| Paper | Title | Page |
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| TUPTS025 | Arc and Convertor Current Transient Studies for Multi-cusp Cesiated Surface Conversion H− Source at Lansce | 1983 |
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| The Multi-cusp Cesiated Surface Conversion H− Ion Source at the Los Alamos Neutron Science Center (LANSCE) has provided beam at ~14 mA, 120 Hz, and 10% D.F. for many years of neutron science research. Recently, random high current transients were discovered in the arc current used to ionize hydrogen in the LANSCE H− ion source, and in the convertor current used to convert protons to H− ions. Most have no effect, but more severe transients can cripple beam output. Hypothesized causes are related to cesiation effects, plasma potential changes, tungsten filament vaporation/sputtering, or from the pulsed power system. A dedicated study was recently done on the LANSCE H− Ion source test stand to determine the cause of these transients. Current understanding indicates that the more severe transients come from a combination of cesiation effects and plasma potential changes. The status of these current transient studies on the LANSCE H− ion source will be discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS025 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| TUPTS051 | Recent Beam Commissioning of LEAF at IMP | 2043 |
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| LEAF (Low Energy intense-highly-charged ion Accelerator Facility) has been successfully commissioned with several beams in CW regime, covering the M/Q from 2 to 7, such as H2+, He2+, C4+, O4+, He+, Kr13+, N2+ et al. This paper presents recent beam commissioning results. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS051 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| TUPTS095 | Global Model of Multi-Chamber Negative Hydrogen Ion Sources with Updated Hydrogen Plasma Chemistry | 2144 |
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Funding: This work was performed under the auspices of the Department of Energy, Office of Basic Energy Sciences Award #DE-SC0009585. Global models of plasma discharges are used to calculate volume averaged number densities and temperatures of plasma components. The wall fluxes are estimated based on heuristic expressions that "patch" together analytic and semi-analytic solutions covering from low-pressure to high-pressure regimes. Due to the nature of the wall fluxes estimation, the global models are limited to single chamber designs. We present the extension of the Global Enhanced Vibrational Kinetic Model (GEVKM) * for the multi-chamber design with the updated hydrogen plasma chemistry **. The extended GEVKM consists of separate global models for macroscopic parameters of all species in each chamber coupled through interface boundary conditions. We compare our model with fluid simulation results for a plasma composition and species temperatures in the negative hydrogen ion source developed at IPP Garching. * Averkin S.N. et al, IEEE Trans. Plasma Sci., Vol. 43, N. 6, pp. 1926-1943, 2015. ** Yang W. et al, Phys. Plasmas, 25, 113509, 2018. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS095 | |
| About • | paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| TUPTS096 | Fluid Models of Inductively Coupled Plasma Sources for Negative Hydrogen Ion Sources | 2147 |
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Funding: This work was performed under the auspices of the Department of Energy, Office of Basic Energy Sciences Award #DE-SC0009585. Negative hydrogen ion sources are widely used to produce neutron beams via spallation both for neutron science in its own right, and as neutron sources for fusion devices. Numerical modeling is a useful tool for trying to optimize negative hydrogen ion sources. However there are significant numerical and computational challenges that have to be overcome, including code performance and resolution of separation of time scales between ion and electron motions. One method is to utilize fluid models to simulate inductively coupled ion sources (ICPs). We have been developing algorithms to simulate negative hydrogen production in high-power, external-antenna ICP sources. We present simulation results using the USim*,** framework to model plasma chemistry that produces negative hydrogen, and model the effects of electron temperature on overall production rates. The numerical plasma chemistry models include processes of ionization, dissociation, recombination, as well as reactive dissociation of vibrationally resolved states and de-excitation of atomic hydrogen. We benchmark our plasma chemistry model results using plasma parameters relevant to experiments being carried out at the D-Pace Ion Source Test Facility. We have also been developing fluid-based drift/diffusion models for multi-component plasmas, such as those in negative hydrogen sources. These simulation results demonstrate enhancement of the effective diffusion rates in plasmas that contain both electrons and negative ions. * J. Loverich and A. Hakim, J. Fusion Sci., 29(6), 2010. ** J. Loverich et al., AIAA, Vol. 4012, 2011. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS096 | |
| About • | paper received ※ 19 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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