R. Barnsley N. J. Peacock J. Dunn I. M. Melnick I. H. Coffey et al.
A family of Johann configuration curved crystal spectrometers has been designed to share the basic engineering features of compactness, modularity, facility of alignment and focus, and incorporation of solid-state charge coupled device detector arrays. These detectors have intrinsically low noise, useful energy resolution, two-dimensional position …
PublishedJ. M. A. Ashbourn I. M. Melnick N. J. Peacock
We present a comparison of measured and theoretically modeled Lyman- a intensity ratios of hydrogenlike Al XIII impurity ions in a deuterium base plasma in the COMPASS-D tokamak. The time evolution of the intensity ratios is computed from a collisional-radiative model using measured plasma parameters and compared with line-of-sight integral values …
PublishedN. J. Peacock R. Barnsley M. G. O’Mullane M. R. Tarbutt D. Crosby et al.
The equilibrium state in tokamak core plasmas has been studied using the relative intensities of resonance x-ray lines. A full spatial analysis involves comparison of the line intensities with ion diffusion calculations, including relevant atomic rates. A zero-dimensional model using a global ion loss rate approximation has also been demonstrated b…
PublishedN. J. Peacock K. D. Lawson R. Barnsley H. Chen
An empirical procedure, ‘‘LINT,’’ for relating emission line intensities of intrinsic impurity ions to their elemental contributions to the total, bolometric, radiation loss and the volume-averaged effective ion charge, Zeff , has been developed and applied to limiter plasmas in the JET tokamak. In this article we discuss extensions to the …
PublishedN. J. Peacock R. Barnsley K. D. Lawson I. M. Melnick M. G. O’Mullane et al.
Crystal and synthetic multilayer diffractors, deployed either as flat Bragg reflectors, or curved, as in the Johann configuration, are used to study the spectrum of COMPASS-D and other tokamaks in the wavelength region of 1–100 A. In this article, we concentrate on the measurement of absolute photon fluxes and the derivation of volume emissivitie…
PublishedN. J. Peacock R. Barnsley A. Patel M. O’Mullane M. Singleton et al.
Quantitative measurements of the line and continua emissivities and the analyses of spectral line profiles are essential steps in the interpretation of the x-ray emission from high-temperature fusion plasmas. One method of placing the emissivities on an absolute basis is to use an absolutely calibrated spectrometer to record the data. The overall s…
PublishedR. Barnsley A. Abbey J. Dunn S. Lea N. J. Peacock
This spectrometer was designed to give access to a wide range of Bragg angles and crystal focal lengths while using the Rowland circle radius as a free parameter. Stability is achieved using a rigid beam or “Rowland chord,” which provides a reference axis for all the critical alignments, the chord length being variable between about 0.2 and 5 m…
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