RESUMEN

A new compact, multi-channel Solid State Neutral Particle Analyzer (SSNPA) diagnostic based on silicon photodiode array has been designed and is being fabricated for the National Spherical Torus Experiment-Upgrade (NSTX-U). The SSNPA system utilizes a set of vertically stacked photodiode arrays in current mode viewing the same plasma region with different filter thickness to obtain fast temporal resolution (∼120 kHz bandwidth) and coarse energy information in three bands of >25 keV, >45 keV, and >65 keV. The SSNPA system consists of 15 radial sightlines that intersect existing on-axis neutral beams at major radii between 90 and 130 cm, 15 tangential sightlines that intersect new off-axis neutral beams at major radii between 120 and 145 cm. These two subsystems aim at separating the response of passing and trapped fast ions. In addition, one photodiode array whose viewing area does not intersect any neutral beams is used to monitor passive signals produced by fast ions that charge exchange with background neutrals.

RESUMEN

An overview of the developments postcirca 1980s in the instrumentation and application of charge exchange neutral particle diagnostics on magnetic fusion energy experiments is presented. First, spectrometers that employ only electric fields and hence provide ion energy resolution but not mass resolution are discussed. Next, spectrometers that use various geometrical combinations of both electric and magnetic fields to provide both energy and mass resolutions are reviewed. Finally, neutral particle diagnostics based on utilization of time-of-flight techniques are presented.

RESUMEN

A motional Stark effect diagnostic has been utilized to reconstruct the parallel current density profile in a spherical-torus plasma for the first time. The measured current profile compares favorably with neoclassical theory when no large-scale magnetohydrodynamic instabilities are present in the plasma. However, a current profile anomaly is observed during saturated interchange-type instability activity. This apparent anomaly can be explained by redistribution of neutral beam injection current drive and represents the first observation of interchange-type instabilities causing such redistribution. The associated current profile modifications contribute to sustaining the central safety factor above unity for over five resistive diffusion times, and similar processes may contribute to improved operational scenarios proposed for ITER.

RESUMEN

Lead toxicity, a man-made disease of young children, has only recently come to the focus of professional and public awareness. Lead has become increasingly bioavailable to humans as a direct result of industrial processing and manufacturing. While lead-based paint in older dwellings is the primary cause of lead toxicity among young children, airborne lead from gasoline fumes and factory emissions, plus dirt and dust into which high concentrations of lead have settled, are also significant sources of undue exposure. A variety of consumer products, including kitchen utensils, newsprint, and cosmetics are likewise potentially hazardous because of their high lead content. Exposure to excessive amounts of lead is especially harmful for young children: they are biologically and developmentally more vulnerable to its toxic effects. Even at levels of absorption that produce no medical symptoms, lead may impede children's overall developmental progress by interfering with their performance in serveral crucial areas. Although the United States has been reluctant to assume an aggressive regulatory position toward lead, the federal government currently supports comprehensive lead poisoning control programs in 60 American cities.

Asunto(s)

Intoxicación por Plomo/prevención & control , Programas Nacionales de Salud/organización & administración , Niño , Salud Ambiental , Humanos , Estados Unidos

RESUMEN

In conventional applications of the radio-frequency quadrupole mass analyzer, the ion injection energy is usually limited to less than the order of 100 eV due to constraints on the dimensions and power supply of the device. However, requirements often arise, for example in fusion plasma ion diagnostics, for mass analysis of much more energetic ions. A technique easily adaptable to any conventional quadrupole analyzer which circumvents the limitation on injection energy is documented in this paper. Briefly, a retarding potential applied to the pole assembly is shown to facilitate mass analysis of multikiloelectron volt ions without altering the salient characteristics of either the quadrupole filter or the ion beam.