In-line and following-up tests of perspective fusion-reactor materials in plasma focus devices

The paper presents results of recent experiments, as performed with the PF-1000 and PF-6 Plasma-Focus facilities, which were aimed at investigation of the correlation between processes of the irradiation of different materials of fusion devices and results of this irradiation. Among the irradiated samples there were pure tungsten, tantalum, copper, aluminum, and alloys, based on these metals, various steels, carbon and carbon-based materials, which are designed for plasma facing components or constructional parts of future thermonuclear reactors of the inertial- and magnetic-confinement types. The corpuscular radiation consisted of high-energy (E _D>100 keV) deuterium ion beams and fast (v _str ≥ 10⁷ cm/s) deuterium-plasma streams. They were investigated by a number of methods with spatial and temporal resolution. Particular attention was paid to the verification of diagnostic techniques, which might be used for time- and space-resolved studies of the interaction process. Correlation of these data with information obtained from subsequent analytical investigation of some of the irradiated specimens, as performed by means of a number of methods typical for material sciences, gives possibility to deduce physical mechanisms of the deuterium implantation and radiation damage of the investigated materials in dependence on the conditions of their irradiation.     

Non-steady-state photocurrents in SnS2 crystals

We report on non-steady-state photocurrent measurements of SnS₂ grown by vapor transport method. The main characteristics of photoinduced carriers, such as type of photoconductivity, average diffusion length, dielectric relaxation time, and the Debye screening length, were estimated for the excitation wavelengths in the red and blue region of the spectrum. Received: 12 November 1998 / Revised version: 22 December 1998 / Published online: 31 March 1999     

Echolocation system of the bottlenose dolphin

The hypothesis put forward by Vel’min and Dubrovsky [1] is discussed. The hypothesis suggests that bottlenose dolphins possess two functionally separate auditory subsystems: one of them serves for analyzing extraneous sounds, as in nonecholocating terrestrial animals, and the other performs the analysis of echoes caused by the echolocation clicks of the animal itself. The first subsystem is called passive hearing, and the second, active hearing. The results of experimental studies of dolphin’s echolocation system are discussed to confirm the proposed hypothesis. For the active hearing of dolphins, the notion of a critical interval is considered as the interval of time within which the formation of a merged auditory image of the echolocation object is formed when all echo highlights of the echo from this object fall within the critical interval.     

Irina Borisovna Andreeva (January 20, 1918–December 5, 2002)

Chronicle

Irina Borisovna Andreeva (January 20, 1918–December 5, 2002)     

Audibility thresholds for a pure tone in the presence of a pulse jam in the bottlenose dolphin

The effect of a pulse jam on the audibility of pure tones in the bottlenose dolphin (Tursiops truncatus) is investigated. The pulse jam consists of a sequence of pairs of identical short pulses with a pulse spacing of 50 µs in each pair and with a pair repetition rate of 300 s^?1. The test signal is represented by pure tones in the frequency range 20–100 kHz. The audibility thresholds for the test signals are measured at 10-kHz steps, both in the presence of the pulse jam and in its absence, on the basis of the conditioned-reflex method with food reinforcement. The resulting dependence of the threshold shifts (TS) due to the pulse jam on the frequency of the test signal has a complex form. This dependence can be separated into three components: (1) the oscillations of the TS curve that correlate with the extrema of the spectral density of the jam, so that the peaks and dips of the TS curve correspond to the maxima and minima of the spectral density, respectively; (2) the component monotonically decreasing as the frequency grows up to 80 kHz, which distinguishes the TS curve under consideration from the rising curve obtained for masking by random noise; and (3) the frequency-independent component of the TS curve. The following auditory features are associated with these components: component 1 determines the timbre of the pulse jam; component 2 is presumably related to the pitch corresponding to the frequency 1/τ; and component 3 exhibits a rather strong auditory feature of random noise due to the random neural activity caused by the pulse jam in the whole auditory filter band.     

Analytical approximation of the thermal and caloric equations of state for real gases over a wide density and temperature range

The thermal and caloric equations of state of the main components of gas mixtures normally used in calculations of gas dynamic processes, including combustion and detonation, as well as in problems of internal ballistics, are presented in an analytical form. The formulas obtained for the equations of state contain a relatively small number of parameters and provide an average error of approximation of less than 1% at temperatures from 500 to 2000–2500 K and densities up to the critical.     

On an exact solution of master equations for the model of reversible growth

The set of master equations for the monomer quasi-chemical reversible-growth model in a heterogeneous open medium material is studied. The exact solution to the master equations is obtained for the case where the velocity constants for the growth and decay reactions are linear in the particle number. It is shown that the model under consideration is canonically invariant w.r.t. the Polya distribution with a time-dependent mean size of the clusters.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 108, No. 2, pp. 327–336, August, 1996.     

Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.