After many years of fusion research, the conditions needed for a D–T fusion reactor have been approached on the Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. For the first time the unique phenomena present in a D–T plasma are now being studied in a laboratory plasma. The first magnetic fusion experiments to study plasmas using nearly equal concentrations of deuterium and tritium have been carried out on TFTR. At present the maximum fusion power of 10.7 MW, using 39.5 MW of neutral-beam heating, in a supershot discharge and 6.7 MW in a high-βp discharge following a current rampdown. The fusion power density in a core of the plasma is ≊2.8 MW m−3, exceeding that expected in the International Thermonuclear Experimental Reactor (ITER) [Plasma Physics and Controlled Nuclear Fusion Research (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 239] at 1500 MW total fusion power. The energy confinement time, τE, is observed to increase in D–T, relative to D plasmas, by 20% and the ni(0) Ti(0) τE product by 55%. The improvement in thermal confinement is caused primarily by a decrease in ion heat conductivity in both supershot and limiter-H-mode discharges. Extensive lithium pellet injection increased the confinement time to 0.27 s and enabled higher current operation in both supershot and high-βp discharges. Ion cyclotron range of frequencies (ICRF) heating of a D–T plasma, using the second harmonic of tritium, has been demonstrated. First measurements of the confined alpha particles have been performed and found to be in good agreement with TRANSP [Nucl. Fusion 34, 1247 (1994)] simulations. Initial measurements of the alpha ash profile have been compared with simulations using particle transport coefficients from He gas puffing experiments. The loss of alpha particles to a detector at the bottom of the vessel is well described by the first-orbit loss mechanism. No loss due to alpha-particle-driven instabilities has yet been observed. D–T experiments on TFTR will continue to explore the assumptions of the ITER design and to examine some of the physics issues associated with an advanced tokamak reactor.

The confinement and heating of supershot plasmas are significantly enhanced with tritium beam injection relative to deuterium injection in the Tokamak Fusion Test Reactor [Plasma Phys. Controlled Fusion 26, 11 (1984)]. The global energy confinement and local thermal transport are analyzed for deuterium and tritium fueled plasmas to quantify their dependence on the average mass of the hydrogenic ions. Radial profiles of the deuterium and tritium densities are determined from the D-T fusion neutron emission profile. The inferred scalings with average isotopic mass are quite

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The t(d, n)n and d(d, n) He neutron emissivity profiles are measured in a deuterium neutral-beamheated plasma where a small amount of tritium (T) gas has been puffed. The tritium density is inferred from the neutron emissivities, and transport coefficients (D, V) are determined. The particle diffusivities of T and He and the thermal diffusivity are similar in magnitude and profile shape. The convective velocity is small for r/a ( 0.6, and is anomalous for r/a ) 0.6. These are the first measurements of D and V for a hydrogen isotope in a tokamak plasma. PACS numbers: 52.55.Fa, 52.25.Fi An understanding of transport properties in confined plasmas is important to the design of a fusion reactor. It is well established that neoclassical theory, which deals only with classical collisional processes, cannot account for the experimentally observed rates of plasma transport. The leading explanation is that collective (e.g., wave-particle interaction) dynamics driven by microinstabilities play a role in increasing transport losses, especially in the interior regions of the plasma where complications due to atomic physics and boundary conditions are not expected to be dominant [1]. The microinstabilities can be electrostatic or magnetic in nature, and can affect both the particle and heat transport. In the area of particle transport, the first experiments were on the T-3 tokamak, where changes in the electron density due to a small gas puff were measured with interferometry [2]. Similar studies were completed on many tokamaks with interferometry and Thomson scattering measuring the electron density [3 -6]. Ion transport studies have relied on spectroscopic measurements of high-Z impurity elements, including iron, germanium, and selenium [7,8]. Recent developments in charge-exchange recombination spectroscopy diagnostics have provided a means of studying fully stripped low-Z elements such as helium and carbon [9,10]. However, the measurement of hydrogenic ion transport has remained elusive, because no spectroscopic technique has been identified with sufficient accuracy to measure the local ion density. Fusion product techniques were used to study He transport with limited spatial resolution, and a similar approach was proposed to infer the trace tritium density in a deuterium plasma from the 14.1 MeV t(d, n)n and 2.5 MeV d(d, n) He neutron emissivities [11,12]. In the tritium beam experiments on JET, the local 14.1 MeV t(d, n)n and 2.5 MeV d(d, n)3He neutron emissivity profiles have been measured, and the transport using various mixing models to predict the local evolution of tritium and deuterium was studied with the global introduction of tritium by neutral beam injection [13,14].In November 1993, TFTR started tritium operation to explore tritium and alpha particle physics [15,16]. This paper reports the results of tritium transport studies where small amounts of tritium gas were puffed into deuterium neutral-beam -fueled plasmas. The local 14.1 MeV t(d, n)n and 2.5 MeV d(d, n) He neutron emissivity profiles were measur...

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The use of x-ray induced fluorescence to measure elemental densities in a metal–halide lighting arc is described. High-energy synchrotron radiation generated on the Sector 1 Insertion Device beam line at the Advanced Photon Source induces K-shell fluorescence in a high-pressure plasma arc. The detected fluorescence is spectrally resolved, so that multiple elemental species are observed simultaneously. Absolute calibration of the measured densities is straightforward and robust. The penetrating nature of high-energy photons allows these measurements to be made in situ, with the arc contained by an optically translucent polycrystalline alumina (Al2O3) arc tube and a glass vacuum jacket. Spatial distributions extending from one end of the arc tube to the other and from the arc core all the way to the wall have been obtained for all the principal elements in the arc. A volume element measuring 1 mm × 1 mm × 1 mm is resolved in the present work, with significantly better spatial resolution possible. Densities as low as 2×1016 cm−3 have been observed. X-ray induced fluorescence is useful for the observation of many important high-pressure plasma lighting chemistries including those containing Hg, Tl, Dy, Tm, Ho, Cs, Sn, I, and Xe.

The first spectroscopic measurements of tritium Balmer-alpha (Tot) emission from a fusion plasma were made on TFTR using a Fabry-Perot interferometer. The Tot emission line is partially blended with the Dot line (deuterium-alpha), commonly used in edge plasma diagnostics, and the contributions of Hot, Do:, and Tot, are separated by spectral analysis. The data are a measure of the fueling of the plasma by tritium accumulated in the TFTR limiter, as well as the amount of neutral tritium generated by charge exchange of plasma ions. The To: line first became detectable in a high power, tritium only, neutral beam injection discharge at the level of Tot/(Hot+Dot+To0 = 2%. Subsequently this ratio has increased to as high as 7.5%. Data on the time evolution of the Tot emission during a single discharge and over a series of tritium and deuterium discharges are presented.

Both global and thermal energy confinement improve in high-temperature supershot plasmas in the Tokamak Fusion Test Reactor (TFTR) when deuterium beam heating is partially or wholly replaced by tritium beam heating. For the same heating power, the tritium-rich plasmas obtain up to 22% higher total energy, 30% higher thermal ion energy, and 20-25% higher central ion temperature. Kinetic analysis of the temperature and density profiles indicates a favorable isotopic scaling of ion heat transport and electron particle transport, with 7-~i (a / 2) c x (A)