Double einzel lens extraction for the JYFL 14 GHz ECR ion source designed with IBSimu

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

doi:10.1088/1748-0221/8/05/p05003

Cited by 25 publications

(23 citation statements)

References 40 publications

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“…The energy resolution of the setup provided by the set of collimators and the distance between them is estimated to be better than 500 eV. The energy dependent transmission efficiency of the electrons leaking from the ion source through the beamline sections and the bending magnet was calculated assuming that the electron distribution at the extraction aperture is independent of energy and has a KV-distribution [11]. The first two collimators sample a fraction of the beam, which is directly proportional to the energy of the electron beam as long as the beam completely illuminates the collimators (electron energy <100 MeV).…”

Section: Methodsmentioning

confidence: 99%

Measurements of the energy distribution of electrons lost from the minimum B-field—The effect of instabilities and two-frequency heating

Izotov

Tarvainen

Skalyga

et al. 2020

Review of Scientific Instruments

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Further progress in the development of ECR ion sources (ECRIS) 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 EED in 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 a stable and unstable plasmas. It was found that nonlinear phenomena alter the EED noticeably. The electron losses are enhanced in both unstable regime and 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.

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Section: Methodsmentioning

confidence: 99%

Measurements of the energy distribution of electrons lost from the minimum B-field—The effect of instabilities and two-frequency heating

Izotov

Tarvainen

Skalyga

et al. 2020

Review of Scientific Instruments

View full text Add to dashboard Cite

show abstract

“…The data were taken by sweeping the solenoid currents (equal current in both coils) across the transition from stable to unstable operation regime at various microwave powers and neutral gas pressures with 10 kV source potential. The voltages of the focusing einzel lenses of the extraction system 24 were kept constant during the magnetic field sweep at each power/pressure combination while the beamline optics, i.e., two solenoids and the analyzing magnet, were optimized for all data points. The voltage of the biased disc at the injection was set to a constant value of −150 V.…”

Section: Methodsmentioning

confidence: 99%

Limitations of electron cyclotron resonance ion source performances set by kinetic plasma instabilities

Tarvainen

Laulainen

Komppula

et al. 2015

Review of Scientific Instruments

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Limitations of electron cyclotron resonance ion source performances set by kinetic plasma instabilities Tarvainen, Olli; Laulainen, Janne; Komppula, Jani; Kronholm, Risto; Kalvas, Taneli; Koivisto, Hannu; Izotov, I.; Mansfeld, D.; Skalyga, V.Tarvainen, O., Laulainen, J., Komppula, J., Kronholm, R., Kalvas, T., Koivisto, H., . . . Skalyga, V. (2015). Limitations of electron cyclotron resonance ion source performances set by kinetic plasma instabilities. Electron cyclotron resonance ion source (ECRIS) plasmas are prone to kinetic instabilities due to anisotropy of the electron energy distribution function stemming from the resonant nature of the electron heating process. Electron cyclotron plasma instabilities are related to non-linear interaction between plasma waves and energetic electrons resulting to strong microwave emission and a burst of energetic electrons escaping the plasma, and explain the periodic oscillations of the extracted beam currents observed in several laboratories. It is demonstrated with a minimum-B 14 GHz ECRIS operating on helium, oxygen, and argon plasmas that kinetic instabilities restrict the parameter space available for the optimization of high charge state ion currents. The most critical parameter in terms of plasma stability is the strength of the solenoid magnetic field. It is demonstrated that due to the instabilities the optimum B min -field in single frequency heating mode is often ≤ 0.8B ECR , which is the value suggested by the semiempirical scaling laws guiding the design of modern ECRISs. It is argued that the effect can be attributed not only to the absolute magnitude of the magnetic field but also to the variation of the average magnetic field gradient on the resonance surface. C 2015 AIP Publishing LLC.[http://dx

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“…However, the results obtained with the scanner have been correlated with the beam transmission efficiency at JYFL (see e.g. [22]) and it has been shown experimentally that Allison scanners and pepper pot emittance meters provide consistent results [23]. The first section of the low energy beam transport downstream from the JYFL 14 GHz ECRIS and the locations of the diagnostics is presented in Fig.…”

Section: Experimental Setup and Proceduresmentioning

confidence: 91%

“…After the collar experiments the extraction has been replaced with a new system providing improved performance [22].…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

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

Toivanen

Tarvainen

Komppula

et al. 2013

Nuclear Instruments and Methods in Physics Research Section A:

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Double einzel lens extraction for the JYFL 14 GHz ECR ion source designed with IBSimu

Cited by 25 publications

References 40 publications

Measurements of the energy distribution of electrons lost from the minimum B-field—The effect of instabilities and two-frequency heating

Measurements of the energy distribution of electrons lost from the minimum B-field—The effect of instabilities and two-frequency heating

Limitations of electron cyclotron resonance ion source performances set by kinetic plasma instabilities

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

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