Semi-classical understanding of flux quantization in superconductors

Like electric charge, magnetic flux is also quantised. Theoretically, one can show that the flux quantum must be h/e, as observed in the quantum Hall effect. However, in the superconducting systems, the flux quantum is experimentally observed as h/2e. There is no fundamental explanation for the empirical result. In this article, we argue that this phenomenon is fundamentally linked to the nonlocality problem of the Aharonov-Bohm effect and present a new semi-classical explanation for the magnetic flux quantum in superconductivity. This work will also show why the flux quantum should be h/e in the case of the quantum Hall effect.Comment: 8 page

Revisiting the image of a magnetic dipole in front of a superconducting sphere

The method of images to solve certain electrostatic boundary-value problems is taught worldwide in undergraduate-level physics courses. Though it is also possible to employ this technique for solving the magnetostatic boundary value problems, examples of this usage are not commonly found in textbooks, or in physics pedagogy literature. In particular, the problem of finding the field due to a magnetic dipole kept in front of a superconducting sphere is an interesting one, because (i) it helps the students to compare with the grounded conducting sphere image problem in electrostatics, (ii) offers a greater degree of difficulty since the source is a dipole (vector), rather than an electric charge (scalar). The problem has been solved using the method of images in the traditional research journal (Qiong-Gui, 2006) by first examining the pattern of the image of a magnetic monopole, and then by superimposing the images of closely spaced monopoles. In the present work we are presenting, however, we demonstrate a simple but instructive method of solving the problem. The case in which the source dipole is oriented with respect to the centre of the sphere is solved with a single dipole image. In our presentation, we will also make general comments on the case where the dipole is oriented transversely with respect to the centre and corresponding boundary conditions. REFERENCE Qiong-Gui L. (2006). Theoretical development of the image method for a general magnetic source in the presence of a superconducting sphere or a long superconducting cylinder. Physical Review B, 74(2):024510

Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)

The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) is designed to study the atmospheric neutrinos and antineutrinos separately over a wide range of energies and path lengths. The primary focus of this experiment is to explore the Earth matter effects by observing the energy and zenith angle dependence of the atmospheric neutrinos in the multi-GeV range. This study will be crucial to address some of the outstanding issues in neutrino oscillation physics, including the fundamental issue of neutrino mass hierarchy. In this document, we present the physics potential of the detector as obtained from realistic detector simulations. We describe the simulation framework, the neutrino interactions in the detector, and the expected response of the detector to particles traversing it. The ICAL detector can determine the energy and direction of the muons to a high precision, and in addition, its sensitivity to multi-GeV hadrons increases its physics reach substantially. Its charge identification capability, and hence its ability to distinguish neutrinos from antineutrinos, makes it an efficient detector for determining the neutrino mass hierarchy. In this report, we outline the analyses carried out for the determination of neutrino mass hierarchy and precision measurements of atmospheric neutrino mixing parameters at ICAL, and give the expected physics reach of the detector with 10 years of runtime. We also explore the potential of ICAL for probing new physics scenarios like CPT violation and the presence of magnetic monopoles.Comment: 139 pages, Physics White Paper of the ICAL (INO) Collaboration, Contents identical with the version published in Pramana - J. Physic

Triplet lifetime in gaseous argon

MiniCLEAN is a single-phase liquid argon dark matter experiment. During the initial cooling phase, impurities within the cold gas ($<$140 K) were monitored by measuring the scintillation light triplet lifetime, and ultimately a triplet lifetime of 3.480 $\pm$ 0.001 (stat.) $\pm$ 0.064 (sys.) $\mu$s was obtained, indicating ultra-pure argon. This is the longest argon triplet time constant ever reported. The effect of quenching of separate components of the scintillation light is also investigated

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