Abstract: An asymmetric magnetron H~- source with grooved cathode is built toreplace a standard-magnetron H~- source. This new cathode has a semi-cylindrical groove and its height is reduced so that the cathode-anode spacing in the back of the source increased from 1 mmto 3.6 mm. This leads to an improvement by a factor of three to four inreducing arc power, which depend on the utilization factor of the cathode area.In addition, arc starting was easier than the standard magnetron H~--source. Less influence of the arc current fluctuation and the deviation from thegrooved cathode-anode extracting slit are observed. Also, it is showed gas efficiencyis improved in our source. A new discharge arc chamber and the experimental results on the desk test ofthis device are reported in detail.