0000000000331591
AUTHOR
B. S. Bhaskar
Diagnostic techniques of minimum-B ECR ion source plasma instabilities.
The performance of a minimum-B Electron Cyclotron Resonance Ion Source (ECRIS) is traditionally quantified by measuring the beam current and quality of the extracted ion beams of different charge state ions. The stability of the extracted ion beam currents has drawn more attention recently as the technology is pushing its limits toward higher ion charge states and beam intensities. The stability of the extracted beam is often compromised by plasma instabilities manifesting themselves as rapid oscillations of the beam currents in millisecond scale. This paper focuses on practical aspects of diagnostics techniques of the instabilities, showcases examples of instability-related diagnostics sig…
Influence of axial mirror ratios on the kinetic instability threshold in electron cyclotron resonance ion source plasma
International audience; 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 (Bmin). This work focuses to study the role o…
Quasi-periodical kinetic instabilities in minimum-B confined plasma
We present the results of an experimental investigation of quasi-periodical kinetic instabilities exhibited by magnetically confined electron cyclotron resonance heated plasmas. The instabilities were detected by measuring plasma microwave emission, electron losses, and wall bremsstrahlung. The instabilities were found to be grouped into fast sequences of periodic plasma losses, separated by ∼100 µs between the bursts, followed by 1–10 ms quiescent periods before the next event. Increasing the plasma energy content by adjusting the plasma heating parameters, in particular the magnetic field strength, makes the instabilities more chaotic in the time domain. Statistical analysis reveals that …