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  • AIP Publishing  (15)
  • 1
    Online Resource
    Online Resource
    Preparations for deuterium–tritium experiments on the Tokamak Fusion Test Reactor*
    AIP Publishing ; 1994
    In:  Physics of Plasmas Vol. 1, No. 5 ( 1994-05-01), p. 1560-1567
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 1, No. 5 ( 1994-05-01), p. 1560-1567
    Abstract: 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 diagnostics for confined α particles. Experimental results and theoretical modeling in support of the D–T experiments are reviewed.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.870707
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1994
    detail.hit.zdb_id: 1472746-8
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  • 2
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    High-beta operation and magnetohydrodynamic activity on the TFTR tokamak
    AIP Publishing ; 1990
    In:  Physics of Fluids B: Plasma Physics Vol. 2, No. 6 ( 1990-06-01), p. 1287-1290
    Details
    In: Physics of Fluids B: Plasma Physics, AIP Publishing, Vol. 2, No. 6 ( 1990-06-01), p. 1287-1290
    Abstract: 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, on TFTR the studies have been extended to high pressure (plasma pressure greater than 4×105 Pa) and low collisionality [vi*(a/2) & lt;0.002, ve*(a/2) & lt;0.01].
    Type of Medium: Online Resource
    ISSN: 0899-8221
    URL: Article
    DOI: 10.1063/1.859544
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1990
    detail.hit.zdb_id: 2130787-8
    detail.hit.zdb_id: 648023-8
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  • 3
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    Review of deuterium–tritium results from the Tokamak Fusion Test Reactor
    AIP Publishing ; 1995
    In:  Physics of Plasmas Vol. 2, No. 6 ( 1995-06-01), p. 2176-2188
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 2, No. 6 ( 1995-06-01), p. 2176-2188
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.871303
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1995
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  • 4
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    Deuterium–tritium plasmas in novel regimes in the Tokamak Fusion Test Reactor
    AIP Publishing ; 1997
    In:  Physics of Plasmas Vol. 4, No. 5 ( 1997-05-01), p. 1714-1724
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 4, No. 5 ( 1997-05-01), p. 1714-1724
    Abstract: Experiments in the Tokamak Fusion Test Reactor (TFTR) [Phys. Plasmas 2, 2176 (1995)] have explored several novel regimes of improved tokamak confinement in deuterium–tritium (D–T) plasmas, including plasmas with reduced or reversed magnetic shear in the core and high-current plasmas with increased shear in the outer region (high li). New techniques have also been developed to enhance the confinement in these regimes by modifying the plasma-limiter interaction through in situ deposition of lithium. In reversed-shear plasmas, transitions to enhanced confinement have been observed at plasma currents up to 2.2 MA (qa≈4.3), accompanied by the formation of internal transport barriers, where large radial gradients develop in the temperature and density profiles. Experiments have been performed to elucidate the mechanism of the barrier formation and its relationship with the magnetic configuration and with the heating characteristics. The increased stability of high-current, high-li plasmas produced by rapid expansion of the minor cross section, coupled with improvement in the confinement by lithium deposition has enabled the achievement of high fusion power, up to 8.7 MW, with D–T neutral beam heating. The physics of fusion alpha-particle confinement has been investigated in these regimes, including the interactions of the alphas with endogenous plasma instabilities and externally applied waves in the ion cyclotron range of frequencies. In D–T plasmas with q0 & gt;1 and weak magnetic shear in the central region, a toroidal Alfvén eigenmode instability driven purely by the alpha particles has been observed for the first time. The interactions of energetic ions with ion Bernstein waves produced by mode conversion from fast waves in mixed-species plasmas have been studied as a possible mechanism for transferring the energy of the alphas to fuel ions.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.872274
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1997
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  • 5
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    Correlations of heat and momentum transport in the TFTR tokamak
    AIP Publishing ; 1990
    In:  Physics of Fluids B: Plasma Physics Vol. 2, No. 6 ( 1990-06-01), p. 1300-1305
    Details
    In: Physics of Fluids B: Plasma Physics, AIP Publishing, Vol. 2, No. 6 ( 1990-06-01), p. 1300-1305
    Abstract: 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 & gt;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 high-temperature, peaked-density plasmas the observed gradient scale length parameter ηtoti=d ln Ti/d ln ne correlates reasonably well with predictions of the threshold for exciting ion-temperature-gradient-driven turbulence (ITGDT), as would be expected for plasmas at marginal stability with respect to this strong transport mechanism. In L-mode plasmas where ITGDT is expected to be too weak to enforce marginal stability, ηtoti exceeds this threshold considerably. However, preliminary experiments have failed to observe a significant increase in ion heat transport when ηtoti was rapidly forced above ηc (the threshold for exciting ITGDT) using a perturbative particle source, as would have been expected for a plasma at marginal stability.
