39 research outputs found
Resonance structures in coupled two-component model
We present a numerical study of the process of the kink-antikink collisions
in the coupled one-dimensional two-component model. Our results reveal
two different soliton solutions which represent double kink configuration and
kink-non-topological soliton (lump) bound state. Collision of these solitons
leads to very reach resonance structure which is related to reversible energy
exchange between the kinks, non-topological solitons and the internal
vibrational modes. Various channels of the collisions are discussed, it is
shown there is a new type of self-similar fractal structure which appears in
the collisions of the relativistic kinks, there the width of the resonance
windows increases with the increase of the impact velocity. An analytical
approximation scheme is discussed in the limit of the perturbative coupling
between the sectors. Considering the spectrum of linear fluctuations around the
solitons we found that the double kink configuration is unstable if the
coupling constant between the sectors is negative.Comment: 21 pages, 19 figure
Spatial Control of Photoemitted Electron Beams using a Micro-Lens-Array Transverse-Shaping Technique
A common issue encountered in photoemission electron sources used in electron
accelerators is the transverse inhomogeneity of the laser distribution
resulting from the laser-amplification process and often use of frequency up
conversion in nonlinear crystals. A inhomogeneous laser distribution on the
photocathode produces charged beams with lower beam quality. In this paper, we
explore the possible use of microlens arrays (fly-eye light condensers) to
dramatically improve the transverse uniformity of the drive laser pulse on UV
photocathodes. We also demonstrate the use of such microlens arrays to generate
transversely-modulated electron beams and present a possible application to
diagnose the properties of a magnetized beam.Comment: arXiv admin note: text overlap with arXiv:1609.0166
Hopfion canonical quantization
We study the effect of the canonical quantization of the rotational mode of
the charge Q=1 and Q=2 spinning Hopfions. The axially-symmetric solutions are
constructed numerically, it is shown the quantum corrections to the mass of the
configurations are relatively large.Comment: 11 pages, 3 figures, Physics Letters B, in pres
X-ray Parametric Down Conversion at the APS Synchrotron
We present measurements of X-ray Parametric Down Conversion at the Advanced
Photon Source synchrotron facility. We use an incoming pump beam at 22 keV to
observe the simultaneous, elastic emission of down-converted photon pairs
generated in a diamond crystal. The pairs are detected using high count rate
silicon drift detectors with low noise. Production by down-conversion is
confirmed by measuring time-energy correlations in the detector signal, where
photon pairs within an energy window ranging from 10 to 12 keV are only
observed at short time differences. By systematically varying the crystal
misalignment and detector positions, we obtain results that are consistent with
the constant total of the down-converted signal
Some Recent Developments on Kink Collisions and Related Topics
We review recent works on modeling of dynamics of kinks in 1+1 dimensional
theory and other related models, like sine-Gordon model or
theory. We discuss how the spectral structure of small perturbations can affect
the dynamics of non-perturbative states, such as kinks or oscillons. We
describe different mechanisms, which may lead to the occurrence of the resonant
structure in the kink-antikink collisions. We explain the origin of the
radiation pressure mechanism, in particular, the appearance of the negative
radiation pressure in the and models. We also show that the
process of production of the kink-antikink pairs, induced by radiation is
chaotic.Comment: 26 pages, 9 figures; invited chapter to "A dynamical perspective on
the {\phi}4 model: Past, present and future", Eds. P.G. Kevrekidis and J.
Cuevas-Maraver; Springer book class with svmult.cls include
Magnetothermodynamics of BPS baby skyrmions
The magnetothermodynamics of skyrmion type matter described by the gauged BPS
baby Skyrme model at zero temperature is investigated. We prove that the BPS
property of the model is preserved also for boundary conditions corresponding
to an asymptotically constant magnetic field. The BPS bound and the
corresponding BPS equations saturating the bound are found. Further, we show
that one may introduce pressure in the gauged model by a redefinition of the
superpotential. Interestingly, this is related to non-extremal type solutions
in the so-called fake supersymmetry method. Finally, we compute the equation of
state of magnetized BSP baby skyrmions inserted into an external constant
magnetic field and under external pressure , i.e., , where
is the "volume" (area) occupied by the skyrmions. We show that the BPS baby
skyrmions form a ferromagnetic medium.Comment: Latex, 39 pages, 14 figures. v2: New results and references added,
physical interpretation partly change
An Ultra-Compact X-Ray Free-Electron Laser
In the field of beam physics, two frontier topics have taken center stage due
to their potential to enable new approaches to discovery in a wide swath of
science. These areas are: advanced, high gradient acceleration techniques, and
x-ray free electron lasers (XFELs). Further, there is intense interest in the
marriage of these two fields, with the goal of producing a very compact XFEL.
In this context, recent advances in high gradient radio-frequency cryogenic
copper structure research have opened the door to the use of surface electric
fields between 250 and 500 MV/m. Such an approach is foreseen to enable a new
generation of photoinjectors with six-dimensional beam brightness beyond the
current state-of-the-art by well over an order of magnitude. This advance is an
essential ingredient enabling an ultra-compact XFEL (UC-XFEL). In addition, one
may accelerate these bright beams to GeV scale in less than 10 meters. Such an
injector, when combined with inverse free electron laser-based bunching
techniques can produce multi-kA beams with unprecedented beam quality,
quantified by ~50 nm-rad normalized emittances. These beams, when injected into
innovative, short-period (1-10 mm) undulators uniquely enable UC-XFELs having
footprints consistent with university-scale laboratories. We describe the
architecture and predicted performance of this novel light source, which
promises photon production per pulse of a few percent of existing XFEL sources.
We review implementation issues including collective beam effects, compact
x-ray optics systems, and other relevant technical challenges. To illustrate
the potential of such a light source to fundamentally change the current
paradigm of XFELs with their limited access, we examine possible applications
in biology, chemistry, materials, atomic physics, industry, and medicine which
may profit from this new model of performing XFEL science.Comment: 80 pages, 24 figure