Novel reaction force for ultra-relativistic dynamics of a classical point charge

The problem of the electromagnetic radiation of an accelerated charged particle is one of the most controversial issues in Physics since the beginning of the last century, representing one of the most popular unsolved problems of the Modern Physics. Different equations of motion have been proposed throughout history for a point charge including the electromagnetic radiation emitted, but all these expressions show some limitations. An equation based on the principle of conservation of energy is proposed in this work for the ultra-relativistic motion. Different examples are analyzed showing that the energy lost by the charge agrees with the Li\'enard formula. This proposed equation has been compared with the Landau-Lifshitz equation obtaining a good agreement in the range of application of the Landau-Lifshitz formula.Comment: 9 pages, 10 figure

Numerical study of dark current dynamics in a high-gradient backward travelling wave accelerating cavity using the electromagnetic simulation software CST studio.

High-Gradient accelerating cavities are one of the main research lines in the development of compact linear colliders. However, the operation of such cavities is currently limited by nonlinear effects that are intensified at high electric fields, such as dark currents and radiation emission or RF breakdowns. A new normal-conducting High-Gradient S-band Backward Travelling Wave accelerating cavity for medical application (v=0.38c) designed and constructed at Conseil Européen pour la Recherche Nucléaire (CERN) is being tested at Instituto de Física Corpuscular (IFIC) High Power RF Laboratory. The objective consists of studying its viability in the development of compact linear accelerators for hadrontherapy treatments in hospitals. Due to the high surface electric field in the cavity, electrons are emitted following Fowler- Nordheim equation, also known as dark currents. The emission and dynamic of these electrons are of fundamental importance on different phenomena such as RF Breakdowns or radiation dose emission. In this work, 3D electromagnetic numerical simulations have been performed using the computer simulation technology software CST Studio Suite. Then, the resulting EM field maps are used to study the emission and electron dynamics inside the cavity. The simulation results are compared with experimental data and first conclusions discussed

Relativistic particle motion of a charge including the radiation reaction

The problem of the electromagnetic radiation of an accelerated charged particle is one of the most controversial issues in Physics since the beginning of the last century representing one of the most popular unsolved problems of the Modern Physics. Different equations of motion for a point charge including the electromagnetic radiation emitted have been proposed throughout history, but all these expressions show some limitations. An equation based on the principle of conservation of energy is proposed for the ultra-relativistic motion. Different examples are analyzed showing that the energy lost by the charge agrees with the relativistic generalization of the Larmor formula. This proposed equation has been compared with the Landau-Lifshitz equation obtaining a good agreement in the range of application of the Landau-Lifshitz formula. Finally, it is discussed a possible variation of the typical relativistic particle integrators (e.g. Boris, Vay or Higuera-Cary methods) in order to include the radiation reaction

Study of the RF pulse heating phenomenon in high gradient accelerating devices by means of analytical approximations

The main objective of this work is to present a simple method, based on analytical expressions, for obtaining a quick approximation of the temperature rise due to the Joule effect inside the metallic walls of an RF accelerating device. This proposal relies on solving the 1D heat-transfer equation for a thick wall, where the heat sources inside the wall are the ohmic losses produced by the RF electromagnetic fields penetrating the metal with finite electrical conductivity. Furthermore, it is discussed how the theoretical expressions of this method can be applied to obtain an approximation to the temperature increase in realistic 3D RF accelerating structures, taking as an example the cavity of an RF electron gun. These theoretical results have been benchmarked with numerical simulations carried out with commercial finite-element method codes, finding good agreement among them

Two-dimensional simulation of the electron transport in a photomultiplier tube

Photomultiplier tubes are widely used in experimental physics because they convert small light signals into a measurable electric current. Although their working principle is well known, it is very difficult to find simulations of the electron transport in these devices. For this reason, the electron transport in the Hamamatsu R13408-100 photomultiplier tube has been simulated in 2D. The software SUPERFISH is used for calculating the electrostatic fields and the Boris method for the effective electron dynamics. The secondary electron emission in the dynodes is implemented using an effective electron model and the modified Vaughan’s model. Some figures of merit for photomultiplier tubes (e.g. the gain, the electron transit time or the transit time spread) in function of the supply voltage and an external magnetic field have been studied obtaining a good qualitative accordance with the Hamamatsu datasheet. In further studies, we are going to compare our simulations with experimental measurements

