7,787 research outputs found
Calculation of The Lifetimes of Thin Stripper Targets Under Bombardment of Intense Pulsed Ions
The problems of stripper target behavior in the nonstationary intense
particle beams are considered. The historical sketch of studying of radiation
damage failure of carbon targets under ion bombardment is presented. The simple
model of evaporation of a target by an intensive pulsing beam is supposed.
Stripper foils lifetimes in the nonstationary intense particle can be described
by two failure mechanisms: radiation damage accumulation and evaporation of
target. At the maximal temperatures less than 2500K the radiation damage are
dominated; at temperatures above 2500K the mechanism of evaporation of a foil
prevails. The proposed approach has been applied to the discription of
behaviour of stripper foils in the BNL linac and SNS conditions.Comment: 12 pages, 5 figure
Solving the two-center nuclear shell-model problem with arbitrarily-orientated deformed potentials
A general new technique to solve the two-center problem with
arbitrarily-orientated deformed realistic potentials is demonstrated, which is
based on the powerful potential separable expansion method. As an example,
molecular single-particle spectra for C + C Mg are
calculated using deformed Woods-Saxon potentials. These clearly show that
non-axial symmetric configurations play a crucial role in molecular resonances
observed in reaction processes for this system at low energy
Estimates in Beurling--Helson type theorems. Multidimensional case
We consider the spaces of functions on the
-dimensional torus such that the sequence of the Fourier
coefficients belongs to
. The norm on is defined by
. We study the rate of
growth of the norms as
for -smooth real
functions on (the one-dimensional case was investigated
by the author earlier). The lower estimates that we obtain have direct
analogues for the spaces
Magnetic studies of multi-walled carbon nanotube mats: Evidence for the paramagnetic Meissner effect
We report magnetic measurements up to 1200 K on multi-walled carbon nanotube
mats using Quantum Design vibrating sample magnetometer. Extensive magnetic
data consistently show two ferrromagnetic-like transitions at about 1000 K and
1275 K, respectively. The lower transition at about 1000 K is associated with
an Fe impurity phase and its saturation magnetization is in quantitative
agreement with the Fe concentration measured by an inductively coupled plasma
mass spectrometer. On the other hand, the saturation magnetization for the
higher transition phase (1.0 emu/g) is about four orders of magnitude
larger than that expected from the measured concentration of Co or CoFe, which
has a high enough Curie temperature to explain this high transition. We show
that this transition at about 1275 K is not consistent with a magnetic
proximity effect of Fe-carbon systems and ferromagnetism of any carbon-based
materials or magnetic impurities but with the paramagnetic Meissner effect due
to the existence of Josephson junctions in a granular superconductor.Comment: 5 pages, 4 figure
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