The Focusing Structure Of The Prague Proton Synchrotron For Hadron Therapy

This paper reports a lattice design of a dedicated proton synchrotron for hadron therapy. This synchrotron, named as a Prague Medical Synchrotron (PRAMES), will be used as a kernel of an accelerator complex of a Prague Oncological Hospital (Czech Republic). The synchrotron will be able to accelerate high-intensity proton beam of 625.10(10) protons per pulse till the energy of 60 divided by 220 MeV with the 1 Hz repetition rate. The active scanning of rumours is assumed. To satisfy this requirement, the slow (third-order) extraction scheme is analysed. The single turn injection of the proton beam is utilised to get the trapped proton beam with small transverse emittance on the injection energy of 12 MeV. The developed focusing structure of the ring has two superperiods with two long straight sections to install the injection, acceleration and extraction systems. Each period is composed of two achromatic cells to provide, first of all, a high efficiency of the slow extraction. The cell consists of two rectangular dipole magnets with the 45 degree bending angle and 22.5 degree edge angle at both ends, and a triplet of quadrupole lenses. To adjust the working point to the slow extraction, an additional quadrupole triplet in the superperiod is utilised. The output horizontal and vertical tunes are 2.666 and 1.8, respectively. The slow extraction scheme of the accelerated proton beam is discussed in the paper.