Residual gas analysis for long-pulse, advanced tokamak operation

Area of Science:

• Fusion energy research
• Plasma physics
• Diagnostic instrumentation

Background:

• Tore Supra tokamak requires advanced diagnostics for long-pulse operations.
• Monitoring neutral gas composition is crucial for understanding plasma behavior and optimizing performance.
• Residual Gas Analyzers (RGAs) offer a method for in-situ gas analysis.

Purpose of the Study:

• To implement and utilize a shielded Residual Gas Analyzer (RGA) system for real-time monitoring during Tore Supra plasma discharges.
• To assess the RGA's capability in monitoring the H(2)/D(2) isotopic ratio for particle balance studies.
• To evaluate the RGA's role in optimizing ion cyclotron resonance heating and assessing plasma-facing component integrity.

Main Methods:

• Deployment of a shielded RGA system in a pumping duct of the toroidal pumped limiter.
• Continuous monitoring of up to 15 masses simultaneously during long-pulse (up to 6 min) discharges.
• Comparison of RGA-measured H(2)/D(2) isotopic ratios with data from an energetic neutral particle analyzer.

Main Results:

• The diagnostic RGA successfully operated during plasma discharges, providing continuous monitoring.
• RGA measurements of the H(2)/D(2) isotopic ratio in exhaust gas correlated with plasma core measurements, enabling particle balance monitoring.
• RGA data on hydrocarbon pressures indicated proper operation of carbon-based plasma-facing components during long pulses (>4 min).
• Observed increases in H(2) pressure were linked to thermodesorption from overheated components.

Conclusions:

• The diagnostic RGA is a valuable tool for real-time monitoring of neutral gas composition in fusion devices.
• The RGA system aids in particle balance assessment, optimization of heating systems, and evaluation of plasma-facing component performance.
• The RGA contributes to understanding plasma-wall interactions and operational limits in long-pulse fusion experiments.