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Temporal evolution of radial profiles of end-loss-ion currents, ion temperatures, and ion-confining potentials φ[sub c] is investigated in the GAMMA 10 tandem mirror by the use of our newly designed electrostatic ion-energy-spectrometer arrays. In tandem-mirror experiments, plasma-confining potentials produced by electron-cyclotron heatings (ECH's) play one of the most critical roles in the improvement of simple-mirror plasma confinement. For the observations of these confining potentials, the development of ion-diagnostics equipment providing clear energy spectra without disturbances from ECH produced energetic electrons is of essential importance, since conventional multigrided Faraday cup signals are seriously influenced by such incident electrons. Each spectrometer unit in our developed array has a specific structure with obliquely placed multiple grids with respect to the direction of the ambient lines of magnetic force for plasma confinement. The relation between the spatial profiles of end-loss-ion fluxes I[sub ELA] and those of φ[sub c] is investigated by the use of these newly designed ion-energy-spectrometer arrays installed in both end regions of GAMMA 10. The first remarkable finding of axisymmetric profiles of φ[sub c] having a good correlation with axisymmetric plugging distributions in I[sub ELA] along with the central-cell density n[sub c] increase is made; while, the contrary result without n[sub c] increase even during a plugging period is found with asymmetric profiles of φ[sub c] with asymmetric plugging profiles in I[sub ELA]. In the article, detailed data comparison between the two is reported by the use of each single-plasma discharge with the developed ion-spectrometer arrays. [ABSTRACT FROM AUTHOR]

Results of H[sub α] measurement in the GAMMA 10 tandem mirror are described, with a particular focus on the behavior of neutrals in the anchor minimum-B region. Recently a set of H[sub α] line-emission detector arrays was designed and installed in the anchor-cell, where the shape of the magnetic flux tube becomes flat and the cross section of plasma is elongated elliptically. The detector consists of H[sub α] interference filter, optical fiber, and photomultiplier with magnetic shield, and is absolutely calibrated by using a standard lamp. In standard ion-cyclotron-range-of-frequency heated, hot-ion-mode plasmas, detailed measurements of H[sub α] line-emission form the central-cell to the anchor-cell were carried out, and the dependence of the H[sub α] intensity on the quantity of gas puffing was investigated. The characteristic behavior of neutrals in the nonaxisymmetric anchor-cell is also discussed, based on the result of neutral transport simulation. [ABSTRACT FROM AUTHOR]

Measurement of spectra in the wavelength range from vacuum ultraviolet (VUV) to soft x ray is an important means to diagnose impurity behavior in magnetically confined plasmas used in fusion plasmas. Recently, a space- and time-resolving flat-field grazing-incidence VUV spectrograph was constructed for the simultaneous observation of spatial, temporal, and spectral distributions of plasma radiation in the wavelength range of 150–1050 Å. Absolute calibration experiments were performed at beamline 11C and beamline 12A in the Photon Factory at the High Energy Acceleration Research Organization. The absolute sensitivity of the VUV spectrograph was measured under both P and S polarized light conditions. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Observes behaviors of high energy ions in the GAMMA 10 tandem mirror. Effective use of the ion cyclotron range of frequency heating; Value of the ion temperature; Observation of pitch angle distribution; Significance of the temporal evolution of the endloss high energy ions; Enhancement of the loss of high energy ions.

Investigates the behavior of impurity ions using visible spectroscopy in the GAMMA 10 tandem mirror. Development of a visible spectrometer system for measurements of ion temperature and ion flow velocity; Components of the spectrometer; Measurement of the spectra from low ionization states of oxygen; Observation of high ion temperatures in the anchor region.

Describes the development and characteristics of semiconductor ion detectors for plasma diagnostics in the range over 0.3 keV. Response studies of the semiconductor ion detector using a monoenergetic ion-beam line; Investigations of the critical structure beneath the semiconductor-surface region for low-energy-ion detections using synchrotron-radiation data.

An idea for using semiconductor detectors to simultaneously observe both plasma ion T[sub i] and electron T[sub e] temperatures is proposed. The idea is also experimentally verified in tandem-mirror plasma shots. This method is developed on the basis of an alternative "positive" use of a semiconductor "dead layer" as an energy-analysis filter. Filtering dependence of charge-exchange neutral particles from plasmas on the thickness of a thin (on the order of nm thick) SiO[sub 2] layer is employed for analyzing T[sub i] in the range from hundreds to thousands of eV. Even under the conditions of simultaneous incidence of such particles and x rays into semiconductor detectors, the different dependence on their penetration lengths and deposition depths in semiconductor materials makes it possible to distinguish particles (for T[sub i]) from x rays (for T[sub e]). In this letter, proof-of-principle plasma experiments for the proposed idea are carried out to verify the availability of this concept of distinguishing and identifying each value of T[sub i] and T[sub e] by the use of various thin filtering materials prior to the use of thinner dead layers. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the benefits of compact pinhole camera for observing spatial distributions of hot ions. Obtainment of neutral atoms and x-ray images in the same geometry; Implication of associated images for plasma physical analyses.

The first experimental demonstration of simultaneous measurements of temporally and spatially resolved ion-confining potentials φc and end-loss-ion fluxes IELA has been carried out during a single plasma discharge alone by the use of newly designed ion-energy-spectrometer arrays installed in both end regions of the GAMMA 10 tandem mirror. This position-sensitive ion-detector structure is proposed to obtain precise ion-energy spectra without any perturbations from simultaneously incident energetic electrons into the arrays. The relation between φc and IELA is physically interpreted in terms of Pastukhov’s potential confinement theory. In particular, the importance of axisymmetric φc formation is found for the plasma confinement. [Copyright &y& Elsevier]