Perfect crystals with asymmetric surface cut were studied to evaluate their influence on the coherence of x-rays. An analysis of single- and double-crystal setups in both Bragg and Laue geometries is presented. The Bragg case was studied experimentally. The experiments were performed at Optics Beamline BM5 of the European Synchrotron Radiation Facility. A virtual source created by an asymmetric crystal was probed using an interferometry technique based on fringe analysis, which were produced by boron fiber. The conditions required to preserve coherence in a double-crystal setup are obtained theoretically, and proved experimentally in case of Bragg diffraction.

In SPring-8, the first crystals with pin-post water path have widely used at x-ray undulator beamlines. The crystals have been fabricated by using metal diffusive bonding technique. Although the initial crystals had sufficient endurance for high heat load, deterioration of the performance due to the strain induced by the water pressure was observed. Newly designed crystal showed better diffraction properties. Some problems to be improved are also discussed.

Most SPring-8 x-ray beamlines are installed double-crystal monochromators that are standardized. For x-ray undulator beamlines where power density of the beam are quite high, rotated-inclined double-crystal geometry is usually adopted, which enlarges the footprint of the incident beam on the crystal surface to reduce the power density. On the other hand, adjustable-inclined double-crystal geometry is adopted for bending-magnet beamlines to extend the available energy range with a limited Bragg angle range. The standardized monochromator mechanism is compatible to both of the geometries, only by changing crystal mounts. Detailed description of the monochromator mechanism is presented.

Both simulations and recent experiments conducted at the Advanced Photon Source showed that the performance of liquid- nitrogen-cooled single-silicon crystal monochromators can degrade in a very rapid nonlinear fashion as the power and/or power density is increased. As a further step towards improving the performance of silicon optics, we propose cooling with liquid helium, which dramatically improves the thermal properties of silicon beyond that of liquid nitrogen and brings the performance of single silicon-crystal-based synchrotron radiation optics up to the ultimate limit. The benefits of liquid helium cooling as well as some of the associated technical challenges will be discussed, and results of thermal and structural finite elements simulations comparing the performance of silicon monochromators cooled with liquid nitrogen and helium will be given.

With the help of new and old dynamical diffraction theory of the diffraction in single crystals it is shown that reflections usually considered as forbidden, strictly speaking, are not. For sufficiently thick crystals they can be as strong s nonforbidden ones, but their width is 4 - 5 orders of magnitude lower.

The aim of this paper is to review the performances of the multi-segmented piezoelectric bimorph mirrors currently installed at the European Synchrotron Radiation Facility (ESRF). These innovative devices effectively combine the possibility of varying dynamically the average spherical bending radius (active mode) with the capability of acting locally on the reflecting surface shape (adaptive mode). A first generation consisting of two prototypes (450 and 750 mm long) was completely characterized in the ESRF metrology laboratory and the mirrors are installed and fully operational on the ID26 and ID32 beamlines since October 1997. A second generation prototype mirror (450 mm long) has been designed, manufactured, tested in the ESRF metrology laboratory, installed and commissioned at ID26 in early 1998. This last mirror exhibits sub-(mu) rad residual slope error rms in its central portion, 1 angstrom rms averaged microroughness and can routinely achieve a vertical beam size as small as 7 micrometer FWHM at a focal distance of almost 3 m.

Advanced Wolter X-ray microscope is developed to diagnose laser-produced plasmas and for the researching Inertial Confinement Fusion (ICF). The microscope is composed of two aspherical mirrors. We present X-ray Imaging Diagnostic and imaging studies we have performed with two kinds of X-ray source: an x-ray generator and a plasma laser x-ray source obtained with a power laser facility at 'Centre d'etudes de Limeil-Valenton,' France. A spatial resolution of better than 4 micrometer has been obtained in the 1 - 5 keV range over a field of 500 micrometer and for different magnifications varying from 15 to 40.

