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Experiments with plasmas having nearly equal concentrations of deuterium and tritium have been carried out on TFTR. To date (September 1995), the maximum fusion power has been 10.7 MW, using 39.5 MW of neutral beam heating, in a supershot discharge and 6.7 MW in a high beta P discharge following a current ramp-down. The fusion power density in the core of the plasma has reached 2.8 MW/m3, exceeding that expected in the International Thermonuclear Experimental Reactor (ITER). The energy confinement time tau E is observed to increase in DT, relative to D plasmas, by 20% and the n1(0).T1(0). tau E 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 beta P discharges. First measurements of the confined alpha particles have been performed and found to be in good agreement with TRANSP simulations assuming classical confinement. Measurements of the alpha ash profile have been compared with simulations using particle transport coefficients from helium gas puffing experiments. The loss of energetic 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. ICRF heating of a DT plasma, using the second harmonic of tritium, has been demonstrated. DT experiments on TFTR will continue both to explore the physics underlying the ITER design and to examine some of the physics issues associated with an advanced tokamak reactor

Routine tritium operation in TFTR has permitted investigations of alpha particle physics in parameter ranges resembling those of a reactor core. ICRF wave physics in a DT plasma and the influence of isotopic mass on supershot confinement have also been studied. Continued progress has been made in optimizing fusion power production in TFTR, using extended machine capability and Li wall conditioning. Performance is currently limited by MHD stability. A new reversed magnetic shear regime is being investigated with reduced core transport and a higher predicted stability limit.

The first experiments utilizing high‐power radio waves in the ion cyclotron range of frequencies to heat deuterium–tritium (D–T) plasmas have been completed on the Tokamak Fusion Test Reactor [Fusion Technol. 21, 13 (1992)]. Results from the initial series of experiments have demonstrated efficient core second harmonic tritium (2ΩT) heating in parameter regimes approaching those anticipated for the International Thermonuclear Experimental Reactor [D. E. Post, Plasma Physics and Controlled Nuclear Fusion Research, Proceedings of the 13th International Conference, Washington, DC, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 239]. Observations are consistent with modeling predictions for these plasmas. Efficient electron heating via mode conversion of fast waves to ion Bernstein waves has been observed in D–T, deuterium‐deuterium (D–D), and deuterium–helium‐4 (D–4He) plasmas with high concentrations of minority helium‐3 (3He) (n3He/ne≳10%). Mode conversion current drive in D–T plasmas ...

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.

TFTR has begun its campaign to study deuterium-tritium fusion under reactor-like conditions. Variable amounts of deuterium and tritium neutral beam power have been used to maximize fusion power, study alpha heating, investigate alpha particle confinement, and search for alpha driven plasma instabilities. Additional areas of study include energy and particle transport and confinement, ICRF heating schemes for DT plasmas, tritium retention, and fusion in high βp plasmas. The majority of this work is done in the TFTR supershot confinement regime. To obtain supershots, extensive limiter conditioning using helium fueled ohmic discharges and lithium pellet injection into ohmic and neutral beam heated plasmas is performed, resulting in a low recycling limiter. The relationship between recycling and core plasma confinement has been studied by using helium, deuterium and high-Z gas puffs to simulate high recycling limiter conditions. These studies show that confinement in TFTR supershots is very sensitive to the influx of neutral particles at the plasma edge.

The deuterium-tritium (D-T) experimental program on the Tokamak Fusion Test Reactor (TFTR) is underway and routine tritium operations have been established. The technology upgrades made to the TFTR facility have been demonstrated to be sufficient for supporting both operations and maintenance for an extended D-T campaign. To date fusion power has been increased to {approximately}9 MW and several physics results of importance to the D-T reactor regime have been obtained: electron temperature, ion temperature, and plasma stored energy all increase substantially in the D-T regime relative to the D-D regime at the same neutral beam power and comparable limiter conditioning; possible alpha electron heating is indicated and energy confinement improvement with average ion mass is observed; and alpha particle losses appear to be classical with no evidence of TAE mode activity up to the P{sub FUS} {approximately}6 MW level. Instability in the TAE mode frequency range has been observed at P{sub FUS} > 7 MW and its effect on performance is under investigation. Preparations are underway to enhance the alpha particle density further by increasing fusion power and by extending the neutral beam pulse length to permit alpha particle effects of relevance to the ITER regime to be more fullymore » explored.« less

