Fundamental studies on the Cs dynamics under ion source conditions.

Area of Science:

• Plasma Physics
• Surface Science
• Ion Source Technology

Background:

• Negative hydrogen ion sources are crucial for fusion energy and industrial applications.
• Their performance is critically dependent on caesium (Cs) dynamics and surface interactions.
• Understanding these interactions is key to optimizing ion source efficiency.

Purpose of the Study:

• To investigate the influence of caesium on plasma parameters in hydrogen (H2) and deuterium (D2) plasmas.
• To elucidate the role of caesium in negative ion generation mechanisms within surface conversion sources.
• To analyze the effects of caesium coating on vessel surfaces and plasma volume.

Main Methods:

• Utilizing a flexible laboratory setup for fundamental investigations in vacuum and plasma environments.
• Systematic studies on H2 and D2 plasmas with varying ion source parameters.
• In-situ analysis of plasma characteristics and surface interactions under caesium influence.

Main Results:

• Bulk plasma parameters, including electron density (ne) and electron temperature (Te), remain unaffected by relevant caesium concentrations.
• No significant isotopic differences were observed in H2 and D2 plasmas concerning bulk plasma parameters.
• Caesium coating on vessel surfaces leads to substantial hydrogen atom gettering from the plasma volume.
• A decrease in electron density (ne) near sample surfaces was observed, attributed to negative ion formation.

Conclusions:

• Caesium primarily influences negative ion generation through surface interactions rather than bulk plasma modification.
• Surface gettering of hydrogen atoms by caesium is a significant factor affecting negative ion density.
• Optimizing caesium coverage on surfaces is critical for enhancing negative ion yields in surface conversion sources.