Intrinsic molybdenum impurity density and radiative power losses with their scalings in ohmically and ICRF heated Alcator C-Mod and FTU tokamak plasmas

Abstract

A new radiative cooling curve for molybdenum, determined from the Hebrew University, Jerusalem - Lawrence Livermore atomic code (HULLAC) has been used to estimate the radiative power losses from various ion cyclotron resonance frequency (ICRF) and ohmically heated Alcator C-Mod tokamak plasmas and ohmically heated Frascati tokamak upgrade (FTU) plasmas. This cooling curve has been found to accurately predict the radiative losses from molybdenum ions in plasma. Radiative losses from molybdenum computed by using the HULLAC cooling curve could typically account for greater than 60% of the total radiative losses as measured by bolometry in Alcator C-Mod tokamak plasmas. The molybdenum density was found to be as high as particles in ICRF heated plasmas. Plasmas after botonization of the plasma facing surfaces had the lowest molybdenum density and radiated power of all the plasmas examined; ICRF heated plasmas had the highest. The molybdenum density and radiative power losses were found to increase roughly linearly with input ICRF power during different heating schemes in plasmas with both H-mode and L-mode confinement. Although the molybdenum densities were found to decrease with increasing electron density, the radiative power losses did not change significantly for all types of plasmas studied in Alcator C-Mod and FTU: diverted plasmas heated with ICRF and both limited and diverted plasmas heated ohmically.