Decision-support tools to build climate resilience against emerging infectious diseases in Europe and beyond

Climate change is one of several drivers of recurrent outbreaks and geographical range expansion of infectious diseases in Europe. We propose a framework for the co-production of policy-relevant indicators and decision-support tools that track past, present, and future climate-induced disease risks across hazard, exposure, and vulnerability domains at the animal, human, and environmental interface. This entails the co-development of early warning and response systems and tools to assess the costs and benefits of climate change adaptation and mitigation measures across sectors, to increase health system resilience at regional and local levels and reveal novel policy entry points and opportunities. Our approach involves multi-level engagement, innovative methodologies, and novel data streams. We take advantage of intelligence generated locally and empirically to quantify effects in areas experiencing rapid urban transformation and heterogeneous climate-induced disease threats. Our goal is to reduce the knowledge-to-action gap by developing an integrated One Health—Climate Risk framework

The 2024 Europe report of the Lancet Countdown on health and climate change: unprecedented warming demands unprecedented action

Record-breaking temperatures were recorded across the globe in 2023. Without climate action, adverse climate-related health impacts are expected to worsen worldwide, affecting billions of people. Temperatures in Europe are warming at twice the rate of the global average, threatening the health of populations across the continent and leading to unnecessary loss of life. The Lancet Countdown in Europe was established in 2021, to assess the health profile of climate change aiming to stimulate European social and political will to implement rapid health-responsive climate mitigation and adaptation actions. In 2022, the collaboration published its indicator report, tracking progress on health and climate change via 33 indicators and across five domains. This new report tracks 42 indicators highlighting the negative impacts of climate change on human health, the delayed climate action of European countries, and the missed opportunities to protect or improve health with health-responsive climate action. The methods behind indicators presented in the 2022 report have been improved, and nine new indicators have been added, covering leishmaniasis, ticks, food security, health-care emissions, production and consumption-based emissions, clean energy investment, and scientific, political, and media engagement with climate and health. Considering that negative climate-related health impacts and the responsibility for climate change are not equal at the regional and global levels, this report also endeavours to reflect on aspects of inequality and justice by highlighting at-risk groups within Europe and Europe's responsibility for the climate crisis

Bitwise Signature Comparison: Enabling more Efficient Similarity Estimation

Estimating the similarity of sets of data is a common operation in computing. Minhash is widely used to estimate similarity by computing a signature for each set and then comparing their signatures. Therefore, signature comparison is an important part of similarity estimation. To make the comparison efficient, the size of the signature components is commonly set to the word size of the processor or to one half or one fourth of it. This enables efficient data manipulation and comparison but is not optimal in terms of storage. For example, 48-bit signatures may be more than enough in many applications but since that size cannot be easily manipulated by most processors, 64-bit signatures are used. This implies a 33.3% memory overhead. In this paper, Bitwise Signature Comparison (BSC), a method that enables the efficient comparison of signature components of any bitwidth is presented and evaluated. The results show that BSC achieves a similar speed to that of the traditional comparison implementation regardless of the size of the signature components. This enables the use of any signature component size enabling better trade-offs in the implementation of similarity estimation sketches

X-band RF photoinjector design for the CompactLight project

RF photoinjectors have been under development for several decades to provide the high-brightness electron beams required for X-ray Free Electron Lasers. This paper proposes a photoinjector design that meets the Horizon 2020 CompactLight design study requirements. It consists of a 5.6-cell, X-band (12 GHz) RF gun, an emittance-compensating solenoid and two X-band traveling-wave structures that accelerate the beam out of the space-charge-dominated regime. The RF gun is intended to operate with a cathode gradient of 200 MV/m, and the TW structures at a gradient of 65 MV/m. The shape of the gun cavity cells was optimized to reduce the peak electric surface field. An assessment of the gun RF breakdown likelihood is presented as is a multipacting analysis for the gun coaxial coupler. RF pulse heating on the gun inner surfaces is also evaluated and beam dynamics simulations of the 100MeV photoinjector are summarized

Spectrum/Space Switching and Multi-Terabit Transmission in Agile Optical Metro Networks

An SDN-enabled modular photonic system architecture, including VCSEL-based bandwidth/bitrate variable transceivers, for multi-terabit capacity transmission and agile spectrum/space switching in optical metro networks is presented, providing the proposed technological solutions, programmability aspects and preliminary assessment