The invention comprises a charged particle beam injection method and apparatus used in conjunction with multi-axis charged particle radiation therapy of cancerous tumors. The negative ion beam source includes a negative ion beam source, vacuum system, an ion beam focusing lens, and/or a tandem accelerator. The negative ion beam source uses electric field lines for focusing a negative ion beam. The negative ion source plasma chamber includes a magnetic material, which provides a magnetic field barrier between a high temperature plasma chamber and a low temperature plasma region. The injection system vacuum system and a synchrotron vacuum system are separated by a conversion foil, where negative ions are converted to positive ions. The foil is sealed to the edges of the vacuum tube providing for a higher partial pressure in the injection system vacuum chamber and a lower pressure in the synchrotron vacuum system.
