Continuous emission spectrum measurement is applied for the inconvenient diagnosticsof low-temperature collisional plasmas.According to the physical mechanism of continuousemission,a simplified model is presented to analyze the spectrum in low temperature plasma.Thevalidity of this model is discussed in a wide range of discharge parameters,including electron temperatureand ionization degree.Through the simplified model,the continuous emission spectrumin a coUisional argon internal inductively coupled plasma is experimentally measured to determinethe electron temperature distribution for different gas pressures and radio-frequency powers.Theinverse Abel transform is also applied for a better spatially resoluted results.Meanwhile,theresult of the continuous emission spectrum measurement is compared to that of the electrostaticdouble probes,which indicates the effectiveness of this method.
The plasma density and electron temperature of a multi-source plasma system com-posed of several collisional inductively coupled plasma(ICP)cells were measured by a double-probe.The discharges of the ICP cells were shown to be independent of each other.Furthermore,the total plasma density at simultaneous multi-cell discharge was observed to be approximatelyequal to the summation of the plasma density when the cells discharge separately.Based on thelinear summation phenomenon,it was shown that a larger area plasma with a uniform densityand temperature profile could be constructed with multi-collisional ICP cells.
Plasma absorption probe (PAP) was developed for measuring the electron density inplasmas processing based on the surface-wave characteristics. In order to diagnose the plasma withlower density and higher pressure, a sensitive PAP was also developed. Both types of PAP wereanalyzed theoretically under the quasi-static approximation, which is highly problematic when aconductor exists in the resonance region of the probe. For this reason, a theoretical model for thePAP is presented in this paper. The model is derived from the electromagnetic wave equation.Its principle is then verified via experiments and numerical simulations. Both experimental andnumerical results show that the electromagnetic theoretical model is valid as compared with thequasi-static model. Consequently, a new type of PAP, named as the electromagnetic PAP, is thusproposed for the measurement of electron density.
A method is proposed to built up plasma based on a nonlinear enhancement phenomenonof plasma density with discharge by multiple internal antennas simultaneously. It turnsout that the plasma density under multiple sources is higher than the linear summation of thedensity under each source. This effect is helpful to reduce the fast exponential decay of plasmadensity in single internal inductively coupled plasma source and generating a larger-area plasmawith multiple internal inductively coupled plasma sources. After a careful study on the balancebetween the enhancement and the decay of plasma density in experiments, a plasma is builtup by four sources, which proves the feasibility of this method. According to the method, moresources and more intensive enhancement effect can be employed to further build up a high-density,large-area plasma for different applications.