Peak fusion power production of 6.2 ± 0.4 MW has been achieved in TFTR plasmas heated by deuterium and tritium neutral beams at a total power of 29.5 MW. These plasmas have an inferred central fusion alpha particle density of 1.2 x 1017 m ₋3 without the appearance of either disruptive magnetohydrodynamics events or detectable changes in Alfven wave activity. The measured loss rate of energetic alpha particles agreed with the approximately 5% losses expected from alpha particles which are born on unconfined orbits.

The final hardware modifications for tritium operation have been completed for the Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. These activities include preparation of the tritium gas handling system, installation of additional neutron shielding, conversion of the toroidal field coil cooling system from water to a FluorinertTM system, modification of the vacuum system to handle tritium, preparation, and testing of the neutral beam system for tritium operation and a final deuterium–deuterium (D–D) run to simulate expected deuterium–tritium (D–T) operation. Testing of the tritium system with low concentration tritium has successfully begun. Simulation of trace and high power D–T experiments using D–D have been performed. The physics objectives of D–T operation are production of ≊10 MW of fusion power, evaluation of confinement, and heating in deuterium–tritium plasmas, evaluation of α‐particle heating of electrons, and collective effects driven by alpha particles and testing of diag...

Krypton has been injected into ohmically-heated TFTR plasmas with peak electron temperatures of 6 key to study the effects of krypton on the plasma performance and to investigate the emitted krypton line radiation, which is of interest for future-generation tokamaks such as ITER, both as a diagnostic of the central ion temperature and for the control of energy release from the plasma by radiative cooling. The emitted radiation was monitored with a bolometer array, an X-ray pulse height analysis system, and a high-resolution Johann-type crystal spectrometer; and it was found to depend very sensitively on the electron temperature profile. Satellite spectra of heliumlike krypton, KrXXXV, near 0.95 [Angstrom] including lithiumlike, berylliumlike and boronlike features were recorded in second order Bragg reflection. Radiative cooling and reduced particle recycling at the plasma edge region were observed as a result of the krypton injection for all investigated discharges. The observations are in reasonable agreement with modeling calculations of the krypton ion charge state distribution including radial transport.

Empirical scaling relations are deduced describing the neutron emission from TFTR supershots using a database that includes all of the supershot plasmas (525) from the 1990 campaign. A physics based scaling for the neutron emission is derived from the dependence of the central plasma parameters on the machine settings and the energy confinement time. This scaling has been used to project the fusion rate for equivalent DT plasmas in TFTR, and to explore the machine operation space that optimizes the fusion rate. Increases in neutron emission are possible by either increasing the toroidal magnetic field or further improving the limiter conditioning

This paper discusses the influence that salinity has on the bioavailability of the two largest classes of contaminants, trace metals and organic compounds will be discussed. Although data on contaminant toxicity will be used to draw inferences about chemical availability, this discussion will focus on the properties that contaminants are likely to exhibit in waters of varying salinities. In addition, information on physiological changes that are affected by salinity will be used to illustrate how biological effects can alter the apparent availability of contaminants.

Recent research on TFTR has emphasized optimization of performance in deuterium plasmas, transport studies and studies of energetic ion and fusion product physics in preparation for the D-T experiments that will commence in July of 1993. TFTR has achieved full hardware design parameters, and the best TFTR discharges in deuterium are projected to QDT of 0.3 to 0.5.The physics phenomena that will be studied during the D-T phase will include: tritium particle confinement and fueling, ICRF heating with tritium, species scaling with tritium, collective alpha-particle instabilities, alpha heating of the plasma and helium ash buildup. It is important for the fusion program that these physics issues be addressed to identify regimes of benign alpha behavior, and to develop techniques to actively stabilize or control instabilities driver by collective alpha effects.

