Published June 1987 | Version v1
Report

Radiation behaviour of gas and pellet refuelled high density discharges in ASDEX

Description

Pellet and gas refuelled high density divertor discharges in ASDEX are investigated with regard to their radiation behaviour and energy balance. Exclusively ohmically heated deuterium plasmas in a non-carbonized (NC), carbonized (C) and titanium gettered (DP) vacuum vessel are considered. In gas refuelled plasmas the radiation power profiles are hollow with a central emissivity ε(0) ≤ 10mW/cm3 in C and ε(0) ≤ 40mW/cm3 in NC and DP discharges. In C discharges PRAD/PΩ rises from 0.2 at anti ne = 3.2 . 1019m-3 to 0.3 at the density limit. In NC and DP plasmas higher values from 0.3 to 0.45 are observed. Radiation from the X-points can amount to 14% of PΩ. In pellet refuelled discharges a central peaking of the emissivity ε is observed. A sudden transition from negligible or slow impurity accumulation to a fast rise could be detected in many discharges. In NC and DP pellet discharges a self-triggering of impurity accumulation was found. Measured inward drift velocities range from 60 cm/s to 130 cm/s at r=15 cm. (orig.)

Additional details

Publishing Information

Imprint Title
ASDEX contributions to the 14th European conference on controlled fusion and plasma physics
Imprint Pagination
135 p.
Journal Page Range
p. 7-14.
Report number
IPP--III/120

Conference

Title
14. European conference on controlled fusion and plasma physics.
Dates
22-26 Jun 1987.
Place
Madrid (Spain).