Contents
Section 1. Topics on experimental electrodynamics
Observation of dynamic fluctuation phase transition of conductivity of silver island film
P.O. Ksenofontova, R.T. Sibatov, M.A. Saurov, A.P. Orlov
Abstract
In this paper, we propose a method for forming silver island films (SIF) in the critical region of the metal-insulator transition based on the optimization of the annealing time of the initially conducting film. It was found that the resulting SIF has a fractal structure with the Hausdorff dimension of the largest clusters D = 1.6. When a constant voltage is applied, the SIF conductivity begins to fluctuate in time. The statistical analysis of the conductivity fluctuations showed that below a certain threshold there are small Gaussian fluctuations, and above the threshold, events of decrease and increase (jumps) in conductivity are observed, the time intervals between which are distributed according to a power law. The distribution of the jump values is consistent with the asymptotics of the stable Levy law. Thus, we consider the statistics of the SIF conductivity in the critical region of the metal-insulator transition as a fluctuation phase transition separating small Gaussian fluctuations and large jumps corresponding to the Levy distribution.
Keywords: silver island films, critical behavior, neuromorphic computing, Levy distribution
Flat lens as a collimator for a tapered anechoic chamber
D.P. Korolev, N.L. Menshikh, S.A. Fedorov
Abstract
This paper investigates the use of a flat lens as a collimator for a tapered anechoic chamber. A method for realization of a gradient medium and estimation of its effective permittivity is proposed. The design and creation process is described. The field distribution formed by the flat lens was measured in the experiment using a scaled model of a tapered anechoic chamber. It is shown that the lens enables the formation of a sufficiently phase-uniform electromagnetic field in the chamber's quiet zone, although it increases amplitude non-uniformity. Experiments with different lens positions within the horn were carried out, and the optimal lens placement - where phase non-uniformity does not exceed 10° - was determined. An electrodynamic model allowing numerical calculation of the amplitude and phase of the field in the horn chamber's working area is considered. A comparison between experimental results and numerical simulations demonstrates good agreement.
Keywords: gradient lens, flat lens, compact range, tapered anechoic chamber, lens collimator
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