The imaging fast ion D-alpha diagnostic (IFIDA) on DIII-D

Area of Science:

• Plasma physics
• Fusion energy research
• Diagnostic instrumentation

Background:

• Energetic particle (EP) transport is crucial for fusion reactor performance.
• Accurate validation of EP transport models requires high-resolution diagnostics.
• Existing spectroscopic Fast Ion D-alpha (FIDA) diagnostics have limitations in spatial resolution.

Purpose of the Study:

• To introduce and validate the Imaging Fast Ion D-alpha (IFIDA) diagnostic.
• To assess the improvements in energetic particle profile reconstruction using IFIDA.
• To compare IFIDA performance against the standard spectroscopic FIDA diagnostic.

Main Methods:

• Development of an IFIDA diagnostic with high optical spatial resolution (≤2 mm).
• Acquisition of 2D FIDA signal images in the radial-poloidal plane.
• Utilizing a narrow passband filter (650-652 nm) for specific EP energy ranges (40-80 keV).
• Employing a beam modulation technique to isolate the active FIDA signal component.

Main Results:

• IFIDA provides 2D images of FIDA signals with high spatial resolution.
• Beam modulation enhances the accuracy of EP profile and gradient computation.
• Comparison with spectroscopic FIDA demonstrates improved EP profile reconstruction.

Conclusions:

• The IFIDA diagnostic is a significant advancement for validating EP transport models.
• IFIDA offers superior accuracy in EP profile reconstruction compared to standard methods.
• This diagnostic contributes to a better understanding of energetic particle behavior in fusion plasmas.