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TFTR Twenty Year Perspective

Description: Deuterium-tritium (D-T) plasmas with core parameters almost identical to those expected in the core of ignited plasmas in ITER (International Thermonuclear Experimental Reactor) have served as a test bed to carry out the first detailed studies of D-T plasma physics, including the first observations of alpha-particle heating and alpha-driven instabilities. TFTR operated above the original engineering design requirements and with high availability in D-T until experimental operation was terminated due to U.S. fusion budget cutbacks. A most valuable lesson learned was that D-T operation of a large experimental device is feasible, as TFTR operation could have continued many more years while remaining within tritium and neutron activation limits. The flexibility and control of plasma parameters (e.g., plasma rotation) and the comprehensive diagnostic system enabled TFTR to make seminal contributions to tokamak plasma science, such as first confirmation of the bootstrap current in a tokamak, detailed turbulence studies leading to a new paradigm for transport understanding, first observations of neoclassical tearing modes, and detailed measurements and modeling of plasma disruptions. Recent advances in understanding the fundamental processes controlling plasma transport provide new opportunities for improving tokamak plasma performance. Implementation of recent knowledge could lead to D-T operating regimes with strong alpha heating with modest extensions of the TFTR operating regimes.
Date: April 1, 1998
Creator: Meade, D.M.
Partner: UNT Libraries Government Documents Department

Tritium experience in the Tokamak Fusion Test Reactor

Description: Tritium management is a key enabling element in fusion technology. Tritium fuel was used in 3.5 years of successful deuterium-tritium (D-T) operations in the Tokamak Fusion Test Reactor (TFTR) at the Princeton Plasma Physics Laboratory. The D-T campaign enabled TFTR to explore the transport, alpha physics, and MHD stability of a reactor core. It also provided experience with tritium retention and removal that highlighted the importance of these issues in future D-T machines. In this paper, the authors summarize the tritium retention and removal experience in TFTR and its implications for future reactors.
Date: July 1, 1998
Creator: Skinner, C.H.; Blanchard, W.; Hosea, J.; Mueller, D.; Nagy, A.; Brooks, J.N. et al.
Partner: UNT Libraries Government Documents Department

Results from D-T Experiments on TFTR and Implications for Achieving an Ignited Plasma

Description: Progress in the performance of tokamak devices has enabled not only the production of significant bursts of fusion energy from deuterium-tritium plasmas in the Tokamak Fusion Test Reactor (TFTR) and the Joint European Torus (JET) but, more importantly, the initial study of the physics of burning magnetically confined plasmas. As a result of the worldwide research on tokamaks, the scientific and technical issues for achieving an ignited plasma are better understood and the remaining questions more clearly defined. The principal research topics which have been studied on TFTR are transport, magnetohydrodynamic stability, and energetic particle confinement. The integration of separate solutions to problems in each of these research areas has also been of major interest. Although significant advances, such as the reduction of turbulent transport by means of internal transport barriers, identification of the theoretically predicted bootstrap current, and the study of the confinement of energetic fusion alpha-particles have been made, interesting and important scientific and technical issues remain for achieving a magnetic fusion energy reactor. In this paper, the implications of the TFTR experiments for overcoming these remaining issues will be discussed.
Date: July 14, 1998
Creator: Hawryluk, R.J. and the TFTR Group
Partner: UNT Libraries Government Documents Department

Studies of tritiated co-deposited layers in TFTR

Description: Plasma facing components in TFTR contain an important record of plasma wall interactions in reactor grade DT plasmas. Tiles, flakes, wall coupons, a stainless steel shutter and dust samples have been retrieved from the TFTR vessel for analysis. Selected samples have been baked to release tritium and assay the tritium content. The in-vessel tritium inventory is estimated to be 0.56 g and is consistent with the in-vessel tritium inventory derived from the difference between tritium fueling and tritium exhaust. The distribution of tritium on the limiter and vessel wall showed complex patterns of co-deposition. Relatively high concentrations of tritium were found at the top and bottom of the bumper limiter, as predicted by earlier BBQ modeling.
Date: June 28, 2000
Creator: Skinner, C.H.; Gentile, C.A.; Ascione, G.; Carpe, A.; Causey, R.A.; Hayashi, T. et al.
Partner: UNT Libraries Government Documents Department

