Optical design of hard x-ray beamlines can be accurately performed through ray tracing simulation technique. We
describe here the way and the tools we use at SOLEIL to develop hard x-ray beamlines such as PSICHÉ, which is a
wiggler beamline performing diffraction and tomography experiments from 20 to 50 keV. This beamline is made of two
focusing stages, one with a long vertical focusing mirror together with a sagittal focusing crystal monochromator to gain
a spot of 100x50 μm and the other one applying a set of graded multilayer KB mirrors to reach 10x10 μm spot. Ray
tracing simulations are performed with SpotX, which provides optical properties of the beamline taking into account
thermal load on optics, surface polishing defects from the profilometer measurements.
The X-ray emission of the HU52 Apple2 undulator of the SOLEIL DEIMOS (Dichroism Experimental Installation for
Magneto-Optical Spectroscopy) beamline is analyzed using the Bragg diffraction of a Si(111) crystal at various
undulator gaps in linear horizontal polarization. Measurements are compared with simulations in order to determine
undulator properties. The method allows also to get information on the electron beam.
In this article, a stitching Shack-Hartmann profilometric head is presented. This instrument has been developed to answer
improved needs for surface metrology in the domain of short-wavelength optics (X/EUV). It is composed of a highaccuracy
Shack-Hartmann wavefront sensor and an illumination platform. This profilometric head is mounted on a
translation stage to perform bidimensional mappings by stitching together successive sub-aperture acquisitions. This
method ensures the submicroradian accuracy of the system and allows the user to measure large surfaces with a submillimetric
We particularly emphasize on the calibration method of the head; this method is validated by characterizing a super-flat
reference mirror. Cross-checked tests with the Soleil's long-trace profiler are also performed. The high precision of
profilometric head has been validated with the characterization of a spherical mirror. We also emphasize on the large
curvature dynamic range of the instrument with the measurement of an X-ray toric mirror.
The instrument, which performs a complete diagnostic of the surface or wavefront under test, finds its main applications
in metrology (measurement of large optics/wafers, post-polishing control and local surface finishing for the industry,
spatial quality control of laser beam).
In third generation synchrotron radiation beamlines, a focussed X-ray beam is often employed. However, in some cases users need to modify their spot size in order to match the broad range of samples sizes. This is the case for XPEEM microscopy beamline which need a homogeneous beam with a spot size varying from 2 to 50 μm. These specifications requires that the beamline works out of focus, and in this case the spot becomes non homogenous (as already observed experimentally on several synchrotron beamlines). In this paper, we will explain, using a geometrical approach, that this effect on the spot is produced by mirrors slope errors. We propose a new optical solution that overcomes these difficulties. Our optical solution has been validated experimentally on the second branch of the Nanospectroscopy beamline at Elettra, where we have obtained homogenous spot sizes of 10, 20 and 30 μm with the same optical design.
In 2002, first experiments at the Advanced Light Source (ALS) at Berkeley, allowed us to test a first prototype of EUV Hartmann wave-front sensor. Wave-front measurements were performed over a wide wavelength range from 7 to 25 nm. Accuracy of the sensor was proved to be better than λEUV/120 rms (λEUV = 13.4 nm, about 0.1 nm accuracy) with sensitivity exceeding λEUV/600 rms, demonstrating the high metrological performances of this system.
At the Swiss Light Source (SLS), we succeeded recently in the automatic alignment of a synchrotron beamline by Hartmann technique. Experiments were performed, in the hard X-ray range (E = 3 keV, λ = 0.414 nm), using a 4-actuators Kirkpatrick-Baez (KB) active optic. An imaging system of the KB focal spot and a hard X-ray Hartmann wave-front sensor were used alternatively to control the KB. The imaging system used a genetic algorithm to achieve the highest energy in the smallest spot size, while the wave-front sensor used the KB influence functions to achieve the smallest phase distortions in the incoming beam. The corrected beam achieved with help of the imaging system was used to calibrate the wave-front sensor. With both closed loops, we focused the beam into a 6.8x9 μm2 FWHM focal spot. These results are limited by the optical quality of the imaging system.
The European Photon Imaging Camera (EPIC) is one of the major instruments on board the European Space Agency's X-ray Multi-Mirror cornerstone mission planned for launch at the end of the century. Ground calibrations have been performed in 1997 and 1998 on the electrical and flight models of the MOS-CCD and on the flight model of the p-n-CCD focal plane cameras at he Synchrotron facility at IAS Orsay in France. The complexity of the imaging systems required a correspondingly sophisticated calibration equipment, capable of automatically setting and calibrating the synchrotron beam at a particular energy, controlling the camera head movement in synchronism with the CCD frame readout, initializing the instrument and acquiring both the instrument data and the facility monitor data in realtime. Furthermore, always in real-time, the data stream was unpacked and stored as photon lists in FITS format and made available via NFS to the off-line analysis software. Contemporaneously, a quick look program allowed the operator to continuously monitor the calibration procedure from a scientific point of view, ensuring the correct operation of the system. The calibration system from the point of view of the instrument and the current status of the project is described.
Using a diode rf-sputtering technique, different magnesium silicide based multilayer systems have been deposited in very thin films for optical applications in the soft x-ray range. A detailed structural analysis of the different multilayers has been made using in-situ kinetic ellipsometry, ex-situ grazing x-ray reflection at the copper K-(alpha) line and transmission electron microscopy. The multilayer performances have been measured by synchrotron radiation at the magnesium K-(alpha) and L-(alpha) lines and related to the structural characteristics. For short wavelength, the W/Mg2Si system shows characteristics very similar to those of the more common W/Si system. Non-negligible interdiffusion and limited interface roughness allow the layer thicknesses to be reduced to very low values. Well-defined Bragg peaks are observed even when the double period is as low as 44 angstrom. First Bragg peak reflectivity as high as 31 has been measured at 9.89 angstrom for a multilayer with a double period equal to 84 angstrom and a limited number of periods. This preliminary result is very promising for future applications in the field of x-ray fluorescence analysis. W/Mg2Si and Si3N4/Mg2Si multilayers have also been fabricated for use at higher wavelengths around the Mg L-(alpha) line (286 angstrom). In the case of the W/Mg2Si multilayers have also been fabricated for use at higher wavelengths around the Mg L-(alpha) line (286 angstrom). In the case of the W/Mg2Si system, the tungsten layers are crystallized due to their higher thickness and consequently the interface roughness is slightly higher. In spite of this, more than 20 reflectivity at the first Bragg peak has been measured at normal incidence on different W/Mg2Si samples, with a selectivity two times better than conventional Mo/Si mirrors ((lambda) /(delta) (lambda) approximately equals 20). When we replace tungsten by a thin silicon nitride layer deposited by reactive sputtering, we increase the selectivity up to (lambda) /(delta) (lambda) approximately equals 30, and the thermal stability is drastically improved ( 800 degree(s)C).
We report on the fabrication of linear and circular reflective Bragg-Fresnel zone
plates made by a multistep process using microfabrication technologies. The zone plate
patterns were generated by electron beam lithography on a Mo/C triode sputtered
multilayer interference mirror. The minimum zone size was 0.3 p.m wide. The pattern
was transferred anisotropically into the multilayer by reactive ion etching in a fluorinated
plasma. An intermediate metallic mask made by lift-off was used for the transfer
process. The groove depth was monitored by following the reflectivity of the structure
with a helium-neon laser during the etching process. The groove profile and dimensional
control were considered.