Faraday-cup-type lost fast ion detector on Heliotron J.

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Particle Diagnostics

Background:

• Understanding fast ion behavior is crucial for magnetic confinement fusion.
• Magnetohydrodynamic (MHD) instabilities can affect plasma confinement and performance.
• Neutral beam injection (NBI) is a key heating method in fusion devices.

Purpose of the Study:

• To design and implement a probe for studying fast ion interactions with MHD instabilities.
• To measure specific ranges of fast ion energies and pitch angles in Heliotron J.
• To investigate the role of energetic particles in driving plasma instabilities.

Main Methods:

• A Faraday-cup type lost-fast ion probe (FLIP) was designed and installed.
• The FLIP was used to measure co-going fast ions with energies from 1.7-42.5 keV (proton).
• Measurements covered pitch angles from 90° to 140°, focusing on NBI-injected ions.

Main Results:

• The FLIP successfully detected re-entering passing ions.
• Trapped lost-fast ions, driven by energetic particle modes, were measured.
• The probe demonstrated capability in NBI-heated plasmas within Heliotron J.

Conclusions:

• The developed FLIP is effective for diagnosing fast ions in fusion plasmas.
• The measurements provide insights into fast ion-driven energetic particle modes.
• This diagnostic tool contributes to understanding plasma-MHD instability interactions.