To complement Alan's picture, here is a short movie on agitation of Ni powder in a glass tube:
https://drive.google.com/open?…B4lzXLFc9dNUNyM0d4SFV3WUE
Glass vial diameter is ~25 mm, height ~100 mm. Ni powder particles size is 20-50 mkm. Magnets - neodimium, N35, D8xL6 mm. Grey powder at the vial's bottom - LiAlH4. It was separated from the mixed fuel powder by movement of Ni powder with magnets.
The simplest way to constantly agitate Ni powder inside the tube chamber - is to periodically switch current in two DC coils separated by a small distance over the tube.
As can be seen in the movie, with sharp switching of magnets - the Ni powder just jumps between two magnets. With gradual switching of the strength of the magnetic field between magnets, one can achieve "flying powder" effect, and even "fluid-like" motion of the powder. The same coils can be used for heating as well.
Note that with two magnets the very fine structures of Ni powder can be formed and maintained, such as spikes, needles and fibers spreading over large distances and with diameters close to the powder particles size and up. (The smallest Ni fibers in the movie are ~ 50 mkm.)
This technique greatly increases the surface area of Ni powder and can also help to prevent its sintering.
This magnetic agitation can be used during hydrogen loading into Ni powder, as it is performed at temperatures lower than Curie temperature of Ni of ~360 C.
For magnetic agitation of the fuel mix at high temperatures, the Cobalt powder can be added to the fuel, with its Curie temperature being of over 1100 C (compared to ~360 C for Ni).
As David Fojt mentioned above, Cobalt rods can also be used inside fuel chamber as magnetic field concentrators and also as permanent magnets to shape the magnetic field in a particular way.