Here you can find details about our current state of the experiment.
The sample chamber contains the glass spheres (shown in gray) and is shaken by voice coils below (obscured by the stepmotor). The cap, bottom and a lower wall section of this chamber are covered by the same glass spheres (not shown in the schematic drawing). To ensure that charge separation only occurss due to same surface tribocharging, lowering the cap with a stepmotor reduces the volume inside the chamber. This limits the movement of the spheres to a small volume (with matching surfaces) and enables also to restart the experiment. The sample agglomeration is observed with a camera in transmitted LED-light configuration. The experiment is controlled via a Rasberry Pi Zero (in front of the stepmotor) and an electronic board. Higher power consumption and inrush peaks are buffered with a powerbank, shown on the left side.
We are planing to record series of images which will be interpreted on the ground. This will give us information about the formation, structure and size of the clusters.
Drop-Tower-Experiments on tribocharging of particles consisting of the same material have shown, that mm-sized glass beads are strongly charged by collisions.
In the image above one can see trajectories of the glass beads. On the right side (not included in this image) the glass beads are shaken (similar to the setup that will be used for ARISE). With a capacitor an electric field is applied from the bottom to the top. The non-linear trajectories indicate that the glass beads are accelerated within the electric field. This shows the charging of the beads.
Closer observations of the particles shows that the charging changes the clustering behaviour significantly. In the graphic below a series of images is shown in which one can observe a collision of two particles. These bounce off after the first contact. However they are then accelerated towards each other and stick together after the second contact.
These experiments indicate, that tribocharging can change the clustering behaviour of mm-sized glass beads which will be further investigated with ARISE.