Laser-induced fluorescence velocimetry measurements obtained from the interior of a 6-kW Hall thruster using the Xe I 6s3=2 0 2 ! 6p3=2 2 transition at 823.4 nm (vacuum) and the Xe I 6s 0 1=2 0 1 ! 6p 0 3=2 2 transition at 834.9 nm (vacuum) are presented. The thruster is operated under seven conditions, with discharge voltages ranging from 150 to 600 V and anode mass flow rates ranging from 10 to 30 mg=s. Velocimetry results along the channel centerline show that the neutral propellant leaves

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... e anode at a bulk axial velocity of 100 m=s and accelerates to 300-400 m=s by the exit plane. The temperature of the neutrals starts out at 1000-1600 K near the anode but cools down to 500-800 K near the exit plane. The anode mass flow rate appears to have a bigger influence on the bulk velocity and temperature of the neutrals than the discharge voltage. Radial sweeps across the channel exit plane revealed the presence of near-wall boundary layers approximately a few millimeters thick. The experimental results are compared with MONACO and HPHall-2 simulation results. The comparison suggests that the neutral-flow acceleration is due to a combination of wall thermalization, hydrodynamic, and ionization effects.