Johann-type Spectrometer Research Articles

Experimental investigation of the origin of the TiKα″satellites

The Ti $K{\ensuremath{\alpha}}^{\ensuremath{''}}$ satellite is investigated using a Johann-type spectrometer on the BL15XU undulator beam line of SPring-8 at excitation energies between 4996 and $7000\phantom{\rule{0.3em}{0ex}}\text{eV}$. The intensity of the $K{\ensuremath{\alpha}}^{\ensuremath{''}}$ satellite relative to that of $K{\ensuremath{\alpha}}_{1,2}$ exhibits an abrupt jump from $0%$ to $\ensuremath{\sim}1%$ in a range of $10\phantom{\rule{0.3em}{0ex}}\text{eV}$ around an excitation energy of $5010\phantom{\rule{0.3em}{0ex}}\text{eV}$. The energy range to reach saturation is $\ensuremath{\sim}500\phantom{\rule{0.3em}{0ex}}\text{eV}$. The creation of spectator holes is implicated to be due to shake-up processes, inducing the emergence of the $K{\ensuremath{\alpha}}^{\ensuremath{''}}$ satellite. The onset energy for the appearance of the satellite is $5011.0\phantom{\rule{0.3em}{0ex}}\text{eV}\ifmmode\pm\else\textpm\fi{}0\text{.8}\phantom{\rule{0.3em}{0ex}}\text{eV}$, corresponding to the $[1s3p]$ double-ionization threshold energy by a $Z+1$ approximation. The experimental results obtained in this work confirm that the $K{\ensuremath{\alpha}}^{\ensuremath{''}}$ satellite originates from a $3p$ spectator hole, as predicted theoretically by Scott [Phys. Rev. A 34, 4438 (1986)].

X-ray line diagnostics on the Tore Supra tokamak

We describe a multi-crystal, high-resolution, fully remote-controlled, absolutely calibrated, Johann-type spectrometer for the 1–4 Å region. Spectra from the helium- and lithium-like charge states of impurity elements from Ar to Cu are analyzed by least-squares fitting of synthetic spectra. The intrinsic impurity elements Cr and Fe are used for a routine, time-resolved, hands-off diagnostic for electron and ion temperatures, and for toroidal rotation velocities. Impurity densities are obtained from absolute line intensities. Injection of Ar, Ti, Mn, and Ni, is used for transport studies. We have also obtained the precise wavelengths of transitions in neon-like and near-neon-like charge states of Pd and Ag, which are of much interest in atomic physics.

Development of high-resolution vacuum crystal spectrometer in a compact helical system and large helical device

A vacuum crystal spectrometer that covers a wavelength range of 1.0–2.5 nm has been developed to observe light (oxygen) and heavy (titanium and iron) impurities for large helical device (LHD) diagnostics. A Johann-type spectrometer (2 R = 60 cm and 3 m, RAP crystal, 2 d = 2.612 nm) was constructed and installed in a compact helical system (CHS). The O VII resonance line was successfully observed through a thin (3.3 μm t) polypropylene film, although the metallic impurity lines were not seen. In the case of a crystal with 2 R = 3 m, however, the spectral resolution λ/Δλ was limited to 440, whereas the replacement by the crystal with 2R = 60 cm improved the resolution to 610. The result is discussed with regard to the quality of the bent crystal.

Application of a position-sensitive detector to soft X-ray emission spectroscopy

The authors describe a gas proportional detector (42*18 mm2) for detection of soft X-rays in the region 1-3 keV operating with 1 atm argon-methane utilizing a backgammon one-dimensional readout. A detailed account of the design, fabrication and operational characteristics of the detector is presented. Trade-offs encountered in the design are highlighted. The detector has achieved high spatial linearity and intensity response. The authors report on the use of the detector in a high vacuum Johann-type crystal spectrometer for measurements of soft X-ray emission bands of solids.

Kα X-rays from magnesium, some of its compounds and alloys

Magnesium Kα3,4 satellite spectra along with the Kα1,2 diagram line and the Kα' satellite line from magnesium, its oxide, halides, sulphate, acetate and binary alloys with silver, cadmium, indium, tin and antimony have been recorded in direct excitation using a Johann-type crystal spectrometer with a MoS2 crystal (2d = 12.30 Å). It is found that the chemical environment surrounding the emitting atoms affects the satellite intensity ratio (IKα4/IKα3) strongly. No obvious trend between the electronegativity differences of the compounds and the intensity ratios of the Kα4/Kα3 satellites is evident. No linear relationship between the satellite intensity ratios (IKα4/IKα3) and the magnesium content in the alloy is observed as reported by Baun and Fischer for the aluminium system. The origin of the Kα3 and Kα4 satellites is discussed.

Curved Crystal Spectrometer with Position-Sensitive Solid-State Detector for Plasma Diagnostics

The characteristics of a Johann-type crystal spectrometer with a photodiode array (PDA) are described. The crystal used is LiF(200) with a bending radius of 100 cm, and the sensitivity of the PDA is measured for X-rays of 4 to 17 key. The collection efficiency η of charges created in the PDA is determined as a function of the X-ray energy E(keV): η=-0.026E+0.68. An asymmetrical spectral profile is observed when a monochromatic X-ray beam is incident on the PDA with an angle larger than 40°. The sensitivity of the spectrometer is also calibrated against a conventional X-ray tube. The PDA is used for the observation of X-ray lines from a high-temperature plasma in a vacuum spark. The resultant Fe Kα spectrum shows a spread over several channels due to blooming, when compared with that recorded on Kodak no-screen X-ray film.

High-throughput, high-resolution soft X-ray crystal spectrometer for Tokamak-plasma studies

A Johann-type reflection spectrometer with a wavelength resolution of 15000 at 0.229 nm (CrKalpha ) is described. The diffracting crystal is a (310)-quartz plate with 50*30 mm2 total and useful area, bent to a radius of 1380 mm. The use of a novel, simple crystal bending device and of a position-sensitive proportional counter makes this instrument interesting also for other domains of X-ray spectroscopy. Results of extended calculations on diffraction properties of quartz as a function of diffraction plane index and wavelength are also presented.

High resolution study of soft X rays from collisions of 1 MeV H 2+ and 500 keV Ar + with carbon

A Johann-type spectrometer with lead stearate analyzer was used to investigate the carbon-K X-ray emission lines produced from 1 MeV H 2 + → carbon and 500 keV Ar + → carbon collisions.