Vertical orbit excursion Fixed Field Accelerators (vFFAs) feature highly non-linear magnetic fields and strong transverse motion coupling. The detailed study of their Dynamic Aperture (DA) requires computation codes allowing long-term tracking and advanced analysis tools to take the transverse motion linear and non-linear coupling into account. This coupling completely transforms the beam dynamics compared to a linear uncoupled motion, and an explicit definition of the DA is needed to characterize the performance and limitations of these lattices. A complete study of the DA in the 4D phase space in highly non-linear and strongly coupled machines must give a measure of the stability domain but also means to assess the operating performance in the physical coupled space. This work presents a complete set of methods to perform such detailed analysis. These methods were explored and compared to compute and characterize the DA of an example vFFA lattice. The whole procedure can be further applied to evaluate DA using realistic models of the magnetic fields, including fringe fields and errors.

The IBA ProteusOne (P1) system is suitable to treat ocular tumors and achieves efficient dose conformality using state-of-the-art pencil beam scanning. Nevertheless, with the limited cyclotron current of the P1 system, clinically relevant (> 15 Gy/min) dose rates can barely be achieved in eye tumors treatment cases with the baseline configuration of the system due to the significantly high energy degradation required (from 230 to 70 MeV). One way to improve this dose rate is to modify the degrader to use a material causing a smaller emittance increase. In this work, we compare the performances of the P1 system in the context of eye tumors treatment when using Beryllium degrader on the one hand and Diamond degrader on the other. For the latter case, the optics is modified to reduce the losses along the beamline and ultimately increase the dose rate of the system while maintaining a symmetrical spot at the isocenter. Using Beam Delivery SIMulation, the dosimetric properties of the system are assessed and compared for the two configurations, and the differences in dose rate are quantified and discussed in detail.

Vertical orbit excursion Fixed Field Accelerators (vFFAs) feature highly non-linear magnetic fields and strong transverse motion coupling. The detailed study of their Dynamic Aperture (DA) requires computation codes allowing long-term tracking and advanced analysis tools to take the transverse motion linear and non-linear coupling into account. This coupling completely transforms the beam dynamics compared to a linear uncoupled motion, and an explicit definition of the DA is needed to characterize the performance and limitations of these lattices. A complete study of the DA in the 4D phase space in highly non-linear and strongly coupled machines must give a measure of the stability domain but also means to assess the operating performance in the physical coupled space. This work presents a complete set of methods to perform such detailed analysis. These methods were explored and compared to compute and characterize the DA of an example vFFA lattice. The whole procedure can be further applied to evaluate DA using realistic models of the magnetic fields, including fringe fields and errors.

Proton therapy provides significant advantages over classic radiotherapy for specific cancerous diseases, notably by limiting the delivered dose to organs at risk (OARs). Novel treatment modalities such as flash and arc therapy require changing the energy delivered at the isocenter while providing a high dose rate. Fixed-field achromatic transport lattices satisfy both constraints, allowing ultra-fast energy modulation and excellent transmission efficiency while providing a compact footprint. Prior studies [1] have shown that lattices using scaling fixed field magnets allow the achromatic transport of energies between 70 and 230 MeV. We investigate the use of straight scaling FFAG line that uses nonlinear fields, fulfilling the straight scaling conditions for achromatic transport, to be used as a matching section for the CASPRO ("Compact Achromatic System for Proton Therapy") project.

Hadron therapy is established as a method of choice for a number of cancerous diseases, and its advantages are well-established for specific malignancies. Modern medical particle accelerators still struggle to fulfil critical features required by advanced treatment modalities, such as variable energy beams, high repetition rate, and pulse-by-pulse intensity modulation. Fixed Field Accelerators (FFAs) are suited to tackle these challenges as they can accelerate particles over a wide energy range with fixed magnetic fields. Vertical orbit excursion FFAs feature constant tunes and a small horizontal footprint, making them excellent candidates for medical applications. We propose a conceptual design of a medical vFFA. Its linear and nonlinear beam dynamics is presented in-depth. This study demonstrates the vFFA potential to provide a new direction for the study and design of medical FFAs suitable for next-generation particle therapy systems.

The IBA ProteusOne (P1) system is suitable to treat ocular tumors and achieves efficient dose conformality using state-of-the-art pencil beam scanning. Nevertheless, with the limited cyclotron current of the P1 system, clinically relevant (> 15 Gy/min) dose rates can barely be achieved in eye tumors treatment cases with the baseline configuration of the system due to the significantly high energy degradation required (from 230 to 70 MeV). One way to improve this dose rate is to modify the degrader to use a material causing a smaller emittance increase. In this work, we compare the performances of the P1 system in the context of eye tumors treatment when using Beryllium degrader on the one hand and Diamond degrader on the other. For the latter case, the optics is modified to reduce the losses along the beamline and ultimately increase the dose rate of the system while maintaining a symmetrical spot at the isocenter. Using Beam Delivery SIMulation, the dosimetric properties of the system are assessed and compared for the two configurations, and the differences in dose rate are quantified and discussed in detail.