Yong-Sup Choi

Development of a 30-kW Plasma Gun System With a Long Lifetime

A hollow cathode that has extremely stable discharge characteristics has been developed. It is composed of two separated lanthanum hexaboride (LaB6) disks in the tube as the electron emitters. The design accomplishes great advantages by extending the surface discharge area of LaB6, an extension that is also useful for optimal fixing of LaB6. The hollow cathode is capable of producing 30 kW (100 V and 300 A) of power continuously. The plasma beam generated by the hollow cathode passes through holes in the centers of two intermediate electrodes covered with tungsten, which is water cooled due to the high plasma temperature entailed (greater than 3000degC ). The combination of the hollow cathode and the two intermediate electrodes is practically useful for an ion plating plasma beam source.

Determination of plasma flow velocity by mach probe and triple probe with correction by laser-induced fluorescence in unmagnetized plasmas

Plasma flow velocity was measured by Mach probe (MP) and laser-induced fluorescence (LIF) methods in unmagnetized plasmas with supersonic ion beams. Since the ion gyro-radius was much larger than the probe radius, unmagnetized Mach probe theory was used to determine plasma flow in argon RF plasma with a weak magnetic field (<200 G). In order to determine flow velocities, the Mach probe is calibrated via LIF in the absence of the ion beam, where existing probe theories may be valid although they use different geometries (sphere and plane) and analyzing tools [particle-in-cell (PIC) and kinetic models]. For the comparison of the average plasma flow velocities by MP and LIF, the supersonic ion beam velocity was measured by LIF and then incorporated into a simple formula for average plasma velocity with provisions for background plasma density and beam-corrected electron temperature (Te) measured by a triple probe.

Effect of ion―neutral collision on the deduction of Mach number in collisional plasmas

A new unmagnetized collisional Mach probe theory is developed in order to resolve the collisional effect on Mach probe analysis by including ionization, charge and momentum transfer of ions in the perturbation region of a Mach probe. A fluid model is established by assuming Boltzmann electrons and taking the moments of the one-dimensional Boltzmann transport equation, which contains the two-dimensional transport information as a source, after adding a collisional term. A new relation between the flow velocity and the ratio of the ion sheath current densities is obtained, and is compared with those by a collisionless kinetic theory and a particle-in-cell simulation in the applicable range of these theories. A new relation between flow velocity and the ratio of the ion sheath current densities shows that ion–neutral collisions have a very strong effect to produce much smaller Mach numbers from the same ratio than those by collisionless models.

Characteristics of multi GUN MgO physical vapor deposition system

Summary form only given. MgO thin film is used as a protective layer of dielectric layer in plasma display panel. The MgO film is usually coated by physical vapor deposition process, in which plasma gun or electron gun is used as a heating source. To reduce the production cost, most PDP panel makers produce several PDP panel at once by using a large glass. To make uniform MgO film on such a large glass of 100 inches, the MgO PVD evaporator should have multi plasma or electron guns. In the multi gun evaporation system, one could expect symmetric profile of evaporated film with symmetric gun condition. In the electron gun system, evaporation rate shows linear relation with electron gun power, regardless of the gun position. However, there is strong dependence of evaporation rate with gun position in plasma gun evaporation system, i.e. the profile of MgO film is not symmetric even if the plasma gun conditions of geometry, power, magnetic field and others are all symmetric. In this paper, evaporation profiles of the electron and plasma gun evaporator systems will be analyzed based on plasma dynamics. The abnormal evaporation behavior of multi plasma gun evaporation system will be explained by plasma drift motion

Optimization of Hanyang University Plasma Focus Device as a Neutron Source

The optimum focusing conditions of the Hanyang University Plasma Focus (HUPF) device have been obtained by determining maximum power input to the focusing plasma while changing pressure at one fixed electrode, which leads to the maximum neutron generation. Six electrodes of different lengths have been used according to the snow-plow model to determine the conditions for the maximum neutron production of the HUPF device, namely 1.6×108 (n/shot) with 17 cm electrode length and a 3.4 Torr pressure.

Temporal behaviors of charged particles in cylindrical corona reactors

Summary form only given, as follows. Temporal variation of electrons and ions are measured in two different pulsed corona discharge reactors, which are from the dissociation of NO/sub x/ and SO/sub x/ from the flue gases of combustion engines and power plants. Industrial scale reactor with height of 3 m and diameter of 0.5 m was made for dissociation of 500 liters of flue gas per hour. The reactor is made as a three-stage cylinder-cylinder type with a rugged inner cylindrical electrode. Another reactor is scaled by one of tenth of the industrial reactor. Electric probes have been installed in both the electrodes in order to measure the density of charged particle along with floating potential. After correcting the contribution from the displacement current, effects of system parameters on the variation of charged particles and dissociation efficiency are studied along with numerical simulation.