Bolometric measurements and the role of radiation in Alcator power balance

Abstract

A bolometric study of global power balance on the Alcator A tokamak has shown that neither high- nor low-Z impurities play a dominant role in plasma energy confinement for ‘well-behaved’ discharges. Spatially and temporally resolved measurements of the power lost in radiation and particles have shown that in the region 0 < r < 3 cm these loss mechanisms account for only 15% of the local Ohmic power input. The radiative losses from the central plasma regions are attributed to molybdenum. Variation of the emissivity with density has shown that radiative and particle losses become more important at densities less than 2 × 1014 cm−3. A study of disruptive discharges and discharges showing anomalous increases in the plasma resistance has shown that radiation can be the dominant loss mechanism under these conditions.