Asymmetric Concentric Microring Resonator Label-Free Biosensors

A study of label-free silicon nitride asymmetric double-microring resonators is presented. The use of highly accurate 3D vector modal techniques permits an extensive exploration of the parameter space defining the architecture of the proposed device in the search for optimal geometries and reaching configurations not addressed in previous studies that had been limited to symmetrical configurations. Asymmetry, on the other hand, permits to access resonances that exploit the radiation-quenching properties of the structure in an optimal way. The analysis presented also includes the effect of absorption in the sensor aqueous cladding that is generally omitted. The results of the numerical survey indicate that the optimized geometries bring about a substantive performance improvement at small microring radii that are impractical for more conventional single-ring geometries due to the high radiation losses. Therefore, lower footprint devices, and a larger scale of integration, can be attained with the proposed structure.

Mode spectra of magnetic and dielectric plasmon spheres obtained from Mie scattering and free oscillation theories

This paper presents Mie scattering theory as compared to rigorous electromagnetic theory of free oscillations in magnetic and electric plasmon spheres. It is shown that the maxima of Mie scattering and absorption spectra well correspond to resonance frequencies of plasmon modes occurring in dielectric and magnetic spheres, similarly as it takes place for ordinary dielectric resonator modes. Mie theory is well applicable to determine resonance frequencies and scattering parameters of spherical plasmons. However, this theory cannot be applied to determine intrinsic properties of modes induced in the object by the incident plane wave, like quality factors. On the contrary, rigorous electromagnetic theory of free oscillations allows one to determine the complex resonance frequency of each mode that can occur in a given object, and the corresponding quality factor accounting for various kind of losses, including medium and radiation losses. The advantage of the free oscillations theory, as shown in this paper, is in the determination of the quality factors of modes occurring in magnetic plasmon spheres made of a strongly dispersive magnetic medium. Graphical Abstract

Studies on impurity seeding and transport in edge and SOL of tokamak plasma

We present numerical simulation studies on impurity seeding using Nitrogen, Neon, and Argon gases. These impurity gases are ionized by the electron impact ionization. These ions can be at multiply ionized states, recombine again with the plasma electrons, and radiate energy. The radiation losses are estimated using a non-coronal equilibrium model. A set of 2D model equations to describe their self-consistent evolution are derived using interchange plasma turbulence in the edge and SOL regions and solved using BOUT++. It is found that impurity ions (with single or double-positive charges) move in the inward direction with a velocity ∼ 0.02cs so that these fluxes are negative. These fluxes are analyzed for different strengths of an effective gravity that help to understand the impurity ion dynamics. Increased gravity shows an accumulation of certain charged species in the edge region. The radiation loss is seen to have a fluctuation in time with frequency 5-20 kHz that closely follows the behavior of the interchange plasma turbulence. The simulation results on the radiated power and its frequency spectrum compare favourably with observations on the Aditya-U tokamak. The negative fluxes of the impurity ions, their dynamics in the edge region, and the fluctuating nature of the radiation loss are the most important results of this work.

RADIATION LOSS DETERMINATION AT COLLISION OF ELECTRONS WITH LECTRONEGATIVE ATOMS AND IONS IN PLASMA CURRENT SWITCH DISCHARGES. PART II

Specific radiation-loss power values have been determined for a variety of electronegative elements (C, O, F, Cl) as functions of electron temperature and impurity particle concentration. The maximum radiation-loss power level has been registered for chlorine (≤770 W/cm3) at an electron/impurity density of 1014 cm-3. The minimum radiation-loss power level for the other three elements lies in the range from 0.4 to 2 W/cm3. Considerable radiation losses due to the presence of electronegative elements in the interelectrode discharge may lead to its destabilization, to the change in the plasma parameters (ne, Te), and eventually, to degradation of the current-voltage characteristic of the plasma current switch.

General Formula for Impulse Losses in the Process of Emission of Neutrino Pairs by Electrons in a Magnetic Field

Considered formula pulsed radiation losses pairs neutrinos electrons in a magnetic field. Gas consisting of polarized electrons in the direction of the magnetic field and spins composed of polarized electrons in the opposite direction of the magnetic field would receive a different impulse due to the asymmetric transmission of the impulse.

Heat Flux Distribution Estimation for CSP Applications

In this paper the concept of a new method for the estimation of the heat flux distribution and the total power in CSP applications is presented. This method requires appropriate analysis of the temperature evolution on a target, or directly on a receiver. A 3-D thermal conduction model with boundary conditions to take into account the convection and radiation losses has been developed. A parametric analysis was performed and we checked how the physical parameters affect the applicability of the method. Having proven numerically the potential of this method, it was experimentally implemented in the central tower CSP plant of The Cyprus Institute at PROTEAS facilities successfully. The experience gained from the numerical and experimental application of this method is discussed.