Limitation of the ECRIS performance by kinetic plasma instabilities (invited)

Tarvainen, O.; Kalvas, Taneli; Koivisto, H.; Komppula, J.; Kronholm, Risto; Laulainen, Janne; Izotov, I. V.; Mansfeld, D. A.; Skalyga, V. A.; Toivanen, V.; Machicoane, G.

doi:10.1063/1.4931716

Cited by 39 publications

(47 citation statements)

References 18 publications

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“…The field strength was chosen so that the B min /B ECR -ratio of 0.72 is below the threshold of kinetic plasma instabilities, typically appearing at a B min /B ECR -ratio of 0.75 at the (maximum) microwave power and gas pressure used in this study. 26 However, at certain tuner position / microwave frequency combinations the plasma exhibited "mode-hopping" as described further in Secs. III and IV.…”

Section: +mentioning

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: +mentioning

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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“…12,13 It has been proven that the kinetic instabilities of cyclotron type are the reason for the aforementioned periodic oscillation of the extracted beam current with a maximum amplitude of several tens of percent 14,15 and simultaneous powerful bursts of microwave and x-ray radiation. It has been shown that the cyclotron instabilities lead to significant electron losses and subsequent increase of the plasma potential perturbing the ion confinement 16 at temporal interval which is less than the production time 17 of high charge state ions. Therefore, the kinetic instabilities are especially detrimental for high charge state production as demonstrated in Refs.…”

Section: Introductionmentioning

confidence: 99%

Broadband microwave emission spectrum associated with kinetic instabilities in minimum-B ECR plasmas

et al. 2017

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Izotov, I.; Kalvas, Taneli; Koivisto, Hannu; Kronholm, Risto; Mansfeld, D.; Skalyga, V.; Tarvainen, Olli Izotov, I., Kalvas, T., Koivisto, H., Kronholm, R., Mansfeld, D., Skalyga, V., & Tarvainen, O. (2017). Broadband microwave emission spectrum associated with kinetic instabilities in minimum-B ECR plasmas. Physics of Plasmas, 24 (4) Plasmas of electron cyclotron resonance ion sources (ECRISs) are prone to kinetic instabilities due to the resonant heating mechanism resulting in anisotropic electron velocity distribution.Frequently observed periodic oscillations of extracted ion beam current in the case of high plasma heating power and/or strong magnetic field have been proven to be caused by cyclotrontype instabilities leading to a notable reduction and temporal variation of highly charged ion production. Thus, investigations of such instabilities and techniques for their suppression have become important topics in ECRIS research. The microwave emission caused by the instabilities contains information on the electron energy distribution and growth mechanism of the instability. The emission has been studied earlier in the frequency range of 8-14 GHz allowing us to deduce the probable excited mode. A more detailed study of the microwave emission spectrum of a minimum-B ECR plasma, sustained by 14 GHz microwave radiation, is presented in this work. It was found that the frequencies of the microwaves emitted by the plasma consist of several harmonics of the main band and extend from 6 GHz up to 25 GHz, being independent of the plasma parameters. Published by AIP Publishing.[http://dx

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“…Plasmas of minimum-B Electron Cyclotron Resonance Ion Sources (ECRIS) have been shown to be plagued by kinetic instabilities arising from the anisotropy of the electron velocity distribution [1]. The appearance of the instabilities limits the parameter space available for the optimization of the high charge state ion beam currents extracted from ECRIS [2]. A recent study with the 14.5 GHz PHOENIX ECRIS charge breeder has revealed that the injection of 133 Cs + or 85 Rb + beam can perturb the charge breeder oxygen plasma sufficiently to trigger (or sometimes suppress) kinetic instabilities [3].…”

Section: Introductionmentioning

confidence: 99%

The effect of plasma instabilities on the background impurities in charge breeder ECRIS

Tarvainen

Angot

Izotov

et al. 2018

AIP Conference Proceedings

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Limitation of the ECRIS performance by kinetic plasma instabilities (invited)

Cited by 39 publications

References 18 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

Broadband microwave emission spectrum associated with kinetic instabilities in minimum-B ECR plasmas

The effect of plasma instabilities on the background impurities in charge breeder ECRIS

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