Voids’ layer structures in silicon irradiated with high doses of high-energy helium ions

Structural and optical properties of single crystal silicon irradiated with 27.2 MeV helium ions by using fluences Ф ≥ 10¹⁶ ion/cm² were studied at various beam currents. It was found that at currents 0.25 to 0.45 μА, heavily damaged layers containing voids were formed in ion path in Si and behind it. The number of layers in the ion path region depends on the beam intensity. With increasing the beam current up to ~1 μA, the layer structures consisting of voids were observed only in the ion path. As helium is poorly soluble in Si, during implantation it collects in the gas-filled vacancy complexes. We consider that, like to the case of keV-ion implantation at fluences of Ф ≥ 10¹⁶ ion/cm² , an amorphous layer is created in the ion stopping region at annealing. Moving by recrystallization fronts on both sides of the amorphous layer, vacancy clusters are collected inside, coalesce and form voids. It is a combination of high energy and high fluence helium implantation that can form layered structure with voids in silicon, as observed by us. At present, there is no strict explanation of the mechanism of voids’ ordering (forming of superlattice of them). Especially, it concerns the void layer formation beyond helium ion path. The concept of mobile solitons is used. Formation of the “lattice” from the voids leads to swelling of the material. Further researches are necessary to understand these processes and control them

Special traits of the millimeter wave relativistic magnetron

A 8 mm band relativistic magnetron is investigated experimentally and by means of numerical simulation. The physical effects are analyzed which influence negatively the r.f. generation. The processes capable of reducing effectiveness of the generation and duration of the generated pulse include forward and backward axial flows of electrons, and intense electric fields – the generated microwaves and the fields owing to the space charge.Экспериментально и методами численного моделирования проведено исследование релятивистского магнетрона 8-миллиметрового диапазона и анализ факторов, оказывающих негативное действие на генерацию. Отмечается, что к процессам, уменьшающим эффективность и длительность импульса генерации, относятся прямые и обратные осевые потоки электронов, интенсивные собственные ВЧ-поля и поля объемного заряда.Експериментально й методами чисельного моделювання досліджено релятивістський магнетрон діапазону 8 мм та проведено аналіз факторів, що негативно впливають на генерацію. Визначено, що до процесів, котрі зменшують ефективність та тривалість імпульсу генерації, відносяться прямі та зворотні осьові потоки електронів, інтенсивні власні ВЧ-поля і поля об’ємного заряду

Spatial-temporeral changes in the geomagnetic field and seismisity

This paper presents the results of an analysis of spatial-temporeral changes in the Earth’s magnetic field and its seismicity for the period 1950—2015. The International Geomagnetic Field of the 12 generation (BIGRF-12) was analyzed. This model allows one to study the characteristic features of magnetic anomalies with dimensions of the first thousands of kilometers. To determine the temporal changes in the geomagnetic field (dB/dt), digital datasets of BIGRF were developed for the period 1950—2015 in a 1°Ч1° grid and for an interval of 5 years. Temporal changes were divided into the virtual long-wave core-generated and short-wave mantle-lithospheric — generated components. There were revealed 2 negative and 3 positive foci of the core-generated component. For the 65 y period the component changes in these foci range from –6600 to 2000 nT (from –100 to 30 nT/y), the foci being characterized by the significant westward drift. 12 positive and 10 negative foci were delineated in the mantle-lithospheric-caused component. During 65 years most of the foci do not change their location. The changes in magnitude of positive and negative foci are 175—490 nT, (2,5—7,5 nT/y) and –(220—535) nT, (–(3,4—8,2) nT/y) respectively. In the southwestern domain of the Earth the intensity of seismicity is lower and the core-originated component is significantly decreased in comparison with the northwestern domain. The relationship is observed between areas of increased seismic activity, foci of the mantle-lithospheric component of the geomagnetic field and areas of its positive increase, which tectonically correspond to the junction zones of lithospheric plates of the «subduction», «collision» and «mid-ocean-rift» types. On the basis of the regularities revealed, two mechanisms of such an association are proposed: a) «temperature-magnetic», caused by discending the magnetic blocks of the oceanic crust in a subduction zone and also serpentinization of ultrabasic rocks of the upper mantle; b) «fluid-gas-magnetic», based on the formation and transformation of ferruginous minerals under the influence of the mantle gases and fluids. The magnetic blocks of the Earth’s lithosphere are more solid than those of the non-magnetic. Therefore, within the blocks, as well as on their margins, the accumulation of large stresses is possible and, consequеntly, the preconditions are created for the formation of earthquake foci