A noise source based on an IMPATT-diode self-oscillating system

The efficiency of noise generation by an IMPATT diode in a centimeter-band self-oscillating system is studied.     

Resonance phenomena during vapor condensation in a cooled tube

Experiments show evidence of the resonance phenomena during vapor condensation inside a cooled tube. The resonance sharpness depends on the region of application of an external perturbation (vapor or condensed phase).     

Preparation and scintillation properties of YCl3:Ce crystals

Ce³⁺-activated YCl₃ crystals have been grown by the Bridgman-Stockbarger method, and their scintillation properties have been investigated. The luminescence spectrum of YCl₃:Ce has a complex character and consists of two overlapping peaks at 390 and 410 nm, characteristic of Ce³⁺ luminescence. The light output of YCl₃:Ce as a function of Ce³⁺ concentration has a maximum at 1 mol % Ce³⁺. Original Russian Text ? V.L. Cherginets, T.V. Ponomarenko, L.N. Trefilova, N.V. Rebrova, N.N. Kosinov, V.D. Alekseev, O.V. Zelenskaya, 2009, published in Neorganicheskie Materialy, 2009, Vol. 45, No. 8, pp. 1017–1020.     

New refined data about the adiabatic thermal coefficient of pressure for liquid cesium in the region of anomalous behavior of thermal properties

New experimental data are obtained about the temperature dependence of the adiabatic thermal coefficient of pressure (ATCP) for liquid cesium in the temperature range from 300 to 630 K. The measurements are performed in an improved facility which is a realization of the version of the method for ATCP measurements, in which the quasi-adiabatic variation of pressure is performed in a periodic mode [1]. The data on the temperature dependence of the ATCP of liquid cesium which were previously obtained in this facility [2] required additional verification because of inadequate reproducibility of the absolute values of measured quantities, this resulting from the inadequacy of the thermal contact between thermocouple and sample. In this study, new measurements of the ATCP for cesium are performed after the introduction of procedural improvements enabling one to reach a much higher degree of repeatability of results. This makes it possible to considerably refine the shape and location of the anomaly on the curve of temperature dependence of the ATCP. It is found that the refined parameters of the anomalous region of the ATCP are in good agreement with the respective parameters of the anomaly of the coefficient of thermal expansion [3], this leading one to detect features of second-order phase transition in the behavior of the observed anomalies.     

Possible THz Bloch gain in dc–ac-driven superlattices

We study theoretically the feasibility of amplification and generation of THz radiation in dc–ac-driven semiconductor superlattices in the absence of electric domains. We find that if in addition to dc bias strong ac pump fields are applied, Bloch gain profile for a small THz signal can be achieved under conditions of positive static differential conductivity. We briefly review the case of THz pump and present preliminary results on the use of pump fields belonging to the microwave frequency band.     

Millimeter-Wave Absorption by Cutaneous Blood Vessels: A Computational Study

The aims of the present study were to calculate the specific absorption rate (SAR) and EMield distributions inside cutaneous blood vessels and in surrounding tissues (dermis and fat) depending on the frequency of millimeter wave exposure. Most calculations were performed using the finite-difference time-domain (FDTD) technique. A rectangular block of homogeneous or multilayer tissue with blood vessels located in the center of the block was used as the basic geometry. We found that the SAR reached its maximal value in a long blood vessel oriented parallel to the E-field. It exceeded the SAR in the surrounding dermis by 40%- 42% at 42.25 GHz. However, in the same blood vessel oriented perpendicularly to the E-field, the SAR was lower than that of the surrounding dermis. Absorption of millimeter waves in a cutaneous blood vessel was higher at 61.22 GHz than at 42.25 GHz. The SAR distribution in a blood vessel was nearly uniform. Because of the small sizes of cutaneous blood vessels relative to the wavelength, the SAR distributions in these blood vessels can be calculated by using quasi-static theory.