Results obtained from experiments utilizing high‐power ion cyclotron range of frequencies (ICRF) heating to stabilize sawtooth oscillations on Tokamak Fusion Test Reactor (TFTR) [Hawryluk et al., Plasma Phys. Controlled Fusion 33, 1509 (1991)] are reviewed. The key observations include existence of a minimum ICRF power required to achieve stabilization, a dependence of the stabilization threshold on the relative size of the ICRF power deposition profile to the q=1 volume, and a peaking of the equilibrium pressure and current profiles during sawtooth‐free phases of the discharges. In addition, preliminary measurements of the poloidal magnetic field profile indicate that q on axis decreases to a value of 0.55±0.15 after a sawtooth‐stabilized period of ∼0.5 sec has transpired. The results are discussed in the context of theory, which suggests that the fast ions produced by the ICRF heating suppress sawteeth by stabilizing the m=1 magnetohydrodynamic (MHD) instabilities believed to be the trigger for the sawtooth oscillations. Though qualitative agreement is found between the observations and the theory, further refinement of the theory coupled with more accurate measurements of experimental profiles will be required in order to complete quantitative comparisons.

High-resolution electron cyclotron emission and x-ray image reconstructions have been made simultaneously during the sawtooth crash in the fast rotating plasma with neutral beam injection heating on TFTR. The measured x-ray emission is identical as metal impurity radiation. The results suggest that the sawtooth crash is a full reconnection process of the TFTR sawteeth. The crescent shaped ``hot spot'' in the x-ray emissivity is found not to present flux surfaces. New features are observed during the sawtooth crash, such as an oval-shaped hot spot and a cooler region between the island and the hot spot.

In the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Fusion 26, 11 (1984)], the highest neutron source strength Sn and D–D fusion power gain QDD are realized in the neutral‐beam‐fueled and heated ‘‘supershot’’ regime that occurs after extensive wall conditioning to minimize recycling. For the best supershots, Sn increases approximately as P1.8b. The highest‐Q shots are characterized by high Te (up to 12 keV), Ti (up to 34 keV), and stored energy (up to 4.7 MJ), highly peaked density profiles, broad Te profiles, and lower Zeff. Replacement of critical areas of the graphite limiter tiles with carbon‐fiber composite tiles and improved alignment with the plasma have mitigated the ‘‘carbon bloom.’’ Wall conditioning by lithium pellet injection prior to the beam pulse reduces carbon influx and particle recycling. Empirically, QDD increases with decreasing pre‐injection carbon radiation, and increases strongly with density peakedness [ne(0)/〈ne〉] during the beam pulse. To date, the best fusion resu...

Satellite spectra of the K\ensuremath{\alpha} line of heliumlike nickel, Ni xxvii, recorded from tokamak-fusion-test reactor (TFTR) Ohmic plasmas with well-defined experimental conditions and central electron temperatures in the range 2--5 keV, have been compared with theoretical predictions. The relevant plasma parameters that determine the spectral features, i.e., the electron and ion temperatures, and the relative abundances of Ni xxv, Ni xxvi, and Ni xxvii have been obtained from least-squares fits of synthetic spectra to the experimental data. Both the dielectronic satellites and the satellites which are produced by collisional inner-shell excitation are well described by the theory given by Bombarda et al. [Phys. Rev. A 37, 504 (1988)] and Vainshtein and Safronova (unpublished). The electron-temperature results derived from the fits are in good agreement with electron-temperature measurements from independent diagnostics. However, the values obtained for the relative abundances of Ni xxv, Ni xxvi, and Ni xxvii are larger by factors of 1.3--2 compared to recent coronal-equilibrium predictions of Zastrow, K\"allne, and Summers [Phys. Rev. A 41, 1427 (1990)]. Plasma-modeling calculations performed with the multi-ion-species-transport [R. A. Hulse, Nucl. Technol. Fusion 3, 259 (1983)] code show that these deviations can be explained by radial ion transport assuming for the ion-transport diffusion coefficient D values in the range 1--2.5 ${\mathrm{m}}^{2}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$.However, the observed deviations may be partially ascribed to theoretical uncertainties of the ionization and recombination rate coefficients used for the coronal-equilibrium calculations. Systematic discrepancies are found to exist between the predicted and observed intensity ratios, x/w, y/w, and z/w, of the heliumlike lines w, 1${\mathit{s}}^{2}$ $^{1}$${\mathit{S}}_{0}$--1s2p $^{1}$${\mathit{P}}_{1}$; x, 1${\mathit{s}}^{2}$ $^{1}$${\mathit{S}}_{0}$--1s2p $^{3}$${\mathit{P}}_{2}$; y, 1${\mathit{s}}^{2}$ $^{1}$${\mathit{S}}_{0}$--1s2p $^{3}$${\mathit{P}}_{1}$; and z, 1${\mathit{s}}^{2}$ $^{1}$${\mathit{S}}_{0}$--1s2s $^{3}$${\mathit{S}}_{1}$.

