[en] The authors report on the results of a new approach to investigating hydrogen in metals by the positron lifetime technique. Molybdenum and nickel have been irradiated with 6 MeV protons at 15 K. Detailed information is achieved about radiation-induced lattice defects, hydrogen-defect interactions and void nucleation by isochronal annealing studies

[en] The TF coils of ITER are one of the largest, heaviest and possibly most complex superconducting coils ever conceived. The composite based pre-compression rings will hold tightly together the 18 TF coils with a centripetal pre-load of 70 MN per coil on their top and bottom side. Their presence will achieve a dramatic reduction of the operational cyclic stresses in different regions of the TF coils allowing fatigue endurance beyond the 30000 expected cycles. An extensive R and D campaign carried out has given a thorough understanding of the expected mechanical performance. Possible failure modes of the full scale rings have also been assessed. The particular operational conditions of the rings are demanding: continuously stressed to around 400 MPa in hoop direction and 40 MPa of radial compression, undergoing thermal cycles from RT to 4K, ionizing radiation of hundreds of kGy and cyclic loads at up to 10% of nominal stress. Combining the obtained results with possible scaling factors from the model rings to the full size rings has triggered this study of the rings following the Kinetic Theory of Fracture on an atomic scale and Fracture Mechanics for polymers to improve the understanding of long term behavior. An expression that predicts the life of the model rings under long duration stress relaxation tests has been obtained. (author)

[en] The stability analysis of the Poloidal Field Coils of the ITER Project, specially the PF5, PF3 and PF2 coils for scenario 2, normal mode has been performed using the Gandalf code. The conductor stability is assessed in the most severe operating conditions, at the minimal temperature margin time of the 4. pulse. It consists in determining the maximal deposited energy (perturbation in mJ/cm³ of superconducting strands) which can be absorbed without runaway. This study is performed for three initial different designs: Cu-non-Cu ratio of 2.3, 1.6 and 4.4 for PF5, and Cu-non-Cu ratio of 2.3, 1.6 and 6.9 for PF3 and PF2. The results are presented as well as a discussion about the phenomena, important parameters and uncertainties. For each type of perturbation, the calculated stability limits are quite similar from one design to another. The low Cu-non-Cu ratios do not show significant stability degradation compared to the original ITER design with high ratios. (authors)

[en] In the framework of the development of High Temperature Superconducting current leads (HTSCL), one demonstrator was tested in 2004 together with a conventional current lead, both were connected by a superconducting short circuit NbTi conductor, referred as busbar III (BBIII). Here the BBIII was used for current distribution measurements. In addition to a 64 Hall Probe (HP) system, two additional 4-HP heads from CEA were assembled at both ends of the BBIII. This system, already successfully used during the TFMC (toroidal field model coil) test phase II, was now adapted to the present BBIII set-up. Electrical tests were performed for conductor currents up to 80 kA without background magnetic field. In this paper, the analysis of the current distribution is presented using two methods: - First the current barycenter excursion was investigated in various runs. A comparative study is presented between resistive and inductive hypotheses where the current is supposed to be uniformly distributed. In particular, we show that the two hypotheses lead to different results. - Second a global model of the current bundles distribution between four artificial sub-cables is investigated. More quantitative results show current imbalances between sub-cables to be either significant or weak, depending on whether the resistive or the inductive hypothesis is considered. A discussion on why the second solution is thought to be more likely is presented. In addition, a global comparison with results previously obtained during the TFMC tests will be shown. (authors)

[en] A short sample of the NbTi cable-in-conduit conductor (CICC) manufactured for the ITER PF insert coil has been tested in the SULTAN facility at CRPP. The short sample consists of two paired conductor sections, identical except for the sub-cable and outer wraps, which have been removed from one of the sections before jacketing. The test program for conductor and joint includes DC performance, cyclic load and AC loss, with a large number of voltage taps and Hall sensors for current distribution. At high operating current, the DC behavior is well below expectations, with temperature margin lower than specified in the ITER design criteria. The conductor without wraps has higher tolerance to current unbalance. The joint resistance is by far higher than targeted. (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] Native vacancies are evidenced from positron lifetime measurements in as-grown CdTe, HgTe and Hg_0.8Cd_0.2Te. The positron lifetime depends on the conducting type of the materials rather than on the growing conditions. The native vacancies have two levels of ionisation and are identified as Cd-vacancies (VCd) in CdTe. (author) 2 figs., 2 tabs., 9 refs