B. S. Fraenkel

Polar Properties of ZnS Crystals and the Anomalous Photovoltaic Effect

ZnS platelets grown from the vapor phase, bounded by (211), (011), and (111) faces, were used. The crystals showed birefringence bands perpendicular to the [111] axis. X‐ray rotation, oscillation, and Laue photographs showed that the bands are due to changes in crystal structure (cubic, hexagonal, and polytypes) and one‐dimensional stacking disorder. The polarity of the common [111] axis of the various bands was determined by several techniques. On the (211) faces, heating with H2O2 caused the appearance of triangular etch pits, aligned with bases parallel to the [011] direction and apexes pointing all in the same sense. The (111) face towards which the triangles pointed was attacked faster by the etchant than was the opposite one. The same (111) face became negatively charged if a (211) face was uniformly illuminated by 343 mμ radiation. Furthermore, the same face turned out to be a zinc plane, as revealed by comparing the intensity of two (111) reflections, using wavelengths at both sides of the Zn...

Imaging x-ray crystal spectrometers for the National Spherical Torus Experiment

A new type of high-resolution x-ray imaging crystal spectrometers is described for implementation on the National Spherical Torus Experiment (NSTX) to provide spatially and temporally resolved data on the ion temperature, toroidal and poloidal plasma rotation, electron temperature, impurity ion-charge state distributions, and impurity transport. These data are derived from observations of the satellite spectra of heliumlike argon, Ar XVII, which is the dominant charge state for electron temperatures in the range from 0.4 to 3.0 keV and which is accessible to NSTX. Experiments at the Torus Experiment for Technology Oriented Research (TEXTOR) demonstrate that a throughput of 2×105 photons/s (corresponding to the count-rate limit of the present detectors) can easily be obtained with small, nonperturbing argon gas puffs of less than 1×10−3 Torr l/s, so that it is possible to record spectra with a small statistical error and a good time resolution (typically 50 and 1 ms in some cases). Employing a novel design, which is based on the imaging properties of spherically bent crystals, the spectrometers will provide spectrally and spatially resolved images of the plasma for all experimental conditions, which include ohmically heated discharges as well as plasmas with rf and neutral-beam heating. The conceptual design, experimental results on the focusing properties, and relevant spectral data from TEXTOR are presented.A new type of high-resolution x-ray imaging crystal spectrometers is described for implementation on the National Spherical Torus Experiment (NSTX) to provide spatially and temporally resolved data on the ion temperature, toroidal and poloidal plasma rotation, electron temperature, impurity ion-charge state distributions, and impurity transport. These data are derived from observations of the satellite spectra of heliumlike argon, Ar XVII, which is the dominant charge state for electron temperatures in the range from 0.4 to 3.0 keV and which is accessible to NSTX. Experiments at the Torus Experiment for Technology Oriented Research (TEXTOR) demonstrate that a throughput of 2×105 photons/s (corresponding to the count-rate limit of the present detectors) can easily be obtained with small, nonperturbing argon gas puffs of less than 1×10−3 Torr l/s, so that it is possible to record spectra with a small statistical error and a good time resolution (typically 50 and 1 ms in some cases). Employing a novel design...

Spatially resolved spectra from a new x-ray imaging crystal spectrometer for measurements of ion and electron temperature profiles (invited)

A new type of high-resolution x-ray imaging crystal spectrometer is being developed to measure ion and electron temperature profiles in tokamak plasmas. The instrument is particularly valuable for diagnosing plasmas with purely ohmic heating and rf heating, since it does not require the injection of a neutral beam—although it can also be used for the diagnosis of neutral-beam heated plasmas. The spectrometer consists of a spherically bent quartz crystal and a two-dimensional position-sensitive detector. It records spectra of helium-like argon (or krypton) from multiple sightlines through the plasma and projects a de-magnified image of a large plasma cross section onto the detector. The spatial resolution in the plasma is solely determined by the height of the crystal, its radius of curvature, and the Bragg angle. This new x-ray imaging crystal spectrometer may also be of interest for the diagnosis of ion temperature profiles in future large tokamaks, the Korea Superconducting Tokamak Advanced Research tok...

Classification of Transitions in the euv Spectra of Y ix–xiii, Zr x–xiv, Nb xi–xv, and Mo xii–xvi*

The spectra of Y ix–xiii, Zr x–xiv, Nb xi–xv, and Mo xii–xvi were investigated in the range of 45–350 A. Spectroscopic transitions belonging to the isoelectronic sequences of Co i, Ni i, Cu i, and Ga i were classified. Some unclassified lines are also listed.

Nickel-like spectra of elements Y xii to Ag xx from a vacuum spark

The spectra of elements Y, Zr, Nb, Mo, Ru, Rh, Pd, and Ag in the 10–100-A range were obtained from a high-power vacuum spark and a grazing-incidence high-resolution spectrograph. The transitions 3d10–3d94p, 3d10–3d94f, 3d10–3d95p, and 3d10–3d95f were identified. The agreement with ab initio relativistic calculations is good. The relevance of the jj coupling scheme for level labeling is discussed, as is the importance of relativistic effects, by comparing the scheme with other results on high-Z atoms (up to Pt).

Evidence for high temperatures in minute plasma points from X-ray spectra of FeXXV and FeXXVI

Abstract Analysis of profiles and intensities of lines emitted by FeXXVI and FeXXV in a vacuum spark show presence of extremely high temperatures. Electronic temperatures higher than 4 keV and ionic temperatures as high as 30 keV exist in minute plasma points.

Monochromatic x‐ray images of x‐ray emitting sources

A method is demonstrated for obtaining monochromatic aberration‐free images of x‐ray emitting sources, through the process of double Bragg reflection. Space‐resolved ion and temperature distribution in hot plasmas may therefore be obtained.

Identification of magnetic quadrupole lines of highly ionized Ni, Cr, Fe in the TFR600 Tokamak plasma

Abstract Forbidden lines (magnetic quadrupole) in spectra of NeI like CrXV, FeXVII and NiXIX, were identified in the TFR600 Tokamak plasma, in the 10–20 A range.

New Lines in Isoelectronic Sequences of Argon I from V vi to Ni xi and in Isoelectronic Sequences of Potassium i from Cr vi to Cu xi

A method of differentiation between highly ionized spectra has enabled extension of the argon i isoelectronic sequences of the 3p54s and 3p5 5s levels. A sequence of 3p5(²P32)4d and 3p5(²P12)4d levels is established. The potassium i isoelectronic sequences of 3p63d–3p6nf transitions are also extended.Lines of the following ions are reported: V vi, Cr vi and vii, Mn viii, Fe viii and ix, Co ix and x, Ni x and xi, Cu xi.

Vacuum Ultraviolet Spectrometer

A grazing incidence vacuum spectrometer is described. It is based on a 2‐m, 30 000‐lines/in., Siegbahn glass grating. Both plate holder and grating are held on arms fastened to the axis of the Rowland circle. The wavelength range extends up to 2300 A. Instrumental considerations for obtaining high resolution in the short wavelength range are discussed.