Viewers of star trek hear of an antimatter drive on the starship enterprise. one possibility for such a futuristic energy source is to store antimatter charged particles in a vacuum chamber, circulating in a magnetic field, and then extract them as needed. antimatter annihilates with normal matter, producing pure energy. ? ? what strength magnetic field in t is needed to hold antiprotons, moving at 3.5 × 10^7 m/s in a circular path 1.8 m in radius? antiprotons have the same mass as protons but the opposite (negative) charge