Temporal evolution of the decaying spheromak in the CTCC-I experiment

Uyama, Tadashi; Honda, Yoshihide; Nagata, Masayoshi; Nishikawa, Masahiro; Ozaki, A.; Satomi, N.; Watanabe, Kenji

doi:10.1088/0029-5515/27/5/009

Cited by 26 publications

(15 citation statements)

References 27 publications

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“…A set of experiments are currently being proposed [24] for the RACE experiment at LLNL to address this question. One investigation is into the problem of whether the high mass debris can be electronically gated from the main D-T plasma ring by virtue of the lower velocity of the debris, as originally suggested by Uyama et al [25]. The prospects for this look encouraging.…”

Section: Conclusion: Advantages Uncertainties and Applications Of Ct ...mentioning

confidence: 99%

Deep penetration fuelling of reactor-grade tokamak plasmas with accelerated compact toroids

Perkins

Hammer

1988

Nucl. Fusion

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The application of a novel but practical technique for central fuelling of reactor-grade tokamak plasmas by compact torus (CT) plasma rings driven by a coaxial accelerator is examined. It is emphasized that this is the only advanced method of controlled and localized deep penetration fuelling which can be developed in the near term and which is already applied in a currently operating experimental system. Assessment of the dynamics of the CT as it traverses the plasma requires quantification of several interrelated constraints, including ring decay, tilting, field line reconnection, deceleration in the external field gradient and ring expansion/contraction. A self-consistent, radial zoning scheme is employed to model the transport of the CT to the desired plasma deposition point. It is demonstrated that the injection velocity requirements are usually dominated by CT tilting and reconnection with the external toroidal field of the tokamak. The implications for CT fuel transport around the reconnection point are then examined. The application of this formalism to the TIBER Engineering Test Reactor permits the parameterization of fuelling requirements in terms of injection velocity, fuel mass, penetration distance, CT dimensions and repetition rate. The hardware implications for near-term applications are also assessed.

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Section: Conclusion: Advantages Uncertainties and Applications Of Ct ...mentioning

confidence: 99%

Deep penetration fuelling of reactor-grade tokamak plasmas with accelerated compact toroids

Perkins

Hammer

1988

Nucl. Fusion

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“…MHD-driven flows have been observed over a wide range of scales from terrestrial experiments (coaxial gun accelerators [1,2], plasma thrusters [3], high-current arcs [4], Z-pinch formation [5], spheromak formation [6,7], and sustainment [8]) to extraterrestrial phenomenon (solar coronal mass ejections [9] and astrophysical jets [10]). …”

mentioning

confidence: 99%

Nonequilibrium Alfvénic Plasma Jets Associated with Spheromak Formation

Kumar

Bellan

2009

Phys. Rev. Lett.

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“…In CTX, the n = 2 mode appears to approximately saturate in size and continues to coherently rotate for the lifetime of the plasma [2,12] without a return of the magnetic equilibrium towards the minimum energy state. This coherent non-linear behaviour [46] is in contrast [45] to that observed on CTCC-I [15,16] or S-l [47], where the plasma undergoes 'stepwise instabilities' that relax the plasma towards the minimum energy state.…”

Section: Theorymentioning

confidence: 78%

“…The technical operation of CTX is similar to that of the Beta-II experiment at Livermore National Laboratory [14,1] and the CTCC-I experiment at Osaka University [15]. Primary differences include 1. long-pulse sustainment by helicity injection [9]; 2. use of mesh flux conserver [13]; 3. operation with filling gas to replace particle loss [2].…”

Section: Ctx Operationmentioning

confidence: 99%

“…In CTX the observations of the current density profiles and the resulting MHD internal kink modes [12] are consistent with relaxation towards the minimum energy state tending to drive currents near the separatrix. Previous experiments which inserted metal conductors down the geometric axis always saw current flowing in the conductor [38,[15][16][17]. However, some spheromak experiments with various limiters have shown unpublished evidence for current holes [39].…”

Section: Theoretical Backgroundmentioning

confidence: 99%

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Improvement of Sensor for Noncontact Capacitance/Voltage Measurement and Lifetime Measurement of Bare Silicon(100)

Sakai¹,

Kohno²,

Okada³

et al. 1997

Jpn. J. Appl. Phys.

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The paper presents experiments and analysis of energy confinement on the CTX spheromak. Compared to previous published results from 0.4 m radius flux conservers, in a 0.67 m radius mesh flux conserver (with the current density kept constant), the magnetic field increases while the plasma density is kept the same. However, the electron temperature does not rise, and hence (fi) yol drops. The plasma resistivity remains constant (the resistance drops as the size increases), and the energy confinement time stays the same. Plasma energy content results from spheromaks during sustainment by helicity injection are also presented and show confinement equivalent to that during the decay phase. Increased magnetic field in the same size experiment produces very little improvement in electron temperature and a decrease in confinement time. The resistive decay time is found to be empirically independent of the core electron temperature. It is, instead, proportional to the strength of the magnetic field at constant plasma density, while the ratio of magnetic field to decay time depends on plasma density, consistently with ionization breakdown at the edge of the spheromak dominating helicity dissipation. The possible causes of this observed confinement are examined separately in detailed quantitative and qualitative studies. Absolutely calibrated multichord bolometry shows that impurity radiation is not the cause of the low electron temperatures. The particle confinement time has increased with size, but does not show an increase with increasing magnetic field. At the lower (/3) vo) of the larger experiment, the particle replacement power cannot explain the unaccounted energy losses. Any important role of pressure driven modes in the CTX energy balance is shown to be inconsistent with the available CTX data. The possibility that rotating coherent current driven kink modes can seriously degrade energy confinement is evaluated and discounted owing to the lack of improvement when the modes are absent. The role of anomalous ion heating is examined, and the available data are presented. Finally, a hypothesis explaining these results is presented, suggestions for future work are made, and the results are summarized.

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Temporal evolution of the decaying spheromak in the CTCC-I experiment

Cited by 26 publications

References 27 publications

Deep penetration fuelling of reactor-grade tokamak plasmas with accelerated compact toroids

Deep penetration fuelling of reactor-grade tokamak plasmas with accelerated compact toroids

Nonequilibrium Alfvénic Plasma Jets Associated with Spheromak Formation

Improvement of Sensor for Noncontact Capacitance/Voltage Measurement and Lifetime Measurement of Bare Silicon(100)

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