167 research outputs found
Development of the RF Ion Sources for Focused Ion Beam Accelerators
The paper presents the results of investigations of ion sources developed in the IAP of NAS of Ukraine for generation of high brightness ion beams with small energy spread. A series of RF ion sources operated at the frequency of 27.12 MHz were studied: the inductive RF ion source, the helicon ion source, the multi-cusp RF ion source, and the sputter type RF source of metal ions. A global model and transformer model were applied for calculation of RF source plasma parameters. Ion energy spread, ion mass, and ion current density of some sources were measured in the wide range of RF power, extraction voltage and gas pres-sure.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3555
On O-X mode conversion in 2D inhomogeneous plasma with a sheared magnetic field
The conversion of an ordinary wave to an extraordinary wave in a 2D
inhomogeneous slab model of the plasma confined by a sheared magnetic field is
studied analytically.Comment: sub. to PPC
Observation of kink instability during small B5.0 solar flare on 04 June, 2007
Using multi-wavelength observations of SoHO/MDI, SOT-Hinode/blue-continuum
(4504 \AA), G-band (4305 \AA), Ca II H (3968 \AA) and TRACE 171 \AA, we present
the observational signature of highly twisted magnetic loop in AR 10960 during
the period 04:43 UT-04:52 UT at 4 June, 2007. SOT-Hinode/blue-continuum (4504
\AA) observations show that penumbral filaments of positive polarity sunspot
have counter-clock wise twist, which may be caused by the clock-wise rotation
of the spot umbrae. The coronal loop, whose one footpoint is anchored in this
sunspot, shows strong right-handed twist in chromospheric SOT-Hinode/Ca II H
(3968 \AA) and coronal TRACE 171 \AA\, images. The length and the radius of the
loop are 80 Mm and 4.0 Mm respectively. The distance between
neighboring turns of magnetic field lines (i.e. pitch) is estimated as
10 Mm. The total twist angle, 12 (estimated for the
homogeneous distribution of the twist along the loop), is much larger than the
Kruskal -Shafranov instability criterion. We detected clear double structure of
the loop top during 04:47-04:51 UT on TRACE 171 \AA \ images, which is
consistent with simulated kink instability in curved coronal loops
(T{\"o}r{\"o}k et al. 2004). We suggest, that the kink instability of this
twisted magnetic loop triggered B5.0 class solar flare, which occurred between
04:40 UT and 04:51 UT in this active region.Comment: 24 pages, 5 Figures; The Astrophysical Journa
On handling urban informality in southern Africa
In this article I reconsider the handling of urban informality by urban planning and management systems in southern Africa. I argue that authorities have a fetish about formality and that this is fuelled by an obsession with urban modernity. I stress that the desired city, largely inspired by Western notions of modernity, has not been and cannot be realized. Using illustrative cases of top–down interventions, I highlight and interrogate three strategies that authorities have deployed to handle informality in an effort to create or defend the modern city. I suggest that the fetish is built upon a desire for an urban modernity based on a concept of formal order that the authorities believe cannot coexist with the “disorder” and spatial “unruliness” of informality. I question the authorities' conviction that informality is an abomination that needs to be “converted”, dislocated or annihilated. I conclude that the very configuration of urban governance and socio-economic systems in the region, like the rest of sub-Saharan Africa, renders informality inevitable and its eradication impossible
Swift iodine ion modification of the structural and magnetotransport properties of Fe/Cr systems
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