A Penning trap is a device that uses a combination of low temperatures and electromagnetic fields to store antimatter. While Penning traps can only store incredibly small quantities, they will help in developing the technologies needed for advanced propulsion concepts. The photo on the left shows a Penning trap at the Laboratory for Energetic Particle Science at Pennsylvania State University. The diagram on the right is a schematic of the interior of the device. A cloud of antiprotons (the fuzzy bluish spot) is kept cold and quiet by liquid nitrogen and helium and a stable magnetic field.

Penning trap at Penn State