A variety of experiments have been performed on the TFTR tokamak [Wilson et al., Plasma Physics and Controlled Nuclear Fusion Research 1988 (IAEA, Vienna, 1989), Vol. 1, p. 691] utilizing ion cyclotron range of frequencies (ICRF) heating. Of special interest has been the insight into plasma performance gained by utilizing a different heating scheme other than the usual neutral beam injection (NBI). Utilizing ICRF heating allows control over the power deposition profile independent of the plasma fueling profile. In addition, by varying the minority concentration the power split between ion and electron heating can be varied. Confinement has been examined in high recycling gas fueled discharges, low recycling supershot plasmas, and peaked density pellet fueled discharges. Global confinement is found not to be affected by the method or localization of plasma heating, but the calculated local diffusivities vary with the power deposition profile to yield similar global values. In addition, sawtooth stabilizati...

The dielectronic recombination rate coefficients associated with the Δn = 1 radiative core transitions have been determined for Ti XXI, Fe XXV, Ni XXVII, and Ti XXII as a function of the electron temperature from the analysis of x-ray satellite spectra emitted from tokamak plasmas. The results obtained are in good agreement with the recent theoretical predictions of Bely-Dubau et al., and Karim and Bhalla.

The time history of the central toroidal plasma rotation velocity in Tokamak Fusion Test Reactor (TFTR) experiments [Phys. Rev. Lett. 55, 2587 (1985)] with auxiliary heating by neutral deuterium beam injection and major‐radius compression has been measured from the Doppler shift of the emitted Ti XXI Kα line radiation. The experiments were conducted for neutral beam powers in the range 2.1–3.8 MW and line‐averaged densities in the range 1.8–3.0×1019 m−2. The observed rotation velocity increase during compression is consistent with theoretical estimates.

Measurements of the toroidal rotation speed vφ(r) driven by neutral beam injection in tokamak plasmas and, in particular, simultaneous profile measurements of vφ, Ti, Te, and ne, have provided new insights into the nature of anomalous transport in tokamaks. Low‐recycling plasmas heated with unidirectional neutral beam injection exhibit a strong correlation among the local diffusivities, χφ≊χi>χe. Recent measurements have confirmed similar behavior in broad‐density L‐mode plasmas. These results are consistent with the conjecture that electrostatic turbulence is the dominant transport mechanism in the tokamak fusion test reactor tokamak (TFTR) [Phys. Rev. Lett. 58, 1004 (1987)], and are inconsistent with predictions both from test‐particle models of strong magnetic turbulence and from ripple transport. Toroidal rotation speed measurements in peaked‐density TFTR ‘‘supershots’’ with partially unbalanced beam injection indicate that momentum transport decreases as the density profile becomes more peaked. In hi...

Magnetohydrodynamic (MHD) activity within three zones (core, half‐radius, and edge) of TFTR [Plasma Physics and Controlled Nuclear Fusion Research 1986 (IAEA, Vienna, 1987), Vol. 1, p. 51] tokamak plasmas are discussed. Near the core of the plasma column, sawteeth are often observed. Two types of sawteeth are studied in detail; one with complete, and the other with incomplete, magnetic reconnection. Their characteristics are determined by the shape of the q profile. Near the half‐radius the m/n=3/2 and 2/1 resistive ballooning modes are found to correlate with a beta collapse. The pressure and the pressure gradient at the mode rational surface are found to play an important role in stability. MHD activity is also studied at the plasma edge during limiter H modes. The edge localized modes (ELM’s) are found to have a precursor mode with a frequency between 50–200 kHz and a mode number m/n=1/0. The mode does not show a ballooning structure. While these instabilities have been studied on many other machines, ...

