Pulse Operated MIP-MASS Sectroscopy

本文研制了一种新型的微波诱导等离子体源，它具有轴向可变口径放电管，能够将液体气溶胶直接引入等离子体中。用有限元法计算了MIP TM 010谐振腔的谐振频率和电场。轴向变化的放电管大大增强了等离子体放电管的边缘和中心的电场。为了确认新开发的放电管的效果，测量了电子数密度和等离子体温度。结果表明，随着温度的升高，密度也随之升高。在各种工作条件下对等离子体温度和电子数密度进行了测量。所观察到的温度和电子数密度表现出显着的增加，但降低氩发射强度，在水溶液样品的引入。实验结果表明，在所采用的测量条件下，局域热力学平衡是不一致的，与高能电子碰撞产生的原子物种的激发和电离占主导地位，使用新的MIP源，即使直接引入液体气溶胶，也能在相对较低的前向微波功率（-20W）下获得稳定的等离子体。测量了载气流量、等离子体气体流量和正向功率对Cd线强度的影响，得到了最佳操作条件。为了评估新的MIP作为原子发射光谱法（AES）的激发源，线性动态范围和检测限的几个元素也进行了测量。

In this work a new Microwave Induced Plasma(MIP) source with an axially-varied bore discharge tube was developed, whiche is able to introduce liquid aerosols directly into the plasma. The resonant frequency and electric field in the MIP TM010 cavity were calculated using the finite element method. The axially-varied tube highly enhanced the electric field on the edge an the center of the plasma discharge tube.To confirm the effect of the discharge tube newly developed, the electron number density and the plasma temperatures were measured. The result shows that the density and the temperatures were both elevated. Accordingly, the calculation seems to be qualitatively adequate.The measurements on plasma temperatures and on electron number density were made at a variety of operating conditions. Observed temperatures and electron number density exhibit significant increase, but decrease of argon emission intensity, upon the aqueous sample introduction. Experimental results suggest that local thermodynamic equilibrium is not consistent and excitation and ionization of atomic species due to collision with high energy elactron is dominant under the operating conditions employed for the measurements.Using the new MIP source without cooling system, a stable plasma at relatively low forward microwave power (-20W) was obtained even with direct introduction of liquid aerosols. The effects of carrier gas flow rate, plasma gas flow rate and forward power on the intensity of Cd line were measured and the most suitable operating conditions were obtaind. To evaluate the new MIP as an excitation source for atomic emission spectrometry(AES), the linear dynamic range and the detection limits for several elements were also measured.