212 research outputs found
GigaGauss solenoidal magnetic field inside of bubbles excited in under-dense plasma
Magnetic fields have a crucial role in physics at all scales, from
astrophysics to nanoscale phenomena. Large fields, constant or pulsed, allow
investigation of material in extreme conditions, opening up plethora of
practical applications based on ultra-fast process, and studying phenomena
existing only in exotic astro-objects like neutron stars or pulsars. Magnetic
fields are indispensable in particle accelerators, for guiding the relativistic
particles along a curved trajectory and for making them radiate in synchrotron
light sources and in free electron lasers. In the presented paper we propose a
novel and effective method for generating solenoidal quasi-static magnetic
field on the GigaGauss level and beyond, in under-dense plasma, using
screw-shaped high intensity laser pulses. In comparison with already known
techniques which typically rely on interaction with over-dense or solid
targets, where radial or toroidal magnetic field localized at the stationary
target were generated, our method allows to produce gigantic solenoidal fields,
which is co-moving with the driving laser pulse and collinear with accelerated
electrons. The solenoidal field is quasi-stationary in the reference frame of
the laser pulse and can be used for guiding electron beams and providing
synchrotron radiation beam emittance cooling for laser-plasma accelerated
electron and positron beams, opening up novel opportunities for designs of the
light sources, free electron lasers, and high energy colliders based on laser
plasma acceleration.Comment: 15 pages, 9 figures. Main text (without abstract, References and
Appendix): 12 page
Asymmetric Dual Axis Energy Recovery Linac for Ultra-High Flux sources of coherent X-ray/THz radiation: Investigations Towards its Ultimate Performance
In order for sources of coherent high brightness and intensity THz and X-Ray
radiation to be accepted by university or industrial R&D laboratories, truly
compact, high current and efficient particle accelerators are required. The
demand for compactness and efficiency can be satisfied by superconducting RF
energy recovery linear accelerators (SRF ERL) allowing effectively minimising
the footprint and maximising the efficiency of the system. However such set-ups
are affected by regenerative beam-break up (BBU) instabilities which limit the
beam current and may terminate the beam transport as well as energy
recuperation. In this paper we suggest and discuss a SRF ERL with asymmetric
configuration of resonantly coupled accelerating and decelerating cavities. In
this type of SRF ERL an electron bunch is passing through accelerating and
decelerating cavities once and, as we show in this case, the regenerative BBU
instability can be minimised allowing high currents to be achieved. We study
the BBU start current in such an asymmetric ERL via analytical and numerical
models and discuss the properties of such a system
Studies of surface two-dimensional photonic band-gap structures
Two-dimensional (2D) surface photonic band-gap (SPBG) structures can be obtained by providing a shallow corrugation of the inner surface of a waveguide wall. It can be used as a distributed mirror, a cavity, or a filter in integrated optics or microwave electronics. These structures can also be an alternative to conventional 2D PBG or 1D Bragg structures. In this article, we present the results of theoretical and experimental studies of 2D SPBG structures. Data obtained from experiments are compared with theoretical results and good agreement between theory and experiment is demonstrated. Comparison of a coaxial 2D SPBG structure with a conventional 1D Bragg structure is also presented
Cylindrical, periodic surface lattice — theory, dispersion analysis, and experiment
A two-dimensional surface lattice of cylindrical topology obtained via perturbing the inner surface of a cylinder is considered. Periodic perturbations of the surface lead to observation of high-impedance, dielectric-like media and resonant coupling of surface and non-propagating volume fields. This allows synthesis of tailored-for-purpose "coating" material with dispersion suitable, for instance, to mediate a Cherenkov type interaction. An analytical model of the lattice is discussed and coupled-wave equations are derived. Variations of the lattice dispersive properties with variation of parameters are shown, illustrating the tailoring of the structure's electromagnetic properties. Experimental results are presented showing agreement with the theoretical model
Multibody System Mechanics: Modelling, Stability, Control, and Robustness by V. A. Konoplev and A. Cheremensky
BOOK REVIEWS
Multibody System Mechanics: Modelling, Stability, Control, and Ro-
bustness, by V. A. Konoplev and A. Cheremensky, Mathematics and its Appli-
cations Vol. 1, Union of Bulgarian Mathematicians, Sofia, 2001, XXII + 288 pp.,
$ 65.00, ISBN 954-8880-09-01The Union of Bulgarian Mathematicians starts a new series of publica-
tions: Mathematics and Its Applications. The first issue of the series is “Multi-
body System Mechanics: Modelling, Stability, Control and Robustness”.
