Direct measurement of thrust induced by a magnetron sputtering source

The direct measurement of thrust imparted by a magnetron sputtering source operated in argon is performed using a pendulum thrust balance immersed in vacuum, where various target materials are tested. The imparted thrust is clearly changed by the target material, while the ion density, which is expected to be mostly the argon ions, is unchanged. The maximum thrust-to-power ratio of 10-12 mN/kW is obtained for a copper target, which has a maximum sputtering yield in the target materials tested here. It is shown that the plasma pressure force is much smaller than the detected thrust, demonstrating the thrust generation via the material ejection by the sputtering process.