Multi-view fast-ion D-alpha spectroscopy diagnostic at ASDEX Upgrade

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Spectroscopy

Background:

• Fast ions play a crucial role in heating and sustaining fusion plasmas.
• Accurate diagnostics are essential for understanding and controlling fast-ion behavior in fusion devices.

Purpose of the Study:

• To introduce and validate a novel fast-ion D-alpha (FIDA) diagnostic system.
• To enable continuous, high-resolution analysis of fast-ion populations.
• To improve the understanding of fast-ion dynamics in fusion plasmas.

Main Methods:

• Installation of a new high-photon-throughput spectrometer and low-noise EM-CCD camera.
• Calibration using an integrating sphere for absolute intensities and a neon lamp for wavelength dependence.
• Identification and subtraction of perturbative spectral contributions (e.g., D2-molecular lines, Stark broadened emission).
• Utilizing radially distributed lines of sight and three independent viewing geometries for spatial and velocity-space information.

Main Results:

• Achieved 2 ms exposure time for FIDA measurements.
• Successfully minimized spectral interferences, allowing analysis of FIDA radiation at large Doppler shifts.
• Obtained radial information on fast ions.
• Enabled detailed investigation of fast-ion velocity distributions through tomographic reconstructions.

Conclusions:

• The novel FIDA diagnostic is a significant advancement for fast-ion research at ASDEX Upgrade.
• The system provides unprecedented detail on fast-ion behavior, crucial for fusion energy development.
• This diagnostic capability will enhance control and optimization of future fusion reactors.