration recently performed for a CEA Z-pinch facility is also presented.

Thin film X-ray waveguides: ‘Condenser systems’ for experiments with X-ray beams of 0.1 μm dimension

This report discusses the latest performance data for X-ray waveguides applied in the production of hard X-ray micro-spots. It is possible to compress an X-ray radiation beam in a thin film waveguide in one direction down to the level of about 0.1 μm, a value which has not been achieved routinely with any other device. A gain factor of about 5 could be achieved in this case for a photon energy of 17 keV. The thin film waveguides were found to provide increasing transmission from 11 keV to 25 keV. As the exiting beam is not only of small size but also highly coherent and divergent it can be used in a number of microscopic techniques: e.g. micro-diffraction, micro-fluorescence, Gabor-holography, phase contrast microscopy.

X-ray grating spectrometer for opacity measurements in the 50 eV to 250 eV spectral range at the LULI 2000 laser facility

An x-ray grating spectrometer was built in order to measure opacities in the 50 eV to 250 eV spectral range with an average spectral resolution ∼ 50. It has been used at the LULI-2000 laser facility at École Polytechnique (France) to measure the Δn = 0, n = 3 transitions of several elements with neighboring atomic number: Cr, Fe, Ni, and Cu in the same experimental conditions. Hence a spectrometer with a wide spectral range is required. This spectrometer features one line of sight looking through a heated sample at backlighter emission. It is outfitted with one toroidal condensing mirror and several flat mirrors cutting off higher energy photons. The spectral dispersion is obtained with a flatfield grating. Detection consists of a streak camera sensitive to soft x-ray radiation. Some experimental results showing the performance of this spectrometer are presented.

Experimental multilayer survey in the VUV

We present an experimental survey of the performance of various multilayer systems to be used in the soft x-ray range with special emphasis on the water window. The multilayers have been designed as high reflectance normal incidence mirrors and, for polarimetry purposes, as detectors for circularly polarized synchrotron radiation, respectively. Seven different multilayer systems with spacer materials of C or the transition metals Sc, Ti, V, Cr in combination with the absorber materials Fe, W and Ni were investigated. At the 1s- and 2p absorption edges, respectively, they show a strong resonant enhancement of the reflectance due to anomalous dispersion. By tailoring the layer thickness and the thickness ratio for use at and below the resonance energy in normal incidence ((theta) equals 90 degree(s)) and at (theta) equals 45 degree(s), respectively, an excellent performance with respect to reflectance, transmission and polarizance, respectively, in the water window was achieved for multilayers with period thicknesses down to 1.4 nm.

Application of resonance-enhanced X-ray standing waves to the study of layered structures by grazing-incidence X-ray reflectometry and secondary radiation

Abstract In this work we present a review of results on reflectivity, fluorescence and photoelectron spectra investigated in layered samples, in which resonance-enhanced X-ray standing waves (RE–XSW) are formed. The new experimental results of photoelectron energy distribution excited in a thin carbon film deposited on a Ni mirror, as well as results obtained earlier, are compared and discussed. The new photoelectron measurements were performed using a conventional X-ray tube as radiation source for the energy Cu Kα (8047 eV), and recorded with a flow proportional electron counter of about 15% energy resolution. Also, new results of grazing-angle reflectivity from a X-ray waveguide sample recorded with a 13-keV synchrotron radiation is reported. Comparison of the results with theoretical models based on the Fresnel formula and Parratt recursive algorithm is done. The reflectivity and in-depth electric field distribution dependencies on wavelength, roughness, as well as composition of structures are calculated and compared to experimental spectra. The possible fields of application of the resonance-enhanced XSW to the study of layered structures, showing also some limitations inherent to the method are discussed.