[en] Thin alkali halide films are currently used as transmissive UV-photocathodes and as protecting layers for visible photocathodes. The surface morphology of 20 and 75 nm thick evaporated CsI, NaI and CsBr films was investigated by means of a scanning electron microscope, to which the samples were transferred, under vacuum, with practically no contact with air. It is shown that the film continuity, in particular that of NaI, is strongly affected by short exposure to moisture. CsI, which is the less hygroscopic material among the three, exhibits the most continuous structure

[en] Gas avalanche detectors, combining solid photocathodes with fast electron multipliers, provide an attractive solution for photon localization over very large sensitive areas and under high illumination flux. They offer single-photon sensitivity and the possibility of operation under very intense magnetic fields. We discuss the principal factors governing the operation of gas avalanche photomultipliers. We summarize the recent progress made in alkali-halide and CVD-diamond UV-photocathodes, capable of operation under gas multiplication, and novel thin-film protected alkali-antimonide photocathodes, providing, for the first time, the possibility of operating gas photomultipliers in the visible range. Electron multipliers, adequate for these photon detectors, are proposed and some applications are briefly discussed

[en] We report on a multi-institute comparison of critical current data measured on a modern NbTi wire for the Large Hadron Collider (LHC), which has shown a standard deviation below 1% in critical current density spread in more than 1500 measurements. Interlaboratory comparisons on Nb₃Sn wires have shown ambiguities that could be attributable to strain related differences in critical current density, originating from differences in sample handling, reaction, and mounting techniques, or also to differences in the magnetic field and current calibrations between the institutes. A round robin test of a well characterized NbTi wire provides a baseline variance in critical current results that is presumed to be attributable only to differences in the characterization systems. Systematic differences on the order of 3.5% are found in the comparison. The most likely cause for the observed differences is a small diameter holder that brings the wire into a strain regime in which strain effects can no longer be ignored. A NbTi round robin test, when performed properly, will separate system differences from sample specific differences and provide laboratories with an opportunity to calibrate equipment against a standard measurement.

[en] The Next European Dipole (NED) activity is aimed at the development of a large-aperture, high-field superconducting magnet relying on high-performances Nb₃Sn conductors. Part of the NED program is devoted to the mechanical study of a new generation of Nb₃Sn wires and to predict and describe their behavior under the severe loading conditions of the cabling process. The deformation resulting from the cabling process was simulated through mechanical analyses by Finite Elements (FE). The ensuing results of FE analyses are presented, allowing the wire behavior under simple uni-axial loads to be described. They are compared to cross section micrographs of deformed wires. (authors)

[en] The International Thermonuclear Experimental Reactor (ITER) is an international project aimed to build a fusion reactor using a plasma magnetic confinement (Tokamak) in Cadarache, France, which will demonstrate that such a machine can produce at least 10 times more energy than the one spent to sustain the fusion reaction. The project involves 7 partners: China, European Union (EU), India, Japan (JA), South Korea, Russian Federation and United States of America, all of whom will provide 'in-kind' contributions to the central ITER Organization (IO) in the form of components required to build the machine. Each of the seven partners is represented by a Domestic Agency (DA) in order to comply with their in-kind contributions. The European Joint Undertaking for ITER and the Development of Fusion Energy or 'Fusion for Energy' (F4E) is a type of European organization known as a Joint Undertaking created under the Euratom Treaty by a decision of the Council of the European Union and it is the ITER European DA. F4E has three main objectives: a) Providing European contributions to the ITER international fusion energy research project being built in Cadarache, France; b) Providing European contributions to a number of joint projects with Japan that aim to accelerate the development of fusion - the 'Broader Approach'; c) Coordinating a program of activities to prepare for the first demonstration fusion reactors that can generate electricity. ITER superconducting magnet system, working at 4.5 K, consists of 18 Toroidal Field (TF) coils, 6 Central Solenoid (CS) modules, 6 Poloidal Field (PF) coils and 18 Correction Coils (CC). F4E is responsible for the procurement of about 25% of the magnet system. In this paper we are reporting on the main challenges to be faced during the manufacturing processes in terms of weld and their inspection. (authors)

[en] The main purpose of Next European Dipole (NED) project is to design and to build an Nb₃Sn ∼ 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

