Small Linear Accelerators for Charged Microparticles

Researching cosmic dust requires terrestrial facilities for accelerating analogues of different sizes and masses. To address the area of very lightweight particles, electrostatic accelerators like Van-de-Graaf accelerators or Linear Accelerators (LINACs) have proven adequate. A new variable frequency switched 6-stage LINAC of 120 kilovolts (kV) potential was built at the Institute of Space Systems, University of Stuttgart. It utilizes negative voltages, no storage-capacitors, isometric drift tubes, one semiconductor-based high-voltage switch per stage and there is no voltage drop during acceleration. The electronics limit the particle rate at 33 particles per second. By setting a target speed window, the control software and circuitry autonomously chooses the right amount of acceleration-stages to meet that requirement, if possible. Micron-sized iron particles were accelerated successfully achieving speed increase rates of up to 3-times the pre-LINAC speed and a total speed of up to 1300 meters per second (m/s). This platform provides a new tool for dust sensor calibration, impact physics and material surface processing due to its ability to bring particles of different charge-to-mass ratios to a defined target speed. To further increase the speed, mass and ratio of accelerated microparticles, a new setup is under construction. It will utilize 20 stages with up to 25 kV potential each, resulting in a total acceleration potential of 500 kV. The theoretically achievable particle rate for particles between 500 m/s and 2 km/s will be 1000 particles per second.