Ion Density Distribution in an Inductively Coupled Plasma Chamber

The ion density distribution in the reaction chamber was diagnosed by a Langmuir probe. The rules of the ion density distribution were obtained under the pressures of 9 Pa, 13 Pa, 27 Pa and 53 Pa in the reaction chamber, different radio-frequency powers and different positions. The result indicates that the ion density decreases as the pressure increases, and increases as the power decreases. The ion density of axial position z =0 achieves 5.8×1010 on the center of coil under the power of 200 w and pressure of 9 Pa in the reaction chamber.     

Ion Collection from Resonance-Photoionized Plasma by Applying Radio-Frequency Voltage

Ions were collected on electrodes from laser resonance photoionized plasma by applying 2 MHz radiofrequency voltage to the electrodes. It was demonstrated that the ions are collected in a shorter time at the same kinetic energy of the collected ions compared with ion collection by applying DC voltage to the electrode. A simple one-dimensional model was extended for prediction of ion collection times in the cases of applications of not only DC voltage but also radio-frequency voltage. The ion collection times estimated with the simple one-dimensional model agreed with the experimental values in the case of application of radiofrequency voltages as well as DC voltage. Though the experimental conditions such as ion density are far from those of the plant of atomic vapor laser isotope separation (AVLIS), the simple one-dimensional model shows that radio-frequency voltage method is effective under the conditions close to those of the AVLIS plant.     

The Gridless Plasma Ion Source （GIS） for Plasma Ion Assisted Optical Coating

High-quality optical coating is a key technology for modern optics. Ion-assisted deposition technology was used to improve the vaporized coating in 1980's. The GIS (gridless ion source), which is an advanced plasma source for producing a high-quality optical coating in large area, can produce a large area uniformity＞1000 mm(diameter), a high ion current density ～ 0.5mA/cm2, 20 eV ～ 200 eV energetic plasma ions and can activate reactive gas and film atoms. Now we have developed a GIS system. The GIS and the plasma ion-assisted deposition technology are investigated to achieve a high-quality optical coating. The GIS is a high power and high current source with a power of I kW ～ 7.5 kW, a current of 10 A ～ 70 A and an ion density of 200μA/cm2 ～ 500μA/cm2. Because of the special magnetic structure, the plasma-ion extraction efficiency has been improved to obtain a maximum ion density of 500μA/cm2 in the medium power (～ 4 kW) level. The GIS applied is of a special cathode structure, so that the GIS operation can be maintained under a rather low power and the lifetime of cathode will be extended. The GIS has been installed in the LPSX-1200 type box coating system. The coated TiO2, SiO2 films such as antireflective films with the system have the same performance reported by Leybold Co, 1992, along with a controllable refractive index and film structure.     

Computer-Controlled System for Plasma Ion Energy Auto-Analyzer

A computer-controlled system for plasma ion energy auto-analyzer was technically studied for rapid and online measurement of plasma ion energy distribution. The system intelligently controls all the equipments via a RS-232 port, a printer port and a home-built circuit. The software designed by LabVIEW G language automatically fulfils all of the tasks such as system initializing, adjustment of scanning-voltage, measurement of weak-current, data processing, graphic export, etc. By using the system, a few minutes are taken to acquire the whole ion energy distribution, which rapidly provides important parameters of plasma process techniques based on semiconductor devices and microelectronics.     

On-Line Measurement of Ion Density in Atmospheric Nitrogen Discharge Filaments via Radiation Signals from Plasma Oscillation

Diagnosis of the particle number density of plasma plays an important role in the understanding of plasma sources and processing.Regular radiation signals from plasma oscillation in filaments of atmospheric nitrogen discharge,which were excited by the injection of secondary electron beams during the propagation of the streamer,are employed to determine the ion density of plasma and its evolution in the filaments.Results show that the density of N_4~+ in a filament of atmospheric nitrogen discharge is of the order of 10~(13) cm~(-3).It is also found that the recombination processes play a dominant role in plasma decay,and that the ion density decreases non-monotonically with time during streamer propagation.     

Experimental Study of a Minitype Atmospheric Non-equilibrium Plasma Source

A mini-type of plasma source was studied experimentally. The results showed that the plasma density, which was generated by an atmospheric non-equilibrium plasma source, rises with the increase in driving electric-field and the momentum of gas particles. For a driving electricfield of 56 kV/cm and a gas particles＇ momentum of 10^9 × 10^-22 g·m/s, the ion density can exceed 10^10/cm^3 while the effective volume of the plasma source is only 2.5 cm^2. This study may help develop a method to generate a minitype plasma source with low energy consumption but high ion concentration. This source can be used in chemical industry, environmental engineering and military applications.     

