Retarding field energy analyzers for the ion temperature measurements in the SOL plasmas of the tokamak ISTTOK and the TJ-II stellarator
Measurements of the ion temperature in the plasma boundary of fusion devices typically employs the Retarding Field Analyzer (RFA) that is based on selective rejecting or retarding the plasma ions by a varying braking electric field. Normally, the RFA comprises an input slit and collector electrode with two or more separately biased fine grids placed in front of it. With an assumption of Maxwellian ion distribution, the exponential decay of the RFA collector currentvoltage characteristic is determined by the ion temperature. This contribution describes 1- and 3channels RFAs for the ion temperature measurements in the scrape-off-layer of the tokamak ISTTOK and the TJ-II stellarator. Selected results of the ion temperature measurements on the ISTTOK and the TJ-II are presented. In addition, limitations related to the RFA operation (including the alignment along magnetic field direction and plasma loading) are considered.
Electrostatic Energy Analyzer for Studying Gas‐Focused Electron Beams and Their Background Media
An analyzer is described which is especially suitable for the study of electrostatically self‐focusing electron beams and their associated background media, and, in general, for media which by their nature are very sensitive to direct insertion of probes or other diagnostic devices. The basic difficulties with devices of this nature, namely, (a) the continually changing work functions of metal surfaces due to sorbed films and (b) the lens effect defocusing due to nonuniformities of the potential in the neighborhood of grid wires, have been identified and effectively overcome. The analyzer is employed flush with the boundary of the medium under study and it incorporates a shielding electrode so that the disturbance of the medium is insignificant. When the dimensions of the instrument are scaled so that the space charge effects are absent, it can be utilized successfully to detect energy spreads as small as a few tenths of an electron volt.
Physical Processes in Inorganic Scintillators
BASIC PRINCIPLES AND PROCESSES Physical Mechanism of Scintillation Creation of Electron Hole Pairs Excitation and Emission of Luminescence Centers Scintillation Materials Halides Oxides and Oxide Systems Chalcogenides Glasses Interaction of Ionizing Radiation with Scintillators High Energy Photons Charged Particles Neutral Particles General Characteristics of Inorganic Scintillators Light Yield Duration of Scintillation Pulse Afterglow Temperature Response Optical Properties Radiation Hardness Density Emission Spectra Mechanical and Chemical Properties Physical Parameters Cost Consideration Scintillator Requirements in Various Applications High Energy Physics Intermediate Energy Physics Positron Emission Tomography Gamma Spectroscopy Energy Resolution Intrinsic Scintillator Resolution Nonproportional Response Time Resolution Low Energy Quanta and Electrons CONVERSION OF ELECTRONIC EXCITATIONS IN SOLIDS Charge Carrier Behaviors Delta Rays Secondaries Excitation of Luminescence Centers Effect of Ionization Density Energy Losses Simple Phenomenological Model Plasmon Model Polaron Model Scintillation Yield Spectra Vacuum Ultraviolet Region Ultrasoft X-Rays X-Rays Gamma Rays Heavy Ionizing Particles INTRINSIC LUMINESCENCE OF INORGANIC SCINTILLATORS Excitonic Luminescence Alkali Halide Crystals Alkaline-Earth Fluorides Ternary Halide Compounds Excitonic-Like Luminescence Cesium Iodide Tungstate and Molybdate Phosphors Core-to-Valence Transitions First Evidence for Radiative Core-to-Valence Transitions Excitation Spectra Emission Spectra Experiment Theory Luminescence Kinetics Experimental Theoretical Investigations Temperature Dependence of Luminescence Parameters Conditions of Detection Prospects for Research EXTRINSIC LUMINESCENCE OF INORGANIC SCINTILLATORS Thallium-Activated Halide Scintillators Crystals with NaCl-Type Structure Crystals with CsCl-Type Structure Other Thallium-Based and Thallium-Doped Crystals Crystals Containing Other ns2 Ions Bismuth Germanate (BGO) Sodium-Activated Cesium Iodide Rare-Earth-Activated Crystals General Considerations Europium-Activated Crystals Cerium-Activated Compounds Preliminary Comments LaF3-CeF3 Systems Cerium Chloride Barium Fluoride Gadolinium-Containing Crystals Lu- and Y-Containing Crystals Nd- and Pr-Activated Crystals DEFECT FORMATION BY IONIZING RADIATION Effect on Scintillator Characteristics Mechanisms of Defect Formation Efficiency of Defect Production Geometrical Factor Separation between F and H Centers Temperature Dependence of Production Efficiency Role of Halogen Ion Impurities Effect of Cation Impurities Formation Time of F-H Pairs Closing Comments References Index