Beam test of the ion beam facility based on the metal vapor vacuum arc ion source at Korea multi-purpose accelerator complex

The ion beam irradiation system based on the Metal Vapor Vacuum Arc (MEVVA) ion source has been developed at Korea Multi-purpose Accelerator Complex (KOMAC). The ion irradiation system consists of MEVVA ion source, ion irradiation chamber and sample stage along with the auxiliary systems such as power supplies, vacuum pumps, beam diagnostics and the control system. The initial beam test was carried out using the chromium ions after the system was installed. During stability measurement, peak beam current was measured to be 335 mA at the cathode voltage of 30 kV and its fluctuation was less than 5% in rms for 100 min. The beam extraction characteristic curve was measured depending on the arc power and cathode voltage from 30 to 60 kV. The beam profile was monitored through two different methods; multi-wire beam profile monitor and a small Faraday cup which measures the local current density along the radial direction. The results showed good agreements within 5%. The beam radius was measured depending on the arc power and a matched extraction condition of the ion source could be found. The average charge state of the beam was measured to be 2.18 which is an important parameter to specify the dose on the sample. The erosion rate of the cathode was found to be 34.2 μg/C.