Proton Simulation of Irradiation-Induced Creep

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Abstract
An apparatus was developed that utilizes light ions to simulate the effect of a fusion reactor first wall environment on the creep properties of metals and alloys. The creep apparatus includes a wire specimen stressed in the torsional mode. Rotation or strain is measured by an optically coupled photocell tracking system. Temperature control of the specimen is obtained by varying the temperature of flowing helium passing perpendicularly across the specimen. The initial study involved bombarding a 20% cold-worked AISI Type 316 stainless-steel specimen at 400°C with 14.8-MeV protons at a beam intensity of ~10 µA/cm2 or a displacement rate of ~3.4 × 10−7 dpa/s. The accelerator was operated intermittently to accumulate 130 h of beam time and a total dose of ∼0.2 dpa. Strain rates on the order of 5 × 10−4% shear strain per hour were observed during irradiation, whereas negligible strain rates were observed when the accelerator was turned off. On a dpa basis, proton-induced irradiation creep rates were approxima...