Study of plasma meniscus and beam halo in negative ion sources using three dimension in real space and three dimension in velocity space particle in cell model

Nishioka, S.; Miyamoto, K.; Okuda, S.; Goto, Isao; Hatayama, A.; Fukano, Azusa

doi:10.1063/1.4854976

Cited by 18 publications

(12 citation statements)

References 8 publications

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“…This beam halo was considered to have large divergence angles in comparison with the beam core region, while the origin of the beam halo is unclear. Therefore, the mechanism of the formation of the beam halo is being studied experimentally [6] and theoretically [7]. Recently, detail particle-in-cell (PIC) simulations suggested that beam halo is formed by non-uniformity of ion current caused by difference on the extraction route of produced negative ions depending on the position of their production on a plasma grid (PG) [8][9].…”

mentioning

confidence: 99%

Determination of the meniscus shape of a negative ion beam from an experimentally obtained beam profile

Ichikawa

Kojima

Chitarin

et al. 2017

AIP Conference Proceedings

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mentioning

confidence: 99%

Determination of the meniscus shape of a negative ion beam from an experimentally obtained beam profile

Ichikawa

Kojima

Chitarin

et al. 2017

AIP Conference Proceedings

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“…The potential is constant or slowly varies in most of the volume inside the reservoir. Similar meniscus studies were also performed [15,25,26] but for fusion sources. The importance of the plasma screening effect on the NI extraction can be easily seen in figure 8, where the NI trajectories are represented for two cases, for the extraction of the source IS01.…”

Section: Plasma Screeningmentioning

confidence: 86%

Beam formation in CERNs cesiated surfaces and volume H⁻ion sources

2016

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At CERN, a high performance negative ion (NI) source is required for the 160 MeV H − linear accelerator named Linac4. The source should deliver 80 mA H − ion beams within an emittance of 0.25 mm·mrad. For this purpose two ion sources were developed: IS01 is based on the NI volume production and IS02 provides additional NI by surface production via H interaction on a cesiated Molybdenum plasma electrode. The development of negative ion sources for Linac4 is accompanied by modelling activities. ONIX code has been modified and adapted to investigate the transport of NI and electrons in the extraction region of the CERN negative ion sources. The simulated results from modeling of IS01 and IS02 extraction regions, which were obtained in 2012 during source commissioning, are presented and benchmarked with experimental measurements obtained after 2013. The formation of the plasma meniscus and the screening of the extraction field by the source plasma are discussed. The NI production is compared between two types of sources, the first one based on volume production only and the second one encompassing NI cesiated surface production. For the IS02 source, different states of conditioning were simulated by changing the NI emission flux from the plasma electrode and Cs + density in the bulk plasma region. The numerical results show that in low work function regime, with high NI surface emission rate of 3000 A m −2 and Cs-density of n Cs+ =3.8 × 10 16 m −3 , the total extracted NI current could reach~80 mA. At the less favorable Cscoverage, when the surface NI emission rate becomes significantly lower, namely 300 A m −2 with n Cs+ =3.3 × 10 15 m −3 , the total extracted NI current only reaches~20 mA. A good agreement between simulation and experimental results is observed in terms of extracted NI current for both extraction systems, including the case of reversed extraction potential that corresponds to positive (H + ) ion extraction.

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“…One of the most important factors that determines the beam focusing is the formation of a plasma meniscus, which is the boundary between the source plasma and the beam [21,22]. The meniscus is physically defined as the equipotential surface, where the quasi-neutrality is broken [23,24]. The meniscus plays a role of an electrostatic lens for the first stage of the beam acceleration.…”

Section: Introductionmentioning

confidence: 99%

Characterisation of negative ion beam focusing based on phase space structure

et al. 2020

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Negative ion beam focusing is a key element for advanced applications of negative ion beams such as accelerators for particle physics, compact accelerators for medical fields, and plasma experiments for nuclear fusion because complicated magnetic fields exist both inside of the source plasma and the grid system. In order to understand the beam focusing, phase space structure measurements for a single beamlet have been performed with a research-and-development negative ion source at the National Institute for Fusion Science. A complicated phase space structure is observed in the direction parallel to the filter magnetic field in the vicinity of the plasma grid, while a single-Gaussian beamlet structure is observed in the direction perpendicular to the filter field. Detailed analyses for the phase space structure of the single beamlet reveal that the complicated structure can be identified as a combination of three beam components with different beam axes. The shifts of each axis are also observed to depend on the ratio of the acceleration voltage for the extraction voltage, which may significantly degrade the beamlet focusing.

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Study of plasma meniscus and beam halo in negative ion sources using three dimension in real space and three dimension in velocity space particle in cell model

Cited by 18 publications

References 8 publications

Determination of the meniscus shape of a negative ion beam from an experimentally obtained beam profile

Determination of the meniscus shape of a negative ion beam from an experimentally obtained beam profile

Beam formation in CERNs cesiated surfaces and volume H⁻ion sources

Characterisation of negative ion beam focusing based on phase space structure

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Study of plasma meniscus and beam halo in negative ion sources using three dimension in real space and three dimension in velocity space particle in cell model

Cited by 18 publications

References 8 publications

Determination of the meniscus shape of a negative ion beam from an experimentally obtained beam profile

Determination of the meniscus shape of a negative ion beam from an experimentally obtained beam profile

Beam formation in CERNs cesiated surfaces and volume H−ion sources

Characterisation of negative ion beam focusing based on phase space structure

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Beam formation in CERNs cesiated surfaces and volume H⁻ion sources