A preliminary life test of a low-power DC arcjet anode was conducted using a 500-W-class laboratory-model arcjet. In order to overcome the anode deterioration, which is considered to be the most critical life-limiting issue for DC arcjet, a tungsten anode made of four coarse grains was constructed and compared with a conventional pure tungsten anode consisting of multiple fine grains of several tens of micrometer in diameter. After a continuous operation of 60-hours, both materials showed nearly the same amount of degradation as a result of so-called constrictor closure, however, cracks are found only along the grain boundaries. This grain embrittlement plays an important role in weakening the anode material under high temperature operation, and the anode degradation is expected to be suppressed by removing these grain boundaries from the tungsten anode, that is, by the anode monocrystalization.
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