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Abstract

A novel o-axis gun (OAG) with its cathode displaced from the central axis, which is therefore free of any obstacles, was built into a compact room temperature electron beam ion trap (EBIT). The chosen geometry of the gun grants optical access to trap center along the beam axis, where highly charged ions can be used as a new in situ calibration standard for high energy photon beams as provided e.g. by ultra brilliant radiation sources like synchrotrons and free electron lasers. First measurements of dielectronic recombinations on argon and iron ions have shown stable operations of the OAG with a 25mA electron beam and up to 8 keV beam energy. A high energy beam resolution of 2:6(1) eV could be achieved using low beam currents.