FLUKA is a general purpose Monte Carlo code able to describe the transport and interaction of any particle and nucleus type in complex geometries over an energy range extending from thermal neutrons to ultrarelativistic hadron collisions. It has many different applications in accelerator design, detector studies, dosimetry, radiation protection, medical physics, and space research. In 2019, CERN and INFN, as FLUKA copyright holders, together decided to end their formal collaboration framework, allowing them henceforth to pursue different pathways aimed at meeting the evolving requirements of the FLUKA user community, and at ensuring the long term sustainability of the code. To this end, CERN set up the FLUKA.CERN Collaboration1. This paper illustrates the physics processes that have been newly released or are currently implemented in the code distributed by the FLUKA.CERN Collaboration2 under new licensing conditions that are meant to further facilitate access to the code, as well as intercomparisons. The description of coherent effects experienced by high energy hadron beams in crystal devices, relevant to promising beam manipulation techniques, and the charged particle tracking in vacuum regions subject to an electric field, overcoming a former lack, have already been made available to the users. Other features, namely the different kinds of low energy deuteron interactions as well as the synchrotron radiation emission in the course of charged particle transport in vacuum regions subject to magnetic fields, are currently undergoing systematic testing and benchmarking prior to release. FLUKA is widely used to evaluate radiobiological effects, with the powerful support of the Flair graphical interface, whose new generation (Available at http://flair.cern) offers now additional capabilities, e.g., advanced 3D visualization with photorealistic rendering and support for industry-standard volume visualization of medical phantoms. FLUKA has also been playing an extensive role in the characterization of radiation environments in which electronics operate. In parallel, it has been used to evaluate the response of electronics to a variety of conditions not included in radiation testing guidelines and standards for space and accelerators, and not accessible through conventional ground level testing. Instructive results have been obtained from Single Event Effects (SEE) simulations and benchmarks, when possible, for various radiation types and energies. The code has reached a high level of maturity, from which the FLUKA.CERN Collaboration is planning a substantial evolution of its present architecture. Moving towards a modern programming language allows to overcome fundamental constraints that limited development options. Our long term goal, in addition to improving and extending its physics performances with even more rigorous scientific oversight, is to modernize its structure to integrate independent contributions more easily and to formalize quality assurance through state-of-the-art software deployment techniques. This includes a continuous integration pipeline to automatically validate the codebase as well as automatic processing and analysis of a tailored physics-case test suite. With regard to the aforementioned objectives, several paths are currently envisaged, like finding synergies with Geant4, both at the core structure and interface level, this way offering the user the possibility to run with the same input different Monte Carlo codes and crosscheck the results.

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work.

Laser-driven radiation sources are attracting increasing attention for several materials science applications. While laser-driven ions, electrons and neutrons have already been considered to carry out the elemental characterization of materials, the possibility to exploit high-energy photons remains unexplored. Indeed, the electrons generated by the interaction of an ultra-intense laser pulse with a near-critical material can be turned into high-energy photons via bremsstrahlung emission when shot into a high-Z converter. These photons could be effectively exploited to perform Photon Activation Analysis (PAA). In the present work, laser-driven PAA is proposed and investigated. We develop a theoretical approach to identify the optimal experimental conditions for laser-driven PAA in a wide range of laser intensities. Lastly, exploiting the Monte Carlo and Particle-In-Cell tools, we successfully simulate PAA experiments performed with both conventional accelerators and laser-driven sources. Under high repetition rate operation (i.e. 1−10 Hz) conditions, the ultra-intense lasers can allow performing PAA with performances comparable with those achieved with conventional accelerators. Moreover, laser-driven PAA could be exploited jointly with complementary laser-driven materials characterization techniques under investigation in existing laser facilities.

Circular muon colliders offer the prospect of colliding lepton beams at unprecedented center-ofmass energies. The continuous decay of stored muons poses, however, a significant technological challenge for the collider and detector design. The secondary radiation fields induced by decay electrons and positrons can strongly impede the detector performance and can limit the lifetime of detector components. Muon colliders therefore require an elaborate interaction region design, which integrates a custom detector shielding together with the detector envelope and the final focus system. In this paper, we present design studies for the machine-detector interface and we quantify the resulting beam-induced background for different center-of-mass energies. Starting from the optics and shielding design developed by the MAP collaboration for 1.5 TeV, we devise an initial interaction region layout for the 10 TeV collider. In particular, we explore the impact of lattice and shielding design choices on the distribution of secondary particles entering the detector. The obtained results serve as crucial input for detector performance and radiation damage studies.

Laser-driven radiation sources are attracting increasing attention for several materials science applications. While laser-driven ions, electrons and neutrons have already been considered to carry out the elemental characterization of materials, the possibility to exploit high energy photons remains unexplored. Indeed, the electrons generated by the interaction of an ultra-intense laser pulse with a near-critical material can be turned into high energy photons via bremsstrahlung emission when shot into a high-Z converter. These photons could be effectively exploited to perform Photon Activation Analysis (PAA). In the present work, the possibility to perform laser-driven PAA is proposed and investigated. By means of a theoretical and numerical approach, we identify the optimal near-critical material and converter parameters for laser-driven PAA in a wide range of laser intensities. Finally, exploiting the Monte Carlo and Particle-In-Cell tools, we simulate PAA experiments performed with both conventional accelerators and laser-driven sources.