An equivalence relation of a family of arrays defined under a linear transformation is established. By means of this theorem the far field of an elliptical array can be obtained from that of an equivalent circular array; similarly for two and three dimensional arrays. As an example a uniformly excited cophasal elliptical array is considered. For non-uniform excitation, the method of symmetrical components may be applied despite the fact that there is no rotational symmetry for elliptical arrays. This theory can also be applied to the case of continuous source distribution on an ellipse or in an elliptical aperture. In so doing solutions can be obtained without using the complicated wave functions pertaining to the original geometry. As an example an optimum array in the sense of Dolph-Chebyshev is considered. Similarly, a Taylor distribution for an elliptical aperture can also be achieved.

Intense fluxes of 14‐MeV neutrons from deuterium–tritium (DT) fusion reaction in TFTR resulted in significantly enhanced background noise levels and reduced quality of data from the shielded UV (SPRED) and visible (VIPS) grating spectrometers and the x‐ray imaging system (XIS) camera. Both enhanced background levels, attributed to gamma rays and small angle neutron scattering, and large spikes, attributed to nuclear reactions in the silicon detectors, were observed. Both the enhanced background and the frequency of spikes were higher, on a per neutron basis, and the spike amplitudes were higher for DT than for DD operation. The VIPS shield reduced noise by 1/100 for DD radiation; the noise per DT neutron was 4 times higher than per DD neutron. The SPRED detector shield reduction factor was 1/12 in DD; extension of the shield around the vacuum chamber resulted in another factor of 1/5.5 reduction for DT plasmas. Spikes with amplitude up to 10 MeV were observed in the XIS detectors. The shielding effectiveness agrees with predictions. The spike heights are consistent with (n,p) and (n,α) reactions in the silicon detectors.

Line brightness calculations for the parameters at the International Thermonuclear Experimental Reactor (ITER) and results from recent experiments on the Tokamak Fusion Test Reactor (TFTR) indicate that time‐resolved measurements of the central ion temperature and other central plasma parameters should be feasible on ITER with nonperturbing amounts of krypton. Since the measurements will have to be performed in the presence of high fluxes of 14‐MeV neutrons from DT‐fusion reactions, the size of windows, apertures and x‐ray detectors must be as small as possible. Under these conditions, the use of doubly focussing crystals can significantly enhance the signal‐to‐noise ratio. This paper describes numerical studies of the focussing properties of spherically bent crystals and their application to ITER.

Reduction of indigenous metal impurities in tokamak plasmas and impurity requirements for the x‐ray diagnosis of central plasma parameters necessitates artificial introduction of metal atoms. A new inexpensive method is described using ferrocene, Fe(C5H5)2, a substance which sublimes. A prototype device was tested at the Atomic‐Beam Facility at PPPL. Ferrocene was injected into a pulsed helium plasma with an electron density of 2×1013 cm−3 and an electron temperature of 5 eV. The injected amount of ferrocene was controlled by varying the sublimation temperature in the range from 70 to 150 °C and adjusting the pulse length of a solenoid valve; the resulting iron atom concentration in the plasma was determined by monitoring the intensity of the Fe line at 5269 A. The device and the test results are presented.

Present‐day tokamak x‐ray imaging (XIS) and pulse height analysis (PHA) diagnostics will require special shielding and x‐ray optics to permit use on fusion reactors without prohibitive noise and detector damage from neutrons and gamma rays; x‐ray curved‐crystal spectrometers (XCS) may work with extensive shielding and collimation, but radiation damage of crystals and attainment of adequate impurity concentrations for ion‐temperature measurement are concerns. We consider the use of one or more reflections at grazing incidence from x‐ray mirrors or from Bragg layered synthetic microstructures (LSM) to decouple the x‐ray diagnostic from the direct fusion neutron beam. We present calculations of expected x‐ray line brightnesses from ITER and total instrument throughput. We also consider the use of hollow glass capillaries embedded in radiation shields to precede the XIS detector and reduce the ratio of neutron plus gamma radiation to x rays by a factor of ∼0.01 or better. Compatibility of capillary schemes with the PHA and XCS are discussed.

