Indirect Charged Particle Detection: Concepts and a Classroom Demonstration

Abstract

We describe the principles of macroscopic charged particle detection in the laboratory and their connections to concepts taught in the physics classroom. Electrostatic dust accelerator systems, capable of launching charged dust grains at hypervelocities (1–100 km/s), are a critical tool for space exploration. Dust grains in space typically have large speeds relative to the probes or satellites that encounter them. Development and testing of instruments that look for dust in space therefore depends critically on the availability of fast, well-characterized dust grains in the laboratory. One challenge for the experimentalist is to precisely measure the speed and mass of laboratory dust particles without disturbing them. Detection systems currently in use exploit the well-known effect of image charge to register the passage of dust grains without changing their speed or mass. We describe the principles of image charge detection and provide a simple classroom demonstration of the technique using soup cans and pith balls.