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 /sub e/ , ion temperature T /sub i/ , and local plasma density, n /sub 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 about 1.0cm have been measured, but those for ion and electron temperature are much longer. Calculated values of T /sub i/ range from 50 to a few hundred eV, those for T /sub 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 x 10/sup 19/m/sup -3/), the sputtering rises with increasing density during neutral injection, although a fall in T /submore » i/ is calculated.« less