High-gradient low- β accelerating structure using the first negative spatial harmonic of the fundamental mode

• Published in: Physical review. Accelerators and beams 2017-12, Vol.20 (12), p.120401, Article 120401
• Main Authors: Kutsaev, Sergey V., Agustsson, Ronald, Boucher, Salime, Fischer, Richard, Murokh, Alex, Mustapha, Brahim, Nassiri, Alireza, Ostroumov, Peter N., Plastun, Alexander, Savin, Evgeny, Smirnov, Alexander Yu
• Format: Article
• Language: English
• Subjects: Cancer; Electromagnetic fields; Linear accelerators; PARTICLE ACCELERATORS; Radiation therapy; Superhigh frequencies
• ISSN: 2469-9888; 2469-9888
• DOI: 10.1103/PhysRevAccelBeams.20.120401

The development of high-gradient accelerating structures for low-β particles is the key for compact hadron linear accelerators. A particular example of such a machine is a hadron therapy linac, which is a promising alternative to cyclic machines, traditionally used for cancer treatment. Currently, the practical utilization of linear accelerators in radiation therapy is limited by the requirement to be under 50 m in length. A usable device for cancer therapy should produce 200–250 MeV protons and/or 400–450MeV/u carbon ions, which sets the requirement of having 35MV/m average “real-estate gradient” or gradient per unit of actual accelerator length, including different accelerating sections, focusing elements and beam transport lines, and at least 50MV/m accelerating gradients in the high-energy section of the linac. Such high accelerating gradients for ion linacs have recently become feasible for operations at S-band frequencies. However, the reasonable application of traditional S-band structures is practically limited to β=v/c>0.4 . However, the simulations show that for lower phase velocities, these structures have either high surface fields (>200MV/m ) or low shunt impedances (