Results of the reconstructed MEDEBIS

The electron beam ion source (EBIS) can deliver sufficiently short and intense pulses of fully stripped light ions for single turn injection into a dedicated synchrotron for hadron therapy. The technology of such a MEDEBIS resembles travelling wave tubes used in satellites and can also be designed for lifetimes up to ten years. In a first setup using a normal conducting solenoid of 0.75 T and a trap length of 0.25 m the source delivered high charge states of light ions like O⁸⁺, O⁷⁺, O⁶⁺ and C⁶⁺, C⁵⁺[1]. The fast ion extraction in less than 2 μs is realised trough a special electrostatic structure providing a pulsed extraction potential gradient along the axis of the whole ion trap. The first results were very promising, but the residual gas pressure in the ionisation region was too high to make use of a sufficiently long confinement time in order to reach full abundance of bare nuclei. For the reconstructed MEDEBIS the inner two windings of the solenoid were drilled out to allow for a vacuum tube of about twice the diameter with better conductance. Together with the implementation of NEG getter material the residual gas pressure should be lowered sufficiently to reach the required yield of the fully stripped ions. Iron disks of high permeability have been added at both ends of the solenoid to increase the homogeneity of the magnetic field as well as to reduce the field in the gun and collector regions for a higher focussed current density in the trap region. The new MEDEBIS is under test and new experimental results will be presented