This paper presents experimental and simulation results of discharge in spherically convergent beam fusion device. The deuterium-deuterium (D-D) fusion reaction in that device will generate neutron. The experimental device is consists of a vacuum chamber made of stainless steel, spherical mesh type anode and concentric grid cathode of 5cm diameter. The pressure of chamber maintained constant by injecting gas and pulsed voltage applied to grid cathode. A star mode discharge which has possibility of neutron generation was observed.