Majority ion heating near the ion-ion hybrid layer in tokamaks

Description: Efficient direct majority ion heating in a deuterium-tritium (D-T) reactor-grade plasma via absorption of fast magnetosonic waves in the ion cyclotron range of frequencies (ICRF) is discussed. Majority ion heating results from resonance overlap between the cyclotron layers and the D-T ion-ion hybrid layer in hot, dense plasmas for fast waves launched with high parallel wavenumbers. Analytic and numerical models are used to explore the regime in ITER plasmas.
Date: August 1, 1995
Creator: Phillips, C.K.; Hosea, J.C.; Ignat, D.; Majeski, R.; Rogers, J.H.; Schilling, G. et al.
Partner: UNT Libraries Government Documents Department

DT results of TFTR`s alpha collector

Description: An escaping alpha collector probe has been developed for TFTR`s DT phase to complement the results of the lost alpha scintillator detectors which have been operating on TFTR since 1988. Measurements of the energy distribution of escaping alphas have been made by measuring the range of alphas implanted into nickel foils located within the alpha collector. Exposed samples have been analyzed for 4 DT plasma discharges at plasma currents of 1.0 and 1.8 MA. The results at 1.0 MA are in good agreement with predictions for first orbit alpha loss at 3.5 MeV. The 1.8 MA results, however, indicate a large anomalous loss of partially thermalized alphas at an energy {approximately}30% below the birth energy and at a total fluence nearly an order of magnitude above expected first orbit loss. This anomalous loss is not observed with the lost alpha scintillator detectors in DT plasmas but does resemble the anomalous delayed loss seen in DD plasmas. Several potential explanations for this loss process are examined. None of the candidate explanations proposed thus far are fully consistent with the anomalous loss observations.
Date: November 1, 1996
Creator: Herrmann, H.W.; Zweben, S.J.; Darrow, D.S.; Timberlake, J.R.; Chong, G.P.; Haasz, A.A. et al.
Partner: UNT Libraries Government Documents Department

Scaling of confinement with isotopic content in deuterium and tritium plasmas

Description: The scaling of the electron thermal diffusivity, {chi}{sub e}, with relative gyro radius, {rho}*, has been measured on TFTR by comparing nearly identical ICRF-heated discharges which differ only in hydrogenic isotopic content. Contrary to the gyro-Bohm scaling ({chi}{sub e} {approximately} {chi}{sub B}{rho}*, where {chi}{sub B} is the Bohm diffusivity) observed on DIII-D when {rho}* was varied through a scan of magnetic field strength, {chi}{sub e} is found to scale inversely with {rho}*. Hence, global energy confinement is 8--11% higher in deuterium-tritium plasmas than in deuterium only plasmas, with the higher stored energy attributed almost entirely to the electrons.
Date: January 1, 1997
Creator: Phillips, C.K.; Scott, S.D. & Bell, M.
Partner: UNT Libraries Government Documents Department

MAGO-3 results of the experiment. Final report

Description: In this report the results of joint LANL-VNIIEF experiment MAGO-3 are given. The experiment was aimed to investigate the of magnetized plasma parameters when it overflows trough Laval nozzel. The details of the experiment are described, data obtained by VNIIEF experts are given.
Date: December 31, 1996
Creator: Garanin, S.F.; Mokhov, V.N.; Volkov, G.I. & Ivanov, V.A.
Partner: UNT Libraries Government Documents Department

Tritium removal by CO{sub 2} laser heating

Description: Efficient techniques for rapid tritium removal will be necessary for ITER to meet its physics and engineering goals. One potential technique is transient surface heating by a scanning CO{sub 2} or Nd:Yag laser that would release tritium without the severe engineering difficulties of bulk heating of the vessel. The authors have modeled the heat propagation into a surface layer and find that a multi-kW/cm{sup 2} flux with an exposure time of order 10 ms is suitable to heat a 50 micron co-deposited layer to 1,000--2,000 degrees. Improved wall conditioning may be a significant side benefit. They identify remaining issues that need to be addressed experimentally.
Date: October 1, 1997
Creator: Skinner, C.H.; Kugel, H.; Mueller, D.; Doyle, B.L. & Wampler, W.R.
Partner: UNT Libraries Government Documents Department

Operations with tritium neutral beams on TFTR

Description: In late 1993 the Tokamak Fusion Test Reactor began operating with a deuterium-tritium (DT) fuel mixture instead of the pure deuterium which it had used previously. The major portion of this tritium has initially entered the torus as energetic neutral beam particles. Over 600 deuterium-tritium discharges have now been studied with the aid of more than 2000 tritium ion source shots. The maximum total neutral particle power injected with a mix of deuterium and tritium beams has been 39.6 megawatts, and the maximum injected as tritium neutrals has been 24.3 megawatts. Tritium neutral beam operation has become routine during this time.
Date: December 31, 1996
Creator: Grisham, L.R.; O`Connor, T. & Stevenson, T.N.
Partner: UNT Libraries Government Documents Department