Surface flatness of optical elements like mirrors and multilayers may significantly influence on the experiments exploiting coherence properties of x rays. A wavy mirror surface can be considered as a random-phase object. In the article, brief notes on the coherence propagation downstream from a random-phase object are presented. Image formation of a wavy surface at grazing incidence is analyzed. An approach to the inverse problem solution of phase retrieval from the mirror images in coherent x rays is shown. A performed experiment demonstrates general consistency in surface topography obtained by means of x rays and LTP. The estimates on the coherence degradation due to surface roughness are obtained.

In the past decade, several third-generation synchrotron x-ray sources have been constructed and commissioned around the world. Many of the major problems in the development and design of the optical components capable of handling the extremely high heat loads of the generated x-ray beams have been resolved. It is expected, however, that in the next few years even more powerful x-ray beams will be produced at these facilities, for example, by increasing the particle beam current. In this paper, the design of a next generation of synchrotron x-ray mirrors is discussed. It is shown that contact-cooled mirrors capable of handing x-ray beam heat fluxes in excess of 500 W/mm² (more than three times the present level) can be designed. The limiting factor in these mirrors is thermal stress rather than thermally induced slope error.

At present the most widespread multilayer structures are those, in which low absorbing layers from light elements (from carbon, in particular) alternate with strong absorbing layers from heavy metals. Recently it became possible to manufacture x-ray multilayer mirrors containing only low absorbing carbon layers with different values of densities and, consequently, dielectric constants. The properties of these carbon/carbon multilayers were experimentally investigated at BESSY in the energy range of 50 - 2000 eV. Such multilayers promise to combine high reflectivity and high resolution.

Previously we reported the ability to lift off, via electroforming, multilayers deposited on gold coated flat mandrels. We had shown the multilayers remained intact after separation as the X-ray reflectivity produced peaks in the reflectivity versus energy measurements. Since gold is high a Z material and is not easy to remove via chemical etching, we have now developed the ability to use a low-Z material that is also etchable. Moreover, we improved the quality of the smoothing with the process of amorphous carbon nitride (CN_x) deposition on electroless nickel in both our test chamber and our much larger fabrication chamber. Our method of mandrel preparation is to first deposit CN_x on electroless nickel, then a low-Z release layer, and then the multilayers. We have demonstrated that flat mandrels produced in this manner can be cooled to liquid nitrogen temperatures without harm. This is important as the usual practice is to shrink mandrels that have Wolter I shape via liquid nitrogen. We have coated a truncated-cone-shaped 'engineering' (not high quality in terms of smoothness) mandrel and have removed the layers, intact, on the inside of an electroform with a cylindrical, truncated- cone geometry. We report the details of the fabrication, engineering, and X-ray tests.

We present the results from a systematic study of several different material combinations for multilayer coatings on flat silicon and fused silica substrates. To obtain high reflectivity in a broad energy bandpass for hard X-rays (greater than 10 keV), a graded d-spacing multilayer structure must satisfy a set of conditions, e.g., low surface and interface roughness/diffuseness, good layer thickness uniformity, low residual stresses, etc. The coating process must be stable and accurately controlled over long deposition times, and allow good reproducibility from one run to another. The deposition method used was DC magnetron sputtering at low argon pressures (1.5 to 3.5 mT). The materials selected for the reflector/spacer pair were W/Si, W/C, Ni/C, and Pt/C. The initial work consisted in calibrating the deposition rate and optimizing the process parameters (argon backpressure, target to substrate distance, and cathode current). The main characterization methods used were: Atomic Force Microscopy in tapping mode, stylus profilometry, and specular X-ray reflectivity. In the next stage of the study, constant and graded d-spacing multilayers were deposited on Si and float glass substrates, with the design structure based on a computer modeling of the X-ray reflectivity dependence with grazing angle and energy. A specular reflectivity scan was performed for each sample at 8.05 keV (and also at higher energies for some samples) and was fitted using the IMD software. Cross-sectional TEM was performed on a limited number of samples to offer additional information. The analyses completed for W/Si, W/C, Pt/C, and Ni/C show for the best samples good uniformity and high reflectivity at 8.05 keV. The work in progress for Cu/Si and Mo/Si will be presented at the conference and will conclude this study of candidate materials and optimized designs for hard X-ray multilayer optics.

