Direct Measurement of a Plasma Flow Velocity Using a Mach Probe in Hanbit Magnetic Mirror Device

A plasma flow velocity was measured by using a Much probe in the central cell of Hanbit magnetic mirror device. The Much probe was attached on the fast injection probe system, which can scan the central cell chamber of Hanbit device in the radial direction. The fast injection probe system also has an emissive probe so that the radial profile of the plasma potential is measured simultaneously. Therefore, the flow velocity measured from the Mach probe can be directly compared with E_r×B drift calculated from the measured plasma potential profile. The experimental results are analyzed by using existing theories of the Mach probe. The measured flow velocity shows about 3 km/s, and the flow direction and magnitude is approximately the same as the E_r×B drift velocity.