    Type of Medium: Online Resource
    ISSN: 0899-8221
    URL: Article
    DOI: 10.1063/1.859545
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1990
    detail.hit.zdb_id: 2130787-8
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  • 6
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    High- Q plasmas in the TFTR tokamak
    AIP Publishing ; 1991
    In:  Physics of Fluids B: Plasma Physics Vol. 3, No. 8 ( 1991-08-01), p. 2308-2314
    Details
    In: Physics of Fluids B: Plasma Physics, AIP Publishing, Vol. 3, No. 8 ( 1991-08-01), p. 2308-2314
    Abstract: 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 results are Sn=5×1016 n/sec, QDD=1.85×10−3, and neutron yield=4.0×1016 n/pulse, obtained at Ip=1.6–1.9 MA and beam energy Eb=95–103 keV, with nearly balanced co- and counter-injected beam power. Computer simulations of supershot plasmas show that typically 50%–60% of Sn arises from beam–target reactions, with the remainder divided between beam–beam and thermonuclear reactions, the thermonuclear fraction increasing with Pb. The simulations predict that QDT=0.3–0.4 would be obtained for the best present plasma conditions, if half the deuterium neutral beams were to be replaced by tritium beams. Somewhat higher values are calculated if D beams are injected into a predominantly tritium target plasma. The projected central beta of fusion alphas is 0.4%–0.6%, a level sufficient for the study of alpha-induced collective effects.
    Type of Medium: Online Resource
    ISSN: 0899-8221
    URL: Article
    DOI: 10.1063/1.859988
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1991
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  • 7
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    Enhancement of Tokamak Fusion Test Reactor performance by lithium conditioning
    AIP Publishing ; 1996
    In:  Physics of Plasmas Vol. 3, No. 5 ( 1996-05-01), p. 1892-1897
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 3, No. 5 ( 1996-05-01), p. 1892-1897
    Abstract: Wall conditioning in the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)] by injection of lithium pellets into the plasma has resulted in large improvements in deuterium–tritium fusion power production (up to 10.7 MW), the Lawson triple product (up to 1021 m−3 s keV), and energy confinement time (up to 330 ms). The maximum plasma current for access to high-performance supershots has been increased from 1.9 to 2.7 MA, leading to stable operation at plasma stored energy values greater than 5 MJ. The amount of lithium on the limiter and the effectiveness of its action are maximized through (1) distributing the Li over the limiter surface by injection of four Li pellets into Ohmic plasmas of increasing major and minor radius, and (2) injection of four Li pellets into the Ohmic phase of supershot discharges before neutral-beam heating is begun.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.871984
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1996
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  • 8
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    Ion cyclotron range of frequency heating on the Tokamak Fusion Test Reactor*
    AIP Publishing ; 1993
    In:  Physics of Fluids B: Plasma Physics Vol. 5, No. 7 ( 1993-07-01), p. 2437-2444
    Details
    In: Physics of Fluids B: Plasma Physics, AIP Publishing, Vol. 5, No. 7 ( 1993-07-01), p. 2437-2444
    Abstract: The complete ion cyclotron range of frequency (ICRF) heating system for the Tokamak Fusion Test Reactor (TFTR) [Fusion Tech. 21, 1324 (1992)], consisting of four antennas and six generators designed to deliver 12.5 MW to the TFTR plasma, has now been installed. Recently a series of experiments has been conducted to explore the effect of ICRF heating on the performance of low recycling, supershot plasmas in minority and nonresonant electron heating regimes. The addition of up to 7.4 MW of ICRF power to full size (R∼2.6 m, a∼0.95 m), helium-3 minority, deuterium supershots heated with up to 30 MW of deuterium neutral-beam injection has resulted in a significant increase in core electron temperature (ΔTe=3–4 keV). Simulations of equivalent deuterium–tritium (D–T) supershots predict that such ICRF heating should result in an increase in βα(0)∼30%. Direct electron heating has been observed and has been found to be in agreement with theory. The ICRF heating has also been coupled to neutral-beam heated plasmas fueled by frozen deuterium pellets. In addition ICRF heated energetic ion tails have been used to simulate fusion alpha particles in high-recycling plasmas. Up to 11.4 MW of ICRF heating has been coupled into a hydrogen minority, high-recycling helium plasma and the first observation of the toroidal Alfvén eigenmode (TAE) instability driven by the energetic proton tail has been made in this regime.
    Type of Medium: Online Resource
    ISSN: 0899-8221
    URL: Article
    DOI: 10.1063/1.860728
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1993
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  • 9
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    Enhanced performance of deuterium–tritium-fueled supershots using extensive lithium conditioning in the Tokamak Fusion Test Reactor
    AIP Publishing ; 1995
    In:  Physics of Plasmas Vol. 2, No. 11 ( 1995-11-01), p. 4252-4256
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 2, No. 11 ( 1995-11-01), p. 4252-4256
    Abstract: In the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)] a substantial improvement in fusion performance has been realized by combini ng the enhanced confinement due to tritium fueling with the enhanced confinement due to extensive conditioning of the limiter with lithium. This combination has resulted in not only significantly higher global energy confinement times than have previously been obtained in high current supershots, but also in the highest central ratio of thermonuclear fusion output power to input power observed to date.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.871050
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1995
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  • 10
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    Erratum: ‘‘Anomalous losses of deuterium–deuterium fusion products in the Tokamak Fusion Test Reactor’’ [Phys. Plasmas 1 , 1469 (1994)]
    AIP Publishing ; 1994
    In:  Physics of Plasmas Vol. 1, No. 9 ( 1994-09-01), p. 3138-3138
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 1, No. 9 ( 1994-09-01), p. 3138-3138
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.870506
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1994
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