Hard x-ray focusing devices based on laterally graded multilayers are key elements to fully exploit the advantages of third generation synchrotron sources. We have developed a design method to produce laterally graded multilayers using sputter deposition techniques. The multilayers are adapted to the given application by the proper choice of layer materials, d spacing, and the partition of the two constituent materials. The optimization of all relevant parameters yields an ab initio estimation of the desired layer thickness gradient. The performance and the accuracy of this method are demonstrated. The experimental lateral thickness errors could be reduced below 0.5% RMS over a total length of 300 mm. Reflectivity measurements at different energies are in good agreement with theoretical simulations. During focusing experiments at 13 keV a spot size of 1 micrometer and a gain in flux of 1000 were achieved.

We describe a tunable multilayer monochromator with an adjustable bandpass to be used for reflectivity and grazing incidence diffraction studies on surfaces at energies near 10 keV. Multilayers have a bandpass typically 100 times larger than the Si(111) reflection, and by using multilayers an experimenter can significantly increase data collection rates over those available with a Si monochromator. The transmission through 1 and 2 laterally graded multilayer (LGML) reflections was recorded versus photon energy. The identical LGMLs were comprised of 60 bilayers of W and C on 100 X 25 X 3 mm float glass with a bilayer spacing varying from 35 to 60 angstrom. The average gradient was 0.27 angstrom/mm along the long dimension. The rms deviation of the data for the bilayer spacing from a linear fit was 0.36 angstrom. Data were obtained for a nondispersive (plus or minus) double-multilayer arrangement. The relative bandpass width (FWHM) when the two multilayers exposed the same bilayer spacing was measured to be 2.2% with a transmission of 78.7 plus or minus 1.6%. This value is consistent with the transmission of 88.9% that we also measured for a single LGML at HASYLAB beamline D4. The bandpass was tunable in the range 1.1% to 2.2%.

Wide bandpass multilayer mirrors can be obtained by gradually changing their period. In this paper the theory of such optical elements is developed on a basis of the general theory of wave propagation through layered medium. The results of reflectivity calculation for broadband mirrors are presented. The suggested theory can be used for the solution of inverse problem -- design of multilayers with the required wavelength dependence of reflectivity.

A Long trace profiler II (LTP II) with a stationary optical head and a moving penta prism was set up in our new metrology laboratory. It is a clean room with plus or minus 0.1 degrees Celsius temperature control for the stable measurement of LTP II. Some tests on the stability and repeatability of the LTP II were performed. The long term drift is less than 1 (mu) rad in 15 hours. The repeatability in the forward and backward scan is about 0.2 (mu) rad. Mirrors with different kinds of bending mechanisms were evaluated by the LTP II, some comments on the mounting and bending of the mirrors are discussed.

Metrology of optical components (including 'classical' optics, x-ray optics and neutron optics) is usually performed in two steps: (1) Actual measurement process, resulting in a raw profile of the component under test; (2) Numerical processing of the above data, to obtain actual behavior of the optical beam. The first step can be performed in many ways: Slope profilometry (LTP), Height profilometry (including interferometry), Shack-Hartmann . . . In many cases, the desired accuracy poses a challenge to the experimentalist: Temperature, vibration, reference surfaces, etc. The second step presents a different challenge: In order to extract useful information from the data, this data should be processed according to the actual propagation law of the beam. We may illustrate this in a simplified manner: According to the wavelength of the incident beam, a given defect type may be considered 'roughness' (diffraction), or 'geometric.' In reality, the optical profile is made of an 'infinity' of lateral defect sizes. Also, the coherence area of the individual photon may not cover the whole optical surface. Therefore, one may not simply apply pure low amplitude diffraction, or pure geometrical processing to the raw data. Clearly, more complex numerical processing is required. In this paper, we use the properties of synchrotron X-ray beams to show the proper handling of X-ray mirror raw profile data. These properties include, in particular, the spatial coherence area of the individual photons. We suggest the use of a coherence function in the processing of raw data, to get even nearer the behavior of the optics in real use. This paper is (hopefully) the first of a series of papers on metrology aspects of x-ray mirrors.