Tangential imaging is being pursued on TFTR as a method to study instabilities with high poloidal mode number m. These instabilities cannot be seen with conventional perpendicular viewing soft x‐ray diode arrays because the emission is integrated along a line of sight. Computer simulations of tangential imaging indicate that excellent spatial resolution can be obtained. Prerequisites are (a) that the line of sight is nearly parallel to a magnetic field line at the point of closest approach to the center of the plasma, and (b) that there exists a steep gradient of the plasma radiation that is used for the measurements. The TFTR plans for a tangential, two‐dimensional imaging, soft x‐ray diode array will be outlined.

X‐ray spectra obtained with position‐sensitive detectors which use delay‐line readout systems are subject to distortions at count rates comparable to the inverse of the temporal length of the delay line. These distortions are due to the simultaneous existence of pulses from different photons on the delay line. High incident rates up to several MHz can be obtained on the detectors of the TFTR crystal spectrometer under certain conditions. This paper describes improvements which can be obtained by an interarrival time discriminator circuit.

ICH‐induced toroidal plasma rotation was initially observed from Doppler shift measurements of the FeXXV Kα line using the TFTR horizontal crystal spectrometer for discharges with ion cyclotron heating of 2 MW RF power and without any neutral beam power in a D(H) plasma. The magnitude of plasma rotation depended on the IC resonance location. The observed rotations were in the counter‐plasma‐current direction and of the order of 5×104 m/s. Simple estimates relate the induced rotation to loss of ions from the plasma core. Later experimental results, as recorded by the charge exchange recombination spectrometer during beam blips at the end of the ICH pulse, with up to 6 MW of RF power in a 4He(H) plasma provided the radial profile of rotation.

A peak fusion power production of 9.3±0.7 MW has been achieved on the Tokamak Fusion Test Reactor (TFTR) in deuterium plasmas heated by co and counter injected deuterium and tritium neutral beams with a total power of 33.7 MW. The ratio of fusion power output to heating power input is 0.27. At the time of the highest neutron flux the plasma conditions are: Te(0)=11.5 keV, Ti(0)=44 keV, ne(0)=8.5×1019 m−3, and 〈Zeff〉=2.2 giving τE=0.24 s. These conditions are similar to those found in the highest confinement deuterium plasmas. The measured D‐T neutron yield is within 7% of computer code estimates based on profile measurements and within experimental uncertainties. These plasmas have an inferred central fusion alpha fraction of 0.2% and central fusion power density of 2 MW/m3 similar to that expected in a fusion reactor. Even though the alpha velocity exceeds the Alfven velocity throughout the time of high neutron output in most high power plasmas, MHD activity is not substantially different from that in co...

Concepts for adapting conventional tokamak x-ray diagnostics to the harsh radiation environment of ITER include use of grazing-incidence (GI) x-ray mirrors or man-made Bragg multilayer (ML) elements to remove the x-ray beam from the neutron beam, or use of bundles of glass-capillary x-ray ``light pipes`` embedded in radiation shields to reduce the neutron/gamma-ray fluxes onto the detectors while maintaining usable x-ray throughput. The x-ray optical element with the broadest bandwidth and highest throughput, the GI mirror, can provide adequate lateral deflection (10 cm for a deflected-path length of 8 m) at x-ray energies up to 12, 22, or 30 keV for one, two, or three deflections, respectively. This element can be used with the broad band, high intensity x-ray imaging system (XIS), the pulseheight analysis (PHA) survey spectrometer, or the high resolution Johann x-ray crystal spectrometer (XCS), which is used for ion-temperature measurement. The ML mirrors can isolate the detector from the neutron beam with a single deflection for energies up to 50 keV, but have much narrower bandwidth and lower x-ray power throughput than do the GI mirrors; they are unsuitable for use with the XIS or PHA, but they could be used with the XCS; in particular, thesemore » deflectors could be used between ITER and the biological shield to avoid direct plasma neutron streaming through the biological shield. Graded-d ML mirrors have good reflectivity from 20 to 70 keV, but still at grazing angles (

Three campaigns, prior to July 1994, attempted to increase the fusion power in DT plasmas on the Tokamak Fusion Test Reactor (TFTR). The first campaign was dedicated to obtaining >5 MW of fusion power while avoiding MHD events similar to the JET X-event. The second was aimed at producing maximum fusion power irrespective of proximity to MHD limits, and achieved 9 MW limited by a disruption. The third campaign increased the energy confinement time using lithium pellet conditioning while raising the ratio of alpha heating to beam heating.

