Quench protection analysis in accelerator magnets, a review of the tools

As accelerator magnets see the increase of their magnetic field and stored energy, quench protection becomes a critical part of the magnet design. Due to the complexity of the quench phenomenon interweaving magnetic, electrical and thermal analysis, the use of numerical codes is a key component of the process. In that respect, we propose here a review of several tools commonly used in the magnet design community.Comment: 4 pages, Contribution to WAMSDO 2013: Workshop on Accelerator Magnet, Superconductor, Design and Optimization; 15 - 16 Jan 2013, CERN, Geneva, Switzerlan

Overview of Single-particle Nonlinear Dynamics

We give an overview of the single-particle non linear dynamics in circular accelerators. The main topics are: integration of equations of motion, fast symplectic tracking, dynamic aperture definition, long-term methods, quality factors and lattice optimization. Special emphasis is put on ideas and tools developed during the last decade

Nb-Ti Symmetric Triplets for the LHC luminosity Upgrade

We study a Nb-Ti lay-out for the triplet in the low-beta interaction regions of the Large Hadron Collider, based on a stretched version of the present baseline. The triplet length is increased from the present value of 32 m up to about 60 m. The quadrupoles are based on a two layer coil made with the LHC main dipole cable. A parametric analysis of the dependence of the optics and magnet performances on the triplet length and aperture is carried out

Deteção automática de lesões de esclerose múltipla em imagens de ressonância magnética cerebral utilizando BIANCA

The aim of this work was to design and optimize a workflow to apply the Machine Learning classifier BIANCA (Brain Intensity AbNormalities Classification Algorithm) to detect lesions characterized by white matter T2 hyperintensity in clinical Magnetic Resonance Multiple Sclerosis datasets. The designed pipeline includes pre-processing, lesion identification and optimization of BIANCA options. The classifier has been trained and tuned on 15 cases making up the training dataset of the MICCAI 2016 (Medical Image Computing and Computer Assisted Interventions) challenge and then tested on 30 cases from the Lesjak et al. public dataset. The results obtained are in good agreement with those reported by the 13 teams concluding the MICCAI 2016 challenge, thus confirming that this algorithm can be a reliable tool to detect and classify Multiple Sclerosis lesions in Magnetic Resonance studies.Este trabalho teve como objetivo a conceção e otimização de um procedimento para aplicação de um algoritmo de Machine Learning, o classificador BIANCA (Brain Intensity AbNormalities Classification Algorithm), para deteção de lesões caracterizadas por hiperintensidade em T2 da matéria branca em estudos clínicos de Esclerose Múltipla por Ressonância Magnética. O procedimento concebido inclui pré-processamento, identificação das lesões e otimização dos parâmetros do algoritmo BIANCA. O classificador foi treinado e afinado utilizando os 15 casos clínicos que constituíam o conjunto de treino do desafio MICCAI 2016 (Medical Image Computing and Computer Assisted Interventions) e posteriormente testado em 30 casos clínicos de uma base de dados pública (Lesjak et al.). Os resultados obtidos são em concordância com os alcançados pelas 13 equipas que concluíram o desafio MICCAI 2016, confirmando que este algoritmo pode ser uma ferramenta válida para a deteção e classificação de lesões de Esclerose Múltipla em estudos de Ressonância Magnética.Mestrado em Tecnologias da Imagem Médic

Quench limits in the next generation of magnets

Several projects around the planet aim at building a new generation of superconducting magnets for particle accelerators, relying on Nb3Sn conductor, with peak fields in the range of 10-15 T. In this paper we give an overview of the main challenges for protecting this new generation of magnets. The cases of isolated short magnets, in which the energy can be extracted on an external dump resistor, and chain of long magnets, which have to absorb their stored energy and have to rely on quench heaters, are discussed. We show that this new generation of magnets can pose special challenges, related to both the large current density and to the energy densities.Comment: 7 pages, Contribution to WAMSDO 2013: Workshop on Accelerator Magnet, Superconductor, Design and Optimization; 15 - 16 Jan 2013, CERN, Geneva, Switzerlan

