D. Kuriyama

K. Sawada

M. Goto

N. Yamaguchi

S. Kakura

Y. Kambe

National Institute for Fusion Science (NIFS-Repository)

Construction of a deuterium neutral trans-port code for Large Helical Device bound-ary plasmasSawada, K., Kambe, Y., Kakura, S., Kuriyama, D.,Yamaguchi, N., (Shinshu Univ.), Goto, M.We have developed collisional-radiative models ofatomic and molecular hydrogen as well as a neutraltransport code for hydrogen species. These codes areused to study the reaction and spatial ﬂows of atomsand molecules in Large Helical Device (LHD) edge plas-mas. The purpose of this study is to construct a codefor deuterium plasmas to prepare the future deuteriumdischarge plan for the LHD.The neutral transport code needs reaction rate co-eﬃcients for atoms and molecules. We are constructinga collisional-radiative model for the deuterium moleculeto calculate the reaction rate coeﬃcients that include thecontribution of the excited states. The electron tempera-ture and density of the plasma, which are the input datafor the neutral transport code, are also expected to bedetermined by analyzing the emission intensity of molec-ular bands with the collisional-radiative model becausethe populations of the excited states are a function ofthe electron temperature and density.To construct the collisional-radiative model, wehave calculated the spontaneous transition probabilitiesfor optically allowed transitions for upper states with theprincipal quantum number of the united atom n ≤ 4 con-sidering the electronic, vibrational, and rotational states.This year, as a simple version of the collisional-radiativemodel, we have constructed a corona model for the deu-terium molecule. In the corona model, the population ofeach excited state is calculated from a balance betweenthe electron impact excitation from the ground state andthe spontaneous transition to lower states.Figure 1 shows spectra measured in an RF deu-terium discharge at Shinshu University. Many molecularbands are observed in addition to atomic Balmer lines.We identiﬁed the bands using energy level data in Ref.1.Identiﬁed bands are shown with arrows in Fig. 2. Coronamodels for analyzing the d3Πu → a3Σ+g , J1Δg → C1Πu,and I1Πg → C1Πu bands were applied to the plasmas.For the Fu¨lcher band d3Πu → a3Σ+g , the electronic,vibrational, and rotational states are distinguished in themodel. For the J1Δg → C1Πu and I1Πg → C1Πu bands,because the rotational state resolved electron impact ex-citation cross sections are not available, we distinguishonly the electronic and vibrational states; the initial ro-tational state of the spontaneous transition is assumed tobe the ground state. Using the electron temperature anddensity measured by the double electric probe, we calcu-late the population of the excited state and the emissionintensity. For the Fu¨lcher band, the measured and cal-culated spectra agree well as shown in Figs. 3(a) and3(b). For the J1Δg → C1Πu and I1Πg → C1Πu bands,we summed experimentally obtained populations for therotational state and compared with the result of the cal-culation. For these transitions, there is an apparent dis-crepancy at the present. We will continue to researchthe discrepancy and construct the collisional-radiativemodel.Count800700600500400Wavelength  (nm)DαDβDγFig. 1: Spectra observed in an RF deuterium plasma.151050Energy  (eV) EBHCB, D G I J 3 33 3 3 32221Σg+nsσ npσ npπ ndσ ndπ ndδ 1Σu+ 1Πu1Σg+1Πg 1Δgnsσ npσ npπ ndσ ndπ ndδ 3 3 3 33 32 2a ched g i j Singlets TripletsX 1b 23Σg+ 3Σu+3Πu3Σg+ 3Πg 3ΔgFig. 2: Electronic states of the deuterium molecule.Identiﬁed bands in the RF deuterium plasma are shownwith arrows.640630620610600590580Wavelength  (nm)(a)  experiment640630620610600590580Wavelength  (nm)(b)  calculationFulcher band  Fig. 3: Spectra in the wavelength range of 580-640 nm:(a) experiment, (b) calculation for Fu¨lcher band.1) Robert S. Freund and James A. Schiavone, The Elec-tronic Spectrum and Energy Levels of the DeuteriumMolecule, J. Phys. Chem. Ref. Data 14, (1985).193§2. Construction of a Deuterium Neutral Transport Code for Large Helical Device Boundary PlasmasSawada, K., Kambe, Y., Kakur , S., Kuriyama, D., uchi, .    

Construction of a Deuterium Neutral Transport Code for Large Helical Device Boundary Plasmas

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