Ambipolar potential formation and axial confinement in TMX

Correll, D.L.; Allen, Steven L.; Capser, T.A.; Clauser, John F.; Coakley, Peter; Coensgen, F.H.; Condit, W. C.; Cummins, W.F.; Davis, J.C.; Drake, R. P.; Foote, J. H.; Futch, A.H.; Goodman, R.K.; Grubb, D. P.; Hallock, G. A.; Hooper, E. B.; Hornady, R.S.; Hunt, A. L.; Karmendy, C. V.; Molvik, A.W.; Nexsen, W.E.; Pickles, W.L.; Poulsen, Peter Behrensdorff; Simonen, T.C.; Stallard, B. W.; Strand, O.T.

doi:10.1088/0029-5515/22/2/004

Cited by 41 publications

(17 citation statements)

References 7 publications

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“…As indicated in Fig. 1, in the earlier TMX standard tandem experiment [5][6][7] central cell electrostatic confining potential $ was generated by a high density end plug [8,9] where T" is the electron temperature and n and n are the plug and central cell plasma densities. Low energy ions that are required for end plug ion microstability were supplied by leakage of central cell ions.…”

Section: The Tandem Mirror Experiment-upgrade (Tmx-u) [3] Was Built Tmentioning

confidence: 99%

Initial TMX-U thermal-barrier experiments

Simonen¹,

Allen²,

Berzins³

et al. 1983

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Section: The Tandem Mirror Experiment-upgrade (Tmx-u) [3] Was Built Tmentioning

confidence: 99%

Initial TMX-U thermal-barrier experiments

Simonen¹,

Allen²,

Berzins³

et al. 1983

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“…The Abel transform and an equivalent matrix inversion technique assume cylindrical symmetry and are discussed thoroughly in other references [14,15]. Once E-(r) is known, the impurity density is simply E,(r) "i (r) = n e (r) Qi (r) " (III " 4) Radial profiles of the electron density and excitation rate (discussed in Appendix A) also must be known in order to calculate the ion density radial profile.…”

Section: Iii2 Brightnesses and Ion Densitiesmentioning

confidence: 99%

“…4. Approximately 40% of the total estimated power loss was actually treasured; the remainder included the contributions from over 40 other transitions which were scaled -67- The total radiated losses from the east end cell were approximately 0.6 kW and are therefore negligible; similar losses are assumed from the west end cell.…”

Section: V4 Radiated Power Losses From Tmxmentioning

confidence: 99%

“…The derivation of the expressions describing the axial confinement time of deuterium is thoroughly discussed elsewhere [4,36] and may be generalized for the case of impurities. In the TMX central cell, the plasma densities were such that reither a high density nor low density approximation of particle scattering and loss was sufficient to describe the observed axial confinement times.…”

Section: Vi2 Predicted Axial Confinement Time Of Impuritiesmentioning

confidence: 99%

“…Several journal articles have [2][3][4], or soon will be, published describing various aspects of TMX, so only a brief overview is given here. The first section discusses the physics and enhanced confinement times of TMX.…”

Section: Iil Introductionmentioning

confidence: 99%

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Study of impurities in the Tandem Mirror Experiment using extreme-ultraviolet spectroscopy

Strand¹

1982

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Impurities in the Tandem Mirror Experiment (TMX) have been studied using extreme ultraviolet spectroscopy. Three time-resolving absolutely-calibrated normal-incidence monochromators, one on each section of TMX, were used to study the impurity emissions in the wavelength range of 300 A -1600 A. The instruments on the east end cell and central cell were each capable of obtaining spatially-resolved profiles from 22 chords of the plasma simultaneously while the instrument on the west end cell monitored the central chord. The impurities identified in TMX were carbon, nitrogen, oxygen, and titanium. Emphasis was placed upon determining the impurity densities and radiated power losses of the central cell; results indicate that the impurity concentrations were low-less than 0.4% for each species-and that less than 10% of the total net trapped neutral beam power was lost to radiation. The use of titanium gettering on the central cell walls was observed to decrease the brightnesses of singly-and doubly-ionized carbon and oxygen in the central cell plasma. In the end cells, oxygen was the main impurity with a concentration of about 1.5% and was injected by the neutral beams; the other impurities had concentrations of about 0.5%. Radiated losses from the end cells were negligible.Evidence has been obtained which indicates that impurities in the central cell are subject to a radially outward transport. The density ratios of 0 V to 0 VI indicate a short (0.3-3 ms) central cell confinement time for 0 VI ions, even though calculations predict that axial confinement times should be longer than the TMX shot duration. Impurity puffing experiments performed in the central cell of TMX support this conclusion. Oxygen and neon puffed into the central cell during the TMX shot were observed to accumulate in the outer boundary of the plasma, while only a small fraction penetrated into the central regions. None of the injected impurity was observed in the end cell plasmas; instrumental sensitivity puts an upper limit of 0.03 on the ratio of injected impurity density in the end cells to that in the central cell. Oxygen puffed before the TMX shot was observed to decay from all regions of the plasma during the shot. These results provide an explanation for the observed low concentrations of impurities in the central cell of TMX.

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Plasma-Wall Interactions in Tandem Mirror Machines

Allen

1986

Physics of Plasma-Wall Interactions in Controlled Fusion

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Ambipolar potential formation and axial confinement in TMX

Cited by 41 publications

References 7 publications

Initial TMX-U thermal-barrier experiments

Initial TMX-U thermal-barrier experiments

Study of impurities in the Tandem Mirror Experiment using extreme-ultraviolet spectroscopy

Plasma-Wall Interactions in Tandem Mirror Machines

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