Magnetic Design of Superconducting Magnets

In this paper we discuss the main principles of magnetic design for superconducting magnets (dipoles and quadrupoles) for particle accelerators. We give approximated equations that govern the relation between the field/gradient, the current density, the type of superconductor (Nb-Ti or Nb3Sn), the thickness of the coil, and the fraction of stabilizer. We also state the main principle controlling the field quality optimization, and discuss the role of iron. A few examples are given to show the application of the equations and their validity limits.Comment: 24 pages, contribution to the CAS-CERN Accelerator School: Superconductivity for Accelerators, Erice, Italy, 24 April - 4 May 2013, edited by R. Baile

Modeling of CO2 circulation in the Colli Albani area

The Colli Albani is a quiescent volcano located nearby the city of Roma, characterised by the presence of an active geothermal system, periodic seismic swarms and intense diffuse degassing. Several accidents, some of which lethal, have occurred in recent years associated to episodes of more intense releases and outbursts of volcanic gases, dominantly CO2 and H2S. Gas emissions are presently the most hazardous phenomenon for the highly populated Colli Albani area, along with the potential occurrence of seismic activity. This chapter presents the numerical modeling of heat and fluid circulation applied to study the mechanisms which control the diffuse degassing at Colli Albani volcano. Multi-phase and multi-component simulations were carried out using the TOUGH2 geothermal simulator in a realistic geological context, which includes all available information on the stratigraphy and structure of the Colli Albani substrate, along with data on the total gas flux, the local geothermal gradient, the local hydrogeology, and the thermal characteristics of the rocks. The geothermal reservoir at Colli Albani is hosted by the 2-3000 m thick Mesozoic-Cenozoic carbonatic succession capped by Pliocene clays which act as aquiclude and are few hundreds to over 1000m thick, in turned covered by continental sedimentary and volcanic deposits, which host the shallow hydrogeological system. Numerical simulations evaluate the effects associated with the thickness of the carbonatic basement and its cap rock; the role of CO2 supply rate at depth; and the influence of permeable channelways through the cap rocks. Numerical simulations show that thickness of the geothermal reservoir hosted by the carbonatic basement and of its impervious cover control the vigor of the convection, the extent and depth (and hence temperature) of the lateral recharge area, and the distribution of the carbon dioxide within the system. This result suggests that the temperature distribution and diffuse degassing at surface do not simply reflect the characteristics of the heat and fluid source at depth, but also the specific structure and hydrological properties of the site where they are measured

Hydrothermal Fluid Circulation and its Effect on Caldera Unrest

This paper focuses on the role that hydrothermal systems may play in caldera unrest. Changes in the fluid chemistry, temperature, and discharge rate of hydrothermal systems are commonly detected at the surface during volcanic unrest, as hydrothermal fluids adjust to changing subsurface conditions. Geochemical monitoring is carried out to observe the evolving system conditions. Circulating fluids can also generate signals that affect geophysical parameters monitored at the surface. Effective hazard evaluation requires a proper understanding of unrest phenomena and correct interpretation of their causes. Physical modeling of fluid circulation allows quantification of the evolution of a hydrothermal system, and hence evaluation of the potential role of hydrothermal fluids during caldera unrest. Modeling results can be compared with monitoring data, and then contribute to the interpretation of the recent caldera evolution. This paper: 1) describes the main features of hydrothermal systems; 2) briefly reviews numerical modeling of heat and fluid flow through porous media; 3) highlight the effects of hydrothermal fluids on unrest processes; and 4) describes some model applications to the Phlegrean Fields caldera. Simultaneous modeling of different independent parameters has proved to be a powerful tool for understanding caldera unrest. The results highlight the importance of comprehensive conceptual models that incorporate all the available geochemical and geophysical information, and they also stress the need for high-quality, multi-parameter monitoring and modeling of volcanic activity