The effect of plasma electrode collar structure on the performance of the JYFL 14GHz electron cyclotron resonance ion source

Toivanen, V.; Tarvainen, O.; Komppula, J.; Koivisto, H.

doi:10.1016/j.nima.2013.05.153

Cited by 7 publications

(5 citation statements)

References 28 publications

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“…To our knowledge this is the first systematic study of the CTE, although experiments in which the cavity dimensions were changed either by moving the plasma electrode 20 or the biased disc 21 or by installing sputter samples 22 or so-called collars of varying dimensions around the extraction aperture 23 have been reported. Those experiments, however, were either not focused on the cavity tuning effect or required exposing the ion source to atmospheric pressure between different data points, thus, complicating the interpretation of the results.…”

Section: Introductionmentioning

confidence: 99%

The effect of cavity tuning on oxygen beam currents of an A-ECR type 14 GHz electron cyclotron resonance ion source

Tarvainen

Orpana

Kronholm

et al. 2016

Review of Scientific Instruments

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The effect of cavity tuning on oxygen beam currents of an A-ECR type 14 GHz electron cyclotron resonance ion source Tarvainen, Olli; Orpana, J.; Kronholm, Risto; Kalvas, Taneli; Laulainen, Janne; Koivisto, Hannu; Izotov, I.; Skalyga, V.; Toivanen, V.Tarvainen, O., Orpana, J., Kronholm, R., Kalvas, T., Laulainen, J., Koivisto, H., . . . Toivanen, V. (2016) The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupolea) Rev. Sci. Instrum. 85, 02A740 (2014) The efficiency of the microwave-plasma coupling plays a significant role in the production of highly charged ion beams with electron cyclotron resonance ion sources (ECRISs). The coupling properties are affected by the mechanical design of the ion source plasma chamber and microwave launching system, as well as damping of the microwave electric field by the plasma. Several experiments attempting to optimize the microwave-plasma coupling characteristics by fine-tuning the frequency of the injected microwaves have been conducted with varying degrees of success. The inherent difficulty in interpretation of the frequency tuning results is that the effects of microwave coupling system and the cavity behavior of the plasma chamber cannot be separated. A preferable approach to study the effect of the cavity properties of the plasma chamber on extracted beam currents is to adjust the cavity dimensions. were recorded at various tuner positions and frequencies in the range of 14.00-14.15 GHz. It was observed that the tuner position affects the beam currents of high charge state ions up to several tens of percent. In particular, it was found that at some tuner position / frequency combinations the plasma exhibited "mode-hopping" between two operating regimes. The results improve the understanding of the role of plasma chamber cavity properties on ECRIS performances. Published by AIP Publishing.[http://dx

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Section: Introductionmentioning

confidence: 99%

The effect of cavity tuning on oxygen beam currents of an A-ECR type 14 GHz electron cyclotron resonance ion source

Tarvainen

Orpana

Kronholm

et al. 2016

Review of Scientific Instruments

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“…One option to realize this local control could be to install an additional compact coil close to the extraction mirror. Studies with plasma electrode collar structures 38,39 have shown that inside an ECRIS plasma chamber there exists an amount of space around the extraction aperture which can be utilized without negatively impacting the source performance. A compact coil structure fixed in this location would be well positioned to provide a localized and adjustable modification to the extraction mirror field to control the electron losses.…”

Section: Discussionmentioning

confidence: 99%

Influence of axial mirror ratios on the kinetic instability threshold in electron cyclotron resonance ion source plasma

et al. 2022

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Electron Cyclotron Resonance (ECR) ion source plasmas are prone to kinetic instabilities. The onset of the instabilities manifests as emission of microwaves, bursts of electrons expelled from the plasma volume, and the collapse of the extracted highly charged ion (HCI) currents. Consequently, the instabilities limit the HCI performance of ECR ion sources by limiting the parameter space available for ion source optimization. Previous studies have shown that the transition from stable to unstable plasma regime is strongly influenced by the magnetic field structure, especially the minimum field value inside the magnetic trap (B min ). This work focuses to study the role of the magnetic confinement on the onset of the kinetic instabilities by probing the influence of the injection and extraction mirror field variation on the instability threshold. The experiments have been performed with a room-temperature 14.5 GHz ECR ion source with an axially movable middle coil that provides flexible control over the axial field profile and especially the B min , which was used to quantify the variation in the instability threshold. The experimental results show that variation of the extraction field B ext , which defines the weakest magnetic mirror, correlates systematically with the variation of the instability threshold; decreasing the B ext allows higher threshold B min . The result demonstrates the importance of electron confinement and losses on the plasma stability. The connection between the weakest mirror field and the onset of instabilities is discussed taking into account the variation of magnetic field gradient and resonance plasma volume.

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“…scitation.org/journal/rsi field topology, derived from plasma diagnostics experiments, has been recently reported by Toivanen 52 discussing experiments using a cylindrical structure around the extraction aperture extruding toward the ECRIS plasma with the "collar" exhibiting very little evidence of interaction with plasma particles up to a length of 30-40 mm. This indicates that the volume around the collar could be occupied with an additional coil modifying the magnetic field strength at the extraction mirror without affecting the field near the resonance zone, which would be an inevitable consequence of changing the current of the main extraction coil.…”

Section: Articlementioning

confidence: 95%

“…Such a concept is envisioned to improve the extracted beam currents by reducing the plasma confinement only locally, thus directing the distribution of the escaping particle flux toward the extraction and passing through the "extraction channel," as witnessed in the collar experiment. 52 Controlling the ion losses is seen as a promising method to improve the performances of ECR ion sources as the existence of the well-known afterglow effect, recent OES experiments, 53 and the correlation between the confinement time and the extracted beam current 23 all imply that the extracted currents in cw operation mode could be limited by the electrostatic ion confinement and particle losses rather than the rate of their production by electron impact ionization.…”

Section: Articlementioning

confidence: 99%

Plasma diagnostic tools for ECR ion sources—What can we learn from these experiments for the next generation sources

Tarvainen

Kalvas

Koivisto

et al. 2019

Review of Scientific Instruments

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The effect of plasma electrode collar structure on the performance of the JYFL 14GHz electron cyclotron resonance ion source

Cited by 7 publications

References 28 publications

The effect of cavity tuning on oxygen beam currents of an A-ECR type 14 GHz electron cyclotron resonance ion source

The effect of cavity tuning on oxygen beam currents of an A-ECR type 14 GHz electron cyclotron resonance ion source

Influence of axial mirror ratios on the kinetic instability threshold in electron cyclotron resonance ion source plasma

Plasma diagnostic tools for ECR ion sources—What can we learn from these experiments for the next generation sources

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