ITER Vacuum Vessel is a torus-shaped, double wall structure. The space between the double walls of the VV is filled with In-Wall Shielding Blocks (IWS) and Water. The main purpose of IWS is to ...provide neutron shielding during ITER plasma operation and to reduce ripple of Toroidal Magnetic Field (TF). Although In-Wall Shield Blocks (IWS) will be submerged in water in between the walls of the ITER Vacuum Vessel (VV), Outgassing Rate (OGR) of IWS materials plays a significant role in leak detection of Vacuum Vessel of ITER. Thermal Outgassing Rate of a material critically depends on the Surface Roughness of material. During leak detection process using RGA equipped Leak detector and tracer gas Helium, there will be a spill over of mass 3 and mass 2 to mass 4 which creates a background reading. Helium background will have contribution of Hydrogen too. So it is necessary to ensure the low OGR of Hydrogen. To achieve an effective leak test it is required to obtain a background below 1 × 10-8 mbar 1 s-1 and hence the maximum Outgassing rate of IWS Materials should comply with the maximum Outgassing rate required for hydrogen i.e. 1 x 10-10 mbar 1 s-1 cm-2 at room temperature. As IWS Materials are special materials developed for ITER project, it is necessary to ensure the compliance of Outgassing rate with the requirement. There is a possibility of diffusing the gasses in material at the time of production. So, to validate the production process of materials as well as manufacturing of final product from this material, three coupons of each IWS material have been manufactured with the same technique which is being used in manufacturing of IWS blocks. Manufacturing records of these coupons have been approved by ITER-IO (International Organization). Outgassing rates of these coupons have been measured at room temperature and found in acceptable limit to obtain the required Helium Background. On the basis of these measurements, test reports have been generated and got approved by IO. This paper will describe the preparation, characteristics and cleaning procedure of samples, description of the system, Outgassing rate Measurement of these samples to ensure the accurate leak detection.
We investigate two variants of quantum compass models (QCMs). The first, an orbital-only honeycomb QCM, is shown to exhibit a quantum phase transition (QPT) from a \(XX\)- to \(ZZ\)-ordered phase in ...the \(3d\)-Ising universality class, in accord with earlier studies. In a fractionalized parton construction, this describes a ``superfluid-Mott insulator'' transition between a higher-order topological superfluid and the toric code, the latter described as a \(p\)-wave resonating valence bond state of the partons. The second variant, the spinless fermion QCM on a square lattice, is of interest in the context of cold-atom lattices with higher-angular momentum states on each atom. We explore finite-temperature orbital order-disorder transitions in the itinerant and localized limits using complementary methods. In the itinerant limit, we uncover an intricate temperature (\(T\))-dependent dimensional crossover from a high-\(T\) quasi-\(1d\) insulator-like state, via an incoherent bad-metal-like state at intermediate \(T\), to a \(2d\) symmetry-broken insulator at low \(T\), well below the ``orbital'' ordering scale. Finally, we discuss how engineering specific, tunable, and realistic perturbations in both these variants can act as a playground for simulating a variety of exotic QPTs between topologically ordered and trivial phases. In the cold-atom context, we propose a novel way to engineer a possible realisation of the exotic exciton Bose liquid phase at a QPT between a Bose superfluid and a charge density wave insulator. We argue that advances in the design of Josephson junction arrays and manipulating cold-atom lattices offer the hope of simulating such novel phases of matter in the foreseeable future.
We introduce a novel mean-field theory (MFT) around the exactly soluble two-leg ladder limit for the planar quantum compass model (QCM). In contrast to usual MFT, our construction respects the ...stringent constraints imposed by emergent, lower (here \(d=1\)) dimensional symmetries of the QCM. Specializing our construction to the QCM on a periodic four-leg ladder, we find that a first-order transition separates two mutually dual Ising nematic phases, in good accord with state-of-the-art numerics for the planar QCM. One pseudo-spin-flip excitation in the ordered phase turns out to be two (Jordan-Wigner) fermion bound states, reminiscent of spin waves in spin-\(1/2\) Heisenberg chains. We discuss the novel implications of our work on (1) the emergence of coupled orbital and magnetic ordered and liquidlike disordered phases, and (2) a rare instance of orbital-spin separation in \(d>1\), in the context of a Kugel-Khomskii view of multi-orbital Mott insulators.
We analyze the formation of stripe-like and droplet-like superstructures in a plane with classical magnetic moments forming a square lattice, which is relevant, in particular, to a two-dimensional ...array of π-rings. Each magnetic and orbital moment associated with a single π-ring is oriented perpendicular to the plane. We describe such arrays in the framework a two-dimensional Ising model with both nearest-neighbor and next-nearest-neighbor (diagonal) interactions. Such competing interactions introducing a strong frustration provide a plausible description for a dipole-dipole type of interaction. The model was studied with the use of several methods including exact diagonalization for small clusters, transfer matrix technique, as well as the Monte Carlo simulations for large lattices. The complete phase diagram resulting from this study includes, together with the conventional antiferromagnetic Ising and stripe phases, an additional glassy phase characterized by the formation of large-scale superstructures.
Materials exhibiting high dielectric constant (k) values find applications in capacitors, gate dielectrics, dielectric elastomers, energy storage device, while materials with low dielectric constant ...are required in electronic packaging and other such applications. Traditionally, high k value materials are associated with high dielectric losses, frequency-dependent dielectric behavior, and high loading of a filler. Materials with low k possess a low thermal conductivity. This creates the new challenges in the development of dielectric materials in both kinds of applications. Use of high dielectric constant filler materials increases the dielectric constant. In this study,the factors affecting the dielectric constant and the dielectric strength of polymer composites are explored. The present work aims to study the effect of various parameters affecting the dielectric properties of the materials. The factors selected in this study are the type of a polymer, type of a filler material used, size, shape, loading level and surface modification of a filler material, and method of preparation of the polymer composites. The study is focused on the dielectric enhancement of polymer nanocomposites used in the field of energy storage devices. The results show that the core-shell structured approach for high dielectric constant materials incorporated in a polymer matrix improves the dielectric constant of the polymer composite.
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