Graphite Sublimation Tests for Target Development for the Muon Collider/Neutrino Factory

Graphite sublimation tests have been conducted in a high-temperature oven, which is operated either in high vacuum or in an 1-atm cover gas of helium (or argon). Preliminary data of the sublimation rate of graphite foils at ~2400 K in vacuum are consistent with theoretical prediction. Additional tests of graphite rods (15 mm in diameter and 300 mm long) have been conducted in high vacuum and in cover gases of helium as well as argon. The sublimation mass loss rate at 2350 K is 1.7 mg/h for static argon cover gas (>1 atm) and 0.78 mg/h for static helium cover gas. These values of sublimation mass loss rate for cover gas cases are lower than that of 5.8 mg/h in high vacuum. This unique approach of using cover gas to reduce sublimation rate could allow a robust radiatively cooled graphite target for the Muon Collider/Neutrino Factory as proposed in the conceptual design study. In this paper, the results of graphite sublimation tests, including the test setup and test procedure, are presented and discussed