The Care Accelerator R&D Programme in Europe

CARE, an ambitious and coordinated programme of accelerator research and developments oriented towards high energy physics projects, has been launched in January 2004 by the main European laboratories and the European Commission. This project aims at improving existing infrastructures dedicated to future projects such as linear colliders, upgrades of hadron colliders and high intensity proton drivers. We describe the CARE R&D plans, mostly devoted to advancing the performance of the superconducting technology, both in the fields of RF cavities for electron or proton acceleration and of high field magnets, as well as to developing high intensity electron and proton injectors. We highlight some results and progress obtained so far

Modélisation déterministe de la crue extrême d'un bassin versant de montagne avec application de la description géomorphologique du réseau hydrographique

Les méthodes de calcul des crues de projet pour des grands barrages sont de type statistique ou de type déterministe (PMP/PMF). Ce dernier type de méthodes est principalement utilisé dans le monde anglo-saxon (États-Unis, Australie), mais peut offrir une alternative intéressante aux méthodes statistiques, qui présentent des lacunes pouvant être importantes.Une application des méthodes PMP/PMF sur des bassins suisses a mis en évidence l'intérêt de ces méthodes, mais aussi leurs faiblesses. Une adaptation des outils déterministes est nécessaire pour prendre en compte les particularités des bassins de montagne. Il s'agit principalement de mieux tenir compte des propriétés physiques des bassins versants et des phénomènes de non linéarité. Dans ce but, un concept de modélisation utilisant la description géomorphologique du bassin versant a été utilisé et amélioré. Le premier modèle utilisé est l'hydrogramme unitaire géomorphologique, qui existe depuis 1979. Le deuxième modèle utilise le concept de cascade de réservoirs hydrologiques à vidange non linéaire, dont les éléments sont issus de la description géomorphologique du bassin. C'est là une modélisation nouvelle qui est particulièrement adaptée au contexte des crues extrêmes dans les Alpes. Un travail de calibration et validation du modèle a montré que ce modèle a un bon potentiel d'utilisation. La principale difficulté revient à identifier la signification physique des paramètres du modèle, qui pourrait s'appuyer sur les résultats d'un autre type de modélisation couplant la géomorphologie du bassin aux equations de l'onde cinématique. Ce modèle est en cours de test à l'IATE.Design floods for large dams are computed either with statistical or deterministic methods (Probable maximum precipitation, PMP/probable maximum flood, PMF). The latter presents an interesting alternative to statistical rnethods, whose drawbacks may be significant, especially when hydrometeorological data are deficient.PMP/PMF methods are based on assumption of the existence of an upper limit of the hydrometeorological processes. The prevalent method for PMP estimation is the maximization - transposition technique. Simpler methods, such as the statististically based technique, also exist. However, the most accurate method may well be the use of a meteorological model, but this aspect is still in the research domain.PMF is derived from a PMP using a simplified loss function and a transfer function for which parameters are maximized. The prevalent transfer function is the unit hydrograph model.Application of traditional PMP/PMF method on alpine catchments showed important weaknesses due to the transfer function. Alpine catchments are characterized by steep slopes, thin soil cover, poor vegetation, and large floods are due to heavy, short thunderstorms. Consequently, hydrological response is very sensitive to the topography of the catchment. Nonlinearity must be taken into account in many cases. However, experience showed that a model cannot take into account a detailed description of the catchment.In order to take into account the characteristcs of alpine catchments while staying as simple as possible, we have used the geomorphologic description of the catchment as a modeling basis. This representation is based on the Strahler ordering scheme, and defines all possible path types that a surface runoff dropret may follow to reach the outlet. This description has been used since 1979 in the geomorphologic unit hydrograph (GUH) formulation.We developed a geomorphorogic nonlinear cascade (GNC) in order to take into account nonlinear processes. The GNC model uses the geomorphologic description of the catchment to define the reservoirs of hydrological cascades. A cascade represents a path type; the first reservoir ofa cascade is an overland element and subsequent reservoirs are channels with increasing Strahler's order. Outflow from a reservoir is the inflow of the downstream reservoir. Outflows from all cascades are combined to produce the global catchment response. The two equations used in the GNC model are a global continuity equation: I - O = dV/dt, and a nonlinear outflow equation: O = k Vx, where I is an input term, that is precipitation for the first reservoir, and outflow from the upstream element for channel reservoirs, V is the volume of water stored in a reservoir at time t, k is a consfant, and x an exponent. The parameter k varies with each reservoir as a function of surface area (for overland erements) or rength (for channel elements). The exponent x should be between 1 and 2.The two models, GUH and GNC, have been calibrated with an automatic optimization procedure, and tested on the Vogelbach catchment. This catchment is located in the swiss alps (Arptar, canton of schwytz); it is a third order catchment, and its area is 1,55 km2. Both models gave good results, although the GUH model had a tendency to smooth the dischage.Inorder to improve the physical meaning of the moder parameters, we are testing a third model linking the geomorphologic description with the kinematic wave equations. Results are promising, but are not shorm in this paper.The hydrologic modeling based on the geomorphologic description of the catchment seems to be a good compromise between lumped modeb and detailed distributed models, which are difficult to apply

