This paper examines the radiation profiles and corresponding ionization source profiles of carbon and main plasma ions in matched helium and deuterium. L-mode plasmas in JET. The radiation intensities from C1+, C2+ and C3+ in the helium plasmas showed reduction by factors of 8, 10 and 25, respectively along the inner SOL and divertor leg compared with the deuterium cases. However, the emission in the outer divertor leg was less than a factor of 2 lower in helium. Using photon efficiencies calculated by the UEDGE code for the spectrometer lines of sight, the calculated source rates of C1+ and C3+ along the inner SOL and inner divertor were reduced by factors of 4 and 20, respectively in the helium plasmas. In the outer divertor leg the source rate of C3+ was reduced by a factor of 10 but the C1+ source rate did not change in helium. These measurements are consistent with a model that chemical sputtering of carbon dominates the source from the inner wall and inner divertor in deuterium L-mode plasmas while physical sputtering appears to dominate the source from the outer divertor. (C) 2003 Elsevier Science B.V. All rights reserved.