2-D Profiles of Volume Recombination in the Alcator C-Mod Divertor

C. J. BOSWELL, J. L. TERRY, B. LIPSCHULTZ - PSFC, MIT

Alcator C-Mod currently employs a tangentially viewing divertor TV system consisting of two CCD cameras with nearly identical views. The cameras are filtered, typically for D_g and CII lines (aproximately 515 nm). The recorded images are inverted assuming toroidal symmetry, yielding 2-D emissivity profiles. Due to the low level of carbon after boronization the emission detected by the camera filtered for the CII lines is dominated by continuum radiation. With the 2-D profiles of D_g and continuum emission, effective temperature measurements are obtained using the line-to-continuum ratio method,[1] which assumes that the continuum is due to ion-electron bremsstrahlung and radiative recombination only. However, additional continuum radiation has been observed previously in the divertor region.[2] 2-D plots of D_g, continuum, and effective temperature will be presented.

[1]

Hans R. Griem, Principles of Plasma Spectroscopy, (Cambridge University Press, New York, 1997), p. 291.

[ 2] J. L. Terry et al., in Proc. of the 26th Euro. Phys. Soc. Conf. on Contr. Fus. and Plasma Phys., edited by B. Schweer, G. Van OOst, and E. Vietzke (Institute of Physics, London, UK 2000) pp. 325-328.