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A high resolution (λ/Δλ∼2000) soft x-ray spectrometer has been installed on the Alcator C-Mod tokamak. The system was designed to measure emission line spectra from heliumlike neon (1s12p1→1s2) in a narrow spectral band centered on λ=13.5 Å (920 eV). The instrument is mounted with a poloidal view 20 cm below the midplane (r/a∼0.85). In addition to the neon emission lines, strong fluorine, xenon, iron, and manganese lines have been observed. [ABSTRACT FROM AUTHOR]

The design and the performances of an extreme ultraviolet (EUV)spectrometer/monochromator for generation and diagnostics of high-order harmonics of an ultrashort (<30 fs) pulsed laser focused onto a gas jet are presented. The harmonic generation is optimized using an adaptive mirror before the laser focusing stage. A toroidal mirror is used to focus the XUV radiation in an intermediate stage for pump/probe experiments. A grazing-incidence flat-field spectrometer for the 5–75 nm spectral region has been designed: it adopts a stigmatic toroidal mirror and a varied line-space flat grating mounted in converging light. The almost flat stigmatic spectrum is acquired by a 40-mm-diameter microchannel plate intensifier; the whole detector can be moved to scan various portions of the spectrum. Different detectors allow one to acquire both integrated and single shot spectra at 1 kHz repetition rate. The absolute calibration of the spectrometer is provided. The same optical scheme can be applied to the design of a constant deviation angle EUV monochromator by substituting the detector block with an exit slit. [ABSTRACT FROM AUTHOR]

Diamond, photoconductive devices (DPCDs) have proven to be stable detectors of x-ray emission from plasmas. An array of six DPCDs is used on the OMEGA target chamber to measure the temporal and spectral dependence of x rays emitted from targets. 100 ps laser pulses incident on high-Z targets are used to measure the time response of the detectors, bias circuits, cables, and digitizer. This information is used to deconvolve the measured data to extract the temporal shape of the x-ray emission. The x-ray spectrum is measured by placing absorber filters for a specific x-ray energy region in front of the DPCDs. The data are analyzed with a linear algebraic method to determine the spectral shape. This technique removes the need to apply smoothing to the spectral analysis and provides “confidence bands” for the x-ray spectrum. [ABSTRACT FROM AUTHOR]

X-ray spectrometers using elliptically bent crystals have desirable properties for applications requiring broad spectral coverage, good spectral resolution, and minimized source broadening. Previous work used custom-positioned film or microchannel plate detectors. We find it is also useful and cost-effective to field elliptical crystals in existing snouts on the face-on gated microchannel plate framing cameras commonly used at many facilities. We numerically explored the full design space (spectral range and resolution) of elliptical crystals compatible with the new multipurpose spectrometer snout. We have tested at the Omega laser an elliptical rubidium acid phthalate crystal with 174 mm focal length, 0.9885 eccentricity, and 4.6° inclination, viewing from 1.0 to at least 1.7 keV with spectral resolution E/dE of 300–500. A slit (2×magnification) images 3 mm sources with 70 μm spatial resolution. [ABSTRACT FROM AUTHOR]

A least-squares fit analysis program is being developed for the study of spatially resolved x-ray spectra from tokamak plasmas. The program, written in interactive data language, can handle analysis of spectra from multiple sightlines through the plasma and compare the experimental data with a least-square fit of synthetic spectra, which are constructed from atomic modeling codes. The input parameters such as shot numbers, time groups, spatial range, spectral lines to fit and fitting parameters can be entered interactively through a graphical user interface or automatically via a script. The output consists of graphical presentations of the obtained spectral fits and fit parameter profiles as a function of time, including ion and electron temperature profiles, which are of particular interest. Output can also be sent to any open database connectivity compliant database. The features of the program are demonstrated with the analysis of the spectra of helium-like ArXVII, which were obtained with a new x-ray imaging crystal spectrometer. [ABSTRACT FROM AUTHOR]