How Geometry Affects Sensitivity of a Differential Transformer for Contactless Characterization of Liquids

The electrical and dielectric properties of liquids can be used for sensing. Specific applications, e.g., the continuous in-line monitoring of blood conductivity as a measure of the sodium concentration during dialysis treatment, require contactless measuring methods to avoid any contamination of the medium. The differential transformer is one promising approach for such applications, since its principle is based on a contactless, magnetically induced conductivity measurement. The objective of this work is to investigate the impact of the geometric parameters of the sample or medium under test on the sensitivity and the noise of the differential transformer to derive design rules for an optimized setup. By fundamental investigations, an equation for the field penetration depth of a differential transformer is derived. Furthermore, it is found that increasing height and radius of the medium is accompanied by an enhancement in sensitivity and precision.

London Penetration Depth as a Test of Order Parameter Symmetry in Sodium Cobaltate Superconductors

Temperature dependence of the magnetic field penetration depth λ was calculated for water intercalated sodium cobaltate superconductor Na x CoO 2 · y H 2 O. Assuming that the system is in the chiral d+id–wave superconducting state, it was shown that the shifting of the excitation spectrum nodal points off the normal phase Fermi surface due to variation of the sodium content x changes the functional form of the temperature dependence of λ − 2 from exponential to linear in the low temperatures region. It is argued that this change in the functional form of T–dependence of the λ − 2 can serve as a proof for the chiral symmetry of the superconducting order parameter in the sodium cobaltate.

Sealing by soldering of microblock packages made of diamagnetic alloys using high-frequency heating

The main difficulties of application of high-frequency (HF) heating for sealing by soldering of microblock packages made of aluminum alloys is the low efficiency of heating, long processing time and considerable heating of the internal electronic module while sealing. The purpose of this study was to use effectively the physical phenomena of HF heating in order to optimize the HF heating parameters of sealing by soldering using fusible solders of microwave microblock packages made of diamagnetic alloys. Effects of HF heating (superficial, proximity and concentration of power lines) of the electromagnetic field are applied to sealing using soldering of microwave microblock packages made of diamagnetic alloys. The optimized parameters of HF heating provide energy efficiency and productivity of sealing: frequency of the electromagnetic field and the inductor design. When soldering microelectronic devices containing electronic parts sensitive to the electric field component, the energy of electromagnetic field in the package should be significantly lower than the energy of elements degradation, in which case the skin layer reaches the field penetration depth which is equal to 4 package thickness values. In order to increase the HF heating efficiency, there should be a concentration of the inductor current on the package surface facing the inductor, which is done by using a ferrite magnetic core. Using a ferrite magnetic core inside the inductor concentrates tension of magnetic field due to concentration of power lines of magnetic field in 1,2-1,3 times. The optimal frequency range for HF soldering is 0,4—2,0 MHz when at electromagnetic field penetration depth into the material of the package equal to 4 thickness values of the skin layer, the field strength is 152 times weaker in comparison with the surface.

Noninterferometric Techniques to Determine Terahertz Surface-Plasmon Coplex Refractive Index

Two noninterferometric techniques for mtasurement of THz surface plasmon (SP) refractive index κ are presented. The first method involves splitting of the initial SPs beam into two new ones and measurements of the SP decoupling angle on a diffractional grating. The second method is based on the fact that THz SP field penetration depth δ into air can be expressed through κ and measured directly. Numerical modeling of both techniques has been carried out