Interim report for the International Muon Collider Collaboration (IMCC)

The International Muon Collider Collaboration (IMCC) [1] was established in 2020 following the recommendations of the European Strategy for Particle Physics (ESPP) and the implementation of the European Strategy for Particle Physics-Accelerator R&D Roadmap by the Laboratory Directors Group [2], hereinafter referred to as the the European LDG roadmap. The Muon Collider Study (MuC) covers the accelerator complex, detectors and physics for a future muon collider. In 2023, European Commission support was obtained for a design study of a muon collider (MuCol) [3]. This project started on 1st March 2023, with work-packages aligned with the overall muon collider studies. In preparation of and during the 2021-22 U.S. Snowmass process, the muon collider project parameters, technical studies and physics performance studies were performed and presented in great detail. Recently, the P5 panel [4] in the U.S. recommended a muon collider R&D, proposed to join the IMCC and envisages that the U.S. should prepare to host a muon collider, calling this their "muon shot". In the past, the U.S. Muon Accelerator Programme (MAP) [5] has been instrumental in studies of concepts and technologies for a muon collider.Comment: This document summarises the International Muon Collider Collaboration (IMCC) progress and status of the Muon Collider R&D programm

Achromatic gantry design using fixed-field spiral combined-function magnets

Abstract Arc-therapy and flash therapy are promising proton therapy treatment modalities as they enable further sparing of the healthy tissues surrounding the tumor site. They impose strong constraints on the beam delivery system and rotating gantry structure, in particular in providing high dose rate and fast energy scanning. Fixed-field achromatic transport lattices potentially satisfy both constraints in allowing instant energy modulation and sufficient transmission efficiency while providing a compact footprint. The presented design study uses fixed-field magnets with spiral edges respecting the FFA scaling law. The cell structure and the layout are studied in simulation and integrated in a compact gantry. Results and further optimizations are discussed.</jats:p

The Zgoubidoo python framework for ray-tracing simulations with Zgoubi: applications to fixed-field accelerators

Abstract The study of beam dynamics in accelerators featuring main magnets with complex geometries such as Fixed Field Accelerators (FFAs) requires simulation codes allowing step-by-step particle tracking in complex magnetic fields, such as the Zgoubi ray-tracing code. To facilitate the use of Zgoubi and to allow readily processing the resulting tracking data, we developed a modern Python 3 interface, Zgoubidoo, using Zgoubi in the backend. In this work, the key features of Zgoubidoo are illustrated by detailing the main steps to obtain a non-scaling FFA accelerator from a scaling design. The results obtained are in excellent agreement with prior results, including the tune computation and orbit shifts. These results are enhanced by Zgoubidoo beam dynamics analysis and visualization tools, including the placement of lattice elements in a global coordinate system and the computation of linear step-by-step optics. The validation of Zgoubidoo on conventional scaling and non-scaling FFA designs paves the way for future uses in innovative FFA design studies.</jats:p

Dynamic aperture studies for vertical fixed field accelerators

Vertical orbit excursion Fixed Field Accelerators (vFFAs) feature highly nonlinear 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 nonlinear 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 nonlinear 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.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

Upgrade of a proton therapy eye treatment nozzle using a cylindrical beam stopping device for enhanced dose rate performances

Abstract Proton therapy is a well established treatment method for ocular cancerous diseases. General-purpose multi-room systems which comprise eye-treatment beamlines must be thoroughly optimized to achieve the performances of fully dedicated systems in terms of depth-dose distal fall-off, lateral penumbra, and dose rate. For eye-treatment beamlines, the dose rate is one of the most critical clinical performances, as it directly defines the delivery time of a given treatment session. This delivery time must be kept as low as possible to reduce uncertainties due to undesired patient movement. We propose an alternative design of the Ion Beam Applications (IBA) Proteus Plus (P+) eye treatment beamline, which combines a beam-stopping device with the already existing scattering features of the beamline. The design is modelled with Beam Delivery SIMulation (BDSIM), a Geant4-based particle tracking and beam-matter interactions Monte-Carlo code, to demonstrate that it increases the maximum achievable dose rate by up to a factor 3 compared to the baseline configuration. An in-depth study of the system is performed and the resulting dosimetric properties are discussed in detail.</jats:p

Concrete shielding activation for proton therapy systems using BDSIM and FISPACT-II

Abstract Proton therapy systems are used worldwide for patient treatment and fundamental research. The generation of secondary particles when the beam interacts with the beamline elements is a well known issue. In particular, the energy degrader is the dominant source of secondary radiation. This poses new challenges for the concrete shielding of compact systems and beamline elements activation computation. We use a novel methodology to seamlessly simulate all the processes relevant to the activation evaluation. A realistic model of the system is developed using Beam Delivery Simulation (BDSIM), a Geant4-based particle tracking code that allows a single model to simulate primary and secondary particle tracking and all particle-matter interactions. The secondary particle fluxes extracted from the simulations are provided as input to FISPACT-II to compute the activation by solving the rate equations. This approach is applied to the Ion Beam Applications (IBA) Proteus®ONE (P1) system and the shielding of the proton therapy research centre of Charleroi, Belgium. Proton loss distributions are used to model the production of secondary neutrals inside the accelerator structure. Two models for the distribution of proton losses are compared for the computation of the clearance index at specific locations of the design. Results show that the variation in the accelerator loss models can be characterised as a systematic error.</jats:p

Self-consistent numerical evaluation of concrete shielding activation for proton therapy systems:Application to the proton therapy research centre in Charleroi, Belgium

Due to the advancement of proton therapy for cancer treatment, there has been a worldwide increase in the construction of treatment facilities. Therapy centres are often coupled with clinical, biological or material-science research programs. Research activities require proton beams at energies spanning an extensive range with higher beam currents and longer irradiation times than clinical conditions. Additionally, next-generation proton therapy systems are evolving towards more compact designs. In addition to the increased centres’ workloads, reducing the system in size produces a more significant number of secondary particles per unit volume and time. Therefore, the activation level of materials constituting those future proton therapy centres is expected to be higher, increasing the ambient dose and the amount of radioactive waste collected at the end of a centre’s lifetime. These operating conditions pose new challenges for the shielding design and the reduction of the concrete activation. To tackle them, we propose a novel approach to seamlessly simulate all the processes relevant for the evaluation of the concrete shielding activation using, as an illustration, the Ion Beam Applications Proteus® One system. A realistic model of the system is developed using Beam Delivery Simulation (BDSIM), a Geant4-based particle tracking code. It allows a single model to simulate primary and secondary particle tracking in the beamline, its surroundings, and all particle-matter interactions. The code system and library database FISPACT-II allows the computation of the shielding activation by solving the rate equations using ENDF-compliant group library data for nuclear reactions, particle-induced or spontaneous fission yields, and radioactive decay. As input, FISPACT-II is provided with the secondary particle fluences scored using the BDSIM Monte Carlo simulations. This approach is applied to the proton therapy research centre of Charleroi, Belgium. Results compare the evolution of the clearance level and the long-lived nuclide concentrations throughout the facility lifetime when using regular concrete or the newly developed Low Activation Concrete (LAC). A comparison with the initial shielding dimensioning has been performed for all the shielding walls to validate the methodology and highlight the clear benefits of integrating LAC inserts in the shielding design. The effectiveness of coupling BDSIM and FISPACT-II gives a glimpse of the possibility of a complete activation study following the actual workloads of the centre, allowing a better assessment of the shielding activation level at any time of the facility lifespa