Experimental observations in stationary ECRH discharges in TCV show that
additional heating has a strong effect on the electron density profile. In the
absence of MHD activity or strong internal transport barriers, additional electron
heating generally leads to a broadening of the density profiles with respect to
the Ohmic target plasma profiles. In the ECRH L-mode and in the presence of
weak electron internal transport barriers, the density peaking factor depends
on the edge safety factor, the power deposition profile and ECRH power.
Beyond a critical power of some 0.5 MW, the power dependence saturates. The
edge safety factor dependence is supportive of turbulent equipartition (TEP)
theory, which predicts inward convection in the presence of turbulence. The
observation of a reduction in the peaking with central electron heating supports
drift wave turbulence theory, which predicts the decrease of inward particle
convection in addition to the inward convection by TEP, when trapped electron
modes are destabilized, thereby reducing the net inward convection. |