Iterative Calculation of Plasma Density from a Cylindrical Probe Characteristic

A novel method is proposed for treating cylindrical probe characteristics to obtain plasma density. The method consists of exponential extrapolation of the transitional part of the I -V curve to the floating potential for the ion saturation current, other than the existing theories which use the ion branch, and an iterative sheath thickness correction procedure for improved accuracy. The method was tested by treating Langmuir probe I-V characteristics obtained from inductively coupled Ar discharges at various pressures, and comparing the present results with those deduced by existing theories. It was shown that the plasma densities obtained by the present method are in good agreement with those calculated by the Allen-Boyd-Reynolds (ABR) theory, suggesting the effectiveness of the proposed method. Without need of manual setting and adjustment of fitting parameters, the method may be suitable for automatic and real time processing of probe characteristics.     

Plasma Density Measurements in Cable Gun Experiments with a Sensitive He-Ne Interferometer

A time-resolved sensitive He-Ne laser interferometer without complicated active stabilization was built up and applied to low-density plasma measurements. A precision of about 0.2° in phase measurements was achieved with a minimum line-integrated plasma density as low as 8.3× 10^13 cm^-2. With this interferometer, the characteristics of the plasma generated by a cable plasma gun was investigated systematically. The reproducibility, spatial and temporal distributions and the averaged injection velocity of the plasma are presented. In addition, the interaction of the plasma flow with a conductor was studied by placing a metal plate in the downstream of the cable gun.     

The Effect of Ion Motion on Laser-Driven Plasma Wake in Capillary

The effect of ion motion in capillary-guided laser-driven plasma wake is investigated through rebuilding a two-dimensional analytical model.It is shown that laser pulse with the same power can excite more intense wakefield in the capillary of a smaller radius.When laser intensity exceeds a critical value,the effect of ion motion reducing the wakefield rises,which becomes significant with a decrease of capillary radius.This phenomenon can be attributed to plasma ions in smaller capillary obtaining more energy from the plasma wake.The dependence of the difference value between maximal scalar potential of wake for two cases of ion rest and ion motion on the radius of the capillary is discussed.     

Plasma Density Influence on the Properties of a Plasma Filled Rod Pinch Diode

The rod pinch diode is perfect as a source of accelerators for flash X-ray radiography by virtue of a small and stable spot.But it is not suitable for intensive current drivers because of high diode impendence of 40~60Ω.However,by employing pre-filled plasma into diode prior to the driving current,the diode impendence can be efectively reduced.Plasma density plays an important role in this process,especially for sheath formation and space charge current in the diode.Analysis and simulation results show that a proper range of plasma density could be 1015~1016cm-3.     

Spatial Distribution of ECR Plasma Density in ECR-PECVD Reaction Chamber

The spatial distribution of Electron Cyclotron Resonance （ECR） plasma in the ECRPlasma Enhanced Metalorganic Chemical Vapour Deposition （ECR-PECVD） reaction chamber is diagnosed by a Langmuir probe. The uniformity is also investigated. The results show that the ECR plasma in the upper region of the reaction chamber under the influence of magnetic field has poor radial and axial uniformity. However, the plasma in the downstream region of the reaction chamber has fine radial uniformity. This excellent uniform plasma in the downstream has extensive application in plasma process.     

Ion Heating in an ECR Plasma with a Magnetic Mirror Field

Magnetoelectric heating was used to heat ions in an ECR plasma with a magnetic mirror field.The temperature and density of ions were measured by an ion sensitive probe(ISP) before and after magnetoelectric heating in order to investigate the influence of the anode ring’s radius,axial position and working pressure on magnetoelectric heating.Results showed that a suitable radius of the anode ring could improve the ion temperature effectively and the optimal size of the anode ring depended on the cyclotron radius of ions.The radial uniformity of the ion density was improved by increasing the radius of the anode ring after heating.The magnetic mirror field could reduce the loss of ions caused by collision with the wall of the chamber and it was beneficial to increase the ion temperature and the ion density.It was suitable to heat the ions when the anode ring was set at the center of the magnetic mirror field where there was a weaker magnetic field strength.Lower pressure contributed to the increase in the ion temperature and efficiency of magnetoelectric heating.     

