High-speed rotor for microparticle impact studies

We report on the design, construction, and testing of a high-speed rotor intended for use in hypervelocity microparticle impact studies. The rotor is based on a four-wing design to provide rotational stability and includes flat "paddle" impact surfaces of ∼0.5 cm2 at the tips of each wing. The profile of each wing minimizes the variation in tensile forces at any given rotational speed. The rotor was machined using titanium (grade 5) and operated in high vacuum using magnetically levitated bearings. Initial experiments were run at several speeds up to 100 000 rpm (revolutions per minute), corresponding to a tip speed of 670 m/s. Elongation at the wing tips as a function of rotational speed was measured with a precision of several micrometers using a focused diode laser and found to agree with an elastic modulus of 1.16 GPa for the rotor material. Applications to microparticle impact experiments are discussed.