IMPURITY RELEASE FROM HIGH-Z TEST LIMITERS IMMERSED IN TEXTOR-94 EDGEPLASMAS

A W test limiter has been inserted into the plasma edge of TEXTOR beyo nd the magnetic surface of the main ALT graphite limiter, and the rele ase of neutral W as well as carbon and oxygen are examined spectroscop ically. The penetration depth of neutral W has decreased significantly with increasing plasma density and it is as small as 1.2 mm when the local plasma density at the magnetic surface of the limiter increases up to 1.5 x 10(19) m(-3). The flux of neutral W decreases as the local density increases, while the C and D fluxes increase. Radial intensit y distributions of CII line spectrum emission have indicated larger pe netrations of C ions emitted from a W limiter than those from a C limi ter. The penetration length of OII emission from a W limiter is simila r to that from a C limiter and much smaller than that of CII.