Neutralizer for radioactive francium beam

In order to trap francium atoms in a magneto-optical trap, a beam of singly charged francium ions must be neutralized and reduced to thermal energies. Vacuum requirements prevent the use of a gas-filled charge exchange cell. The simple alternative is to implant the ion beam into a hot catcher foil where the ions neutralize within the foil and then diffuse out. The fraction of ions which neutralize depends upon the work function of the foil and first ionization potential of the ion beam. In order to produce such a neutralizer several suitable materials were tested in a variety of different mechanical designs to determine the most effective and robust system.