KMC-1: a high resolution and high flux soft x-ray beamline at BESSY

The crystal monochromator beamline KMC-1 at a BESSY II bending magnet covers the energy range from soft (1.7 keV) to hard x-rays (12 keV) employing the (n,-n) double crystal arrangement with constant beam offset. The monochromator is equipped with three sets of crystals, InSb, Si (111), and Si (422) which are exchangeable in situ within a few minutes. Beamline and monochromator have been optimized for high flux and high resolution. This could be achieved by (1) a windowless setup under ultrahigh-vacuum conditions up to the experiment, (2) by the use of only three optical elements to minimize reflection losses, (3) by collecting an unusually large horizontal radiation fan (6 mrad) with the toroidal premirror, and (4) the optimization of the crystal optics to the soft x-ray range necessitating quasibackscattering crystal geometry (theta(Bragg,max)=82 degrees) delivering crystal limited resolution. The multipurpose beamline is in use for a variety of user facilities such as extended x-ray absorption fine structure, ((Bio-)EXAFS) near-edge x-ray absorption fine structure (NEXAFS), absorption and fluorescence spectroscopy. Due to the windowless UHV setup the k edges of the technologically and biologically important elements such as Si, P, and S are accessible. In addition to these experiments this beamline is now extensively used for photoelectron spectroscopy at high kinetic energies. Photon flux in the 10(11)-10(12) photons/s range and beamline resolving powers of more than E/DeltaE approximately 100.000 have been measured at selected energies employing Si (nnn) high order radiation in quasibackscattering geometry, thus photoelectron spectroscopy with a total instrumental resolution of about 150 meV is possible. This article describes the design features of the beamline and reports some experimental results in the above mentioned fields.     

High resolution absorption spectroscopy of exploding wire plasmas using an x-pinch x-ray source and spherically bent crystal

We present here the use of absorption spectroscopy of the continuum radiation from x-pinch-produced point x-ray sources as a diagnostic to investigate the properties of aluminum plasmas created by pulsed power machines. This technique is being developed to determine the charge state, temperature, and density as a function of time and space under conditions that are inaccessible to x-ray emission spectroscopic diagnostics. The apparatus and its characterization are described, and the spectrometer dispersion, magnification, and resolution are calculated and compared with experimental results. Spectral resolution of about 5000 and spatial resolution of about 20 μm are demonstrated. This spectral resolution is the highest available to date in an absorption experiment. The beneficial properties of the x-pinch x-ray source as the backlighter for this diagnostic are the small source size (<5 μm), smooth continuum radiation, and short pulse duration (<0.1 ns). Results from a closely spaced (1 mm) exploding wire pair are shown and the general features are discussed.     

Calibration of a high resolution grating soft x-ray spectrometer

The calibration of the soft x-ray spectral response of a large radius of curvature, high resolution grating spectrometer (HRGS) with a back-illuminated charge-coupled device detector is reported. The instrument is cross-calibrated for the 10-50 A? waveband at the Lawrence Livermore National Laboratory electron beam ion trap (EBIT) x-ray source with the EBIT calorimeter spectrometer. The HRGS instrument is designed for laser-produced plasma experiments and is important for making high dynamic range measurements of line intensities, line shapes, and x-ray sources.     

Optimizing the operation of a high resolution vertical Johann spectrometer using a high energy fluorescer x-ray source

This paper describes the operation and testing for a vertical Johann spectrometer (VJS) operating in the 13 keV range. The spectrometer is designed to use thin curved mica crystals or thick germanium crystals. The VJS must have a resolution of E/ΔE=3000 or better to measure the Doppler broadening of highly ionized krypton and operate at a small x-ray angle in order to be used as a diagnostic in a laser plasma target chamber. The VJS was aligned, tested, and optimized using a fluorescer type high energy x-ray (HEX) source located at National Security Technologies (NSTec), LLC, in Livermore, CA. The HEX uses a 160 kV x-ray tube to excite fluorescence from various targets. Both rubidium and bismuth fluorescers were used for this effort. This presentation describes the NSTec HEX system and the methods used to optimize and characterize the VJS performance.     

High resolution short focal distance Bent Crystal Laue Analyzer for copper K edge x-ray absorption spectroscopy

We have developed a compact short focal distance Bent Crystal Laue Analyzer (BCLA) for Cu speciation studies of biological systems with specific applications to cancer biology. The system provides high energy resolution and high background rejection. The system is composed of an aluminum block serving as a log spiral bender for a 15 micron thick Silicon 111 crystal and a set of soller slits. The energy resolution of the BCLA-about 14 eV at the Cu Kα line- allows resolution of the Cu Kα(1) and CuKα(2) lines. The system is easily aligned by using a set of motorized XYZ linear stages. Two operation modes are available: incident energy scans (IES) and emission energy scans (EES). IES allows scanning of the incident energy while the BCLA system is maintained at a preselected fixed position--typically CuKα(1) line. EES is used when the incident energy is fixed and the analyzer is scanned to provide the peak profile of the emission lines of Cu.     