High accuracy angle measurement at the sub-(mu) rad level requires extremely high instrument stability. In order to reach sub-(mu) rad stability (0.1 arc second or less) over long time periods, it is necessary to maintain the test object and almost all of the optical components in the measuring instrument in very steady positions. However, mechanical force relaxation, thermal expansion, and asymmetric structures produce angular and linear displacements in the system, resulting in angular measurement error. A Long-Trace-Profiler (LTP)-based stable equipment is used to test precision angular stability with sub-(mu) rad resolution. Long term stability over 15 hours has been measured on different kind of mechanical structures. Temperature monitoring during the tests is extremely important. Some test results showing the effects of thermal variations are presented, which indicate that temperature stability on the order of 0.1 degrees Celsius is absolutely necessary for repeatable sub-(mu) rad measurements. The optical method, using optics with an even number of reflecting surfaces (for example, a right angle prism, pentaprism, or rhomboid prism) to reduce the influence of existing angular displacement, is introduced and the comparison measurement is presented. An optical fiber transfer line is able to reduce the laser angular shift from about 10 (mu) rad to a level of 0.3 (mu) rad rms. Careful system configuration, design and operation are very important for the sub-(mu) rad angle stability.

X-ray reflectometry is usually applied for determination of optical constant of materials on the basis of measurements of angular dependent reflectivity. New reflectometry methods based on measurements of either the derivatives with respect to the grazing angle or the ratios of reflection coefficients for two characteristic wavelengths are suggested in present paper. Calculations and measurements indicate that the method suggested makes it possible to enhance the sensitivity of reflectometry and the accuracy of measuring optical constants. Practical implementation of the method is based on the original system of selecting the monochromatic beams with the use of semitransparent crystals. The results of reflectometry studies of GaAs monocrystals and a Ga_0.25Si_0.75-Si multilayer structure on a Si substrate are reported.

Highly Oriented Pyrolytic Graphite is a very efficient and well-known x-ray and neutron monochromator. The crystal macroscopic properties are determined by its microscopic structure. Our aim is to study the crystal internal structure and correlate it with the crystal optical behavior. We studied the texture of the crystal, in particular its spatial homogeneity, for different samples using x-ray diffraction topography. The experiment was performed at the ESRF beamline BM5 using a laminar 18 keV monochromatic beam. Several samples supplied by different manufacturers have been studied. Images of (002) reflected beam have been acquired at the Bragg angle for each sample, using a phosphor coated CCD digital detector. Contrast profiles have been obtained, and exponential fits has been performed allowing to deduce the secondary extinction coefficient. It has been found that some samples are quite perfect and the results agree with ideally imperfect crystals model. Other samples present well defined granular macrostructures (with dimensions of tens of microns) superposed to the well-known Gaussian-like crystallite distribution. The different behavior between different samples should be explained in terms of sample internal structure, which is also related to the different graphitization process used by manufacturers.

We report the characteristics of 'the thin crystal spectrometer,' which is a new technique for a x-ray spectrometer using a thin crystal. The reflection by a thin crystal in the 'Laue' geometry has a diffraction pattern with a finite width. The reflection angle does not need to be the same to the incident angle. The crystal structure along to the crystal plane makes the interference of the reflected x rays and the reflection angle becomes a function of an x-ray wave length. Therefore, the expected energy resolution of this type of the spectrometer is comparable with a usual Bragg crystal, whereas this new spectrometer can have a certain energy band. We report a simple experiment demonstrating this idea, where we show the energy resolution of (E/(Delta) E greater than 2000) and the energy band of ((Delta) E greater than 6 eV). The applications for a focusing optics are briefly presented.

