EXPERIMENTAL VALIDATION OF THE LIQUID LITHIUM DIVERTOR CONCEPT

In some divertor concepts of future thermonuclear tokamak reactors lithium is considered as a possible plasma facing material. Lithium is evaporated from the plate surface and is ionized under reactor plasma impact, thus lithium plasma is formed in the layers contacting with the first wall elements. These concepts need an essential support of model calculations and of experimental research. Direct plasma experiments with lithium plasma are of extreme significance for the knowledge of consequences of the choice on the first wall. Here the results of experimental work on the lithium divertor concept validation are given. A lithium capillary structure has been developed for high heat flux tests in magnetic field. Experiments were performed in the SPRUT-4 linear facility (Kurchatov Institute) which had been previously used mainly for the study of steady state lithium plasma. Electron beam ( 10 kV, 2 A ) was conducted along magnetic field ( 0.2 ÷ 0.4 T, L=2.5m ) to the capillary surface of lithium filled target (divertor plate imitator). Evaporated lithium balance, power balance and thermal response of the target were investigated. The heat load on the capillary surface was 5 ÷ 50 MW/m 2 . The lithium evaporation rate from capillary surface for 1 ÷ 25 MW/m 2 range was determined (8·10 −2 g/cm 2 ·s for 25 MW/m 2 ) thus giving evidence to high efficiency of such a method of heat removal from the divertor surface. The prospects of the further use of the linear facility for the lithium tokamak concept validation are seen to be promising.