A radiation system includes a radiation source having an accelerator, the radiation source having a magnetic field associated therewith that is resulted from an operation of the accelerator, and a magnetic field source configured to provide a compensating magnetic field to at least partially counteract against the magnetic field that is resulted from the operation of the accelerator. A radiation system includes a radiation device having a radiation source, a patient support, and a protective guard located between the radiation source and the patient support, wherein the protective guard is moveably coupled to the radiation device or the patient support. A radiation system includes a particle generator for generating a particle, an accelerator for accelerating the particle, and a magnetic source for changing a trajectory of the particle, wherein the magnetic source comprises a permanent magnet.