The Experimental Study on Behavior of Carbon-Containing Molecules in the Boundary Plasma

S. Matsuyama, K. Yamaguchi*, S. Tanaka, M. Yamawaki
Department of Quantum Engineering and Systems Science
The University of Tokyo
* Nuclear Engineering Research Laboratory
The University of Tokyo

The present work is one of the series of investigation on fusion reactor material erosion and redeposition processes. Here, the results were presented which were obtained through optical emission spectroscopic diagnostic analyses of molecules resulting from hydrogenic eroded species generated in our divertor simulation facility.
We measured rotational and vibrational excitation temperature of the carbon-containing molecules (CH and C2) and H2 in the laboratory plasma using optical spectroscopy.
For CH excitation temperatures, the rotational temperatures were derived from the vibrational temperatures. When approaching the target, both temperatures became almost equal. This means that thermal equilibrium may be reached in this region of the plasma. For C2 excitation temperatures, the rotational and vibrational temperatures were almost equal at every axial point. This result means that both species are driven by different thermal equilibrium mechanisms. However, the temperatures of both species are of the same order, indicating that the chemically eroded species are thermalized in the plasma gas particles.
Such temperature of carbon-containing molecules will be employed as parameters when the behaviors of chemical sputtering and redeposition in a divertor plasma are to be numerically modeled. Finally, it is suggested that such molecule temperatures in some Tokamak facilities should be measured as a means of evaluating characteristics of chemically sputtered particles.

  1. S. Matsuyama, K. Yamaguchi, S. Tanaka, M. Yamawaki, "The experimental study on behavior of carbon-containing molecules in the boundary plasma", 4th Int. Symp. Fusion Nuclear Technology (ISFNT-4), Tokyo, Japan, April 6-11, 1997, to be published in Fusion Eng. Des.