One might attempt to circumvent the problem by confining the fission fuel magnetically, in a manner similar to the fusion fuel in a tokamak. Unfortunately it is not likely that this arrangement will actually work to contain the fuel, since the ratio of ionization to particle momentum is not favourable. Whereas a tokamak would generally work to contain singly ionized deuterium or tritium with a mass of two or three daltons, the uranium vapour would be at most triply ionized with a mass of 235 dalton (unit). Since the force imparted by a magnetic field is proportional to the charge on the particle, and the acceleration is proportional to the force divided by the mass of the particle, the magnets required to contain uranium gas would be impractically large; most such designs have focused on fuel cycles that do not depend upon retaining the fuel in the reactor.