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The design for the BPX power and particle handling system consists of a double-null (DN) poloidal divertor with an inner-wall bumper limiter. In addition, a substantial portion of the remainder of the inside of the torus is covered with graphite tiles to withstand high heat flux. In divertor operating modes, the diverted plasma is swept across the divertor plates to reduce the time-average heat loads on the plates. The poloidal divertor is designed both to provide access to H-mode operation and to ensure high recycling in the divertor region, which minimizes impurity production and consequent contamination of the main plasma. The device is capable of both single-null (SN) and DN divertor operation. In addition, an inner bumper limiter is designed to provide an alternative to divertor operation. Additional toroidally and/or poloidally localized limiters are provided on the outboard wall for plasma startup and for protection of the radio-frequency (RF) antennas. In this paper the distribution of plasma power on the first-wall components is discussed. Power handling and the choice of material for the divertor plates and limiters is discussed. A discussion is included of the surface temperature limits and erosion mechanisms. The effect of disruptions on the plasma-facing components follows.more » Finally, tritium retention and particle pumping issues related to the choice of graphite as the first-wall material are discussed.« less

The paper describes the present (end of February 1985) status of the plasma confinement studies in the TFTR tokamak with emphasis on those with neutral beam injection (NBI). Recent improvements in the device capabilities have substantially extended operating parameters: B /sub T/ increased to 4.0 T, I /sub p/ to 2.0 MA, injection power (P /sub b/ ) to /sup 5/ MW with H/sup 0/ or D/sup 0/ beams, n /sub e/ to 5 x 10/sup 19/ m/sup -3/ and Z /sub eff/ reduced to 1.4. With ohmic heating (OH) alone, the previously established scaling for gross energy confinement time (T /sub E/ /sup 0/ n /sub e/ q) has been confirmed at higher I /sub p/ and B /sub T/ , and the maximum T /sub E/ of 0.4 sec has been achieved. With NBI at P /sub b/ substantially (by factor > 2) higher than P /sub OH/ , excellent power and particle accountability have been established. This suggest that the less-than-expected increase in stored energy with NBI is not due to problems of power delivery, but due to problems of confinement deterioration. T /sub E/ is observed to scale approximately as I /sub p/ P /sub b/more » /sup 0.5/ (independent of n /sub e/ ), consistent with previous L-mode scalings. With NBI we have achieved the maximum T /sub E/ of 0.2 s and the maximum T /sub i/ (o) of 4.4 keV in the normal operating regime, and even higher T /sub i/ (o) in the energetic-ion regime with low-n /sub e/ and low I /sub p/ operation.« less