Localization of Electrical Insulation Failures in Superconducting Collared Coils by Analysis of the Distortion of a Pulsed Magnetic Field

The localization of possible electrical faults in superconducting accelerator magnets may, in most cases, be a complex, expensive and time-consuming process. In particular, inter-turn short circuits and failures of the ground insulation are well detectable when the magnet is collared, but often disappear after disassembly for repair due to the release of the pre-stress in the coils. The fault localization method presented in this paper is based on the measurement and analysis of the magnetic field generated inside the magnet aperture by a high voltage pulse. The presence of the fault modifies the distribution of the current in the coils and produces a distortion of the magnetic field. The described method aims at locating both the longitudinal and azimuthal position of the fault-affected area. The test method, the transient case FEM models and the implemented experimental set-up are presented and discussed for the LHC dipole models

Development of functional markers specific for seven Pm3 resistance alleles and their validation in the bread wheat gene pool

In the ideal case, molecular markers used for marker-assisted selection are allele-specific even if the alleles differ only by a few nucleotide polymorphisms within the coding sequence of target genes. Such ‘perfect' markers are completely correlated with the trait of interest. In hexaploid wheat (Triticum aestivum L.) the Pm3 locus encodes seven alleles (Pm3a-Pm3g) conferring resistance to different races of Blumeria graminis f.sp. tritici, the agent of powdery mildew, a major disease of bread wheat. All Pm3 alleles are known at the molecular level. Here, we generated specific markers for the Pm3 alleles based on nucleotide polymorphisms of coding and adjacent non-coding regions. The specificity of these markers was validated in a collection of 93 modern or historically important cultivars and breeding lines of wheat and spelt (Triticum spelta L.). These markers confirmed the presence of the predicted Pm3 alleles in 31 varieties and lines known to carry Pm3 resistance alleles. In a few varieties, Pm3 alleles different from alleles previously described based on pathogenicity tests or tightly linked markers were observed. In all these cases, the identity of the marker-detected Pm3 alleles was confirmed by DNA sequence analysis. Pm3 markers confirmed the absence of known Pm3 resistance alleles in 54 European wheat and spelt varieties in which Pm3 alleles had not been previously identified. These results indicate that the developed markers are highly diagnostic for specific Pm3 resistance alleles in a wide range of varieties and breeding lines, and will be useful (1) for identifying Pm3 alleles in the wheat gene pool, (2) for efficient marker-assisted selection of these genes, and (3) for combining multiple Pm3 alleles within a single cultivar through transgenic approache

Modeling of Coil Pre-stress Loss During Cool-down in the Main Dipoles of the Large Hadron Collider

We describe a finite element mechanical model of the main LHC dipole, based on the geometry and on the properties of its components; coil characteristics are derived from measurements on stacks of conductors. We show how to define equivalent properties of cable blocks that take into account the collaring procedure when it is not explicitly modelled. Numerical results are then compared to experimental measurements of loads and deformations in dipole prototypes. At cryogenic temperature, equivalent properties are used to implement in the model a pressure- dependent thermal contraction factor observed in stack measurements. This allows to forecast the large pre-stress loss during the cool-down observed in the LHC dipole prototypes

Nonlinear phase shift from photon-photon scattering in vacuum

We show that QED nonlinear effects imply a phase correction to the linear evolution of electromagnetic waves in vacuum. We provide explicit solutions of the modified Maxwell's equations for the propagation of a superposition of two plane waves, and calculate analytically and numerically the corresponding phase shift. This provides a new framework for the search of all-optical signatures of photon-photon scattering in vacuum. In particular, we propose an experiment for measuring the phase shift in projected high-power laser facilities.Comment: 4 pages, 1 figure. Some references were added, and the comparison with AC Kerr effect has been improve

Validation and Testing of an Analytical Formulation to Compute the Reduction Factor in MV Grids

Global Earthing Systems (GESs) are defined by International Standards IEC 61936-1 and EN 50522 as an equivalent Earthing System (ES) created by the interconnection of local ESs. Thanks to this interconnection, just a percentage of the total fault current is injected to ground in a single ES, reducing the risk of electrocution. However, even if several experiments and models proved this effect, the identification and official certification is still a difficult task. Dangerous scenarios caused by a single-line-to-ground fault can be easily evaluated for a specific MV feeder by measurement or analytic models (quite cumbersome to use), but operative procedures valid for all the scenarios are still not available. In this work, a simplified formula to compute the reduction factor is presented, as well as its rationale. The proposed formula is easy to use and the results provided are sufficiently accurate, taking into account a desired safety margin. For this reason, it could be a valid tool for Distributor System Operators (DSO) and Certification Bodies and a step forward for the GES identification. The proposed formula is finally tested on three study cases

Entanglement as a source of black hole entropy

We review aspects of black hole thermodynamics, and show how entanglement of a quantum field between the inside and outside of a horizon can account for the area-proportionality of black hole entropy, provided the field is in its ground state. We show that the result continues to hold for Coherent States and Squeezed States, while for Excited States, the entropy scales as a power of area less than unity. We also identify location of the degrees of freedom which give rise to the above entropy.Comment: 12 pages, latex, 5 figures. Invited talk by SD at `Recent Developments in Gravity' (NEB XII), Nafplion, Greece, 30 June 2006. To appear in Journal of Physics: Conference Series; V2: References added, Minor changes to match published versio

On Unitarity Based Relations Between Various Lepton Family Violating Processes

Simple "unitarity inspired" relations between two- and three-body lepton flavor violating decays are noted and discussed. In the absence of cancellations, the existing strong bounds on $\mu \to 3e$ and $\mu\to e\gamma\gamma$ severly constrain two-body lepton flavor violating decays.Comment: 5 pages, 3 figure