Status of the development of electron beam ion sources at Frankfurt

The Frankfurt superconducting electron beam ion source (EBIS) is under reconstruction for higher ion yield by employing an immersed gun with a 2-mm-diam cathode for a 3 A electron beam. The trap electrode construction is as simple as possible to avoid any rf production. The ion extraction will be similar to the one applied in our MEDEBIS, using tapered electrodes to create a high axial extraction gradient. Research was continued on the use of oscillating electrons to reduce the power requirements of the beam, investigating the formation of a virtual cathode by decelerating the beam at full magnetic field strength while operating the gun under immersed flow conditions with adjustable compression. The MEDEBIS has proven its quality and reliability for the application as an injector for a medically dedicated synchrotron. To improve its yield of bare nuclei, better vacuum conditions are provided by drilling out the inner windings of the warm solenoid to allow for the installation of higher vacuum conductance. After the successful presentation of our XEBIST principle that delivers highly charged ions as Ar18+ and Ba46+ we have now shown its application for the production of singly charged ions as an injector of metallic ions. Finally, an EBIS/T with an internal Penning trap has been constructed to prepare selected ion species and charge states inside the ionization region. This new device will allow the study of electron-ion interactions in well-defined initial and final charge states, i.e., to be able to distinguish between single and multiple step ionization. If the homogeneity of the magnetic field in the trap region will reach 10(-9), the determination of binding energies of highly charged ions may be better than a 1 eV accuracy. (C) 1998 American Institute of Physics.