A filter and a method for separating ions in a partially ionized plasma according to their mass includes a chamber with crossed electric and magnetic fields established therein. A feed, including metal atoms having ionization potentials in a low range, and gas atoms having an ionization potential in a high range, is introduced into the chamber. An electron temperature below the low range is generated to partially ionize the feed by dissociating the metal atoms from the gas atoms, and by ionizing the metal atoms into light and heavy ions according to their mass to charge ratio. The light and heavy ions are then influenced by the crossed electric and magnetic fields to separate the light ions from the heavy ions.
An isotope separator includes a cylindrical chamber having first and second ends, and a length "L." Inside the chamber, an E.times.B field is applied to produce plasma rotation. The energy in the plasma rotation is chosen to be much higher than the electron temperature which is clamped by radiation. As the plasma then transits the chamber through the length "L", the electrons cool the thermal temperature of the isotope ions while maintaining the rotation. Under these conditions, the minority and majority isotopes become substantially separated from each other before they exit the chamber. To achieve this result, E.times.B is determined using mathematically derived expressions and, in compliance with these parameters, the length "L" of the chamber is determined so that the plasma residence time in the chamber, .tau..sub.1, will be greater than the cooling time, .tau..sub.2 (.tau..sub.1 >.tau..sub.2) necessary to affect isotope separation.
