Method for extracting volume produced negative ions

Bacal, M.; Bruneteau, J.; Devynck, P.

doi:10.1063/1.1139978

Cited by 75 publications

(43 citation statements)

References 8 publications

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“…The positive effect of biasing the plasma grid in negative ion sources is known since the 1980s and is used in many different ion sources [9][10][11][12][13] ; the general effect on the source performance has been reported also for the BATMAN (Bavarian Test Machine for Negative Ions) test facility in earlier publications 6,14 . Variation of the bias voltage changes the potential profile in the sheath in front of the plasma grid from an electron repelling case at low bias towards an electron attracting sheath at high bias.…”

Section: Introductionmentioning

confidence: 99%

Extraction of negative charges from an ion source: Transition from an electron repelling to an electron attracting plasma close to the extraction surface

Wimmer

Fantz

NNBI-Team³

2016

Journal of Applied Physics

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Large-scale sources for negative hydrogen ions, capable of delivering an extracted ion current of several ten amperes, are a key component of the neutral beam injection system of the upcoming ITER fusion device. Since the created heat load of the inevitably co-extracted electrons after magnetic separation from the extracted beam limits their tolerable amount, special care must be taken for the reduction of coextracted electrons -in particular in deuterium operation, where the larger amount of co-extracted electrons often limits the source performance. By biasing the plasma grid (PG, first grid of the extraction system) positively with respect to the source body the plasma sheath in front of the PG can be changed from an electron repelling towards an electron attracting sheath. In this way, the flux of charged particles onto the PG can be varied, thus changing the bias current and inverse to it the amount of co-extracted electrons. The PG bias affects also the flux of surface-produced H − towards the plasma volume as well as the plasma symmetry in front of the plasma grid, strongly influenced by an ⃗ E × ⃗ B drift. The influence of varying PG sheath potential profile on the plasma drift, the negative hydrogen ion density and the source performance at the prototype H − source is presented, comparing hydrogen and deuterium operation. The transition in the PG sheath profile takes place in both isotopes, with a minimum of co-extracted electrons formed in case of the electron attracting PG sheath. The co-extracted electron density in deuterium operation is higher than in hydrogen operation, which is accompanied by an increased plasma density in deuterium.

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Section: Introductionmentioning

confidence: 99%

Extraction of negative charges from an ion source: Transition from an electron repelling to an electron attracting plasma close to the extraction surface

Wimmer

Fantz

NNBI-Team³

2016

Journal of Applied Physics

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“…Experimental data shows that the absolute extracted ion current as well as the ratio of ion current to electron current can easily be changed by varying the bias voltage of the plasma grid and the strength of the magnetic filter field [2,5]. Varying bias voltage and filter strength has collective effects on the plasma, i.e.…”

Section: Introductionmentioning

confidence: 99%

Influence of Magnetic Fields and Biasing on the Plasma of a RF Driven Negative Ion Source

Wünderlich

Gutser

Fantz

2007

AIP Conference Proceedings

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Abstract. The development of a RF driven negative-ion source currently in progress at IPP Garching has made remarkable progresses during the last years. Optimization of the source strongly depends on the understanding of the physics of generation, destruction and extraction of negative ions. Numerical model calculations can provide important information needed for the improvement of this understanding. Since negative ions are mainly produced on Cesium covered surfaces of the source, and have a survival length in the range of a few cm, models for the region close to the plasma grid are of particular interest. The plasma in this region is affected by magnetic filter fields. Another important feature is biasing of the plasma grid which strongly influences the co-extracted electron current. The different effects are treated in two separate models. Their current status is presented: a particle-in-cell-code (PIC) is used to study the influence of filter fields and bias voltage on the plasma flow onto the plasma grid. The motion of the charged particles due to their own and externally applied electric field is simulated in a selfconsistent way. In the second code the survival probability of negative ions produced on the surface of the plasma grid is estimated using test-particles. The Monte-Carlo technique is applied for the treatment of inelastic and elastic collisions.

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“…that production of H − in atom conversion on the caesiated surface leads to H − ion accumulation near that surface in a potential well. Both 2D and 3D simulations showed also that the extracted negative ion current increases with the magnetic field in the extraction area [15][16][17] which was also experimentally observed [18]. Detailed studies of H − and D − ion production and extraction are in progress using both the trajectory-tracking and self-consistent models [12,19].…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Simulations of H^-Ions Extraction

Turek

2017

Acta Phys. Pol. A

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The 2D particle-in-cell method based model of a negative ion source is presented. The spatial distributions of electrostatic potential and plasma component densities are presented. Changes of negative ion distribution and potential as well as the extracted H − current with the plasma grid bias voltage are investigated. The presence of the potential well near the plasma grid surface that traps the negative ions is shown. Increase of the H − ions density inside the chamber with the negative bias voltage is demonstrated. Influence of the H − ion flux outgoing from the plasma grid on the extracted current was checked: increase by factor 2 is observed when the flux rises 4 times. Current-voltage characteristics of the ion source are presented, saturation of the curve is observed above 50 kV

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Method for extracting volume produced negative ions

Cited by 75 publications

References 8 publications

Extraction of negative charges from an ion source: Transition from an electron repelling to an electron attracting plasma close to the extraction surface

Extraction of negative charges from an ion source: Transition from an electron repelling to an electron attracting plasma close to the extraction surface

Influence of Magnetic Fields and Biasing on the Plasma of a RF Driven Negative Ion Source

Two-Dimensional Simulations of H^-Ions Extraction

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Method for extracting volume produced negative ions

Cited by 75 publications

References 8 publications

Extraction of negative charges from an ion source: Transition from an electron repelling to an electron attracting plasma close to the extraction surface

Extraction of negative charges from an ion source: Transition from an electron repelling to an electron attracting plasma close to the extraction surface

Influence of Magnetic Fields and Biasing on the Plasma of a RF Driven Negative Ion Source

Two-Dimensional Simulations of H-Ions Extraction

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Two-Dimensional Simulations of H^-Ions Extraction