Measurements of Edge Temperature and Density Profiles in the DITE Tokamak, Using a Voltage Scanned Heat Flux Probe

ABSTRACT

Plasmas produced while using the MkII Bundle Divertor on DITE have been studied using a combined Langmuir/heat flux probe technique. Ion saturation currents and deposited powers to bolometers facing both the ion and electron drift directions have been measured. A substantial depression of the ion flux on the ion side is recorded, which has been explained by the shorter connection length to the divertor target plate. Radial profiles of electron temperature T_e, ion temperature T_i, and local plasma density, n_e have been calculated from the measurements. These are time resolved and have been studied both before and during neutral beam injection. E-folding lengths for deposited power of ∼ 1.0cm have been measured, but those for ion and electron temperature are much longer. Calculated values of T_i range from 50 to a few hundred eV, those for T_e are an order of magnitude lower. An estimate of carbon limiter sputtering has been made which suggests that for the present discharge conditions (plasma current 150 kA, central density 1.5 – 3 × 10¹⁹ m⁻³), the sputtering rises with increasing density during neutral injection, although a fall in T_i is calculated.