Anomalous Loss of DT Alpha Particles in the Tokamak Fusion Test Reactor

Description: Princeton's Tokamak Fusion Test Reactor (TFTR) is the first experimental fusion device to routinely use tritium to study the deuterium-tritium (DT) fusion reaction,allowing the first systematic study of DT alpha particles in tokamak plasmas. A crucial aspect of alpha-particle physics is the fraction of alphas that escape from the plasma, particularly since these energetic particles can do severe damage to the first wall of a reactor. An escaping alpha collector probe has been developed for TFTR's DT phase. Energy distributions of escaping alphas have been determined by measuring the range of alpha-particles implanted into nickel foils located within the alpha collector. Results at 1.0 MA of plasma current are in good agreement with predictions for first orbit alpha loss. Results at 1.8 MA, however, show a significant anomalous loss of partially thermalized alphas (in addition to the expected first orbit loss), which is not observed with the lost alpha scintillator detectors in DT plasmas, but does resemble the anomalous "delayed" loss seen in DD plasmas. None of the candidate explanations proposed thus far are fully consistent with the anomalous loss observations. An experiment designed to study the effect of plasma major radius shifts on alpha-particle loss has led to a better understanding of alpha-particle dynamics in tokamaks. Intuitively, one might suppose that confined marginally passing alpha-particles forced to move toward higher magnetic field during an inward major radius shift (i.e. compression) would mirror and become trapped particles, leading to increased alpha loss. Such an effect was looked for during the shift experiment, however, no significant changes in alpha loss to the 90 degree lost alpha scintillator detector were observed during the shifts. It is calculated that the energy gained by an alpha-particle during the inward shift is sufficient to explain this result. However, an unexpected loss of partially thermalized alpha-particles ...
Date: June 1, 1997
Creator: Herrmann, Hans W.
Partner: UNT Libraries Government Documents Department

Studies of tritiated co-deposited Layers in TFTR

Description: Plasma facing components in TFTR contain an important record of plasma wall interactions in reactor grade DT plasmas. Tiles, flakes, wall coupons, a stainless steel shutter and dust samples have been retrieved from the TFTR vessel for analysis. Selected samples have been baked to release tritium and assay the tritium content. The in-vessel tritium inventory is estimated to be 0.56 g and is consistent with the in-vessel tritium inventory derived from the difference between tritium fueling and tritium exhaust. The distribution of tritium on the limiter and vessel wall showed complex patterns of co-deposition. Relatively high concentrations of tritium were found at the top and bottom of the bumper limiter, as predicted by earlier BBQ modeling.
Date: May 22, 2000
Creator: Skinner, C. H.; Gentile, C. A.; Ascione, G.; Carpe, A.; Causey, R. A.; Hayashi, T. et al.
Partner: UNT Libraries Government Documents Department

Search for alpha-driven BAE modes in TFTR

Description: A search for alpha-driven beta-induced Alfven eigenmodes (BAE modes) was conducted in low current (1.0--1.6 MA) TFTR supershots. Stable high-beta deuterium-tritium (DT) discharges were obtained with B{rho} = 2.4 and central alpha beta of 0.1%. Instabilities between 75--200 kHz were observed by magnetic probes in many DT discharges, but the activity was also present in deuterium-deuterium (DD) comparison discharges, indicating that these modes are not destabilized (principally) by the alpha-particle population. Losses of fusion products are also similar in the two sets of discharges.
Date: May 1, 1996
Creator: Heidbrink, W.W.; Batha, S. & Bell, R.
Partner: UNT Libraries Government Documents Department

Alpha particle losses from Tokamak Fusion Test Reactor deuterium-tritium plasmas

Description: Because alpha particle losses can have a significant influence on tokamak reactor viability, the loss of deuterium-tritium alpha particles from the Tokamak Fusion Test Reactor (TFTR) has been measured under a wide range of conditions. In TFTR, first orbit loss and stochastic toroidal field ripple diffusion are always present. Other losses can arise due to magnetohydrodynamic instabilities or due to waves in the ion cyclotron range of frequencies. No alpha particle losses have yet been seen due to collective instabilities driven by alphas. Ion Bernstein waves can drive large losses of fast ions from TFTR, and details of those losses support one element of the alpha energy channeling scenario.
Date: January 1, 1996
Creator: Darrow, D.S.; Zweben, S.J. & Batha, S.
Partner: UNT Libraries Government Documents Department

