Recent TFTR results

TFTR experiments have emphasized the optimization of high performance plasmas as well as studies of transport in high temperature plasmas. The recent installation of carbon composite tiles on the main bumper limiter has allowed operation with up to 32 MW of neutral beam injection without degradation of plasma performance by large bursts of carbon impurities ( carbon blooms''). Plasma parameters have been extended to T{sub i}(0) {approximately} 35 keV, T{sub e}(0) {approximately} 12 keV, n{sub e}(0) {approximately}1.2 {times} 10{sup 20} m{sup {minus}3} producing D-D reaction rates of 8.8 {times} 10{sup 16} reactions per second. The fusion parameter n{sub e}(0){tau}{sub E}T{sub i}(0) in supershot plasmas is an increasing function of heating power up to an MHD stability limit, reaching values of {approximately}4.4 {times} 10{sup 20} m{sup {minus}3} sec keV. Peaked-density-profile hot-ion plasmas with the edge characteristics of the H-mode have been produced in a circular cross-section limiter configuration with n{sub e}(0){tau}{sub E}T{sub i}(0) values characteristic of supershots, namely up to four times those projected for standard H-modes with broad density profiles. Reduced transport is also observed in the core of high-density ICRF-heated plasmas when the density profile is peaked. At the highest performance, the central plasma pressure in TFTR reaches reactor level values of 6.5 atmospheres. In these regimes, MHD instabilities with m/n = 1/1, 2/1, 3/2 and 4/3 are often observed concurrent with a degradation in performance. High {beta}{sub p} plasmas with {var epsilon}{beta}{sub p} {approx} 1.6 and {beta}/(I/aB) {approx} 4.7 (%mT/MA) have demonstrated confinement enhancement over the low-mode confinement time with {tau}{sub E}/{tau}{sub L} {approximately} 3.5 and a bootstrap current of about 65% of the total plasma current