Evaluation of the Transfer of Heat from the Coil of the LHC Dipole Magnet to Helium II

During operation of the Large Hadron Collider at CERN, heat will be generated inside the coils of its superconducting magnets as a consequence of ramping of magnetic field, and of the interaction of lost beam particles with the magnet mass. Heat has to be transferred from the conductor into the He II coolant and removed from the magnet environment. During the LHC R&D stage, this transfer has been extensively studied on simulated coil segments at CEA/Saclay, and by analyzing dynamic behavior of short model magnets at CERN. Owing to the importance of efficient cooling for the design of future superconducting accelerator magnets, study of heat transfer has been restored at CERN and in frame of the Next European Dipole Collaboration. The article features two recently performed works: 1. Attempt to analyze archived high ramp rate quench data of 1-m-long LHC model dipole magnets of the 2nd generation. 2. Development of a method for direct measurement of heat transfer on segments of production LHC dipole magnet coils

Quench antenna for superconducting particle accelerator magnets

We report on the design, fabrication, and test of an assembly of stationary pickup coils which can be used to localize quench origins. After describing the pickup coils configuration, we develop a simple model of current redistribution which allows interpretation of the measured voltages and determination of the turn of the magnet coil in which the quench started. The technique is illustrated by analyzing the data from a quench of a 5-cm-aperture, 15-m-long SSC dipole magnet prototype

Low-field Instabilities in Nb3_{3}Sn Multifilamentary Wires: the Possible Role of Unreacted Nb

We report an experimental study aiming to demonstrate the not negligible role of unreacted Nb on the magnetic instabilities in superconducting Nb$_{3}$Sn multifilamentary wires, observable through partial flux jumps at magnetic field values below 0.5 T. The analysed wires were recently developed for use as dipoles required in future high-energy proton accelerators and are based on powder-in-tube technology. We studied both unreacted (only involving Nb filaments) and reacted wires, finding flux jump instabilities in both cases when performing magnetic measurements. The results can be interpreted on the basis of the critical state model and are coherent with the intrinsic stability criterion

Nb3_3Sn conductor development and characterization for NED

The main purpose of Next European Dipole (NED) project is to design and to build an Nb$_{3}$Sn ~ 15 T dipole magnet. Due to budget constraints, NED is mainly focused on superconducting cable development and production. In this work, an update is given on the NED conductor development by Alstom-MSA and SMI, which uses, respectively, Internal-Tin-Diffusion and Powder-In-Tube methods, with the aim of reaching a non-copper critical current density of ~ 3000 A/mm2 at 12 T and 4.2 K. Characterization results, including critical current and magnetization data, are presented and discussed, as well, for conductors already developed by both companies for this project. SMI succeeded to produce a strand with 50 µm diameter filaments and with a critical current of ~ 1400 A at 4.2 K and 12 T, corresponding to a non-copper critical current density of ~ 2500 A/mm2. Cabling trials with this strand were successfully carried out at LBNL