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Measurements of the energy distribution of electrons lost from the minimum B-field : the effect of instabilities and two-frequency heating (2020)

Izotov, I., Tarvainen, O., Skalyga, V., Mansfeld, D., Koivisto, H., Kronholm, R., Toivanen, V., & Mironov, V. (2020). Measurements of the energy distribution of electrons lost from the minimum B-field : the effect of instabilities and two-frequency heating. Review of Scientific Instruments, 91(1), Article 013502. https://doi.org/10.1063/1.5128322

JYU-tekijät tai -toimittajat

Koivisto, Hannu
Kronholm, Risto
Toivanen, Ville

Julkaisun tiedot

Julkaisun kaikki tekijät tai toimittajat: Izotov, I.; Tarvainen, O.; Skalyga, V.; Mansfeld, D.; Koivisto, H.; Kronholm, R.; Toivanen, V.; Mironov, V.

Lehti tai sarja: Review of Scientific Instruments

ISSN: 0034-6748

eISSN: 1089-7623

Julkaisuvuosi: 2020

Volyymi: 91

Lehden numero: 1

Artikkelinumero: 013502

Kustantaja: American Institute of Physics

Julkaisumaa: Yhdysvallat (USA)

Julkaisun kieli: englanti

DOI: https://doi.org/10.1063/1.5128322

Julkaisun avoin saatavuus: Ei avoin

Julkaisukanavan avoin saatavuus:

Julkaisu on rinnakkaistallennettu (JYX): https://jyx.jyu.fi/handle/123456789/67426

Lisätietoja: Invited paper, published as part of the Proceedings of the 18th International Conference on Ion Sources, Lanzhou, China, September 2019.

Tiivistelmä

Further progress in the development of electron cyclotron resonance (ECR) ion sources (ECRISs) requires deeper understanding of the underlying physics. One of the topics that remains obscure, though being crucial for the performance of the ECRIS, is the electron energy distribution (EED). A well-developed technique of measuring the EED of electrons escaping axially from the magnetically confined plasma of an ECRIS was used for the study of the EED in an unstable mode of plasma confinement, i.e., in the presence of kinetic instabilities. The experimental data were recorded for pulsed and CW discharges with a room-temperature 14 GHz ECRIS at the JYFL accelerator laboratory. The measurements were focused on observing differences between the EED escaping from stable and unstable plasmas. It was found that nonlinear phenomena alter the EED noticeably. The electron losses are enhanced in both unstable regimes, with two-frequency heating suppressing the instabilities. It has been shown earlier that two-frequency heating boosts the ECRIS performance presumably owing to the suppression of instabilities. We report the observed changes in EED introduced by the secondary frequency in different regimes, including an off-resonance condition, where the secondary frequency is lower than the minimum frequency satisfying the resonance condition for cold electrons at the magnetic field minimum. Finally, we suggest an experimental method of qualitative evaluation of the energy distribution of electrons confined in the magnetic trap using a method of measuring energy distribution of lost electrons during the plasma decay in pulsed operation of the ion source.

YSO-asiasanat: plasmafysiikka; hiukkaskiihdyttimet

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