Electromagnetic Wave Attenuation in Atmospheric Pressure Plasma

When an electromagnetic （EM） wave propagates in an atmospheric pressure plasma （APP） layer, its attenuation depends on the APP parameters such as the layer width, the electron density and its profile and collision frequency between electrons and neutrals. This paper proposes that a combined parameter -the product of the line average electron density n and width d of the APP layer （i.e., the total number of electrons in a unit volume along the wave propagation path） can play a more explicit and decisive role in the wave attenuation than any of the above individual parameters does. The attenuation of the EM wave via the product of n and d with various collision frequencies between electrons and neutrals is presented.     

Control of Beam Energy and Flux Ratio in an Ion-Beam-Background Plasma System Produced in a Double Plasma Device

Plasmas containing ion beams have various applications both in plasma technology and in fundamental research. The ion beam energy and flux are the two factors characterizing the beam properties. Previous studies have not achieved the independent adjustment of these two parameters. In this paper, an ion-beam-background-plasma system was produced with hotcathode discharge in a double plasma device separated by two adjacent grids, with which the beam energy and flux ratio(the ratio between the beam flux and total ion flux) can be controlled independently. It is shown that the discharge voltage(i.e., voltage across the hot-cathode and anode) and the voltage drop between the two separation grids can be used to effectively control the beam energy while the flux ratio is not affected by these voltages. The flux ratio depends sensitively on hot-filaments heating current whose influence on the beam energy is relatively weak,and thus enabling approximate control of the flux ratio     

离子初始速度对等离子体鞘层厚度的影响

本文从理论上研究了离子初始速度对等离子体鞘层厚度的影响,建立了理论计算公式和数值模拟方法,考察了离子初始速度对鞘层厚度的影响因子。在离子初始能量为3.2 eV情况下,用粒子模拟程序进行了数值模拟,模拟与理论计算得到的空间电场分布十分接近。     

Performance of a New Ion Source for KSTAR Tokamak Plasma Heating

In the experimental campaign of 2010 and 2011 on KSTAR, the NBI-1 system was equipped with one prototype ion source and operated successfully, providing a neutral beam power of 0.7-1.6 MW to the tokamak plasma. The new ion source planned for the 2012 KSTAR campaign had a much more advanced performance compared with the previous one. The target performance of the new ion source was to provide a neutral deuterium beam of 2 MW to the tokamak plasma. The ion source was newly designed, fabricated, and assembled in 2011. The new ion source was then conditioned up to 64 A/100 keV over a 2-hour beam extraction and performance tested at the NB test stand （NBTS） at the Korea Atomic Energy Research Institute （KAERI） in 2012. The measured optimum perveance at which the beam divergence is a minimum was about 2.5μP, and the minimum beam divergent angle was under 1.0° at 60 keV. These results indicate that the 2.0 MW neutral beam power at 100 keV required for the heating of plasma in KSTAR can be delivered by the installation of the new ion source in the KSTAR NBI-1 system.     

Plasma characteristics in the discharge region of a 20A emission current hollow cathode

Numerical calculation and fluid simulation methods were used to obtain the plasma characteristics in the discharge region of the LIPS-300 ion thruster’s 20 A emission current hollow cathode and to verify the structural design of the emitter.The results of the two methods indicated that the highest plasma density and electron temperature,which improved significantly in the orifice region,were located in the discharge region of the hollow cathode.The magnitude of plasma density was about 10~(21)m~(-3)in the emitter and orifice regions,as obtained by numerical calculations,but decreased exponentially in the plume region with the distance from the orifice exit.Meanwhile,compared to the emitter region,the electron temperature and current improved by about 36%in the orifice region.The hollow cathode performance test results were in good agreement with the numerical calculation results,which proved that that the structural design of the emitter and the orifice met the requirements of a 20 A emission current.The numerical calculation method can be used to estimate plasma characteristics in the preliminary design stage of hollow cathodes.     

Measurement of Ion Parameters by Ion Sensitive Probe in ECR Plasma

Ion parameters in electron cyclotron resonance (ECR) microwave plasma were measured by ion sensitive probe and were compared with the electron parameters obtained by double Langmuir probe. The effects of gas pressure and microwave power on the ion temperature and density were analyzed. The spatial distribution of the ion parameters was also investigated by the ion sensitive probes with a tunable radial depth installed on different probe windows along the chamber axis. Results showed that the ion density measured by the ion sensitive probe was in good agreement with the electron density measured by the double Langmuir probe. The influence of gas pressure on the ion parameters was stronger than that of microwave power. With the increase in working pressure, the ion temperature decreased monotonously with a decreasing rate larger than that at higher pressure. The ion density first increased to a peak (42.3?1010cm-3) at 1 Pa and then decreased. The ion temperature and density increased little with the increase in the microwave power from 400 W to 800 W. The plasma far away from the resonant point is found to be radially uniform.