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Author(s):
H. Bolt and A. Miyahara
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Title:
Runaway -Electron- Materials Interaction Studies
Date of publication:
Mar. 1990
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Key words:
runaway-electrons, disruptions, tokamaks, electron linear accelerator, plasma facing materials
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Abstract:
During the operation of magnetic fusion devices it has been frequently observed that runaway electrons can cause severe damage to plasma facing components. The energy of the runaway electrons could possibly reach several 100 MeV in a next generation device with an energy content in the plasma in the order of 100 MJ. In this study effects of high energy electron - materials interaction were determined by laboratory experiments using particle beam facilities, i. e. the Electron Linear Accelerator of the Institute of Scientific and Industrial Research of Osaka University and the 10 MW Neutral Beam Injection Test Stand of the National Institute for Fusion Science. The experiments and further analyses lead to a first assessment of the damage thresholds of plasma facing materials and components under runaway electron impact. It was found that metals (stainless steel , molybdenum, tungsten) showed grain growth , crack formation and/or melting already below the threshold for crack initiation on graphite (14-33 MJ/m^2). Strong erosion of carbon materials would occur above 100 MJ/m^2. Damage to metal coolant channels can occur already below an energy deposition of 100 MJ/m^2. The energy deposited in the metal coolant channels depends on the thickness of the plasma facing carbon material D, with the shielding efficiency S of carbon approximately as S~D^(1.15).
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