Low-charge detector for the monitoring of hyper-velocity micron-sized dust particles

A new low-noise beam detector was developed, assembled and tested for the Heidelberg dust accelerator facility. The detector was used to determine in situ the charge, speed and mass of individual dust grains flying through a highly shielded metal cylinder with a length of 200 mm and integrated with a charge-sensitive amplifier Amptek model A250F/NF. Micron-sized latex and iron particles were fired at speeds between 5 and 50 km s-1. The detector characterizes dust particles with a primary charge of 1 fC, a speed of 20 km s-1 and a size of 0.1 mum with a signal-to-noise ratio of 6. The noise of the integrated detector system is typically 0.15 fC (950 electrons) in a bandwidth from 2 kHz to 10 MHz. The new detector allows the control and selection of particles either with a lower surface potential (low-conductive surfaces of polyaniline-coated polystyrene particles), or smaller grains with very small primary charges (sub-micron-sized grains with speeds above 10 km s-1).