Recent results of studies of magnetic field distribution and neutron scaling on PF-1000 and PF-3 facilities

The recent results of studies of the magnetic field distribution and the neutron yield scaling in two largest plasma focus facilities, PF-3 and PF-1000 is done. The power-law dependence of the neutron yield on the current in the imploding plasma sheath has been demonstrated experimentally. For the first time the presence of the Вz magnetic field components is experimentally shown. In the compression stage, the axial component of the magnetic field reaches several kG that comprises ~10 % of the azimuthal component. The presence of the Bz field is a powerful argument in favor of the existence of closed magnetic configurations, which play an important role in the generating of neutrons.Представлены результаты последних исследований распределения магнитного поля и скейлинга нейтронного выхода на двух крупнейших плазмофокусных установках ПФ-3 и ПФ-1000. Экспериментально показана степенная зависимость нейтронного выхода от величины тока в сжимающейся плазменной оболочке. Впервые экспериментально показано наличие Вz-компоненты магнитного поля. В стадии сжатия величина аксиальной компоненты магнитного поля достигает нескольких килограмм-сил, что составляет ~ 10% от величины азимутальной компоненты. Наличие Bz-поля является весомым аргументом в пользу существования замкнутых магнитных конфигураций, играющих важную роль в механизме генерации нейтронов.Представлено результати останніх досліджень розподілу магнітного поля і скейлінга нейтронного вихoдy на двох найбільших плазмофокусних установках ПФ-3 та ПФ-1000. Експериментально показана ступенева залежність нейтронного виходу від величини струму в плазмовїй оболонці, що стикається. Вперше експериментально показано наявність Вz-компоненти магнітного поля. У стадії стиснення величина аксіальної компоненти магнітного поля досягає декількох кілограм-сил, що складає ~ 10 % від величини азимутальної компоненти. Наявність Вz-поля є вагомим аргументом на користь існування замкнутих магнітних конфігурацій, що мають неаби яку роль у механізмі генерації нейтронів

The Paradox of Being a Teacher: Institutionalized Relevance and Organized Mistrust

In the article "The Paradox of Being a Teacher: Institutionalized Relevance and Organized MistrustW Daniel Tröhler describes the paradoxical nature of the teaching profession which arises out of the mismatch between the excessive expectations imposed on teachers and, at the same time, the constant mistrust shown to them for fulfilling these expectations. The paradox is related to the cultural shift of the educationalization of the Western world – that not only are a wide variety of social, economic and moral problems defined as educational problems but, in addition, education itself is placed at the core of the historical process and expected to fulfil future ideals. According to Tröhler, educationalization was reinforced by the tradition of modern educational thinking and especially by certain inherent fundamental religious motives. The author defends this thesis with the help of two, at first sight very divergent, figures in the history of education: Johan Heinrich Pestalozzi and Burrhus F. Skinner. Common to these thinkers is, according to Tröhler, their argument which is constitutive of the cultural shift of educationalization but, also, their shared view that in order to save the younger generation from the corrupting forces of external society, certain ideal conditions for making the natural development of the children possible are needed. Tröhler underlines the religious motives behind this idea. The task of education is to take care of the salvation of the younger generation, to protect the “God’s creation” against the world of artificial moral corruption. The educator’s task is, then, to be God’s deputy, substitute and imitator, to secure the existence of this moral order. This religious background helps us, according to Tröhler, to understand those enormous expectations that schools and teachers meet even in secular contemporary societies. This raises the question: should one reject expectations, which no one can fulfill

RESPECTIVE ROLES OF IMPURITIES AND DEFECTS IN Al/Ga INTERDIFFUSION IN ION IMPLANTED GaAs-AlxGa1-xAs SUPERLATTICES

L'influence des défauts d'implantation, séparés des effets associés aux charges des impuretés, a été étudiée sur l'interdiffusion d'Al/Ga dans des superréseaux (SR) GaAs-Al0. 3Ga0.7As. L'implantation des éléments isoélectroniques 31P+ et 27Al+ ont été effectués dans des SR à deux températures (25°C et 250°C) dans le but d'obtenir différentes densités de défauts pour chaque élément. Les propriétés de ces structures, avant et après recuits à 850°C durant 6 h, ont été évaluées à l'aide de plusieurs techniques d'analyses. Ainsi, nous avons mis en évidence la dépendance d'interdiffusion sur la densité des défauts et la durée de leur recuit.The influence of implant damage, seperated from impurity change associated effects, has been investigated on Al/Ga interdiffusion. Implants of electrically inactive isoelectronic elements 31P+ and 27Al+ were performed in molecular beam epitaxy grown (MBE) GaAs-Al0.3Ga0.7As superlattices (SLs) at two distinct temperatures (25°C and 250°C) to generate different damage densities. Their properties, before and after anneals at 850°C for periods up to 6 h, were evaluated using several characterization techniques. An unambiguous evidence to the implant damage and anneal duration dependent Al/Ga interdiffusion is presented and discussed

Propagation dynamics of successive emissions in laboratory and astrophysical jets and problem of their collimation

International audienceThe paper presents the results of numerical simulation of the propagation of a sequence of plasma knots in laboratory conditions and the astrophysical environment. The physical and geometric parameters of the simulation have been chosen close to the parameters of the PF-3 facility (Kurchatov Institute) and the jet of the star RW Aur. We found that the low-density region formed after the first knot propagation plays an important role for collimation of the subsequent ones. Assuming only the thermal expansion of the subsequent emissions, qualitative estimates of the time taken to fill this area with the surrounding matter and the angle of jet scattering have been made. These estimates are consistent with observations and results of our modeling