J.G. Wang

M. Kato

T. Kato

National Institute for Fusion Science (NIFS-Repository)

§31. Spectra of Neutral Carbon for Plasma Diagnostics Wang, 1.G.*, Kato, M., Kato, T. 1. Introduction In the magnetic controlled fusion research, the impurity atoms and ions play an important role for plasma cooling, meanwhile, the radiation also contains the information on the nature of plasma, and the spectroscopy of the radiation can be used to measure the plasma parameters. Recently, Sergeev et al [1] have perfomed car-bon pellet experiments on W-7 AS, and observed several CI lines. The situation of the pellet cloud plasma may change from the cold dense plasma ( with cloud density nCL f"'V 1015 - 1017 em -3 and cloud temperature TCL f"'V 1 - 50eV ) to hot am-body recombination processes are included in our caculation. According to the method of the quasi-steady-state solution , the population of excited states can be divided into two components, which are called the recombining plasma and the ionizing plasma, respectively. 3. Ato mic data The collisional excitation rate coefficients for n ::; 4 are calculated by R-matrix, and others are calculated by Mewe's semi-empirical formula us-ing the oscillator strength !ij and excitation en-ergy E ij . Electron impact ionization rate coeffi-cients are estimated by Lotz's empirical formula. Radiative recombination rate coefficient is obtained by detailed balance from the photoionization cross sections. Dielectronic recombination rate coeffi-cient is calculated by Cowan's code. 4. Results and discussion bient plasma ( with electron density ne f"'V (0.5 - In our calculation, we found when Te > 2 e V, 10)1013em-3 and temperature Te f"'V 100-3000eV). the collisional-radiative ionization rate coefficients In so large varied condition, the CR model is needed are much larger than the collisional-radiative re-to calculate the spectra, in which both ionizing combination rate coefficients, in the equilibrium and recombining plasma should be included. In or near-equalibrium region, the ionizing process this article, using the CR model including 79 states dominates the recombining process; when Te < 0.8 with the principal quatumn number n ::; 6 and l::; e V, the collisional-radiative recombination rate co-4, we calculate the line spectra and line intensity efficients are much larger than the collisional- ra-ratios in the ionizing and recOlnbining plasma. In diative ionization rate coefficients, the recombin-the recombining plasma, both the continuum spec- ing process dominate over the ionizing process; tra of radiative recombination and the satellite when 0.8e V < Te < 2e V, no process dominates lines of dielectronic recombination are included in and it is the mixing of the ionizing and recombin-our calculations. ing processes. In different parameter range, the different transition lines should be choosed to mea-2. Rate equation sure the plasma parameters, because they have different dependences on the plasma parameters. The population densities of the i-th state of carbon atoms, n(i), is described by the following rate equation: dn(i) dt { L neCjin(j) + L Ajin(j)} - { :L neCijn( i) + :L Aijn( i)} j-ji j>i j-ji j<i - L neSikn(i) + :L ne(Xkin+(k), k k (1) * Present address: Department of physics and As-tronomy, University of Georgia, Athens, GA 30602, USA. where ne is the electron density and n +(k) is the population density in the k-th state of a singly charged ion. The electron impact excitation [1]. V. Sergeev, private communication, 1998. and ionization, spontaneous radiation, radiative recombination, dielectronic recombination and three-384 

Spectra of Neutral Carbon for Plasma Diagnostics

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