Recent developments with the new tools for collimation simulations in Xsuite

Simulations of single-particle tracking involving collimation systems need dedicated tools to perform the different tasks needed. These include the accurate description of particle-matter interactions when a tracked particle impacts a collimator jaw; a detailed aperture model to identify the longitudinal location of losses; and others. One such tool is the K2 code in SixTrack, which describes the scattering of high-energy protons in matter. This code has recently been ported into the Xsuite tracking code that is being developed at CERN. Another approach is to couple the tracking with existing tools, such as FLUKA or Geant4, that offer better descriptions of particle-matter interactions and can treat lepton and ion beams. This includes the generation of secondary particles and fragmentation when tracking ions. In addition to the development of coupling with Geant4, the SixTrack-FLUKA coupling has recently been translated and integrated into the Xsuite environment as well. In this paper, we present the ongoing development of these tools. A thorough testing of the new implementation was performed, using as case studies various collimation layout configurations for the LHC Run 3

Real-time in situ optical tracking of oxygen vacancy migration in memristors

Resistive switches, which are also known as memristors, are low-power, nanosecond response devices that are used in a range of memory-centric technologies. Driven by an externally applied potential, the switching mechanism of valence change resistive memories involves the migration, accumulation and rearrangement of oxygen vacancies within a dielectric medium, leading to a change in electrical conductivity. The ability to look inside these devices and understand how morphological changes characterise their function has been vital in their development. However, current technologies are often destructive and invasive. Here, we report a non-destructive optical spectroscopy technique that can detect the motion of a few hundred oxygen vacancies with nanometre-scale sensitivity. Resistive switches are arranged in a nanoparticle-on-mirror geometry to exploit the high optical sensitivity to morphological changes occurring in tightly confined plasmonic hotspots within the switching material. Using the approach, we find that nanoscale oxygen bubbles form at the surface of a strontium titanate memristor film leading ultimately to device breakdown on cycling.GD acknowledges support from the Winton Programme for the Physics of Sustainability, J.J.B acknowledges funding from EPSRC grant EP/L027151/1, W.-W.L. and J.L.M.-D. from EPSRC grants EP/L011700/1, EP/N004272/1, EP/P007767/1 and the Isaac Newton Trust. AD acknowledges support from a Royal Society University Research Fellowship URF\R1\180097 and Royal Society Research Fellows Enhancement Award RGF\EA\181038, BdN acknowledges support from the Leverhulme Trust and the Isaac Newton Trust in the form of an ECF. The US-UK collaborative effort was funded by the U.S. National Science Foundation (ECCS-1902644 (Purdue University), ECCS-1902623 (University at Buffalo, SUNY) and the EPRSC, grant EP/T012218/1. J.D. also acknowledges funding from the UK Royal Academy of Engineering, grant CiET1819_24. B.Z. acknowledges support from China Scholarship Council and Cambridge Commonwealth, European and International Trust

Gyrotropic response in the absence of a bias field

Electromagnetic materials lacking local time-reversal symmetry, such as gyrotropic materials, are of keen interest and importance both scientifically and technologically. Scientifically, topologically nontrivial phenomena, such as photonic chiral edge states, allow for reflection-free transport even in the presence of large disorder. Technologically, nonreciprocal photonic devices, such as optical isolators and circulators, play critical roles in optical communication and computing technologies because of their ability to eliminate cross-talk and feedback. Nevertheless, most known natural materials that lack local time-reversal symmetry require strong external fields and function only in a limited range of the electromagnetic spectrum. By taking advantage of metamaterials capable of translating the property of unidirectional active electronic circuits into effective dielectric response, we introduce a microwave gyrotropic metamaterial that does not require an external magnetic bias. Strong bulk Faraday-like effects, observed in both simulations and experiments, confirm nonreciprocity of the effective medium. This approach is scalable to many other wavelengths, and it also illustrates an opportunity to synthesize exotic electromagnetic materials.National Natural Science Foundation (China) (61131002)National Natural Science Foundation (China) (61071063)National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (Award DMR-0819762)United States. Army Research Office. Institute for Soldier Nanotechnologies (Contract W911NF-07-D-0004

Xsuite: an integrated beam physics simulation framework

Xsuite is a newly developed modular simulation package combining in a single flexible and modern framework the capabilities of different tools developed at CERN in the past decades, notably Sixtrack, Sixtracklib, COMBI and PyHEADTAIL. The suite consists of a set of Python modules (Xobjects, Xpart, Xtrack, Xcoll, Xfields, Xdeps) that can be flexibly combined together and with other accelerator-specific and general-purpose python tools to study complex simulation scenarios. The code allows for symplectic modeling of the particle dynamics, combined with the effect of synchrotron radiation, impedances, feedbacks, space charge, electron cloud, beam-beam, beamstrahlung, and electron lenses. For collimation studies, beam-matter interaction is simulated using the K2 scattering model or interfacing Xsuite with the BDSIM/Geant4 library. Tools are available to compute the accelerator optics functions from the tracking model and to generate particle distributions matched to the optics. Different computing platforms are supported, including conventional CPUs, as well as GPUs from different vendors