DII-D currently operates with a singleor double-null open divertor and graphite walls. Active particle control with a divertor cryopump has demonstrated density control, efficient helium exhaust, and reduction of the inventory of particles in the wall. Gas puffing of D2 and impurities has demonstrated reduction of the peak divertor heat flux by factors of 3-5 by radiation. A combination of active cryopumping and feedback-controlled D2 gas puffing has produced similar divertor heat flux reduction with density control. Experiments with neon puffing have shown that the radiation is equally-divided between a localized zone near the X-point and a mantle around the plasma core. The density in these experiments has also been controlled with cryopumping. These experimental results combined with modeling were used to develop the new Radiative Divertor for DIII-D. This is a double-null slot divertor with four cryopumps to provide particle control and neutral shielding for high-triangularity advanced tokamak discharges. UEDGE and DEGAS simulations, benchmarked to experimental data, have been used to optimize the design.

We report new experimental results with the RDP-OB (Radiative Divertor Project-outer baffle) and cryopump in both upper single-null (USN) and double-null (DN) ELMing H-mode discharges. The baffled divertor reduced the core ionization (-2-2.5~), in reasonable agreement with predictions from UEDGEDEGAS modeling (-3.75~). The upper cryopump achieved density control of ne/ngw 0.22 (line density/Greenwald density) with Zee2 in high-6 plasmas. The measured exhaust is comparable to the lower pump, except at lower core electron densities (ne < 5xl019rn-3). Efficient impurity exhaust was obtained with deuterium SOL flow. Preliminary experiments with DN operation has shown that the particle exhaust to the upper pump depends on the up/down magnetic balance. Preliminary experiments indicate that the DN exhaust is roughly 40%-50% of the USN exhaust at ne 4x1019 m-3. STUDIES OF HIGH-S(BAFFLED) AND LOW-G(OPEN) PUMPED DIVERTOR OPERATION ON 0111-0 S.L. ALLEN, et al. STUDIES OF HIGH-8(BAFFLED) AND L O W ~ ( O P E N ) PUMPED DNERTOR OPERATION ON DIII-D