High-resolution duo-multichannel soft x-ray spectrometer for tokamak plasma diagnostics

Abstract

A high-resolution, time-resolving soft x-ray multichannel spectrometer (SOXMOS) that permits the simultaneous measurement of emission in two different spectral ranges has been developed and tested extensively for tokamak plasma diagnostics. The basic instrument is a high-resolution, interferometrically adjusted, extreme grazing incidence Schwob–Fraenkel duochromator. The instrument is equipped with two multichannel detectors that are adjusted interferometrically and scan along the Rowland circle. Each consists of an MgF2 coated, funneled microchannel plate, associated with a phosphor screen image intensifier that is coupled to a 1024-element photodiode array by a flexible fiber-optic conduit. The total wavelength coverage of the instrument is 5–340 Å with a measured resolution (FWHM) of about 0.2 Å when equipped with a 600-g/mm grating, and 5–85 Å with a resolution of about 0.06 Å using a 2400-g/mm grating. The simultaneous spectral coverage of each detector varies from 15 Å at the short wavelength limit to 70 Å at the long wavelength limit with the lower dispersion grating. The minimum readout time for a full spectral portion is 16 ms, but several individual lines can be measured with 1-ms time resolution by selected pixel readout. Higher time resolution can be achieved by replacing one multichannel detector with a single channel electron multiplier detector. Examples of data from the PLT and TFTR tokamaks are presented to illustrate the instrument’s versatility, high spectral resolution, and high signal-to-noise ratio even in the 10-Å region.

Iron emission lines in solar and laboratory plasmas

“…Measurements on the LHD were made with the SOXMOS EUV grazing-incidence spectrometer [17] covering the wavelength range from 158 to 214Å. The instrument utilized a 600 lines/mm grating.…”

Detector system with high time resolution for the continuous measurement of spectra in the vacuum ultraviolet wavelength range

“…Including all amplification and efficiency factors as well as the transmission losses in the detector setup, an individual electron event at the MCP input side leads to a maximum accumulated charge in the C3904-F linear array of about qϷ2.6ϫ10 5 e Ϫ Ϸ0.04 pC, which is 0.16% of the full capacity of the pixels ͑25 pC͒. The usable linear range of the detector is limited by the saturation threshold of the MCP corresponding to a value of 20 pC/ms per pixel.The dimensions of the linear photodiode array ͑Hamamatsu S3904-F͒ with 1024 pixels of 2.5 mm height and 25 m width each are similar to those of the widely used Reticon array, [3][4][5]8,[12][13][14][15][16] …”

“…The dimensions of the linear photodiode array ͑Hamamatsu S3904-F͒ with 1024 pixels of 2.5 mm height and 25 m width each are similar to those of the widely used Reticon array, [3][4][5]8,[12][13][14][15][16] …”

High efficiency extreme ultraviolet overview spectrometer: Construction and laboratory testing

“…However, over the past decades only a limited number of spectrometer concepts have been developed and applied for the diagnostics of magnetic fusion plasmas. Commonly applied spectrometer types on fusion experiments either monitor a limited wavelength range which may be fixed 3 or variable 4,5 , or provide an overview over a wider spectral range with only coarse resolution 6,7 .…”

“…The monitoring of plasma impurities in magnetically confined fusion plasmas is frequently performed using broadband spectrometers in the vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) wavelength range [1][2][3][4][5] . However, over the past decades only a limited number of spectrometer concepts have been developed and applied for the diagnostics of magnetic fusion plasmas.…”