Abstract
A design of a compact hadron driver for future cancer therapies based on the induction synchrotron concept is presented. To realize a slow extraction technique in a fast-cycling synchrotron, which allows energy sweep beam scanning, a zero momentum-dispersion $D(s)$ region and a high flat $D(s)$ region are necessary. The proposed design meets both requirements. The lattice has two-fold symmetry with a circumference of 52.8 m, a 2-m dispersion-free straight section, and a 3-m-long large flat dispersion straight section. Assuming a 1.5-T bending magnet, the ring can deliver heavy ions ($200\text{ }\text{ }\mathrm{MeV}/\mathrm{u}$) at 10 Hz. A beam fraction is dropped from the barrier bucket at the desired timing, and the increasing negative momentum deviation of this beam fraction becomes large enough for the fraction to fall in the electrostatic septum extraction gap, which is placed at the large $D(s)$ region. The programmed energy sweep extraction enables scanning beam irradiation on a cancer site in depth without an energy degrader, avoiding the production of secondary particles and the degradation of emittance. Details of the lattice parameters and computer simulations for slow extraction are discussed. An example extraction scenario is presented. Qualities of the spilled beam such as emittance and momentum spread are discussed, as well as necessary functions and parameters required for the extraction system.
Highlights
Nowadays, 3D spot scanning of hadron beams applied to cancer tissues in human organs is of great concern in society
A beam fraction is dropped from the barrier bucket at the desired timing, and the increasing negative momentum deviation of this beam fraction becomes large enough for the fraction to fall in the electrostatic septum extraction gap, which is placed at the large DðsÞ region
The hadron beam is extracted with the same energy and the before-irradiation beam energy is changed by using a combination of plastic plates with different thicknesses, at the expense of producing a huge number of secondary particles created by interactions with the range shifter material, resulting in large residual radiation and degraded transverse emittance
Summary
3D spot scanning of hadron beams applied to cancer tissues in human organs is of great concern in society. Synchrotron, where the excitation ramping pattern of guiding magnets is varied by using a different acceleration cycle and the beam is continually and slowly extracted on the flat top by a combination of third-integer resonance and rf deflection. The idea of energy sweep extraction in a single acceleration cycle from a fast-cycling synchrotron has been proposed in the iRCMS project [2]. This is depicted, the details are not open to the public. A practical method to realize energy sweep extraction from a fast-cycling synchrotron is proposed. We can obtain a driver beam for cancer therapy with 3D spot scanning, the energy of which changes continuously in a single acceleration cycle.
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