The Analysis Of Ion Source Of Inductively Coupled Plasma Mass Spectrometry

Inductively coupled plasma mass spectrometry?ICP-MS?is widely used in analysis of inorganic elements and isotopes.To promote its practical application value and expand its use,it's significant to understand the characteristics of inductively coupled plasma?ICP?as an ion source.Analyzing the gas temperature and flow field of ICP ion source could help to optimize transport efficiency from plasma torch to sampler and improve the performance of ICP-MS.First,the components of argon plasma below?gas temperature?10000K is calculated based on local thermal equilibrium?LTE?model and transport coefficients of argon plasma are in references'reach.Second,a numerical model of ICP ion source is built based on Fluent 15.0 software and equations are solved according to their computing domains.The differences of electromagnetic field calculated from continuous distribution and constant distribution of electrical conductivity?respectfully has been considered.Third,the distribution of gas temperature,electron density,velocity magnitude with and without sampler is calculated under LTE state and the results are comparable with other researchers'work.In this paper,an expression of??T?is used to improve self-contradictory of numerical solution.Finally,this improved model is utilized to analyze the effects of working parameters such as load coil power,central gas flow rate,auxiliary gas flow rate and structure parameters like sampler orifice diameter.The conclusions of this paper are as follows:1^st,although it will be easier to collect detected ion under the operation of higher load coil power and larger diameter of sampler but better vacuum pump will be need to keep coarse vacuum between sampler and skimmer.2^nd,the gas temperature of central channel depends on relative value of load coil power and central gas flow rate.To get better analyzing characteristic,central gas flow rate should match with load coil power.3^rd,the characteristics of ICP ion source,especially gas temperature and flow field of central channel easily become unstable under the influence of sampler orifice diameter and ambient differential pressure with lower load coil power.4^th,auxiliary gas flow rate have barely an effect on the characteristics of ICP ion source.5^th,the position of shunting point on sampler cone wall almost have nothing to do with load coil power but be determined by interface and ambient differential pressure.