Spatially resolved diagnostics for optimization of large ion beam sources.

Area of Science:

• Plasma Physics
• Accelerator Technology
• Fusion Energy

Background:

• Giant negative ion sources are crucial for neutral beam injectors, utilizing multi-beamlet configurations to achieve high negative ion currents.
• Uniform current extraction across all beamlets is essential for efficient beam source operation and perveance matching.

Purpose of the Study:

• This review investigates the relationship between the vertical beam intensity profile and plasma properties within the extraction region.
• The study focuses on the impact of increasing cesium injection on these correlations.

Main Methods:

• Utilizes a comprehensive suite of source diagnostics for high spatial resolution analysis of beam features.
• Examines plasma properties such as plasma density and electron density in conjunction with beam intensity profiles.

Main Results:

• Comparable plasma density and beamlet currents are observed in the central regions of vertical beam segments.
• Beam and electron density decrease at the edges of central segments, potentially maintaining a fixed electron-to-ion ratio.
• Increased cesium injection effectively compensates for vertical drifts at the source bottom, reducing electron presence and enhancing negative ion yield.

Conclusions:

• Combined analysis of diagnostics is vital for understanding non-uniformities in negative ion beams.
• Cesium injection is a key parameter for optimizing negative ion current extraction and mitigating electron contamination.
• The findings provide insights for improving the operational efficiency of giant negative ion sources.