PARTICLE BALANCE IN DIVERTED PLASMAS IN TEXT-U

Tokamak plasmas in an open divertor configuration with the X-point at the inner equator were compared with plasmas limited by an inner toroi dal belt. This paper describes and compares the particle balance in th ese two types of discharge. The plasma parameters n(e)(r), phi(r), T-e (r), <(n)over tilde(e)>, and <(phi)over tilde> were measured in the sc rape-off layer and in the plasma periphery at one poloidal location an d mapped onto the rest of the plasma by assuming constancy on flux sur faces. Emission from neutral hydrogen was measured throughout the plas ma. The particle source and then the global particle confinement were inferred from these measurements using a 3-D neutral transport simulat ion. The SOL profiles are significantly steeper in the diverted discha rge. Both the source measurements and estimates from the SOL profiles indicate significantly better confinement in the diverted discharge.