Thermal oscillation smoothing of DT solid layers for HAPL and NIF scale targets

Description: Deuterium-Tritium (D-T) solid fuel layers must meet stringent roughness specifications for both the ICF and IFE laser fusion programs and native beta-layering alone is unable to provide sufficient solid layer smoothing to meet these specifications at 18.3 K or below. Consequently, several supplemental smoothing options have been proposed to resolve this issue, including a technique called 'Thermal Breathing'. This technique consists of oscillating the temperature of the solid D-T layer about its equilibration temperature for a period of one to several hours. Recently, thermal oscillations have been used to successfully smooth rough solid D{sub 2} in spherical targets. In order to study this particular smoothing technique, we examined the effects of thermal oscillations on equilibrated D-T solid layers, using both ICF and IFE scale layering cells and layer thicknesses. The D-T solid layers that were Subjected to thermal breathing in these studies were equilibrated at temperatures ranging from 16.0 K to 19.25 K, followed by 1.5 to 2 hours of temperature oscillations. During the HAPL scale experiments the amplitude and period of the oscillations were both varied to examine parametric effects of these variables on final layer roughness. In both sets of experiments, once the oscillations completed we allowed the layers to 'relax' at their initial equilibration temperature for another 1 to 2 hours, to observe any 'rebounding' or re-roughening that might occur. The rCF scale experiments were performed using a 2 mm beryllium torus, for which the layer was free from optical distortions that were observed in our IFE scale cell (a 4 mm dia. sapphire sphere-cylinder). Our results showed a temperature dependent smoothing effect ofthe DT solid layer ranging from 20% to 35% over the temperature range of 17.3 K to 19.0 K for the rCF-scale, 2-mm celL The final RMS roughness for layers grown in this 2-mm ...
Date: January 1, 2009
Creator: Sheliak, John D; Geller, Drew A & Hoffer, James K
Partner: UNT Libraries Government Documents Department

First evidence of collective alpha particle effect on TAE modes in the TFTR D-T experiment

Description: The alpha particle effect on the excitation of toroidal Alfven eigenmodes (TAE) was investigated in deuterium-tritium (d-t) plasmas in the Tokamak Fusion Test Reactor (TFTR). RF power was used to position the plasma near the instability threshold, and the alpha particle effect was inferred from the reduction of RF power threshold for TAE instability in d-t plasmas. Initial calculations indicate that the alpha particles contribute 10--30% of the total drive in a d-t plasma with 3 MW of peak fusion power.
Date: August 1, 1995
Creator: Wong, K.L.; Schmidt, G. & Batha, S.H.
Partner: UNT Libraries Government Documents Department

3D Fokker-Planck modeling of axisymmetric collisional losses of fusion products in TFTR

Description: Results of a 3D (in constants of motion space) Fokker-Planck simulation of collisional losses of fusion products in axisymmetric DT and DD discharges on TFTR are presented. The distributions of escaped ions over poloidal angle, pitch angle, and their energy spectra are obtained. Axisymmetric collisional losses of fusion products are found to be less than (2--5)%. The distribution of confined fusion products is shown to be strongly anisotropic and nonuniform in the radial coordinate mainly for slowed-down fusion products with small longitudinal energy. Comparison of these results of modeling and experimental data is done.
Date: October 1995
Creator: Goloborod`ko, V. Ya.; Reznik, S. N.; Yavorskij, V. A. & Zweben, S. J.
Partner: UNT Libraries Government Documents Department

Recent D-T results on TFTR

Description: 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.
Date: October 1, 1995
Creator: Johnson, D.W.; Arunasalam, V. & Barnes, C.W.
Partner: UNT Libraries Government Documents Department

Results from deuterium-tritium tokamak confinement experiments

Description: Recent scientific and technical progress in magnetic fusion experiments has resulted in the achievement of plasma parameters (density and temperature) which enabled the production of significant bursts of fusion power from deuterium-tritium fuels and the first studies of the physics of burning plasmas. The key scientific issues in the reacting plasma core are plasma confinement, magnetohydrodynamic (MHD) stability, and the confinement and loss of energetic fusion products from the reacting fuel ions. Progress in the development of regimes of operation which have both good confinement and are MHD stable have enabled a broad study of burning plasma physics issues. A review of the technical and scientific results from the deuterium-tritium experiments on the Joint European Torus (JET) and the Tokamak Fusion Test Reactor (TFTR) is given with particular emphasis on alpha-particle physics issues.
Date: February 1, 1997
Creator: Hawryluk, R.J.
Partner: UNT Libraries Government Documents Department