[en] The performance of the toroidal field (TF) magnet conductors for the ITER machine are qualified by a short full-size sample (4 m) current sharing temperature (T_cs) test in the SULTAN facility at CRPP in Villigen, Switzerland, using the operating current of 68 kA and the design peak field of 11.8 T. Several samples, including at least one from each of the six ITER Domestic Agencies participating in TF conductor fabrication (China, European Union, Japan, Russia, South Korea and the United States), have been qualified by the ITER Organization after achieving T_cs values of 6.0–6.9 K, after 700–1000 electromagnetic cycles. These T_cs values exceed the ITER specification and enabled the industrial production of these long-lead items for the ITER tokamak to begin in each Domestic Agency. Some of these samples did not pass the qualification test. In this paper, we summarize the performance of the qualified samples, analyze the effect of strand performance on conductor performance, and discuss the details of the test results. (paper)

[en] Full text: Starting March 2007, over 60 ITER cable-in-conduit conductors (CICC) have been tested in the SULTAN test facility in Villigen, Switzerland, including TF, CS, PF and busbars samples. The conductors are supplied by the ITER Domestic Agencies (DAs) and assembled into SULTAN samples at CRPP. The test reproduces the actual operating conditions in the ITER coils, except for the hoop load and the CS maximum field. Depending on the stage of the procurement, the SULTAN samples are categorized into Design Verification, Supplier Qualification, Process Qualification and Series Production. The number of remaining samples to be tested during the ITER construction phase is about 40. For the NbTi CICC, the results confirm the prediction from the strand data, which are made taking the peak field over the conductor cross section as operating field. At low current density, where the n-index of the transition is measurable, the NbTi CICC and the NbTi strand have the same n-index. All the NbTi samples passed the supplier qualification phase. For the Nb₃Sn CICC, the performance prediction is hindered by the irreversible degradation caused by filament damage occurring during cyclic loading. At the first run of the test campaign, the performance of all the Nb₃Sn samples largely meets the target. Contrary to the NbTi CICC case, the n-index of the transition is substantially lower than in the strands. The performance loss upon load cycles and thermal cycles has a broad range. All the TF conductor samples passed the supplier qualification phase. For the CS conductors, the supplier qualification phase will be finalized in 2012. (author)

[en] Construction of the ITER magnet systems has been started at the end of 2007 following the signature of the first procurement arrangements (PA) for the toroidal field (TF) conductors. Six ITER members are involved in the share of the ITER magnet components and, to date, eighteen PA between the ITER Organization and six domestic agencies have been signed. Substantial progress towards full-scale construction has been achieved with the placement of the first large manufacturing contracts, the production of several tens of tons of advanced Nb₃Sn and NbTi strand, and the set-up of large cabling and jacketing facilities. The detailed design of the coils and support structures has also been finalized. The qualification of the fabrication processes for the TF coils and poloidal field (PF) coils has been initiated. The detailed design of the central solenoid (CS) coils is being developed. The design of the correction coils (CCs) with their support structures has been finalized, as well as for the TF gravity supports and clamps of the PF coils. The manufacture of prototypes of the feeder lines and current leads has been started, while ITER is in charge of the procurement of the required magnet instrumentation. This paper provides a progress report on the ITER magnet construction as per December 2010. (paper)

[en] The ITER magnet system uses cable-in-conduit conductor (CICC) technology with individual strands twisted in several stages resulting in a rope-type cable, which is inserted into a stainless steel conduit. The combination of high current (up to 68 kA) and background magnetic field (up to 13 T) results in large transverse Lorentz forces exerted on the conductors during magnet system operation. The high transverse forces, accompanied with the cyclic nature of the load, have a strong influence on the conductor properties. The Twente Cryogenic Cable Press is used to simulate the effect of the Lorentz forces on a conductor comparable to the ITER magnet operating conditions. An overview is presented of the AC coupling and hysteresis loss, mechanical deformation characteristics and inter-strand contact resistance measurement results obtained on full-size ITER CICCs measured in the Twente Cryogenic Cable Press. The aim of this work is to characterize conductors’ electromagnetic and mechanical properties during cycling of the load up to 30 000 cycles. The evolution of the magnetization (AC coupling loss time constant nτ), mechanical properties and inter-strand resistance R _c between selected strands is presented along with loading history. The R _c between first triplet strands is also measured as a function of applied load. It is shown that transverse load cycling has a strong influence on the CICC properties. An overview of the results for eight toroidal field conductors, two central solenoid conductors, three poloidal field conductors of different types (PF1 and 6, PF4, PF5), one main bus-bar and one correction coil conductor is presented. (paper)