Calculation of steady-state time for plasma impurity

Using the method of parameter transformation, the rate equations of impurities have been transformed to a vector equation with tri-diagonal symmetric coefficient matrix, and then solved numerically. Curves of characteristic parameter neτ as function of electron temperature for a few typical light impurity in fusion plasma (such as helium, carbon, oxygen, neon and argon) have been obtained. Results show that values for the selected light impurities are within 1015-10l9 m-3·s, and average steady-state times have not explicit correlation with nuclear charge Z. The last two peak values for the corresponding impurities are similar, and the time required to reach steady state for the dominant helium-like and neon-like ions is relatively short.