X-ray filter assembly for fluorescence measurements of x-ray absorption fine structure

Fluorescence detection, in principle, permits the detection of the extended x-ray absorption fine structure (EXAFS) of more dilute atoms than can be obtained in absorption. To take advantage of this it is necessary, in practice, to eliminate the background that normally accompanies the fluorescence signal. We describe an x-ray filter assembly that accomplishes this purpose. The unique characteristic of the assembly is a slit system that minimizes the fluorescence background from the filter. The theory of the slit assembly is presented and is found to agree with measurements made on the Fe EXAFS of a dilute sample. The filter assembly has a better effective counting rate in this case than that of a crystal monochromator design.     

Portable x-ray fluorescence spectrometer for coating thickness measurement

A handheld x-ray spectrometer has been realized and tested. The purpose of the device is to measure the thickness of coated samples in the range of 1-1500 nm in an industrial environment. Accuracy of approximately 3% has been achieved in this range with a measurement time of 1 min. Automated software has been implemented to allow utilization by a nonspecialist operator. An automated calibration procedure, based on measurements of reference samples, is used.     

A spectroscopic proton-exchange membrane fuel cell test setup allowing fluorescence x-ray absorption spectroscopy measurements during state-of-the-art cell tests

A test setup for membrane-electrode-assemblies (MEAs) of proton exchange membrane fuel cells which allows in situ fluorescence x-ray absorption spectroscopy studies of one electrode with safe exclusion of contributions from the counter electrode is described. Interference by the counter electrode is excluded by a geometry including a small angle of incidence (< 6°) between primary beam and electrode layer. The cell has been constructed by introducing just minor modifications to an electrochemical state-of-the-art MEA test setup, which ensures realistic electrochemical test conditions. This is at the expense of significant intensity losses in the path of the incident beam, which calls for the brilliance of third-generation synchrotrons to provide meaningful data. In measurements on Pt∕C and Pt-Co∕C cathodes combined with Pt-C anodes (H(2)/O(2) feed), good data quality was demonstrated both for the majority element Pt as well as for Co despite of a low areal Co density in the order of 0.02 mg/cm(2).     

High repetition rate laser produced soft x-ray source for ultrafast x-ray absorption near edge structure measurements

Recent progress in high intensity ultrafast laser systems provides the opportunity to produce laser plasma x-ray sources exhibiting broad spectrum and high average x-ray flux that are well adapted to x-ray absorption measurements. In this paper, the development of a laser based x-ray absorption near edge structure (XANES) beamline exhibiting high repetition rate by using the Advanced Laser Light Source (ALLS) facility 100 Hz laser system (100 mJ, 35 fs at 800 nm) is presented. This system is based on a broadband tantalum solid target soft x-ray source and a grazing incidence grating spectrometer in the 1-5 nm wavelength range. To demonstrate the high potential of this laser based XANES technique in condensed matter physics, material science, or biology, measurements realized with several samples are presented: VO2 vanadium L edge, Si3N4 nitrogen K edge, and BPDA/PPD polyimide carbon K edge. The characteristics of this laser based beamline are discussed in terms of brightness, signal to noise ratio, and compared to conventional synchrotron broadband x-ray sources which allow achieving similar measurements. Apart from the very compact size and the relative low cost, the main advantages of such a laser based soft x-ray source are the picosecond pulse duration and the perfect synchronization between this x-ray probe and a laser pulse excitation which open the way to the realization of time resolved x-ray absorption measurements with picosecond range time resolution to study the dynamics of ultrafast processes and phase transition.     

High resolution extreme ultraviolet spectrometer for an electron beam ion trap

An extreme ultraviolet spectrometer has been developed for spectroscopic studies of highly charged ions with an electron beam ion trap. It has a slit-less configuration with a spherical varied-line-spacing grating that provides a flat focal plane for grazing incidence light. Alternative use of two different gratings enables us to cover the wavelength range 1-25 nm. Test observations with the Tokyo electron beam ion trap demonstrate the high performance of the present spectrometer such as a resolving power of above 1000.     

Time-resolved near-edge x-ray absorption fine structure spectroscopy on photo-induced phase transitions using a tabletop soft-x-ray spectrometer

We present a table-top soft-x-ray spectrometer for the wavelength range λ = 1-5 nm based on a stable laser-driven x-ray source, making use of a gas-puff target. With this setup, optical light-pump/soft-x-ray probe near-edge x-ray absorption fine structure (NEXAFS) experiments with a temporal resolution of about 230 ps are feasible. Pump-probe NEXAFS measurements were carried out in the "water-window" region (2.28 nm-4.36 nm) on the manganite Pr(0.7)Ca(0.3)MnO(3), investigating diminutive changes of the oxygen K edge that derive from an optically induced phase transition. The results show the practicability of the table-top soft-x-ray spectrometer on demanding investigations so far exclusively conducted at synchrotron radiation sources.     

