Microparticle accelerator of unique design

A microparticle accelator of unique design, which produces high-velocity, micrometer-sized projectiles of any cohesive material, is described. In the source, an electrodynamic levitator, single particles are charged by ion bombardment in high vacuum. The vertical accelerator has four drift tubes, each initially at a high negative voltage. After injection of the projectile, each tube is grounded in turn at a time determined by the voltage and charge/mass ratio to give four acceleration stages with a total voltage equivalent to about 1.7 MV. The delay times may be set manually or controlled automatically by the particle's charge/mass ratio measured in the source by the operator just before ejection. At the entrance to the accelerator, the particle generates a signal that initiates the timing sequence. In the target chamber, detectors record the passage of the particle and provide information on charge, velocity, and position. Trajectories usually pass within a 1-mm-radius circle 1 m below the fourth drift tube. Velocities between 0.5 and 15 km/s have been attained with projectiles of various materials and shapes for cratering studies and calibration of micrometeoroid detectors. About 20 projectiles per day can be accelerated.