Effects of Coaxial Cylindrical Nozzle on Induction-Coupled Plasmas

A mathematical model is presented for the calculation of the two dimensional temperature fields in an induction-coupled argon plasma torch. The torch has a coaxial cylindrical nozzle for powder feeding. It is assumed that the radial velocity of gas flow is negligible and the axial velocity pattern is two step function of radius. Results were obtained for a plasma torch, 1.4 cm radius and 20 cm long. The oscillator frequency was 4 MH_z. Temperature fields based on the model were calculated for an atmospheric pressure argon plasma at magnetic flux density levels of 53 Gauss with different plasma gas flow rate over the range of 0 to 30 1/min at 0℃. As the nozzle is inserted into the torch, the plasma is cooled in the nozzle region, however, the nozzle does not greatly affect the temperature plofiles in the downstream below the nozzle region. Increasing the radius of the nozzle, firstly, the maximum power input density does not change and power input inside the torch decreases, secondly, maximum power input density is lowered and finally the torch is extinguished

誘導プラズマに対する同軸円筒ノズルの影響

A mathematical model is presented for the calculation of the two dimensional temperature fields in an induction-coupled argon plasma torch. The torch has a coaxial cylindrical nozzle for powder feeding. It is assumed that the radial velocity of gas flow is negligible and the axial velocity pattern is two step function of radius. Results were obtained for a plasma torch, 1.4 cm radius and 20 cm long. The oscillator frequency was 4 MH_z. Temperature fields based on the model were calculated for an atmospheric pressure argon plasma at magnetic flux density levels of 53 Gauss with different plasma gas flow rate over the range of 0 to 30 1/min at 0℃. As the nozzle is inserted into the torch, the plasma is cooled in the nozzle region, however, the nozzle does not greatly affect the temperature plofiles in the downstream below the nozzle region. Increasing the radius of the nozzle, firstly, the maximum power input density does not change and power input inside the torch decreases, secondly, maximum power input density is lowered and finally the torch is extinguished

Influence of Mechanical Stresses on Dielectric Breakdown Strength of PET and FRP

Electrical insulators are important components in a superconducting magnet. In contrast with the superconducting power cable, insulating materials to be used for the magnet in a large fusion device must have excellent electrical performance and durability for a long period of about 40 years under high mechanical stresses and cryogenic temperature. In the present paper, the problem which may become important for the design of an electrical insulation of the magnet is surveyed and experimental results on the influence of mechanical stresses on the electrical insulation performance of PET (polyethylene telephthalate) and FRP (fiberglass reinforced plastics ; epoxy glass cloth) are reported. Some characteristics are newly found on the relationship between breakdown field strength and mechanical properties of PET and FRP

Assessments of a Microwave Scattering System for the Plasma Wave and Turbulence Measurements

The problems associated with the microwave scattering technique for the plasma wave and turbulence measurements have been pointed out as being the difficulties (i) of estimating the absolute values of the electron density fluctuations from the scattering data, and (ii) of extending the measurable wave-number regions beyond Kλ_D＞__～0.05. Based on the detailed studies using the Langmuir probe and the recent development of the microwave technique, we have proposed the ways to overcome the above difficulties (a) by absolutely-calibrating the microwave scattering system against the known plasma density fluctuations, and (b) by assessing the most favourable scattering system. A preliminary measurement is made of the density fluctuations in the current-driven ion wave of a plasma

Formation of a Unform Plasma Sheet in a Z-pinch Phenomenon

The necessary conditions for the formation of the uniform plasma sheet in gases (0.25-20 torr) are investigated using a device which simulates the initial breakdown and run down phases of the plasma focus. Under various experimental conditions, the structure and the development of the plasma sheet were observed by an image converter camera and diagnosed using a magnetic probe. As a result, the plasma sheet has been found to be filamentary in the region of a higher filling gas pressure and a lower storage energy, and to have a uniform structure in the region of a lower filling gas pressure and a higher storage energy. In addition, following points are found ; (1) when a uniform plasma sheet is formed, its propagation is described by a snowplow model, and (2) in order to form a uniform plasma sheet, there is a lower limit of the input energy density (input energy/particle)

PET と FRP の絶縁破壊強度に及ぼす機械的応力の影響

Electrical insulators are important components in a superconducting magnet. In contrast with the superconducting power cable, insulating materials to be used for the magnet in a large fusion device must have excellent electrical performance and durability for a long period of about 40 years under high mechanical stresses and cryogenic temperature. In the present paper, the problem which may become important for the design of an electrical insulation of the magnet is surveyed and experimental results on the influence of mechanical stresses on the electrical insulation performance of PET (polyethylene telephthalate) and FRP (fiberglass reinforced plastics ; epoxy glass cloth) are reported. Some characteristics are newly found on the relationship between breakdown field strength and mechanical properties of PET and FRP

Measurements of Impurity Densities in High Temperature Plasmas by a Resonance Scattering I.

For the measurement of the impurity densities or fluxes in a magnetically confined fusion device, using a resonance scattering method with a tunable laser, the sensitivity of the method (required laser power, detection limit, resolution of a distribution function) is estimated. A model experiment is carried out with a flash lamp-pumped tunable dye laser and sodium vapor of known density as scattering target atoms, to examine the sensitivity and to clarify the problems of the technique