We present geometrical analysis on optics of x-ray asymmetric reflection in Bragg geometry. For a monochromatic light case, ignoring higher order terms of small deviations from the optical axis introduces Gaussian optics to asymmetric reflection, which is consistent with the conventional picture. It is, however, found that asymmetric reflection has large wave aberration and the wavefront does not transform as expected from Gaussian optics. A complex coherence factor is calculated numerically for Young's interference experiment, revealing the spatial coherence after asymmetric reflection can be explained by introducing an effective distance between the virtual source and the observing point. When x-rays have a finite wavelength spread, chromatic aberration emerges under Gaussian optics and prevents a sharp imaging. Multiple asymmetric reflections might cancel lateral chromatic aberration.

We describe the experimental system used for ultrafast time resolved EXAFS spectroscopy. It consists of a laser driven x- ray diode which generates the ultrashort hard x-ray pulses used in pump/probe experiments and a dispersive spectrometer which makes possible the simultaneous recording of a broad spectrum. The data presented, using this dispersive spectrometer, shows that we can record more than 500 eV simultaneously with a resolution of 8 eV, or 3 eV resolution for 250 eV energy spectrum.

An instrument for measuring polarization typically consists of a phase shifter and a linear polarizer. Up to 600 eV, periodic multilayer structures can be used for this purpose. They consist of alternating layers of two materials, one of which has an absorption edge in the photon energy region of interest. The phase shift of the transmitted beam and the intensity of the reflected beam show maxima at energies just below the edge. Phase shifters on 100 nm thick Si₃N₄ membranes and linear polarizers on Si wafers have been made by DC magnetron sputter deposition. The polarizers were designed to work at the Brewster angle, where only s-polarized radiation is reflected. The corresponding multilayer period decreases from 8.5 nm at 100 eV to 1.4 nm at 600 eV. A reflectance of 6.8% was obtained at 512 eV for 150(V/Ni). In order to extend polarization measurements into the 1 keV region, the use of magnetic effects like magnetic circular dichroism (MCD) is being explored. This effect has been measured in Co/C and FeCoV/Ti transmission multilayers close to the L_2,3 edges of Co and Fe.

By using X-ray resonant magnetic scattering, the correlation of magnetic domains taken vertically in a Co/Cr/Co magnetic trilayer can be statistically quantified as a function of applied magnetic field. From these scans and from element specific magnetic hysteresis loops, we can identify the presence of both interlayer anti-ferromagnetic exchange coupling and ferromagnetic dipolar coupling within the trilayer.

This paper reports on the first characterization of the polarization generated by the crossed overlapped electromagnetic undulator, OPHELIE, of the new high flux/high resolution VUV beamline, SU5, in the Super-ACO storage ring at LURE. The beamline configuration for these tests was reduced after the undulator to a single mirror M1, a TGM monochromator and a multiple-reflection polarimeter. The versatility of polarizations generated by the undulator has been demonstrated around 7 eV by the measurements after the monochromator of highly polarized light either linearly (P_tot greater than 95%) or circularly (P_tot up to 80%). The standard mode of operation which produces a strong vertical linear polarization as well as the other exotic modes like the horizontal and the tilted linear polarizations, the left- and right-handed polarization and the switching between these modes, have been validated for a very large range of photon energies across the undulator spectrum.

The EMW at the BESSRC beam lines at the APS provides high photon flux at high energies with the capability of producing circular polarization on axis. We observe a high degree of circularly polarized x-rays at such energies. The polarization and frequency tunability of the elliptical multipole wiggler (EMW) is an ideal source for many magnetic measurements from X-ray Magnetic Circular Dichroism (XMCD) to Compton scattering experiments. We performed Compton scattering measurements to determine the polarization and photon flux at the sample as a function of the deflection parameters K_y and K_x. We used for our measurements a Si (220) Laue monochromator providing simultaneous photon energies at 50 keV, 100 keV and 150 keV. Magnetic Compton Profiles were determined by either switching the magnet polarity or the photon helicity. The results obtained using Fe(110) single crystals were very similar.

