Electrostatic Plasma-Confinement Experiments in a Tandem Mirror System

Coensgen, F.H.; Anderson, C. A.; Casper, T. A.; Clauser, John F.; Condit, W. C.; Correll, D.L.; Cummins, W.F.; Davis, J.C.; Drake, R. P.; Foote, J. H.; Futch, A.H.; Goodman, R.K.; Grubb, D. P.; Hallock, G. A.; Hornady, R.S.; Hunt, A. L.; Logan, B.G.; Munger, Réjean; Nexsen, W.E.; Simonen, T.C.; Slaughter, D.R.; Stallard, B. W.; Strand, O.T.

doi:10.1103/physrevlett.44.1132

Cited by 106 publications

(85 citation statements)

References 3 publications

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“…The main result is that TMX established electrostatic confining potentials which improved the central cell confinement. Up to a factor of 9 enhancement over the case without electrostatic confinement was observed for deuterium, although factors of 3 to 7 were more typical [3]. This corresponds to a 150-300 volt potential well depth between the end cells and the central cell.…”

Section: Ii4 Major Results From Tmxmentioning

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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Section: Ii4 Major Results From Tmxmentioning

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%

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

Strand¹

1982

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“…[7][8][9][10] The neutral gas due to the shine-through beam recycling, which can significantly enhance the charge exchange loss of the fast ion population, must be promptly removed from the system. It is conceptually straightforward to reduce the shine-through beam recycling by either (i) decreasing the fast particle recycling coefficient at the beam-exposed surface or (ii) minimizing (or delaying) the backstreaming of the recycled gas to the confinement vessel.…”

Section: Introductionmentioning

confidence: 99%

Neutral beam dump with cathodic arc titanium gettering

Smirnov

Krivenko

Murakhtin

et al. 2011

Review of Scientific Instruments

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An incomplete neutral beam capture can degrade the plasma performance in neutral beam driven plasma machines. The beam dumps mitigating the shine-through beam recycling must entrap and retain large particle loads while maintaining the beam-exposed surfaces clean of the residual impurities. The cathodic arc gettering, which provides high evaporation rate coupled with a fast time response, is a powerful and versatile technique for depositing clean getter films in vacuum. A compact neutral beam dump utilizing the titanium arc gettering was developed for a field-reversed configuration plasma sustained by 1 MW, 20-40 keV neutral hydrogen beams. The titanium evaporator features a new improved design. The beam dump is capable of handling large pulsed gas loads, has a high sorption capacity, and is robust and reliable. With the beam particle flux density of 5 × 10(17) H∕(cm(2) s) sustained for 3-10 ms, the beam recycling coefficient, defined as twice the ratio of the hydrogen molecular flux leaving the beam dump to the incident flux of high-energy neutral atoms, is ∼0.7. The use of the beam dump allows us to significantly reduce the recycling of the shine-through neutral beam as well as to improve the vacuum conditions in the machine.

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“…Earlier tandem mirrors [7][8][9][10][11] commonly provided MHD stability with minimum-B end cells which unfortunately introduced neoclassical radial transport. Now it is recognized that there are many other ways to provide axisymmetric MHD stability [12].…”

Section: Introductionmentioning

confidence: 99%

Prospects for an axisymmetric advanced fuel tandem mirror

Fowler

Moir²,

Simonen

2016

AIP Conference Proceedings

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Abstract. We describe a new axisymmetric tandem mirror concept which incorporates advances in physics understanding, recent experimental results and developing technologies. The tandem mirror concept consists of two small high magnetic field axisymmetric mirrors at the ends a solenoidal central cell which axially confines a high beta fusion plasma. High energy neutral beam Injection and high frequency electron cyclotron heating power are applied to the end cells which operate at higher density and temperature to provide both magnetic mirror as well as electrostatic axial plasma confinement of the ignited central cell plasma. Designs fueled with DT and, cat-DD are considered indicating a wide design space warranting further analysis as well as experimental investigations.

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Electrostatic Plasma-Confinement Experiments in a Tandem Mirror System

Cited by 106 publications

References 3 publications

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

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

Neutral beam dump with cathodic arc titanium gettering

Prospects for an axisymmetric advanced fuel tandem mirror

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