High-Current Betatron with Stellarator Fields

By adding an $l=2$ stellarator field to a betatron accelerator, a new configuration is obtained which is capable of accelerating multikiloamp beams and which will tolerate a large (more than 50%) mismatch between the particle energy and the vertical magnetic field. The additional field is a twisted quadrupole which acts as a strong-focusing system. This device has been analyzed both analytically and numerically.