Gerhard Göbel, Thomas Wriedt, and Klaus Bauckhage
Periodic Drag Force and Particle Size Measurement in a Double Ring Electrodynamic Trap
submited for publication in Rev. Sci. Instrum. (1997).
Abstract:
A simple method to determine the size of a spherical particle in an
electrodynamic trap from its dynamic behaviour is introduced.
In contrary to the common usage of electrodynamic traps, gravity is not
compensated completely. The resulting
oscillatory trajectory is phase shifted with respect to the driving ac field
of the trap. A light barrier setup is sufficient to determine the phase lag.
An analytical solution is available in closed form to yield the particle
diameter from the measured phase lag. Numerical trajectory simulations
support this solution. Our method is independent of the optical properties
of the particle. Only the viscosity of the surrounding
gas and the particle mass density have to be known for data evaluation.