A new helical undulator has been built with an hybrid electromagnet/permanent magnet technology and was recently coupled to the ESRF ID12A beamline which is dedicated to polarization dependent X-ray absorption spectroscopy. This insertion device was optimized to produce high fluxes of circularly polarized X-ray photons in the energy range 1.5 - 8 keV. It consists of 19 magnetic periods of length 80 mm with a peak magnetic field of about 0.2 T. With this new undulator, it is possible to flip very rapidly the helicity of the emitted radiation by reversing the current in the coil generating the vertical magnetic field. Magnetic measurements concerning this new insertion device are also reported. Its performances are illustrated by X-ray Natural Circular Dichroism spectra recorded at the Te L-edges with a (alpha) - TeO₂ single crystal.

In practice x-ray studies of ferromagnetic materials require circularly polarized radiation if the weak momentum-dependent signal is to be separated from the dominant charge scattering in either elastic (diffraction) experiments or inelastic (Compton scattering) studies. In both methods it is necessary to modulate the photon's helicity or the sample's magnetization. The former method is the more desirable because it is effective in magnetically hard materials, but it is more difficult to achieve than the latter. To date inelastic Compton scattering, which is solely sensitive to the spin moment, is the better developed technique. It has benefited from the availability of high fluxes of high energy x-rays (60 - 300 keV) at third generation synchrotron sources. This has led to an improvement of a factor of two in resolution, but further improvements are flux limited. In the 3d elemental and compound ferromagnets the method has been used to establish the validity not only of the electronic structure calculation but also the underlying approximations. In compound ferromagnets it has been used to determine site-dependent spin moments. Examples will be given from recent studies of alloys and other rare earth compounds. The development of similar techniques using circularly polarized beams to diffraction studies of spin and orbital magnetization will also be described.

The concomitant development of new x-ray sources, new dedicated instruments and of the theory of resonant X-ray magnetic scattering (RXMS) has opened a permanently developing range of new experiments, where one takes advantage of the coupling of the x-ray beam polarization with the magnetic moments. In rare earths, RXMS allows one to study separately the contributions of the 4f and 5d electrons to the magnetism. We present a preliminary study on samarium and dysprosium and show that qualitative considerations on the energy dependencies of magnetic intensities (peak intensities at magnetic Bragg positions) allows clear identification of the two contributions to the resonance. The energy lineshapes of the resonances are discussed in terms of the introduction of collective effects (band structure of the 5d level) into the single-ion model of the resonance.

The existence of a helical symmetry axis is widespread in systems exhibiting liquid-crystalline order, especially in systems comprised of chiral molecules. Because these systems usually lack three-dimensional positional order, the helical symmetry axis cannot be observed using conventional x-ray scattering. Since the nature of the helical ordering determines the electro-optic response of the liquid crystal phases, it is a crucial structural feature to establish. Important for device applications are the various chiral smectic-C (SmC*) liquid crystal phases that are composed of fluid-like layers of tilted molecules. The electro-optic response of these phases varies from ferro to ferri to antiferroelectric. To elucidate the structure of the SmC* phases, we did resonant x-ray scattering at the sulfur K-edge on sulfur containing compounds. Our polarization-analyzed measurements of the resonant diffraction provided unambiguous evidence that the in-plane tilt direction in these phases exhibits a helical interlayer orientational ordering with a short pitch equals vd where d is the layer spacing. In the lowest temperature SmC* phase, which has antiferroelectric ordering, v was close to 2. At higher temperatures, the ferrielectric phases had v equals 3, then 4, and finally, an incommensurate value varying between 5 and 8 with increasing temperature.

