Abstract: A cyclotron for ion acceleration is magnetically shielded during ion acceleration by passing electrical current in the same direction through both the first and second superconducting primary coils. A first magnetic-field-shielding coil is on the same side of the mid plane as the first superconducting primary coil, while a second magnetic-field-shielding coil is on the same side of the midplane as the second superconducting primary coil and beyond the outer radius of the second superconducting primary coil. Electrical current is also passed through the magnetic-field-shielding coils in a direction opposite to the direction in which electrical current is passed through the superconducting primary coils and generates a canceling magnetic field that reduces the magnetic field generated at radii from the central axis beyond the magnetic-field-shielding coils.

Abstract: A cyclotron for ion acceleration is magnetically shielded during ion acceleration by passing electrical current in the same direction through both the first and second superconducting primary coils. A first magnetic-field-shielding coil is on the same side of the mid plane as the first superconducting primary coil, while a second magnetic-field-shielding coil is on the same side of the midplane as the second superconducting primary coil and beyond the outer radius of the second superconducting primary coil. Electrical current is also passed through the magnetic-field-shielding coils in a direction opposite to the direction in which electrical current is passed through the superconducting primary coils and generates a canceling magnetic field that reduces the magnetic field generated at radii from the central axis beyond the magnetic-field-shielding coils.

Abstract: The invention specifies the use of feedback in the radio frequency (RF) drive for a synchrocyclotron, controlling the phase and/or amplitude of the accelerating field as a means to assure optimal acceleration of the beam, to increase the average beam current and to alter the beam orbit in order to allow appropriate extraction as the beam energy is varied. The effect of space charge is reduced by rapid acceleration and extraction of the beam, and the repetition rate of the pulses can be increased. Several means are presented to monitor the phase of the beam in synchrocyclotrons and to adjust the phase and amplitude of the RF to optimize the acceleration of the beam and to adjust the extraction and injection of the beam. Also, the use of a pulsed ion source that matches the acceptance window of the synchrocyclotron is described.