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Dust Accelerator Laboratory

The Cosmic Dust Research group at the IRS operates the dust accelerator located at the Max-Planck-Institute for Nuclear Physics in Heidelberg. This facility allows the acceleration of electrically conductive grains to speeds between 1 and 100 km/s. Single grains can be selected. Also, the impact ejecta can be studied. The facility operates with a chemical clean vacuum (no oil diffusion pumps) below 10-4 Pa (10-6 mbar) allowing a careful chemical analysis of the target and/or projectile materials.

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Examples of particle data

The following table shows the particles that can be accelerated at the Heidelberg dust accelerator. The materials marked with an asterisk (*) are only tested on a testbench with only 20 kV of acceleration voltage; the speeds are extrapolated.

Material Density [kg/m³] Grain size [µm] Speed [km/s]
Iron 7900  0.02 - 2.50  1.5 - 80.0
Aluminium (Al) 2700  0.05 - 2.50  1.5 - 50.0
Carbon (C) 2200  0.20 - 1.00  1.5 - 25.0
Latex 1100  0.75 ±0.04  4.0 - 21.0
Latex 1100  1.58 ±0.13  1.5 - 8.0
*Latex 1100  2.22 ±0.22  1.5 - 4.0
*Copper (Cu) 8900  0.40 - 1.60  2.0 - 6.0
*Silver (Ag) 10500  0.60 - 2.50  1.5 - 8.0
Description of the accelerator

The dust accelerator facility of the Max-Planck-Institut für Kernphysik consists of a dust particle source, an acceleration path, a drift tube with particle selection unit, and the experiment chamber.

The dust source is made of titanium containing a dust reservoir, a tungsten needle as charging electrode inside the reservoir, an extraction plate and a beam collimator. The dust powder inside the reservoir has to be electrically conductive. The tungsten needle has a potential of approx. 20 kV. While the potential on the needle remains fixed, the reservoir potential is frequently pulsed with amplitudes about 10 kV. A charge is induced on the particles inside. They start to swirl around due to Coulomb repulsion forces. Hitting the tip of the needle, a particle receives its final electric charge and is pulled out of the reservoir by the field of a grounded extraction plate. After passing a collimator, the particle enters the acceleration unit. A Van-de-Graaff belt generator provides the acceleration voltage of 2 MV. Equipotential rings generate an electric field gradient along the acceleration line. The potential energy difference of the particle from 2 MV to ground is converted into kinetic energy in accord to the equation:

½ mv² = qU

Depending on their charge/mass-ratio, the particles reach speeds up to 100 km/s. The smaller the particles, the higher the achievable charge/mass-ratio. Thus, the highest speeds are only reached by the smallest particles.