Research On Measurement Error Of Langmuir Probe In Radio Frequency Ion Source

Magnetic confinement nuclear fusion requires extremely high temperatures in the reaction process.Neutral beam injection heating is an auxiliary heating method with high heating efficiency and simple principle,which is often used in nuclear fusion research.In order to realize the neutral beam injection heating technology,the development of the radio frequency ion source is very important.It is one of the important links in the neutral beam injection heating process.Obtaining accurate plasma parameter information is extremely important for the development of the radio frequency ion source.Therefore,there is an urgent need for a measurement method that can accurately measure plasma parameters and overcome the harsh environment in the radio frequency ion source.The Langmuir probe is a very important diagnostic method.It can not only calculate various plasma parameters through measurement and calculation,but also measure various parts of the plasma.It has simple structure,low cost,and wide application range.Many advantages.Although the probe technology has been developed for nearly a hundred years,there are still large measurement errors in the experimental measurement,making the measured data only have an order of magnitude reference value.Therefore,with the goal of reducing the measurement error of the Langmuir probe,it is of great significance to carry out the error analysis of the Langmuir probe and related simulation research.This thesis explores the main causes of measurement errors in the general Langmuir probe system,and proposes targeted measures to reduce probe measurement errors;explores the disturbance of the Langmuir probe to the plasma inside the radio frequency ion source It is helpful to further study the measurement error of the probe.The main contents are:The finite element analysis software is used to establish a twodimensional axisymmetric model of the probe extended into the radio frequency ion source,and the software is used to observe the different extended lengths of the probe,the different discharge power of the ion source,the different discharge voltage of the ion source and the different secondary electrons.Under the conditions of the emission coefficient value,the degree of disturbance of the probe to the radio frequency ion source;then a three-dimensional model of the radio frequency ion source was built,and compared with the plasma distribution of the two-dimensional axisymmetric model,it was found that the two had good consistency,indicating The model built has certain research significance;finally,the current-voltage characteristic curve of the probe obtained by analysis and measurement is sorted out.This thesis comprehensively analyzes the sources of measurement errors of the Langmuir probe measurement system,and proposes measures to reduce measurement errors from different angles;the analysis of software simulation can better compensate for the fact that Langmuir cannot be visually observed in experiments.The insufficiency of the probe to the internal disturbance of the ion source is conducive to a deeper study of the measurement error of the Langmuir probe and provides a new direction for other researchers.