Radiation effect on the 400-nm-thermoluminescence emission of a potassium-rich feldspar

The UV-blue thermoluminescence (TL) emission of exsolved and twinned potassium feldspars is potentially valid to be employed in the field of dating and retrospective dosimetry. This paper reports about the following results: (i) The dose dependence of the 400 nm TL intensity of a K-rich feldspar exhibits an excellent linearity in the range of 50 mGy–8 Gy. (ii) The stability of the TL signal after 6 months of storage, shows an initial rapid decay (ca. 45%) maintaining the stability from 40 days onwards which indicates that the electron population decreases asymptotically by the X-axis and the involved electrons are located in deeper traps at room temperature. The fading process can be fitted to a first-order decay equation of the sort y=y₀+A exp(−x/t). (iii) The tests of thermal stability at different temperatures confirm a continuous trap distribution with progressive changes in the glow curve shape, intensity and temperature position of the maximum peak. According to this behaviour some physical parameters are defined.     

The glow curve structure for the LiF:Mg,Cu,Na,Si TL detector with dopants concentrations and sintering temperatures

The glow curve structures for LiF:Mg,Cu,Na,Si TL detectors with various dopant concentrations and sintering temperatures were investigated for the improvement of the glow curve structure and sensitivity of the TL detector. The dopant concentrations were varied over the following ranges: Mg (0–0.25 mol%), Cu (0–0.07 mol%), Na and Si (0–1.5 mol%). With increasing Cu concentration, the intensity of the main peak was intensified and reached a maximum at a concentration of 0.05 mol%. The high-temperature peak was reduced. The dependency of the main peak intensity on the Mg concentration exhibits a sharp maximum at 0.2 mol%. The intensity of the high-temperature peak tends to rise slightly with increasing Mg concentration. It was found that the optimum concentrations of the dopants in the LiF:Mg,Cu,Na,Si TL material are Mg: 0.2 mol%, Cu: 0.05 mol%, Na and Si: 0.9 mol%. The dependency of the main peak intensity on sintering temperature exhibits a very sharp maximum at 830°C. The high-temperature peak was rapidly reduced after 825°C.     

Negative luminescence from mid-wave infrared HgCdTe diode arrays

A self-referencing, optical modulation technique was used to measure the negative luminescence efficiencies of an array of mid-wave infrared HgCdTe photodiodes with cutoff wavelength 4.6 μm as a function of sample temperature. The internal efficiency at a wavelength of 4 μm was 93% at 295 K, and nearly independent of temperature in the 240–300 K range. This corresponds to an apparent temperature reduction >50 K at room temperature and >30 K at 240 K. Moreover, the reverse-bias saturation current density was only 0.13 A/cm². The measured transmission and emission spectra were simulated using empirical HgCdTe absorption formulas from the literature.     

Investigation of the X-ray radiation produced by a diffusive discharge in the rod-plane geometry under atmospheric pressure

Spatial parameters of the X-ray radiation produced by a high-voltage nanosecond discharge evolving in air under atmospheric pressure in the rod (cathode)-plane electrode system with a 10-cm electrode spacing are studied experimentally. A ∼170-ns voltage pulse with an amplitude of ∼200 kV and 10-ns rise time is applied to the cathode. The photoelectronic method is used to study, under the same conditions, the integrated (over the gap) characteristics of the radiation, in particular, the duration of its generation. It is found that, when the size of the X-ray source is not smaller than that of the discharge region of diffusive luminescence, radiation from the cathode region of the gap is primarily observed (i.e., from the region where the electric field distribution is sharply inhomogeneous). The X-ray generation is usually observed after the bridging of the discharge gap, the X-ray pulse having a rise time of ∼3 ns, a duration of ∼10 ns, and an effective radiation energy of ∼6 keV.     

Effect of γ radiation from <Superscript>60</Superscript>Co on the formation of metal contacts to GaAs (Al<Subscript>x</Subscript>Ga<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>As) structures

The properties of nonrectifying AuGe/GaAs (Al_0.4Ga_0.6As) contacts exposed to heat treatment, ⁶⁰Co γ radiation, and γ radiation combined with the application of an electrical bias are studied. A correlation between the type of interfacial interaction in the contacts and their resistance is found. Results obtained are explained in terms of a diffusion model with a movable boundary of the metal layer.     

Effects of localization of the areas of sound scattering by surface wind waves

Experimental studies of the scattering of a monochromatic sound signal by a rough sea surface are carried out. The signal is produced by a point source in a shallow-water basin. The measurements are performed with the use of horizontal and vertical linear receiving arrays. The experimental data are compared with the estimates obtained on the basis of the model developed by the authors for resonant sound scattering by surface roughness. A satisfactory agreement between the experiments and the calculations is achieved. It is shown that the scattered signal is formed within small surface areas, whose sizes have the same order of magnitude as the first Fresnel zone with respect to the source and the receiving system.     

The total acoustic impedance of a prolate spheroid performing transverse oscillatory movements

Using the theory of spheroidal wave functions, the total acoustic impedance is determined for a prolate spheroid performing transverse translational and rotational oscillatory movements. Expressions for the radiation resistance, the added mass, and the added moment of inertia are derived. It is shown that, in the lowfrequency approximation, this mass and moment of inertia reach limiting values identical to hydrodynamic ones. The components of the total acoustic impedance are calculated for spheroids of different relative thicknesses at an arbitrary frequency.     

Synthesis of ordered Ge-Si heterostructures containing ultrasmall germanium nanoclusters

Different techniques for the fabrication of structures containing ensembles of ultrasmall germanium nanoclusters distributed with a high density over the substrate surface are discussed. How to control the morphology and ordering of these ensembles is also discussed.     

Electromechanical properties of Pb<Subscript>3</Subscript>Ga<Subscript>2</Subscript>Ge<Subscript>4</Subscript>O<Subscript>14</Subscript> piezoelectric crystals grown from solution in a melt

Single crystals of lead gallium germanate Pb₃Ga₂Ge₄O₁₄ are grown from their own solution melts. The propagation of bulk acoustic waves is investigated, and the elastic, piezoelectric, and dielectric constants are calculated. The temperature dependences of the dielectric constants of this compound are analyzed.