The core imaging x-ray spectrometer (CIXS) is one of several ITER diagnostic systems planned for measurements of the central ion and electron temperature profiles and of the toroidal and poloidal rotation velocity profiles, T i , T e , v φ , and v θ respectively. The diagnostic is based on precision determinations of the Doppler broadening and centroid shift of the lines of highly ionized heavy impurities using a curved Bragg crystal spectral disperser and imager. In a departure from earlier designs, the CIXS employs a novel imaging geometry utilizing spherically bent crystals operating at a Bragg angle near 45 • , which spatially and spectrally resolves the x-ray emission from the plasma. In addition, the working radiation will be the L-shell emission of highly charged tungsten ions. Particular emphasis is placed on the strong 3d 5/2 → 2p 3/2 electric dipole transition in neon-like tungsten W 64+ . Here we present the conceptual design of the instrument, which may include an x-ray calorimeter, and discuss the spectral features used in future measurements.
A focusing Seeman-Bohlin diffractometer of 20 inches diameter has been designed and constructed with special emphasis on its suitability for the examination of polycrystalline thin films. The apparatus employs a pyrolytic graphite monochromator crystal to obtain a high-intensity beam, which is incident upon the specimen at a selected low angle of incidence, so as to increase the path length through the sample. Atmospheric scattering of the diffracted rays is reduced substantially by the use of a helium chamber. The attitude of the X-ray counter is controlled by a simple servomechanism, without the use of lever arms. The unit is operated by a data acquisition and control system, and executes a preset step-scan with data collection on punched cards or paper tape. The performance of the diffractometer is illustrated by a variety of measurements made on metallic films of 150 to 8000 A in thickness. The results demonstrate the utility of the diffractometer for precise lattice parameter measurements, for the determination of internal strains and crystallite size, and as a tool for studying reactions in multicomponent or multilayer films.
The paper describes a new scheme for wide-angle point-to-point x-ray imaging with almost arbitrarily large angles of incidence by a matched pair of spherically bent crystals to eliminate the astigmatism, which is a well-known imaging error of spherical mirrors. In addition to x rays, the scheme should be applicable to a very broad spectrum of the electromagnetic radiation, including microwaves, infrared and visible light, as well as UV and extreme UV radiation, if the crystals are replaced with appropriate spherical reflectors. The scheme may also be applicable to the imaging with ultrasound.
We describe the anticipated performance of an x-ray microcalorimeter instrument on ITER. As part of the core imaging x-ray spectrometer, the instrument will augment the imaging crystal spectrometers by providing a survey of the concentration of heavy ion plasma impurities in the core and possibly ion temperature values from the emission lines of different elemental ions located at various radial positions.
Fast, two-dimensional, soft x-ray imaging is a powerful technique for the study of magnetohydrodynamic instabilities in tokamak plasmas. We have constructed an ultra-fast frame rate soft x-ray camera for the national spherical torus experiment (NSTX). It is based on a recently developed 64ϫ 64 pixel charge-coupled device (CCD) camera capable of capturing 300 frames at up to 500 000 frames per second. A pinhole aperture images the plasma soft x-ray emission ͑0.2-10 keV͒ onto a P47 scintillator deposited on a fiber-optic faceplate; the scintillator visible light output is detected and amplified by a demagnifying image intensifier and lens-coupled to the CCD chip. A selection of beryllium foils provides discrimination of low-energy emission. The system is installed on NSTX with a wide-angle tangential view of the plasma. Initial plasma data and an assessment of the system performance are presented.
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