An example particle accelerator includes a coil to provide a magnetic field to a cavity； a particle source to provide a plasma column to the cavity； a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column, where the magnetic field causes particles accelerated from the plasma column to move orbitally within the cavity； an enclosure containing an extraction channel to receive the particles accelerated from the plasma column and to output the received particles from the cavity； and a structure arranged proximate to the extraction channel to change an energy level of the received particles.本發明揭示一種實例性粒子加速器，其包含：一線圈，其用以提供一磁場至一腔；一粒子源，其用以提供一電漿柱至該腔；一電壓源，其用以提供一射頻(RF)電壓至該腔以使粒子自該電漿柱加速，其中該磁場致使自該電漿柱加速之粒子在該腔內沿軌道移動；一外殼，其含有一提取通道，用以接收自該電漿柱加速之該等粒子且用以輸出來自該腔之該等所接收粒子；及一結構，其配置成接近該提取通道，用以改變該等所接收粒子之一能量位準。