Quasi-Fourier-transform limited, scannable, high energy titanium-sapphire laser source for high resolution spectroscopy

A tunable injection seeded Ti:sapphire laser source has been developed and tested. Slave-master tandem cavity and ramp-lock-and-fire concepts have been implemented and fully controlled by a digital signal processor. A Fourier-transform-based analysis, as well as direct measurements, have demonstrated spectral linewidths in the range of 3.5-15 MHz (HWHM), with potential tunability over the entire Ti:sapphire lasing range. A quasi-Fourier-transform limited spectral linewidth is demonstrated assuming a secant hyperbolic shape of the electromagnetic field. Output energies >100 mJ have been reached with approximately 300 mJ of pump energy. The highest spectral purity is obtained using the quadruple pumping scheme.     

High resolution far-infrared Fourier transform spectroscopy of radicals at the AILES beamline of SOLEIL synchrotron facility

Experimental far-infrared (FIR) spectroscopy of transient species (unstable molecules, free radicals, and ions) has been limited so far in both emission and absorption (mainly by the low probability of spontaneous emission in that spectral range and the low brightness of continuum sources used for absorption measurements, respectively). Nevertheless, the FIR spectral range recently became of high astrophysical relevance thanks to several new observational platforms (HERSCHEL, ALMA...) dedicated to the study of this region suitable for the detection of the emission from cold objects of the interstellar medium. In order to complete the experimental dataset concerning transient species, three discharge experiments dedicated to the recording of high resolution FIR spectra of radicals have been developed at the Advanced Infrared Line Exploited for Spectroscopy (AILES) which extracts the bright FIR synchrotron continuum of the synchrotron facility SOLEIL. These experiments make use of a high resolution (R = 0.001 cm(-1)) Bruker IFS125 Fourier transform (FT) spectrometer. An emission setup (allowing to record spectra of radicals excited at high rotational and vibrational temperatures) and two absorption setups (exploiting the bright synchrotron source at the highest resolution available on the FT) are alternatively connected to the FT. The advantages and limitations of these techniques are discussed on the basis of the recent results obtained on OH and CH radicals. These results constitute the first FIR spectra of radicals using synchrotron radiation, and the first FIR spectrum of a C-bearing radical using FT-spectroscopy.     

Electro-optical multichannel spectrometer for transient resonance Raman and absorption spectroscopy

An optical multichannel system is described, used for time-dependent absorption measurements in the gas phase and the liquid phase and for resonance Raman spectroscopy of short-lived transient species in the liquid phase in pulse radiolysis. It consists of either an image converter streak unit or an image intensifier coupled to a TV camera with computerized data handling. The system enables the recording of time-dependent absorption spectra or resonance Raman spectra of short-lived radicals and excited states with single electron and light pulses.     

Development of a high energy resolution electron energy-loss spectroscopy microscope

We have developed a high energy resolution electron energy-loss spectroscopy (EELS) microscope, which can take spectra from specified small specimen areas and specified small reciprocal space areas to investigate detailed electronic structures. The EELS microscope is equipped with retarding Wien filters as the monochromator and the analyser. The filters are designed to achieve a stigmatic focus. The energy resolutions are 12 meV and 25 meV for cases without and with a specimen, respectively. Spatial and momentum resolutions are 30–110 nm in diameter and 1.1 nm⁻¹ in angular diameter, respectively. EELS spectra are presented to show the performance of this instrument.     

一种X射线荧光分析仪滤光片切换系统的设计

滤光片是荧光分析类设备中的关键部件,与滤光片相关的结构设计和滤片自动切换功能的上下位机实现也就成为荧光类仪器设备的必备功能。     

Determination of conditions for optimum resolution of a high angle thin window energy dispersive spectrometer.

The energy resolution of an energy dispersive spectrometer (EDS) equipped with an ultrathin window (UTW) and mounted at a high take-off angle (72 degrees) on a transmission electron microscope has been studied under a variety of operating conditions. The spectrometer resolution is close to that specified by the manufacturer, up to count rates of 400 cps. Above 400 cps the resolution deteriorates rapidly, and the MCA dead time and zero width increase. Above 10 keV, the height of the background is much greater than expected for bremsstrahlung and shows the shape which has previously been attributed to backscattered electron flux into the detector. It is postulated that the deterioration in resolution with count rate is caused by backscattered electrons reaching the detector through the UTW.     

Simultaneous surface plasmon resonance and x-ray absorption spectroscopy

We present an experimental setup for the simultaneous measurement of surface plasmon resonance (SPR) and x-ray absorption spectroscopy (XAS) on metallic thin films at a synchrotron beamline. The system allows measuring in situ and in real time the effect of x-ray irradiation on the SPR curves to explore the interaction of x-rays with matter. It is also possible to record XAS spectra while exciting SPR in order to study changes in the films induced by the excitation of surface plasmons. Combined experiments recording simultaneously SPR and XAS curves while scanning different parameters can be also carried out. The relative variations in the SPR and XAS spectra that can be detected with this setup range from 10(-3) to 10(-5), depending on the particular experiment.     

四极质谱计高分辨率的获得

在研制LZL - 2 0 2型色质联用仪经验的基础上 ,从设计和制造两方面讨论了四极质谱计质量分辨率的一些问题。LZL - 2 0 2型气相色谱 -四极质谱联用仪的最高质量分辨率达到 6 0 0以上