The Tokamak Fusion Test Reactor (TFTR) has performed initial high-power experiments with the plasma fueled by deuterium and tritium to nominally equal densities. Compared to pure deuterium plasmas, the energy stored in the electron and ions increased by ~20%. These increases indicate improvements in confinement associated with the use of tritium and possibly heating of electrons by α-particles.

[ital K][beta] spectra of heliumlike iron, Fe XXV, have been observed from tokamak-fusion-test-reactor (TFTR) plasmas with a high-resolution crystal spectrometer. The wavelength range of the Fe [ital K][beta] spectrum partially overlaps the spectrum of heliumlike nickel (Ni XXVII), which is used on TFTR and the joint European torus for ion-temperature measurements. The experimental arrangement made it possible to observe the Fe XXV [ital K][beta] lines and their satellite transitions of the type 1[ital s]2[ital l][prime]3[ital l][prime][prime][r arrow]1[ital s][sup 2]2[ital l][prime], as well as the entire satellite spectrum of the Ni XXVII [ital K][alpha] line simultaneously. In order to identify the features of the [ital K][beta] spectra and to study their possible interference with the Ni XXVII spectrum, the intensity of the [ital K][beta] spectrum was enhanced by the injection of iron into the plasma. Accurate wavelengths and intensities have been obtained and compared with different theoretical calculations.

K{beta} spectra of helium-like iron, Fe XXV, have been observed from TFTR plasmas with a high-resolution crystal spectrometer. The wavelength range of the Fe K{beta} spectrum partially overlaps the spectrum of helium-like nickel (Ni XXVII), which is used on TFTR and JET for ion temperature measurements. The experimental arrangement made it possible to observe the Fe XXV K{beta} lines and their satellite transitions of the type 1s2l{prime}31{double_prime} {yields} 1s{sup 2}21{prime}, as well as the entire satellite spectrum of the Ni XXVII K {alpha} line simultaneously. In order to identify the features of the K{beta} spectra and to study their possible interference with the Ni XXVII spectrum, the intensity of the K{beta} spectrum was enhanced by injection of iron into the plasma. Accurate wavelengths and intensities have been obtained and compared with different theoretical calculations.

Results obtained from experiments utilizing high power ICRF (ion cyclotron range of frequency) heating to stabilize sawtooth oscillations on TFTR are reviewed. The key observations include existence of a minimum ICRF power required to achieve stabilization, a dependence of the stabilization threshold on the relative size of the ICRF power deposition profile to the q=1 volume, and a peaking of the equilibrium pressure and current profiles during sawtooth-free phases of the discharges. In addition, preliminary measurements of the poloidal magnetic field profile indicate that q on axis decreases to a value of 0.55{plus minus}0.15 after a sawtooth-stabilized period of {approximately}0.5 sec has transpired. The results are discussed in the context of theory, which suggests that the fast ions produced by the ICRF heating suppress sawteeth by stabilizing the m=1 MHD instabilities believed to be the trigger for the sawtooth oscillations. Though qualitative agreement is found between the observations and the theory, further refinement of the theory coupled with more accurate measurements of experimental profiles will be required in order to complete quantitative comparisons.

A review of TFTR plasma transport studies is presented. Parallel transport and the confinement of suprathermal ions are found to be relatively well described by theory. Cross-field transport of the thermal plasma, however, is anomalous with the momentum diffusivity being comparable to the ion thermal diffusivity and larger than the electron thermal diffusivity in neutral beam heated discharges. Perturbative experiments have studied nonlinear dependencies in the transport coefficients and examined the role of possible nonlocal phenomena. The underlying turbulence has been studied using microwave scattering, beam emission spectroscopy and microwave reflectometry over a much broader range in k perpendicular to than previously possible. Results indicate the existence of large-wavelength fluctuations correlated with enhanced transport.

