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A soft x-ray undulator beamline and an x-ray emission spectrometer have been designed for soft x-ray emission studies. The beamline has a varied-line-spacing plane grating monochromator, which enables the energy resolution over 104 with a beam size down to 10 × 60 μm2. The x-ray emission spectrometer has a Wolter type I mirror, a free-standing transmission grating, and a back-illuminated CCD. A high collection angle up to 1.5 × 10-3 sr is achieved by utilizing the Wolter mirror as a prefocusing system. The CCD is mounted at 1400 mm downstream of the grating on a Rowland torus mount. Diffracted x-rays are detected in the normal incidence geometry, resulting in high detection efficiency. The energy resolution is limited by the figure errors of the optical elements and the spatial resolution of the detector. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Cryogenic X-ray spectrometers operating at temperatures below 1 K combine high energy resolution with broadband efficiency for X-ray energies up to 10 keV. They offer advantages for chemical state analysis of dilute samples by fluorescence-detected X-ray absorption spectroscopy (XAS) in cases where conventional Ge or Si(Li) detectors lack energy resolution and grating spectrometers lack detection efficiency. We are developing soft X-ray spectrometers based on superconducting Nb-Al-AlOx-Al-Nb tunnel junction (STJ) technology. X-rays absorbed in one of the superconducting electrodes generate excess charge carriers in proportion to their energy, thereby producing a measurable temporary increase in tunneling current. For STJ operation at the synchrotron, we have designed a two-stage adiabatic demagnetization refrigerator (ADR) with a cold finger that holds a 3 × 3 array of STJs inside the UHV sample chamber at a temperature of ∼0.1 K within ∼15 mm of a room temperature sample. Our STJ spectrometer can have an energy resolution below 10 eV FWHM for X-ray energies up to 1 keV, and has total count rate capabilities above 100,000 counts/s. We will describe detector performance in synchrotron-based X-ray fluorescence experiments and demonstrate its use for XAS on a dilute metal site in a metalloprotein. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

A new high-precision spectrometer system has been developed and tested for measuring grazing-incidence XAFS spectra, x-ray reflectivity, and standing wave intensity data from adsorbates on oriented single crystals and flat polycrystalline samples. The instrument system was designed for routine, rapid installation and alignment in synchrotron experimental hutches utilized for XAFS measurements. Two major components comprise the system: (a) a strongback cradle on which flexor slits, sample positioners, and detectors are aligned, and (b) a multi-altitudinal detector support, which allows a 30-element Ge detector array to be positioned at vertical down-looking, horizontal side-looking, and intermediate observation angles. Motorized positioners provide seven axes of motion for samples, which allows accurate positioning of large sample cells and samples having uneven shapes. Precision slits located upstream of the sample provide aperture control to about 1 micron precision over a range of motion from zero to 1.5 mm, making possible measurements on mm-diameter samples at very small incidence angles (∼0.15°). An ion chamber detector located downstream of the sample is mounted on a bearing arc to rotate about the sample eucentric for specular reflectivity measurements. This detector can be replaced with an analyzer crystal and proportional counter to provide high-rate counting with high angular/energy resolution. Results from recent measurements demonstrate the utility and precision of this instrument for molecular environmental interface science. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

A coincident measurement between the Compton scattered photon and the recoiled electron gives information about three dimensional electron momentum density (3D-EMD). We improve our (X, eX) spectrometer by introducing a two-dimensional area photon detector which consists of an array of BGO scintillators and a position sensitive photoelectron multiplier tube in order to obtain the 3D-EMD over whole momentum space. We present the details of the improved system, performance and some experimental results. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]