Abstract
The purpose of this study is to develop a method of spectroscopic measurement to estimate the trend of electron temperature. A lowering of electron temperature would decrease the 703 nm emission line by reducing the indirect pumping to the upper level. The experiment is focused on the 703 nm/ 585 nm emission strength ratio measured by spectrometer which was used to compute the relations of electron temperature in terms of sustain voltage, filling gas ratio and gas pressure. Because Ne excited state is generated by high energy electrons (18.96 eV), electron energy was much lower in the anode region that electrons were energetic enough to generate Xe excited state, but not enough for Ne excited state. Therefore, an intensified charge coupled device (ICCD) camera with optical filters was used to measure visible emission from neon at 585 nm and 703 nm at cathode area. A simulation code developed by Chen Lung-Chih and Chiang Hung Chi at ESS PDP lab in NTHU is used in this study. The simulation code is a two-dimensional PDP simulator based on fluid model. The simulator is used to calculate electron temperature and compare to this experiment. Increasing voltage would lead to stronger electric field, and electron can get more energy from the strong electric field, so electron temperature increase. The sustain voltage increases from 170 volt to 190 volt, the ratio of 703 nm/ 585 nm increases 3.92% in whole cell, and increases 5.01% in cathode area. The efficiency decreases 7.61%. The Ne ionization energy (21.56 eV) is higher than Xe (12.13 eV). When Xe concentration increases, electrons are more likely to ionize Xe atoms in stead of Ne atoms. Therefore, the average electron temperature is lower for high Xe concentration. The gas ratio increases from 5% Xe to 10% Xe, the ratio of 703 nm/ 585 nm decreases 49.41% in the whole cell, and decreases 50.45% in cathode area. The electron temperature results from the 2-D fluid numerical calculation decreases 15.19% in the whole cell, and decreases 20.22% in cathode area. The efficiency increases 43.76%. The gas pressure increases from 400 torr to 475 torr, the ratio of 703 nm/ 585 nm increases 0.66% in whole cell, and decreases 4.02% in cathode area. The electron temperature results from the 2-D fluid numerical calculation decreases 9.05 % in the whole cell, and decreases 8.06 % in cathode area. The efficiency increases 4.70%. The reason that high gas pressure results in lower electron temperature is the same as high Xe gas ratio. When the Xe gas concentrations change from 5% to 10%, the Xe particle number has doubled. When the gas pressures change from 400 torr to 475 torr, the Xe particle number increases only 18.75%. Therefore, the dependence of electron temperature on gas pressure is weaker than on Xe gas ratio.