Long pulse, high power operation of the ELISE test facility

Wünderlich, D.; Kraus, Werner; Fröschle, M.; Riedl, R.; Fantz, U.; Heinemann, B.

doi:10.1063/1.4995723

Cited by 10 publications

(7 citation statements)

References 28 publications

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“…One reason for this is the pronounced increase in the co-extracted electrons during the pulses [15,19]. Additionally, due to technical limitations [27] the PF power could not be increased to its maximum: about 57 kW/driver were possible instead of 90 kW. A group of results can be seen with j ex ≈16 mA cm −2 ; these have been obtained with P RF = 40 kW/driver and U ex =10 kV.…”

Section: Initial Caesium Conditioning In D 2 and The Obtained Resultsmentioning

confidence: 99%

Initial caesium conditioning in deuterium of the ELISE negative ion source

Wünderlich

Riedl

Fantz

et al. 2018

Plasma Phys. Control. Fusion

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Negative ion sources used for neutral beam injection in fusion experiments are based on the surface production of H − or D − on caesiated low work function surfaces. The amount of coextracted electrons is much higher in deuterium than in hydrogen and their temporal increase is stronger pronounced. Thus, the transition from a caesium free source by conditioning the source with caesium usually is done in hydrogen. Since for the future application, e.g. in the later operational phases of the international fusion experiment ITER, a direct start-up of the neutral beam heating system in deuterium may be desirable, the test facility ELISE was used for testing initial caesium conditioning in deuterium. This paper describes the conditioning procedure and compares the obtained source performance with results achieved in deuterium after initial conditioning in hydrogen. A comparable general conditioning status can be obtained, i.e. comparable negative ion currents can be extracted for identical source parameters.

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Section: Initial Caesium Conditioning In D 2 and The Obtained Resultsmentioning

confidence: 99%

Initial caesium conditioning in deuterium of the ELISE negative ion source

Wünderlich

Riedl

Fantz

et al. 2018

Plasma Phys. Control. Fusion

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“…(1) The arc-filament discharge using Cs, as in the ion source operating in the Large Helical Device (LHD) [130] and JT-60U in Japan [131] and (2) The RF driven negative ion source using Cs, as in the ion source planned for ITER [132,133].…”

Section: Lessons Obtained From Ion Source Development For Fusionmentioning

confidence: 99%

“…Research and development of negative ion based neutral beam heating systems is directed towards long pulse operation of large, ITER size sources with deuterium [24]. Simonin et al [4] and Fantz et al [2] describe the research and development efforts dedicated in Europe to the NBI for the tokamak DEMO.…”

Section: Introductionmentioning

confidence: 99%

Negative ion source operation with deuterium

Bacal

Wada

2020

Plasma Sources Sci. Technol.

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When the working gas of a negative ion source is changed from hydrogen to its isotope, deuterium, an ‘isotope effect’ is observed; namely, several plasma characteristics such as the electron energy distribution, the atomic fraction and the spectra of rovibrationally excited molecules change. The understanding of the effect becomes more important, as research and development aiming at ITER power level operation is being challenged with feeding deuterium to the ion sources. As a historical review of the effort to develop hydrogen/deuterium negative ion sources, several types of negative ion sources designed for the neutral beam plasma heating are described: double charge exchange sources, volume sources and surface-plasma sources. The early results with volume sources operated with and without cesium are introduced. The characteristics of the source charged with deuterium are compared to those of the source charged with hydrogen. The isotope effect did not appear pronounced as the negative ion density was measured in a small source but became more pronounced when the plasma source size was enlarged and the discharge power density was increased to higher values. Surface plasma sources were optimized for deuterium operation but could not achieve the same performance as a source operated with hydrogen at the same power and pressure. The lower velocity of negative deuterium ions leaving the low work function surface seemed to limit the production efficiency. Fundamental processes causing these differences in negative ion source operation are summarized. After explaining the current status of negative ion source research and development, the acquired knowledge is utilized to the development of large negative ion sources for nuclear fusion research and to the development of compact negative ion sources for neutron source applications.

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“…In long pulses, however, the RF power had to be reduced due to the increasing currents of coextracted electrons. This was more pronounced in deuterium, such that in 2015 only 60 A/m 2 could be extracted in a one hour pulse 3,4 . In this paper the progress which has been achieved in the last operational period in deuterium is described.…”

Section: Introductionmentioning

confidence: 97%

Deuterium results at the negative ion source test facility ELISE

Kraus

Wünderlich

Fantz

et al. 2018

Review of Scientific Instruments

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The ITER neutral beam system will be equipped with large RF driven negative ion sources, with a cross section of 0.9 m x 1.9 m, which have to deliver extracted Dion beams of 57 A at 1 MeV for one hour. On the ELISE test facility a source of half of this size is being operational since 2013. Goal of this experiment is to demonstrate a high operational reliability and to achieve the extracted current densities and beam properties required for ITER. Technical improvements of the source design and the RF system were necessary to provide reliable operation in steady state with an RF power of up to 300 kW. While in short pulses the required D-current density has almost been reached, the performance in long pulses is determined in particular in Deuterium by inhomogeneous and unstable currents of coextracted electrons. By refined caesium evaporation and distribution procedures, and reduction and symmetrization of the electron currents considerable progress has been made and up to 190 A/m 2 D -, corresponding to 66 % of the value required for ITER, have been extracted for 45 minutes.

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Long pulse, high power operation of the ELISE test facility

Cited by 10 publications

References 28 publications

Initial caesium conditioning in deuterium of the ELISE negative ion source

Initial caesium conditioning in deuterium of the ELISE negative ion source

Negative ion source operation with deuterium

Deuterium results at the negative ion source test facility ELISE

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