177,610 research outputs found
The Curved Fast Ramped Superconducting Dipoles for FAIR SIS300 Synchrotron: From First Model to Future Developments
No full textThe synchrotron SIS300 is a fundamental component of the FAIR facility under construction at the GSI laboratory in Darmstadt. The acceleration of high intensity proton and heavy ion beams requires 4.5 T magnets, up to 7.8 m long, to be ramped up at a rate of 1 T/s. These challenging magnets have also the particular characteristic to be geometrically curved with a sagitta of 114 mm. To demonstrate the feasibility of curved fast cycled cos-theta dipoles, R&D activities were performed at the Italian National Institute of Nuclear Physics. Important steps of the R&D have been: 1) the development of a low loss superconducting Rutherford cable; 2) the construction of coil winding models for assessing the constructive feasibility of curved coils; and 3) the construction and tests of a complete model magnet composed of a cold mass enclosed in its horizontal cryostat. During 2012 the cold mass was tested at Italian National Institute of Nuclear Physics-LASA in a vertical cryostat. The paper discusses the main issues of the R&D activity from design to manufacture, results, future developments, and future perspectives
Magnesium Diboride Magnets for Future Particle Detectors
No full textSince 1978, when the CELLO magnet was manufactured, superconducting detector magnets have been wound using NbTi based, Aluminum stabilized conductors. However, other choices are possible and Magnesium Diboride (MgB2) could be an attractive alternative. Magnets wound with MgB2 can be operated at relatively high temperature (10 to 20 K), therefore increasing the cryogenics efficiency. Efficiency is not the only advantage in using MgB2 instead of NbTi: higher operating temperature and higher temperature margin lead to higher enthalpy margin, which means very stable magnets. In addition, MgB2 is much cheaper respect to High Temperature Superconductors. The cost comparison between Al stabilized NbTi magnets and MgB2 magnets must be made considering the entire fabrication process
Effect of pressure on the composition and superconducting Tc value of NbN prepared by combustion synthesis
No full textAppropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
The construction of the model of the curved fast ramped superconducting dipole for FAIR SIS300 synchrotron
No full textThe Facility for Anti-proton and Ion Research (FAIR), under development at GSI, includes the synchrotron SIS300, so called because the magnetic rigidity is 300 Tm. In order to reach the required high intensities of proton and heavy ions beams, the bending dipole magnets have to be pulsed from the injection magnetic field of 1.5 T up to 4.5 T maximum field at the rate of 1 T/s. These 7.8 m long magnets have cos Θ shaped coils with a 100 mm bore and the particular characteristic to be geometrically curved, with a sagitta of 112.9 mm. These challenging requirements triggered R&D activities, aimed at the development of suitable construction technologies for fast ramped curved coils. The heart of the R&D program is the construction of a 3.9 m long model. The paper discusses the main problems faced during the design and the construction of the cold mass, mainly covering the aspects related to the manufacture
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Compact Superconducting High Gradient Quadrupole Magnets for the Interaction Regions of High Luminosity Colliders
No full textRecent developments in the high luminosity e(+)e(-) colliders are based on a collision scheme with a large Piwinski angle, a vertical beta function beta(y) much smaller than the bunch length, and a crab waist transformation. This scheme is being adopted in the SuperB asymmetric collider, to be built in Italy, with a design peak luminosity of 10(36) cm(-2) sec(-1). A crucial role is played by the quadrupole doublets QD0/QF1, which are placed close to the interaction point and generate gradients close to 100 T/m. The available space for the doublets is very small, causing the magnets to be operated with a high engineering current density (2000 A/mm(2)). Starting from the helical coil concept, an advanced design of the quadrupole has been developed. The paper discusses the basic design concepts and the development of a coil model aimed at assessing the design criteria and demonstrating the feasibility of the quadrupole. The successful test of the coil model opens the way to new compact superconducting high gradient quadrupole magnets for the interaction regions of high luminosity colliders
A MgB2 superferric racetrack magnet
No full textA magnesium diboride, cryogen-free, H-dipole magnet with cold iron yoke was constructed and tested. The racetrack coil, 48 cm long, was wound with 350 m of nickel-clad, copper-MgB2 tape. The iron yoke forms a 2.6 cm gap. The magnet was connected to a cryocooler and tested at different temperatures ranging between 8.5 and 24 K. The maximum current, 263 A, was reached, without training, at 8.5 K. The corresponding field in the gap was 2.35 T
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