We have produced recently the very first experimental evidence that X-ray Natural Circular Dichroism (XNCD) can be detected in both uniaxial and biaxial gyrotropic single crystals. XNCD signals are to be assigned to electric dipole-electric quadrupole E1.E2 interference terms which can be quite significant in the X-ray range whereas there can hardly be any detectable contribution of the electric dipole-magnetic dipole E1.M1 terms which dominate CD at optical wavelengths. For heavily absorbing single crystals, the differential absorption between left-handed and right-handed circularly polarized X- ray photons cannot be measured in transmission but circular dichroism can still be detected in fluorescence excitation spectra. XNCD and Fluorescence detected X-ray Natural Circular Dichroism (Fd-XNCD) spectra are strictly identical for uniaxial crystals such a lithium iodate ((alpha) -LiIO₃) but this is only true to the first order for biaxial crystals such as potassium titanyl phosphate (KTP). Such difficult experiments became feasible only with the development of powerful helical undulator sources and with a careful optimization of all components of the beamline.

In x-ray spectroscopies, it is essential to have a full control of the polarization of the incident photons and x-ray phase plates have become in these recent years a key optical element of a beam line. The principle of x-ray phase plates which originates in the dynamical propagation of x-rays at Bragg diffraction is viewed and the different setups which have been experimented are presented. We will concentrate on the very convenient setup which uses the forward-diffracted beam outside the Bragg diffraction peak and diamond crystals. Applications to the production of circularly polarized x-ray beams, polarimetry measurements and x-ray magnetic linear dichroism are then described.

Synchrotron radiation (SR) stimulated process, which has characteristics of high spatial resolution and low damage, is suitable for nano-processes. Si(111) surface after removal of native oxide by SR stimulated desorption was atomically flat with no damage. If the semiconductor surface is chemically modified and chemical bonds having a weak interaction with the substrate electronic states (a localized electronic state) are formed, for example, such as SiH₂ and SiH₃, they can be broken (etched) by the SR irradiations. Efficient site specific bone breaking, overwhelming the secondary electron effects, can be expected by a resonant excitations from a core electronic state to a dissociative valence electron state. The excitation energy and polarization tunability, which is unique characteristic of the SR process, will display its power in the nano-process applications which require the atom level control.

The performances of modern synchrotron x-ray sources (degree of polarization and energy tunability) have led to a large variety of experiments that were formerly considered as impossible due to the inherent weakness of the expected signal. In this presentation, we concentrate on two particular aspects of importance for the study of magnetism: the origin of multi-q magnetic structures and the existence of induced magnetic moments. These two problems can be tackled with the help of resonant and non-resonant x-ray scattering methods through the polarization dependence of the scattering amplitude. The nature of magnetic induced moments can be traced by tuning the photon energy to absorption edges of nominally non-magnetic atoms and by studying the polarization dependence of the resonant intensities. Similarly, the existence of multi-q magnetic structures can be assessed by monitoring the polarization of intensities scattered at forbidden positions in reciprocal space.

In recent years, a number of studies have been conducted on the source properties of linac-driven X-Ray Free-Electron Lasers (XRFELs) operating in the Self-Amplified Spontaneous Emission (SASE) regime. In longitudinal phase space the output of such devices typically consists of a randomly-distributed train of fully-transversely-coherent micropulses of randomly varying intensity and an average length (corresponding to the coherence length) two to three orders of magnitude smaller than the transverse diameter of the beam. Total pulse lengths are typically of the same order of size as the beam diameter. Both of these properties can be shown to significantly impact the performance of otherwise conventional synchrotron radiation optics (viz., mirrors, lenses, zone plates, crystals, multilayers, etc.) designed to filter or modulate the phase space parameters of the radiation pulses. This, in turn, can influence the design and performance of beam line instrumentation (viz., monochromators, spectrometers, etc.) employed to match the phase space acceptance of an experiment to an XRFEL source. In this paper we outline a preliminary investigation of short-pulse effects on the performance and design of selected optical components and instrumentation for the proposed 1.5 Angstrom SLAC Linac Coherent Light Source (LCLS) and discuss the implication of our results for critical applications such as microfocusing and monochromatization.