Influence of methane fuelling on the 2-D line radiation distribution in the JET MkIIGB divertor

In order to study the influence of the impurity sources on line emissions, gas fuelling experiment were performed with controlled CD4 gas inlet into the private flux region (PFR) of the inner and outer divertor legs, as well as into the outer scrape-off layer (SOL) of JET. Comparison discharges were performed with D-2 injection into the outer SOL, with the same deuterium source rate as for the CD4 pulse. Changes in the divertor spectroscopic signals have been analysed and show a similar behaviour for CD, CII and CIII emission during the inner divertor fuelling into either SOL or PFR, indicating that these signals are independent of the location of methane sources. In contrast to the inner divertor puelling, CD4 fuelling into the PFR of the outer divertor shows the strong dependence of CD-emission on the location of injection to the divertor leg. The evolution of carbon impurity profiles in L-mode discharges will be discussed, with respect to its dependence on the location of methane fuelling (inner/outer divertor leg) and on the position of the strike points.