Compac carbon ion linac

Abstract

The invention provides a method for accelerating protons and carbon ions up to 450 MeV/u in a very compact linac, the method comprising subjecting the particles to a radio frequency quadrupole field to accelerate the particles to at least 3 MeV/u, a drift tube linac (DTL) to an energy of 20 MeV/u, followed by a coupled DTL to 45 MeV/u and finally a high-gradient section made of CCL-type standing wave cavities or negative harmonic traveling wave cavities operating at S-band frequencies and capable of delivering voltage gradients of 40 to 60 MV/m. Focusing the accelerated particles while accelerated to higher energy is provided by appropriately placed constant field permanent magnets and electromagnetic quadrupoles. The compactness and power efficiency of the linac is enabled by using high-gradient structure in the S-band frequencies for lower energy particles than ever before. The low-intensity required for hadron therapy allows the use of small-aperture S-band structures and the operation at very high gradient compared to high-intensity machines for research. Operating with very short sub-microsecond pulses at repetition rates up to 400 Hz allows the fast and flexible beam energy and intensity tuning not provided by existing hadron therapy machines. The designed linac is capable of accelerating ions as heavy as neon to the full 450 MeV/u energy, therefore allowing fast beam switching if different ion sources are installed in the front-end of the linac.