Recent developments of the ISOLDE laser ion source

The ISOLDE laser ion source (LIS), in which stepwise resonant laser ionization is performed inside a high-temperature cavity, has been extended to include the elements Be, Zn, Cu and Cd. The ionization efficiencies obtained are discussed with respect to the level of saturation of each step achieved with the available laser beam intensities. Because of a high ionization potential of about 9 eV the first resonant transition of Be, Zn and dd is in the far ultraviolet (UV) region. The UV laser beam needed for the.first resonant step of Be, Zn and Cd is achieved in a new laser setup via frequency tripling of the dye laser Light. The ions created during the 30 ns laser pulse are extracted from the hot cavity of the ion source by the electrical field resulting from the ohmic heating of the cavity. The time distribution of the laser-ionized ion bunches was measured for various cavities and temperatures. The time structure of the ion bunch is discussed in order to gain insight into the development of LIS cavities. (C) 1998 American Institute of Physics.