Alpha Particle Physics Experiments in the Tokamak Fusion Test Reactor

Description: Alpha particle physics experiments were done on the Tokamak Fusion Test Reactor (TFTR) during its deuterium-tritium (DT) run from 1993-1997. These experiments utilized several new alpha particle diagnostics and hundreds of DT discharges to characterize the alpha particle confinement and wave-particle interactions. In general, the results from the alpha particle diagnostics agreed with the classical single-particle confinement model in magnetohydrodynamic (MHD) quiescent discharges. Also, the observed alpha particle interactions with sawteeth, toroidal Alfvén eigenmodes (TAE), and ion cyclotron resonant frequency (ICRF) waves were roughly consistent with theoretical modeling. This paper reviews what was learned and identifies what remains to be understood.
Date: December 14, 1998
Creator: Budny, R.V.; Darrow, D.S.; Medley, S.S.; Nazikian, R.; Zweben, S.J. & al., et
Partner: UNT Libraries Government Documents Department

Fast detection of 14 MeV neutrons on the TFTR neutron collimator

Description: Current mode operation of the NE451 ZnS Scintillation Detectors of the TFTR Neutron Collimator has enabled us to record the development of radial neutron emission profiles with much faster speed and higher accuracy than in the pulse counting mode. During high-power DT operation, the intrinsic shot noise on the detector traces was so low that the authors could observe sawtooth instabilities and disruptions with good precision and, in addition, were able to identify precursor MHD activity and fishbone instabilities. These results demonstrate that in future tritium burning machines like ITER or TPX, the neutron collimator should be designed not only as a monitor of radial fusion power profiles but also as a wave detector for MHD activity.
Date: December 1, 1995
Creator: Goeler, S. von; Roquemore, A.L.; Johnson, L.C.; Bitter, M.; Diesso, M.; Fredrickson, E. et al.
Partner: UNT Libraries Government Documents Department

Alpha diagnostics using pellet charge exchange: Results on TFTR and prospects for ITER

Description: Confinement of alpha particles is essential for fusion ignition and alpha physics studies are a major goal of the TFTR, JET, and ITER DT experiments, but alpha measurements remain one of the most challenging plasma diagnostic tasks. The Pellet Charge Exchange (PCX) diagnostic has successfully measured the radial density profile and energy distribution of fast (0.5 to 3.5 MeV) confined alpha particles in TFTR. This paper describes the diagnostic capabilities of PCX demonstrated on TFTR and discusses the prospects for applying this technique to ITER. Major issues on ITER include the pellet`s perturbation to the plasma and obtaining satisfactory pellet penetration into the plasma.
Date: May 1, 1996
Creator: Fisher, R.K.; Duong, H.H. & McChesney, J.M.
Partner: UNT Libraries Government Documents Department

Transport of Recycled Deuterium to the Plasma Core in TFTR

Description: We report a study of the fueling of the plasma core by recycling in the Tokamak Fusion Test Reactor (TFTR) [Phys. Plasmas 2, 2176 (1995)]. We have analyzed discharges fueled by deuterium recycled from the limiter and tritium-only neutral beam injection. In these plasmas, the DT neutron rate provides a measure of the deuterium influx into the core plasma. We find a reduced influx with plasmas using lithium pellet conditioning and with plasmas of reduced major (and minor) radius. Modeling with the DEGAS neutrals code shows that the dependence on radius can be related to the penetration of neutrals through the scrape-off layer.
Date: October 1, 1997
Creator: Bell, M.G.; Budny, R.V.; Jassby, D.L.; Park, H.; Skinner, C.H. & al, et
Partner: UNT Libraries Government Documents Department

Alpha particle loss in TFTR deuterium-tritium plasmas with reversed magnetic shear

Description: The confinement and loss of fusion alpha particles are examined for reversed magnetic shear plasmas in TFTR. Such plasmas, with high central q and non-monotonic q profiles can exhibit remarkably reduced energy and particle transport of the thermal ions. However, these same conditions are theoretically predicted to produce high levels of stochastic ripple loss of suprathermal particles, which may reduce the efficiency of plasma heating by the alpha particles and other heating schemes involving fast ions. This paper presents calculations of guiding-center code alpha particle orbit loss from deuterium-tritium (DT) simulations of TFTR deuterium-only experiments. They are compared to results of measurements made in DT reversed shear plasmas of both the confined alpha particle distribution and the alpha particles lost from the plasma. Large fast particle losses have also been found in reversed shear ITER simulations (up to 20%) and from measurements of triton burnup in reversed shear experiments on JT-60U (12%).
Date: June 1, 1997
Creator: Redi, M.H.; Batha, S.H. & Budny, R.V.
Partner: UNT Libraries Government Documents Department