Chevron beam dump for ITER edge Thomson scattering system.

Area of Science:

• Fusion energy research
• Plasma physics
• Optical engineering

Background:

• The ITER project requires robust systems for plasma diagnostics.
• The edge Thomson scattering system needs a durable beam dump to handle intense laser and plasma interactions.
• Existing beam dump designs face challenges with thermal, electromagnetic loads, and space constraints.

Purpose of the Study:

• To design and analyze the lifetime of a beam dump for the ITER edge Thomson scattering system.
• To optimize the beam dump structure for enhanced durability under operational stresses.
• To assess the impact of design modifications on performance and longevity.

Main Methods:

• Estimation of beam dump lifetime using multi-pulse laser-induced damage thresholds.
• Structural optimization using a chevron design with bent sheets to mitigate energy concentration.
• Analysis of thermal loads (nuclear heating, plasma radiation) and electromagnetic loads during disruptions.
• Evaluation of stray light and absorbed laser energy profiles, assuming a specific bi-directional reflection distribution function (BRDF).

Main Results:

• The chevron beam dump design effectively avoids concentrated laser pulse energy.
• The optimized structure is projected to withstand expected thermal and electromagnetic loads throughout the ITER project.
• The analysis identified critical issues for lifetime assessment, including BRDF variations due to plasma-derived particle interactions.

Conclusions:

• The chevron beam dump design offers a viable solution for the ITER edge Thomson scattering system.
• Further research is needed to resolve uncertainties related to BRDF variations for precise lifetime predictions.
• The design provides a reasonable margin for peak beam profile factors, ensuring operational reliability.