Development of spectrally selective imaging system for negative hydrogen ion source

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Techniques

Background:

• Hydrogen negative ion sources are crucial for fusion energy.
• Understanding Hα emission distribution is key to optimizing ion source performance.
• Previous diagnostic methods lacked spatial resolution in the extraction region.

Purpose of the Study:

• To develop and implement a spectrally selective imaging system.
• To visualize the two-dimensional distribution of Hα emissions.
• To investigate the impact of beam extraction on Hα emissions.

Main Methods:

• A diagnostic system comprising an aspherical lens, optical filters, fiber image conduit, and CCD detector was utilized.
• The system was installed on a 1/3-scaled hydrogen negative ion source.
• The line of sight was positioned 11 mm from the plasma grid (PG) surface, with a 35 mm viewing angle coverage.

Main Results:

• The system successfully obtained a clear two-dimensional distribution of Hα emissions.
• Hα emissions were observed up to 20 mm from the PG surface.
• A significant reduction in Hα emission was observed in the extraction region near the PG surface due to beam extraction.

Conclusions:

• The developed imaging system effectively visualizes Hα emission distribution.
• Beam extraction causes a widespread reduction in Hα emissions near the plasma grid.
• This diagnostic capability aids in understanding and improving negative ion source performance.