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AlN films on a Si substrate were synthesized by magnetron sputtering method. A dual magnetron system operating in AC mode was used in the experiment. Processes of synthesis were carried out in the atmosphere of a mixture of Ar/N2. Morphology and phase structure of the AlN films were investigated at different pressures. Structural characterizations were performed by means of SEM and X-ray diffraction methods. Our results show that the use of magnetron sputtering method in a dual magnetron sputtering system is an effective way to produce AlN layers which are characterized by a good adhesion to the silicon substrate. The morphology of the films is strongly dependent on the Ar/N2 gas mixture pressure. An increase of the mixture pressure is accompanied by a columnar growth of the layers. The films obtained at the pressure below 1 Pa are characterized by finer and compacter structure. The AlN films are characterized by a polycrystalline hexagonal (wurtzite) structure in which the crystallographic orientation depends on the gas mixture pressure.

Photocathodes are a limiting factor for the next generation of ultrahigh brightness photoinjectors. We studied the behavior of a superconducting Pb cathode in the cryogenic environment of a superconducting rf gun cavity to measure the quantum efficiency, its spatial distribution, and the work function. We will also discuss how the cathode surface contaminants modify the performance of the photocathode as well as the gun cavity and we discuss the possibilities to remove these contaminants.

The results of a study of irreversible changes induced at surfaces of metals, semiconductors, and insulators by extreme ultraviolet (λ

The multi-mJ, 21-nm soft-x-ray laser at the PALS facility was focused onto the surfaces of amorphous carbon (a-C) coatings, developed for heavily loaded XUV/x-ray optical elements. AFM (Atomic Force Microscopy) images show a 3-micrometer expansion of the irradiated material. Raman spectra, measured with an Ar + laser microbeam in both irradiated and unirradiated areas, confirm a high degree of graphitization in the irradiated layer. In addition to this high-fluence (∼ 1 J/cm 2 ), single-shot experiment, it was necessary to carry out an experiment to investigate the consequences of prolonged XUV irradiation at relatively low fluence. A high-order harmonic (HH) beam generated at the LUCA facility of the CEA/Saclay Research Center was used as a source of short-wavelength radiation delivering high-energy photons to the surfaces at a low single-shot fluence but with high-average power. a-C irradiated at low fluence, (< 0.1 mJ/cm 2 ) by many HH shots exhibits an expansion of several nanometers. Although it is a less dramatic change of surface morphology than that due to single-shot x-ray-laser exposures, even the observed nanometer-sized changes caused on an a-C surface by an HH beam could influence the reflectivity of a grazing incidence optical element. These results seem to be important for estimating damage to surfaces of highly irradiated optical elements developed for guiding and focusing the ultra-intense XUV/x-ray beams provided by the new generation of sources (VUV PEL and XFEL in Hamburg; LCLS in Stanford) because, up to now, only melting and vaporization, and not graphitization, have been taken into account.

The size-dependent magnetic properties of small iron clusters deposited on ultrathin nickel films have been studied with circularly polarized synchrotron radiation. With the use of sum rules, orbital and spin magnetic moments have been extracted from x-ray magnetic circular dichroism spectra. The ratio of orbital to spin magnetic moments varies considerably with cluster size, reflecting the dependence of magnetic properties on cluster size and geometry. These variations can be explained in terms of enhanced orbital moments in small clusters.

As part of the BERLinPro study, HZB is developing an SRF photoelectron injector. The R&D will be carried out in three stages, the first of which is currently being installed at HZB's HoBiCaT facility. It consists of an SRF cavity with SC solenoid, electron beam diagnosics and drivelaser systems.

The size-dependent magnetic properties of small iron clusters deposited on ultrathin Ni/Cu(100) films have been studied with circularly polarized synchrotron radiation. For x-ray magnetic circular dichroism studies, the magnetic moments of size-selected clusters were aligned perpendicular to the sample surface. Exchange coupling of the clusters to the ultrathin Ni/Cu(100) film determines the orientation of their magnetic moments. All clusters are coupled ferromagnetically to the underlayer. With the use of sum rules, orbital and spin magnetic moments as well as their ratios have been extracted from x-ray magnetic circular dichroism spectra. The ratio of orbital to spin magnetic moments varies considerably as a function of cluster size, reflecting the dependence of magnetic properties on cluster size and geometry. These variations can be explained in terms of a strongly size-dependent orbital moment. Both orbital and spin magnetic moments are significantly enhanced in small clusters as compared to bulk iron, although this effect is more pronounced for the orbital moment. Magnetic properties of deposited clusters are governed by the interplay of cluster-specific properties on the one hand and cluster-substrate interactions on the other hand. Size dependent variations of magnetic moments are modified upon contact with the substrate.