ABSTRACT
This paper presents the results of the development and testing of a secondary ion accelerator for the diagnostic complex of neutral particle analyzers at ITER. The accelerator is part of an analyzer designed to measure fluxes of neutral deuterium and tritium particles escaping from reactor plasma in a total range of 10-200 keV. The aim of the accelerator is to improve the signal/background ratio of the analyzer. It is especially important for the region with a relatively low energy of 10-50 keV. The accelerator has the function of converting atoms into secondary ions and accelerating them in an electrostatic field with a voltage of up to +100 kV. The accelerator is based on two high-voltage accelerating tubes. A special unit is built into the central electrode of the accelerator, which provides the replacement of stripping foils used for the conversion of the flux of neutral particles into a flux of secondary ions. The high-voltage tube assembly is encompassed by a sealed steel housing, in which electrical insulation is provided by a gas gap (nitrogen at 6 bar). The results of tests of the accelerator under ITER relevant conditions, namely, under high-intensity gamma irradiation and seismic loads, have shown its high reliability for use in the diagnostic complex of the fusion reactor.
ABSTRACT
Bench tests of a 15 keV helium ion source, which has been developed for the neutral particle diagnostic system of the International Thermonuclear Experimental Reactor (ITER), are described. Being part of the diagnostic system, the ion source will be used to monitor the intactness of carbon stripping foils as well as to check the detection and dispersion systems of the main diagnostic instruments-neutral particle analyzers (NPAs). The ion source produces a wide 5-cm diameter (FWHM) ion beam at a distance of about 50 cm; the ion beam uniformity at a 2-cm area corresponding to the size of the stripping foil is not worse than 10%. The beam current over the area of the stripping foil can be adjusted in the range of 0.1 pA-1 pA. After initial heating, the temporal stability of the ion beam is better than 10%. Pulse height measurements of registered signals show that 15 keV He+ ions can be reliably registered by the NPA detector system. The obtained results allow us to conclude that the developed ion source can provide a reliable check of the NPA system during the diagnostic performance on the ITER tokamak.
ABSTRACT
Existing electrooptical experimental techniques applied to a colloid solution allow the determination of different particle parameters, such as rotary diffusion coefficient, size, polarizability anisotropy and others. If the solution is polydisperse, numerical methods can be used to determine the distribution of particles in the solution on their parameters. These techniques can be applied to systems that are prone to lengthy application of electric field. To study polydisperse systems that cannot stand lengthy application of electric field it is proposed to apply short pulses of strong sine-shaped electric field. It is shown that it is still possible to determine the main particle parameters from the experimental data obtained in this technique. The limitations of this approach are studied. This technique was experimentally probed on aqueous colloid solutions of diamond, graphite and palygorskite. It is shown that for these systems the relaxation of the electrooptical effect after application of strong pulses of sine-shaped electric field is similar to the relaxation of the electrooptical effect from the state of saturated orientation induced by sine-shaped electric field, which is proven by the presented correlation coefficients.
ABSTRACT
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.
ABSTRACT
A theoretical analysis is presented that describes wave-mixing processes in thin holographic gratings for phase-modulated beams. Experiments with photorefractive Bi(12)TiO(20) crystals in which the signals for Bragg diffraction and for the first non-Bragg diffraction order were measured support the analysis.
ABSTRACT
Experimental results are reported for four-wave mixing at 633 nm with a photorefractive Bi(12)TiO(20) crystal in a double phase-conjugate mirror geometry. Recording in the presence of an alternating electric field with optimum focusing of interacting Gaussian beams yields up to 40% diffraction efficiency for the hologram.
ABSTRACT
The electroconductivity temperature dependence shows that an anomaly exists at temperature 304-308 K. The special study of electro-optical behaviour frequency dependence demonstrated that a critical frequency vc = 1000Hz exists and divides two typical regions: a) in the first one (below vc) an unoriented hydrodynamic picture was observed, round the layer's defects; b) in the second one (over vc) an oscillating characteristic of the optical pictures (starting at 5 x 10(4) V/cm of the electric field intensity) was observed.
Subject(s)
Bacteriorhodopsins , Carotenoids , Electric Conductivity , Ions , Microscopy, Electron , TemperatureABSTRACT
The Priz light modulator suppresses input data at zero spatial frequency, can provide directional spatial filtering, and can perform dynamic image selection or change detection. In this paper, we summarize the Priz's performance and provide experimental confirmation of the above three image processing applications of this device.
