Beam emittance measurements of transformer coupled plasma ion source for focused ion beam

A transformer coupled plasma (TCP) ion source has been tested in order to test its feasibility as a high brightness ion source for focused ion beam. When operating the TCP ion source with filter magnets in front of plasma electrode for a negative ion source, lower emittances are expected. Extracted beam emittances are measured with an Allison-type scanning device for various plasma parameters and extraction conditions. The normalized emittance has been measured to be around 0.2 (π mm mrad) with beam currents of up to 0.55 mA. In particular, noting that multicusp magnets have a role in decreasing the emittance as well as increasing plasma discharge efficiency, transverse magnetic field has been confirmed to be a useful tool for decreasing emittance via electron energy control.