High-resolution x-ray crystal spectrometer/polarimeter at torus experiment for technology oriented research-94

Abstract

A high-resolution x-ray polarimeter has been installed at the torus experiment for technology oriented research ͑TEXTOR-94͒. The instrument consists of two spectrometers in Johann geometry, utilizing the dependence of Bragg reflection on the polarization. The dispersion plane of the so-called horizontal spectrometer coincides with the midplane of the tokamak, whereas the dispersion plane of the so-called vertical spectrometer lies perpendicular to the midplane of the tokamak. Both spectrometers operate with cylindrically bent quartz crystals of dimensions 153 mmϫ38 mmϫ0.7 mm with a 2d spacing of 4.9130 Å. The radii of curvature of the horizontal and vertical spectrometer crystals are 3820 mm and 4630 mm, respectively. The detectors are multiwire proportional counters having a large entrance window of 180 mmϫ90 mm, with a high count rate capability of up to 2.5ϫ10 5 photons/s, and a spatial resolution of 0.4-0.65 mm, depending on the count rate. The unique data acquisition system makes it possible to record up to 8192 spectra per TEXTOR-94 discharge to study fast events and impurity transport. The instruments are sensitive to spurious amounts of argon in hydrogen or deuterium discharges and aim for x-ray polarization measurements and other core plasma diagnostics like electron temperature, ion temperature, plasma rotation, impurity transport, and relative abundance of Ar 15ϩ /Ar 16ϩ . The first measurements of toroidal rotation speed, ion and electron temperatures show a very good agreement with charge exchange recombination spectroscopy ͑XRS͒ and electron cyclotron emission ͑ECE͒ diagnostics available at TEXTOR-94. The measured values of the ratio Ar 15ϩ /Ar 16ϩ are higher than that predicted from coronal equilibrium. The ratio depends strongly upon the electron density both for ohmic and neutral beam injection cases. This suggests that the charge state distribution is also dependent on diffusion and charge exchange processes in the plasmas.

Detection of the X-ray spectra of imploding neon Z-pinch with elliptically bent mica crystal spectrometer

“…Various Ne IX and Ne X transitions are identified and listed in the table. The experimental results have shown that the calculated spectral resolution (λ/∆λ) approximates 379 with ∆λ being the full-width at half-maximum (FWHM) [13] . Fig.…”

Double-spherically bent crystal high-resolution X-ray spectroscopy of spatially extended sources

“…It is well known that the focusing spectrograph is capable of recording highly resolved spectra with a significantly higher sensitivity [10][11][12] . As an example of such a device, the Johann configuration spectrometer [13,14] can obtain a high luminosity, good spatial resolution, and slightly lower spectral resolution, and has been used from the source on the Rowland circle experiments. In a von Hamos crystal spectrometer setup [15] the energy resolution depends on the size of the effective source.…”

Passive Spectroscopic Diagnostics for Magnetically-confined Fusion Plasmas

“…In recent years, x-ray spectroscopy has been further developed on other MFE devices, such as LHD [244][245][246][247] , TEXTOR [248][249][250][251] , and NSTX [252][253][254][255] . The LHD spectrometer 244 employs a quadrangular crystal holder with four cylindrically bent quartz crystals, allowing the instrument to be tuned for the observation of the He-like ion spectra of argon, titanium, chromium, and iron.…”

“…Accurate measurements of the argon ion charge state distribution as a function of density from TEXTOR discharges with and without neutral beam injection documented large deviations from coronal equilibrium due to charge exchange recombination during neutral-beam injection 249 .…”