DEVELOPMENT OF 18 GHZ NIRS ELECTRON-CYCLOTRON-RESONANCE ION-SOURCE WITH HIGH-VOLTAGE EXTRACTION CONFIGURATION

An 18 GHz ECR ion source with high-voltage extraction configuration (N IRS-HEC) has been developed for the Heavy Ion Medical Accelerator in C hiba (HIMAC), National Institute of Radiological Sciences (NIRS). NIRS -HEC has a high extraction voltage of up to 60 kV in order to reduce t he unwanted space charge effects at the extraction region. NIRS-HEC al so has a strong magnetic field. A radial size of the plasma chamber is made as small as 40 mm, so that a sextupole field strength of Il kG a nd an axial field strength of 12 kG an easily obtained. The experiment al data show that a high extraction voltage is effective to realize th e high beam intensity when the extraction current density is high. It is consistent with the computer calculations of the FUGUN code and TRA PCAD code. (C) 1998 American Institute of Physics.