Development of a novel radio-frequency negative hydrogen ion source in conically converging configuration

Jung, Bokyung; Dang, Jeong-Jeung; An, Younghwa; Chung, Kyoung−Jae; Hwang, Y.S.

doi:10.1063/1.4830424

Cited by 6 publications

(3 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the ion source group at Seoul National University (SNU) in Korea, a lot of research effort has been made towards the development of a volume production H − ion source based on radio-frequency (RF) transformer-coupled plasma (TCP) for long lifetime continuous wave (CW) operation [2][3][4][5][6]. Recently, we reported that the electron temperature in the driver region could be increased by just reducing the effective plasma size [3].…”

Section: Introductionmentioning

confidence: 99%

“…In spite of a lot of theoretical and experimental researches on this subject [8][9][10][11], the exact mechanism of magnetic filtering is still not fully understood. By adopting this conventional technique, we have tried to reduce the electron temperature at low pressure by strengthening the magnetic filter field near the extraction region [4,5]. Although we found some interesting features for the effect of filter field strength [5], the conventional technique has turned out to be not enough to reduce the electron temperature in the extraction region operating at the low pressure regime.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Enhancement of negative hydrogen ion production at low pressure by controlling the electron kinetics property with transverse magnetic field

Kim¹,

Cho²,

Dang³

et al. 2016

Plasma Sources Sci. Technol.

View full text Add to dashboard Cite

In a volume production H − ion source, independent control of electron energy distribution between the driver region and the extraction region is crucial for the efficient production of H − ions due to its unique volume production mechanism. However, at the low pressure regime compatible to ITER operation, it is difficult to control electron energy distribution separately because the nonlocal property dominates the electron kinetics. In this work, we suggest a new method to control the locality of electron kinetics. In this method, an additional pair of permanent magnets is introduced in the vicinity of the skin layer, differently from the conventional method in which the magnetic filter field was strengthened in the extraction region. This magnetic field shortens the energy relaxation length and changes the electron kinetics from nonlocal to local even for low pressure discharges. In this paper, we show that the locality of electron kinetics can be effectively controlled by the additional magnetic field near the skin layer by measuring the electron temperature profile along the center of the discharge chamber as well as by comparing electron energy probability function shapes for different strengths of magnetic field. Using this new method, we demonstrate that control of locality of electron kinetics can greatly enhance the production of H − ions in the extraction region by measuring H − ion beam current extracted from the plasma source.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhancement of negative hydrogen ion production at low pressure by controlling the electron kinetics property with transverse magnetic field

Kim¹,

Cho²,

Dang³

et al. 2016

Plasma Sources Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…We also found that the electron temperature could be easily increased by shortening the length of the discharge chamber [7]. However, the overall increase of electron temperature failed to filter high energy electrons near the extraction hole efficiently [8]. Optimization of filter field strength depending on operating conditions were carried out to resolve this problem [9].…”

Section: Introductionmentioning

confidence: 97%

Kinetics of electrons and neutral particles in radio-frequency transformer coupled plasma H⁻ion source at Seoul National University

et al. 2016

View full text Add to dashboard Cite

In volume production H − ion sources, control of electron temperature is essential due to its close correlation with the generation of vibrationally-excited hydrogen molecules in the driver region as well as the generation of H − ions by dissociative attachment in the extraction region. In the ion source group at Seoul National University (SNU) in Korea, a lot of research effort has been made to the development of a volume production H − ion source based on radio-frequency (RF) transformercoupled plasma (TCP) for long lifetime continuous wave (CW) operation. It has a spiral RF antenna located outside the discharge chamber to generate a plasma with high electron temperature in the driver region and employs a magnetic filter field to prevent high energy electrons from being transported to the extraction region. In this paper, we present the recent progress on understanding of the underlying physics of the RF TCP H − ion source at SNU. Special attention is paid to the characterization of electron kinetics regime for controlling electron energy distribution and the influence of relaxation of neutral particles during the transport across the magnetic filter region. Effect of the degree of dissociation on the production of H − ions is also discussed.Hence, the E-V reaction is more efficient than the e-V reaction to excite hydrogen molecules to higher vibrational states in spite of its higher threshold energy. For example, the rate of E-V reactions is 4-5 orders of magnitude higher than that of e-V reaction for an excitation reaction from u = 0 to u = 7, as depicted in figure 1(a). The second step is a production of H − ions by DA reaction of the highly vibrationally-excited molecules generated from the previous step with low energy electrons. In this step, the electron temperature must be kept low because the cross section for DA reaction depends greatly on the energy of electrons interacting with vibrationally-excited molecules (see figure 1(b)). Also, low electron temperature has a benefit in minimizing the destruction of H − ions by collisional detachment by electrons.

show abstract

Global model analysis of negative ion generation in low-pressure inductively coupled hydrogen plasmas with bi-Maxwellian electron energy distributions

et al. 2015

View full text Add to dashboard Cite

A global model was developed to investigate the densities of negative ions and the other species in a low-pressure inductively coupled hydrogen plasma with a bi-Maxwellian electron energy distribution. Compared to a Maxwellian plasma, bi-Maxwellian plasmas have higher populations of low-energy electrons and highly vibrationally excited hydrogen molecules that are generated efficiently by high-energy electrons. This leads to a higher reaction rate of the dissociative electron attachment responsible for negative ion production. The model indicated that the bi-Maxwellian electron energy distribution at low pressures is favorable for the creation of negative ions. In addition, the electron temperature, electron density, and negative ion density calculated using the model were compared with the experimental data. In the low-pressure regime, the model results of the biMaxwellian electron energy distributions agreed well quantitatively with the experimental measurements, unlike those of the assumed Maxwellian electron energy distributions that had discrepancies. V C 2015 AIP Publishing LLC. [http://dx.

show abstract

Development of a novel radio-frequency negative hydrogen ion source in conically converging configuration

Cited by 6 publications

References 8 publications

Enhancement of negative hydrogen ion production at low pressure by controlling the electron kinetics property with transverse magnetic field

Enhancement of negative hydrogen ion production at low pressure by controlling the electron kinetics property with transverse magnetic field

Kinetics of electrons and neutral particles in radio-frequency transformer coupled plasma H⁻ion source at Seoul National University

Global model analysis of negative ion generation in low-pressure inductively coupled hydrogen plasmas with bi-Maxwellian electron energy distributions

Contact Info

Product

Resources

About

Development of a novel radio-frequency negative hydrogen ion source in conically converging configuration

Cited by 6 publications

References 8 publications

Enhancement of negative hydrogen ion production at low pressure by controlling the electron kinetics property with transverse magnetic field

Enhancement of negative hydrogen ion production at low pressure by controlling the electron kinetics property with transverse magnetic field

Kinetics of electrons and neutral particles in radio-frequency transformer coupled plasma H−ion source at Seoul National University

Global model analysis of negative ion generation in low-pressure inductively coupled hydrogen plasmas with bi-Maxwellian electron energy distributions

Contact Info

Product

Resources

About

Kinetics of electrons and neutral particles in radio-frequency transformer coupled plasma H⁻ion source at Seoul National University