98 research outputs found
Electromagnetic-field distribution measurements in the soft s-ray range: full characterization of a soft x-ray laser beam
Includes bibliographical references (pages 183901-4).We report direct measurement of the electromagnetic-field spatial distribution in a neonlike Ar capillary discharge-driven soft x-ray laser beam. The wave front was fully characterized in a single shot using a Shack-Hartmann diffractive optics sensor. The wave front was observed to be dependent on the discharge pressure and capillary length, as a result of beam refraction variations in the capillary plasma. The results predict ~70% of the laser beam energy can be focused into an area 4 times the size of the diffraction-limited spot, reaching intensities of ~4 × 1013 W/cm2
The European Photon Imaging Camera on XMM-Newton: The MOS Cameras
The EPIC focal plane imaging spectrometers on XMM-Newton use CCDs to record
the images and spectra of celestial X-ray sources focused by the three X-ray
mirrors. There is one camera at the focus of each mirror; two of the cameras
contain seven MOS CCDs, while the third uses twelve PN CCDs, defining a
circular field of view of 30 arcmin diameter in each case. The CCDs were
specially developed for EPIC, and combine high quality imaging with spectral
resolution close to the Fano limit. A filter wheel carrying three kinds of
X-ray transparent light blocking filter, a fully closed, and a fully open
position, is fitted to each EPIC instrument. The CCDs are cooled passively and
are under full closed loop thermal control. A radio-active source is fitted for
internal calibration. Data are processed on-board to save telemetry by removing
cosmic ray tracks, and generating X-ray event files; a variety of different
instrument modes are available to increase the dynamic range of the instrument
and to enable fast timing. The instruments were calibrated using laboratory
X-ray beams, and synchrotron generated monochromatic X-ray beams before launch;
in-orbit calibration makes use of a variety of celestial X-ray targets. The
current calibration is better than 10% over the entire energy range of 0.2 to
10 keV. All three instruments survived launch and are performing nominally in
orbit. In particular full field-of-view coverage is available, all electronic
modes work, and the energy resolution is close to pre-launch values. Radiation
damage is well within pre-launch predictions and does not yet impact on the
energy resolution. The scientific results from EPIC amply fulfil pre-launch
expectations.Comment: 9 pages, 11 figures, accepted for publication in the A&A Special
Issue on XMM-Newto
X-UV INTERFERENTIAL MIRRORS AND NEW POSSIBILITIES FOR PLASMA RADIATION STUDIES
La réalisation de miroirs interférentiels adaptés au domaine X-UV est une possibilité apparue seulement depuis une dizaine d'années. Dans une première partie nous rappelons les caractéristiques principales de tels miroirs. Par comparaison avec les optiques sous incidence rasante seules disponibles jusqu'à maintenant, nous indiquons ensuite les nouvelles voies ouvertes par leur utilisation. Enfin nous donnons quelques exemples de diagnoctic de plasma tirant partie de ces nouvelles possibilités.For about ten years new multilayered X-UV mirrors have been in progress and are now overcoming some of the main dificulties well known with the grazing incidence optics used up to now. The main characteristics of such mirrors are first recalled. Next some of the new possibilities in X-UV spectroscopy and imaging are given. Finally we briefly describe some examples of new set ups using such X-UV interference mirrors for plasma diagnostic
Miroirs interférentiels X et X-UV. Un cas particulier de multicouches métalliques à faibles périodes
Depuis les années 70 on sait préparer des miroirs interférentiels X et X-UV, analogues dans leur principe aux multicouches diélectriques employées dans le domaine visible. Pour cela, à partir de deux matériaux choisis, on doit déposer de façon reproductible et périodique un grand nombre de bicouches. Les interfaces doivent être abruptes et les épaisseurs de matériaux de quelques couches atomiques. Comme pour les autres types de multicouches, les principales méthodes de dépôt ont été essayées ; celles par bombardement ionique apparaissent comme les mieux adaptées pour la préparation de ce type de structures. Peu de méthodes de contrôle in situ existent, bien qu'il reste souhaitable de déposer les couches en vérifiant continûment leurs caractéristiques. Pour ces miroirs, les principales méthodes de caractérisations sont basées sur la diffraction X, si possible à la longueur d'onde et à l'angle d'incidence envisagés pour l'utilisation. La qualité des interfaces est déterminante pour les performances de réflectivité
METALLIC MULTILAYERS MIRRORS : NEW POSSIBILITIES FOR SOFT X-RAY IMAGING AND SPECTROSCOPY
Par évaporation successive de deux matériaux correctement choisis on sait maintenant obtenir des réflecteurs de Bragg pour le domaine X-UV où jusqu'ici seule l'incidence rasante pouvait être employée.Successive evaporations of two correctly choosen elements permit now to obtain high efficient Bragg reflectors in X-UV where until now the grazing incidence optics was the only one solution
X and X-UV multilayered optics: principles, fabrication methods, tests and applications
X and X-UV artificial interferential mirrors are analogous to the dielectric multilayers prepared for the visible range, or to natural and organic crystals used in the X-ray range. Progress in evaporation methods, knowledge of the X-UV optical indices and better understanding of interferential mirror principles have lead to the possibility to optimize the fabrication of efficient X and X-UV optics based on such artificial Bragg reflectors.Specific preparation methods have been developed to obtained regular stacks having periodic ultra thin layers of two materials, convenient from the metallurgical and optical point of views. Testing methods use mainly X ray reflectivity measurements. Comparison with theoretical predictions bring insight to the interface quality and regularity of the layering. New multilayerd optical devices for spectroscopy, imaging in X and X-UV are under development for plasma physics and synchrotron radiation applications. They offer completely new possibilities compared to the total reflection optics which was until to now the only way to work in X-UV
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