Enhanced surface production in H− ion sources by introducing a negatively biased secondary electrode

An, Younghwa; Jung, Bong Ki; Hwang, Y. S.

doi:10.1063/1.3273059

Cited by 11 publications

(8 citation statements)

References 10 publications

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“…153,154 The RF wavefrequency dependence of H À ion production and extraction in a DESY type ion source was also studied at this University. 155,156 The plasma density and temperature determined using a Langmuir probe are correlated to the extracted H À beam current at different frequencies.…”

Section: Volume Negative Ion Sources For Accelerator Applicationsmentioning

confidence: 99%

Negative hydrogen ion production mechanisms

Bacal

Wada

2015

Applied Physics Reviews

241

173

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International audienceNegative hydrogen/deuterium ions can be formed by processes occurring in the plasma volume and on surfaces facing the plasma. The principal mechanisms leading to the formation of these negative ions are dissociative electron attachment to ro-vibrationally excited hydrogen/deuterium molecules when the reaction takes place in the plasma volume, and the direct electron transfer from the low work function metal surface to the hydrogen/deuterium atoms when formation occurs on the surface. The existing theoretical models and reported experimental results on these two mechanisms are summarized. Performance of the negative hydrogen/deuterium ion sources that emerged from studies of these mechanisms is reviewed. Contemporary negative ion sources do not have negative ion production electrodes of original surface type sources but are operated with caesium with their structures nearly identical to volume production type sources. Reasons for enhanced negative ion current due to caesium addition to these sources are discussed. (31 pages, 265 refs

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Section: Volume Negative Ion Sources For Accelerator Applicationsmentioning

confidence: 99%

Negative hydrogen ion production mechanisms

Bacal

Wada

2015

Applied Physics Reviews

241

173

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“…The line-of-sight plasma volume was limited by the 9.5 mm diameter puller electrode aperture and the (6 mm / 8 mm diameter) collimator between the target and the plasma. The target materials used in this study are metals which are typically found in negative hydrogen ion sources as chamber materials (Al, Cu, SS) [8,9,10], filament materials (Ta) [7,11], plasma grid materials (Mo) [12] or so-called collar materials (SS, Mo) [13,14]. The effect of Al, Cu and SS wall materials and Ta covered walls on the volume production of negative hydrogen ions has been studied in [3,15,16].…”

Section: Measurement Setupmentioning

confidence: 99%

Photoelectron emission from metal surfaces induced by VUV-emission of filament driven hydrogen arc discharge plasma

Laulainen

Kalvas

Koivisto

et al. 2015

AIP Conference Proceedings

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Photoelectron emission measurements have been performed using a filament-driven multi-cusp arc discharge volume production H − ion source (LIISA). It has been found that photoelectron currents obtained with Al, Cu, Mo, Ta and stainless steel (SAE 304) are on the same order of magnitude. The photoelectron currents depend linearly on the discharge power. It is shown experimentally that photoelectron emission is significant only in the short wavelength range of hydrogen spectrum due to the energy dependence of the quantum efficiency. It is estimated from the measured data that the maximum photoelectron flux from plasma chamber walls is on the order of 1 A per kW of discharge power.

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“…Cusp magnetic field was introduced to increase the electron density in the discharge chamber [4]. Influence of RF wave frequency and surface material on H − ion production were examined [5,6]. We also found that the electron temperature could be easily increased by shortening the length of the discharge chamber [7].…”

Section: Introductionmentioning

confidence: 92%

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

et al. 2016

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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.

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Enhanced surface production in H− ion sources by introducing a negatively biased secondary electrode

Cited by 11 publications

References 10 publications

Negative hydrogen ion production mechanisms

Negative hydrogen ion production mechanisms

Photoelectron emission from metal surfaces induced by VUV-emission of filament driven hydrogen arc discharge plasma

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

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Enhanced surface production in H− ion sources by introducing a negatively biased secondary electrode

Cited by 11 publications

References 10 publications

Negative hydrogen ion production mechanisms

Negative hydrogen ion production mechanisms

Photoelectron emission from metal surfaces induced by VUV-emission of filament driven hydrogen arc discharge plasma

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

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