10,488 research outputs found
Mapping the dynamic interactions between vortex species in highly anisotropic superconductors
Here we use highly sensitive magnetisation measurements performed using a
Hall probe sensor on single crystals of highly anisotropic high temperature
superconductors to study the dynamic interactions
between the two species of vortices that exist in such superconductors. We
observe a remarkable and clearly delineated high temperature regime that
mirrors the underlying vortex phase diagram. Our results map out the parameter
space over which these dynamic interaction processes can be used to create
vortex ratchets, pumps and other fluxonic devices.Comment: 7 pages, 3 figures, to be published in Supercond. Sci. Techno
On the robustness of ultra-high voltage 4H-SiC IGBTs with an optimized retrograde p-well
The robustness of ultra-high voltage (>10kV) SiC IGBTs comprising of an optimized retrograde p-well is investigated. Under extensive TCAD simulations, we show that in addition to offering a robust control on threshold voltage and eliminating punch-through, the retrograde is highly effective in terms of reducing the stress on the gate oxide of ultra-high voltage SiC IGBTs. We show that a 10 kV SiC IGBT comprising of the retrograde p-well exhibits a much-reduced peak electric field in the gate oxide when compared with the counterpart comprising of a conventional p-well. Using an optimized retrograde p-well with depth as shallow as 1 μm, the peak electric field in the gate oxide of a 10kV rated SiC IGBT can be reduced to below 2 MV.cm -1 , a prerequisite to achieve a high-degree of reliability in high-voltage power devices. We therefore propose that the retrograde p-well is highly promising for the development of>10kV SiC IGBTs
Effective Vortex Pinning in MgB2 thin films
We discuss pinning properties of MgB2 thin films grown by pulsed-laser
deposition (PLD) and by electron-beam (EB) evaporation. Two mechanisms are
identified that contribute most effectively to the pinning of vortices in
randomly oriented films. The EB process produces low defected crystallites with
small grain size providing enhanced pinning at grain boundaries without
degradation of Tc. The PLD process produces films with structural disorder on a
scale less that the coherence length that further improves pinning, but also
depresses Tc
Patient Understanding of Benefits, Risks, and Alternatives to Screening Colonoscopy
While several tests and strategies are recommended for colorectal cancer (CRC) screening, studies suggest that primary care providers often recommend colonoscopy without providing information about its risks or alternatives. These observations raise concerns about the quality of informed consent for screening colonoscopy
The Fluctuations of the Quark Number and of the Chiral Condensate
The distributions of the quark number and chiral condensate over the gauge
fields are computed for QCD in Euclidean space at nonzero quark chemical
potential. As both operators are non-hermitian the distributions are in the
complex plane. Moreover, because of the sign problem, the distributions are not
real and positive. The computations are carried out within leading order chiral
perturbation theory and give a direct insight into the delicate cancellations
that take place in contributions to the total baryon number and the chiral
condensate.Comment: 19 pages, 2 figure
Optimal edge termination for high oxide reliability aiming 10kV SiC n-IGBTs
The edge termination design strongly affects the ability of a power device to support the desired voltage and its reliable operation. In this paper we present three appropriate termination designs for 10kV n-IGBTs which achieve the desired blocking requirement without the need for deep and expensive implantations. Thus, they improve the ability to fabricate, minimise the cost and reduce the lattice damage due to the high implantation energy. The edge terminations presented are optimised both for achieving the widest immunity to dopant activation and to minimise the electric field at the oxide. Thus, they ensure the long-term reliability of the device. This work has shown that the optimum design for blocking voltage and widest dose window does not necessarily give the best design for reliability. Further, it has been shown that Hybrid Junction Termination Extension structure with Space Modulated Floating Field Rings can give the best result of very high termination efficiency, as high as 99%, the widest doping variation immunity and the lowest electric field in the oxide
Vortices Clustering: The Origin of the Second Peak in the Magnetisation Loops of High Temperature Superconductors
We study vortex clustering in type II Superconductors. We demonstrate that
the ``second peak'' observed in magnetisation loops may be a dynamical effect
associated with a density driven instability of the vortex system. At the
microscopic level the instability shows up as the clustering of individual
vortices at (rare) preferential regions of the pinning potential. In the limit
of quasi-static ramping the instability is related to a phase transition in the
equilibrium vortex system.Comment: 11 pages + 3 figure
4-H Youth Development: The Past, the Present, and the Future
The 4-H Program within Cooperative Extension is more than 100 years old. As we celebrate 100 years of Cooperative Extension, the foundation built by the 4-H Program serves as grounds to meet the needs of today\u27s youth. The diversity of the youth who participate continues to grow, families continue to become less traditional, potential volunteers\u27 time continues to shrink, and the growing number of digital devices steal time. These changes demand 4-H adapt and innovate to remain relevant. This commentary examines the role that 4-H Youth Development will play in the next 100 years to face these challenges
A DC magnetic metamaterial
Electromagnetic metamaterials are a class of materials which have been
artificially structured on a subwavelength scale. They are currently the focus
of a great deal of interest because they allow access to previously
unrealisable properties like a negative refractive index. Most metamaterial
designs have so far been based on resonant elements, like split rings, and
research has concentrated on microwave frequencies and above. In this work, we
present the first experimental realisation of a non-resonant metamaterial
designed to operate at zero frequency. Our samples are based on a
recently-proposed template for an anisotropic magnetic metamaterial consisting
of an array of superconducting plates. Magnetometry experiments show a strong,
adjustable diamagnetic response when a field is applied perpendicular to the
plates. We have calculated the corresponding effective permeability, which
agrees well with theoretical predictions. Applications for this metamaterial
may include non-intrusive screening of weak DC magnetic fields.Comment: 6 pages, 3 figure
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