Linearized spectrum correlation analysis for thermal helium beam diagnostics

Area of Science:

• Plasma physics
• Fusion energy research
• Diagnostic techniques

Background:

• Thermal Helium Beam (THB) diagnostics are crucial for understanding plasma behavior in fusion devices.
• Traditional methods relying on line ratios can be susceptible to noise and low signal-to-noise ratios.
• Accurate measurement of plasma parameters like electron density and temperature is essential for reactor control and performance.

Purpose of the Study:

• To develop a new correlation analysis technique for THB diagnostics.
• To improve the accuracy and robustness of plasma parameter measurements under challenging conditions.
• To enable high-resolution measurements of electron density and temperature fluctuations.

Main Methods:

• Applied arithmetic operations to all available He I lines to construct new time series.
• Utilized cross-correlation and ensemble averaging to remove uncorrelated noise.
• Validated the technique using synthetic data and experimental data from ASDEX Upgrade tokamak.

Main Results:

• Demonstrated the capability to derive power spectral densities of electron density and temperature.
• Successfully measured plasma parameter fluctuations even under low-photon-count conditions.
• Resolved electron density and temperature fluctuations up to 90 kHz in a high-power reactor scenario.

Conclusions:

• The proposed correlation analysis technique offers a significant advancement in THB diagnostics.
• This method enhances the reliability of plasma parameter measurements, particularly in noisy or low-light environments.
• The technique's successful application at ASDEX Upgrade validates its potential for future fusion reactor diagnostics.