Calibration improvements expand filterscope diagnostic use.

Area of Science:

• Plasma Physics
• Spectroscopy
• Fusion Energy Research

Background:

• The DIII-D tokamak utilizes a filterscope diagnostic with photomultiplier tubes to measure plasma light emission.
• Previous cross-calibration attempts between the filterscope and other spectroscopic diagnostics were unsuccessful, limiting data accuracy.

Purpose of the Study:

• To significantly upgrade the filterscope diagnostic system for improved accuracy and expanded measurement capabilities.
• To achieve successful cross-calibration with other high-resolution spectroscopic diagnostics.

Main Methods:

• Implemented a dichroic mirror to split light at 550 nm, enabling simultaneous measurement of Dα and other emissions (Dβ, Dγ, W-I, C-III).
• Optimized optical components and calibration techniques to reduce signal error by up to 10% in certain channels.
• Performed cross-calibration measurements with two independent high-resolution spectroscopic diagnostics.

Main Results:

• Achieved excellent agreement in cross-calibration measurements between the upgraded filterscope and other diagnostics for the first time.
• Reduced signal error in specific channels by up to 10% compared to previous methods.
• Successfully enabled measurement of Dα emission without compromising measurements of other visible light emissions.

Conclusions:

• The upgraded filterscope system provides highly accurate plasma emission measurements, crucial for fusion energy research.
• Expanded capabilities include detailed analysis of divertor detachment, emission profiles, edge-localized mode behavior, and plasma-wall interactions.
• Enables direct validation of boundary plasma simulation calculations, advancing theoretical and experimental fusion research.