Tracer-Encapsulated Solid Pellet (TESPEL) injection system for Wendelstein 7-X

Area of Science:

• Nuclear Fusion Science and Engineering
• Plasma Physics
• Stellarator Technology

Background:

• Impurity confinement in fusion plasmas is crucial for reactor performance.
• The Wendelstein 7-X stellarator utilizes an island divertor for impurity screening.
• Investigating core plasma transport mechanisms requires localized impurity injection.

Purpose of the Study:

• To report the detailed design of a novel Tracer-Encapsulated Solid Pellet (TESPEL) injection system.
• To enable the study of impurity transport mechanisms in the Wendelstein 7-X stellarator core plasma.
• To provide a tool for localized impurity release experiments.

Main Methods:

• Design and construction of a new TESPEL injection system.
• Integration of storage and injection units with guiding tubes and differential pumping stages.
• Utilizing light-gate and optical observation systems for tracer deposition localization.

Main Results:

• Successful design and current installation of the TESPEL injection system at Wendelstein 7-X.
• Laboratory tests demonstrated good performance of TESPELs after system realignment.
• The system is ready for investigating core plasma impurity transport.

Conclusions:

• The new TESPEL injection system is a key diagnostic for Wendelstein 7-X.
• This system will significantly advance the understanding of impurity transport in stellarator cores.
• Effective impurity control is essential for future fusion energy devices.