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  • 1
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    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
    Online Resource
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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
    detail.hit.zdb_id: 648023-8
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  • 3
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    Online Resource
    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
    detail.hit.zdb_id: 1472746-8
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  • 4
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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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  • 5
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    Online Resource
    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
    detail.hit.zdb_id: 2130787-8
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  • 6
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    Online Resource
    Microwave proton source development for a high-current linac injector (invited)a)
    AIP Publishing ; 1996
    In:  Review of Scientific Instruments Vol. 67, No. 3 ( 1996-03-01), p. 1296-1301
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 67, No. 3 ( 1996-03-01), p. 1296-1301
    Abstract: Powerful cw proton linear accelerators (100 mA at 0.5–1.0 GeV) are being proposed for spallation neutron-source applications. A 75-keV, 110-mA dc proton injector using a microwave ion source is being tested for these applications. It has achieved 80-keV, 110-mA hydrogen-ion-beam operation. Video and dc beam-current toroid diagnostics are operational, and an EPICS control system is also operational on the 75-keV injector. A technical base development program has also been carried out on a 50-keV injector obtained from Chalk River Laboratories, and it includes low-energy beam transport studies, ion source lifetime tests, and proton-fraction enhancement studies. Technical base results and the present status of the 75-keV injector will be presented.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/1.1146701
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1996
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 7
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    Online Resource
    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
    detail.hit.zdb_id: 2130787-8
    detail.hit.zdb_id: 648023-8
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  • 8
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    The temperatures of ejecta transporting in vacuum and gases
    AIP Publishing ; 2022
    In:  Journal of Applied Physics Vol. 131, No. 19 ( 2022-05-21)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 131, No. 19 ( 2022-05-21)
    Abstract: In this work, we measure continuous thermal radiance from evolving clouds of liquid metal fragments ejected into vacuum, nonreactive, and reactive gas. We implement a model for the thermalization of the ejecta and gas and use this to constrain the absolute temperature of the ejecta cloud. This model enables further analyses of ejecta thermal behavior under a variety of conditions.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/5.0087212
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 9
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    Explosive-induced shock damage in copper and recompression of the damaged region
    AIP Publishing ; 2016
    In:  Journal of Applied Physics Vol. 120, No. 8 ( 2016-08-28)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 120, No. 8 ( 2016-08-28)
    Abstract: We have studied the dynamic spall process for copper samples in contact with detonating low-performance explosives. When a triangular shaped shock wave from detonation moves through a sample and reflects from the free surface, tension develops immediately, one or more damaged layers can form, and a spall scab can separate from the sample and move ahead of the remaining target material. For dynamic experiments, we used time-resolved velocimetry and x-ray radiography. Soft-recovered samples were analyzed using optical imaging and microscopy. Computer simulations were used to guide experiment design. We observe that for some target thicknesses the spall scab continues to run ahead of the rest of the sample, but for thinner samples, the detonation product gases accelerate the sample enough for it to impact the spall scab several microseconds or more after the initial damage formation. Our data also show signatures in the form of a late-time reshock in the time-resolved data, which support this computational prediction. A primary goal of this research was to study the wave interactions and damage processes for explosives-loaded copper and to look for evidence of this postulated recompression event. We found both experimentally and computationally that we could tailor the magnitude of the initial and recompression shocks by varying the explosive drive and the copper sample thickness; thin samples had a large recompression after spall, whereas thick samples did not recompress at all. Samples that did not recompress had spall scabs that completely separated from the sample, whereas samples with recompression remained intact. This suggests that the hypothesized recompression process closes voids in the damage layer or otherwise halts the spall formation process. This is a somewhat surprising and, in some ways controversial, result, and the one that warrants further research in the shock compression community.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.4962013
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2016
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 10
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    Piezoelectric characterization of ejecta from shocked tin surfaces
    AIP Publishing ; 2005
    In:  Journal of Applied Physics Vol. 98, No. 11 ( 2005-12-01)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 98, No. 11 ( 2005-12-01)
    Abstract: Using piezoelectric diagnostics, we have measured densities and velocities of ejected particulate as well as “free-surface velocities” of bulk tin targets shock loaded with high explosive. The targets had finely grooved, machined finishes ranging from 10 to 250μin. Two types of piezoelectric sensor (“piezopins”), lithium niobate and lead zirconate titanate, were compared for durability and repeatability; in addition, some piezopins were “shielded” with foam and metal foil in order to mitigate premature failure of the pins in high ejecta regimes. These experiments address questions about ejecta production at a given shock pressure as a function of surface finish; piezopin results are compared with those from complementary diagnostics such as x-ray radiography and time-resolved optical transmission techniques. The mass ejection shows a marked dependence on groove characteristics and cannot be described by a groove defect theory alone.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.2132521
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2005
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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