Experimental studies were conducted to characterize and improve the performance of the flat-B ECR ion source.The emittance of the source was investigated for the first time.The output beam currents of high-charge-states of Ar(q>8)were nearly doubled by increasing the plasma electrode aperture from 4mm to 6mm in diameter.To investigate possible enhancements with broadband microwave radiation,a“white”Gaussian noise generator was employed with a TWT amplifier to generate microwave radiation with a bandwidth of～200MHz.The performance of the flat-B ECR ion source was found to be much better with narrow bandwidth radiation when the source was operated in the flat-B region.However,the ion beam intensities and charge state distributions were improved with the broadband radiation when the source was tuned off the flat-B region. Experimental studies were conducted to characterize and improve the performance of the flat-B ECR ion source. The emittance of the source was investigated for the first time. The output beam currents of high-charge-states of Ar (q> 8) were nearly doubled by increasing the plasma electrode aperture from 4mm to 6mm in diameter. To investigate possible enhancements with broadband microwave radiation, a “white ” Gaussian noise generator was employed with a TWT amplifier to generate microwave radiation with a bandwidth of ~ 200MHz. performance of the flat-B ECR ion source was found to be much better with narrow bandwidth radiation when the source was operated in the flat-B region. Despite ionospheric intensities and charge state distributions were improved with the broadband radiation when the source was tuned off the flat-B region.