Dielectronic satellite spectra of the FeXXV K{alpha} resonance line observed from the Tokamak Fusion Test Reactor (TFTR) plasmas have been compared with recent explicit calculations for the n = 3 to 8 dielectronic satellites as well as the earlier theoretical predictions, which were based on the 1/n{sup 3} scaling law for n > 4 satellites. The analysis has been performed by least-squares fits of synthetic spectra to the experimental data. The synthetic spectra constructed from both theories are in good agreement with the observed data. However, the electron temperature values obtained from the fit of the present explicit calculations are in better agreement with independent measurements. 20 refs., 4 figs.

A transport code (TRANSP) is used to simulate future deuterium-tritium experiments (DT) in TFTR. The simulations are derived from 14 TFTR DD discharges, and the modeling of one supershot is discussed in detail to indicate the degree of accuracy of the TRANSP modeling. Fusion energy yields and {alpha}-particle parameters are calculated, including profiles of the {alpha} slowing down time, average energy, and of the Alfven speed and frequency. Two types of simulations are discussed. The main emphasis is on the DT equivalent, where an equal mix of D and T is substituted for the D in the initial target plasma, and for the D{sup O} in the neutral-beam injection, but the other measured beam and plasma parameters are unchanged. This simulation does not assume that {alpha} heating will enhance the plasma parameters, or that confinement will increase with T. The maximum relative fusion yield calculated for these simulations is Q{sub DT} {approx} 0.3, and the maximum {alpha} contribution to the central toroidal {beta} is {beta}{sub {alpha}}(0) {approx} 0.5%. The stability of toroidicity-induced Alfven eigenmodes (TAE) and kinetic ballooning modes (KBM) is discussed. The TAE mode is predicted to become unstable for some of the equivalent simulations, particularly after the terminationmore » of neutral beam injection. In the second type of simulation, empirical supershot scaling relations are used to project the performance at the maximum expected beam power. The MHD stability of the simulations is discussed.« less

High resolution ECE and X-ray image reconstructions have been made simultaneously during the sawtooth crash in the fast rotating plasma on TFTR. The X-ray tomography is found not the represent flux surfaces but to show metal impurity behavior. The experimental results show that the reconnection process cause the sawtooth crash, even when the crash time is 20 times faster than the Kadomtsev reconnection time. New features are observed during the sawtooth crash, such as an oval shaped hot spot and a cooler region between the island and the hot spot. 18 refs., 5 figs.

The use of ICRF heating to stabilize the core plasma sawtooth relaxations has been extended to TFTR where such stabilization has been produced at relatively low power in the L Mode regime at moderate density (P{sub RF} = 4 MW, 2.6 MW in helium and deuterium discharges, respectively, for the minority hydrogen ICRF heating regime with {bar n}{sub e}{approx}2.5 {times} 10{sup 13} cm{sup {minus}3}). These results, as in the case of those obtained on JET, are qualitatively consistent with energetic ion stabilization of the m = 1, n = 1 ideal/resistive kink mode. The relevance of sawtooth stabilization to the primary regimes of interest on TFTR -- the high-Q supershot regime and the high density pellet injection regimes -- and on CIT -- the high density ICRF heated regime -- is considered in the context of the present theory and the projected ICRF power deposition characteristics. 35 refs., 11 figs.

Spectra of hydrogenlike iron Fe XXVI have been observed from Tokamak Fusion Test Reactor plasmas with a high-resolution crystal spectrometer. The experimental arrangement permits simultaneous observation of the Fe XXVI Ly-${\mathrm{\ensuremath{\alpha}}}_{1}$ and Ly-${\mathrm{\ensuremath{\alpha}}}_{2}$ lines and the associated dielectronic satellites, which are due to transitions 1snl-2pnl' with n\ensuremath{\ge}2, as well as the heliumlike 1${\mathit{s}}^{2}$${(}^{1}$${\mathit{S}}_{0}$)-1s4p${(}^{1}$${\mathit{P}}_{1}$) and both hydrogenlike Ly-${\mathrm{\ensuremath{\beta}}}_{1}$ and Ly-${\mathrm{\ensuremath{\beta}}}_{2}$ lines from chromium. Relative wavelengths and line intensities can be determined very accurately. The spectral data are in very good agreement with theoretical calculations. The observed spectra have also been used to estimate the total dielectronic recombination rate coefficient of Fe XXVI.