Near Exit Plane Velocity Field of a 200 W Hall Thruster
AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
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This work presents the near exit plane velocity field of the Busek Company BHT-200-X3 200 W Hall thruster at a single operating condition with a 250 V anode potential. The ionized propellent velocities were measured -- using laser induced fluorescence of the 5d472 - 6p352 excited state xenon ionic transition at 834.7 nm. Ion velocities were interrogated from the acceleration channel exit plane to a distance 107 mm from the exit plane 3.3 exit plane diameters. Both axial and radial velocity were measured. A nearly uniform axial velocity profile of approximately 13,800 - 500 ms 130 - 10 eV was measured at the thruster exit plane. The maximum axial velocity measured 107 mm from the exit plane was 16,800 ms 192 eV. The divergent flow exiting the thruster acceleration channel mixes downstream due to the coaxial thruster geometry. This mixing is made evident by regions of multiple radial and axial velocity components. These regions also exhibit broadened fluorescence line shapes which are indicative of collisions between the various velocity populations. The regions where this mixingcollisional behavior occurs correspond to the bright visible plume jet. A limited study at off-nominal conditions near a region of high insulator erosion indicates that the impinging ion energy on the center pole insulator is predictability changed by flow rates and anode potentials however, it also appears to vary significantly with magnetic field strength.
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