The authors are well known mathematicians with various published books
and articles. Professor Vladimir Konoplev works in the Institute of Problems of
Mechanical Engineering, Russian Academy of Sciences (St. Petersburg, Russia),
while Professor Alexander Cheremensky works in the Institute of Mechanics,
Bulgarian Academy of Sciences (Sofia, Bulgaria).
The book contains results of the development of a new computer-aided
mathematical formalism of the multibody system mechanics which may be easily
implemented by the use of computer algebra tools for symbolic computations and
of standard software for numerical ones
GigaGauss solenoidal magnetic field inside bubbles excited in under-dense plasma
This paper proposes a novel and effective method for generating GigaGauss level, solenoidal quasi-static magnetic fields in under-dense plasma using screw-shaped high intensity laser pulses. This method produces large solenoidal fields that move with the driving laser pulse and are collinear with the accelerated electrons. This is in contrast with already known techniques which rely on interactions with over-dense or solid targets and generates radial or toroidal magnetic field localized at the stationary target. The solenoidal field is quasi-stationary in the reference frame of the laser pulse and can be used for guiding electron beams. It can also provide synchrotron radiation beam emittance cooling for laser-plasma accelerated electron and positron beams, opening up novel opportunities for designs of the light sources, free electron lasers, and high energy colliders based on laser plasma acceleration
Natural attenuation of Fukushima-derived radiocesium in soils due to its vertical and lateral migration
Processes of vertical and lateral migration lead to gradual reduction in contamination of catchment soil, particularly its top layer. The reduction can be considered as natural attenuation. This, in turn, results in a gradual decrease of radiocesium activity concentrations in the surface runoff and river water, in both dissolved and particulate forms. The purpose of this research is to study the dynamics of Fukushima-derived radiocesium in undisturbed soils and floodplain deposits exposed to erosion and sedimentation during floods. Combined observations of radiocesium vertical distribution in soil and sediment deposition on artificial lawn-grass mats on the Niida River floodplain allowed us to estimate both annual mean sediment accumulation rates and maximum sedimentation rates corresponding to an extreme flood event during Tropical Storm Etau, 6-11 September 2015. Dose rates were reduced considerably for floodplain sections with high sedimentation because the top soil layer with high radionuclide contamination was eroded and/or buried under cleaner fresh sediments produced mostly due to bank erosion and sediments movements. Rate constants of natural attenuation on the sites of the Takase River and floodplain of Niida River was found to be in range 0.2-0.4 year-1. For the site in the lower reach of the Niida River, collimated shield dose readings from soil surfaces slightly increased during the period of observation from February to July 2016. Generally, due to more precipitation, steeper slopes, higher temperatures and increased biological activities in soils, self-purification of radioactive contamination in Fukushima associated with vertical and lateral radionuclide migration is faster than in Chernobyl. In many cases, monitored natural attenuation along with appropriate restrictions seems to be optimal option for water remediation in Fukushima contaminated areas
Implementation of contact interaction in a finite - element formulation
© 2014 O. A. Sachenkov, V. I. Mitryaikin, T. A. Zaitseva and Yu. G. Konoplev. The paper presents a technique which makes it possible to take into account contact interactions between surfaces based on the finite element method. The technique is based on iterative cycles, determining statuses of the contact elements and renewing the contact forces to satisfy the condition of zero penetration of all active contact elements. The proposed technique allows us also to take account of friction between the contacting elements. The paper considers an example of implementing contact interaction with regard to friction between bodies, and solves a model problem
Ecological and biological features of phacelia tanacetifolia benth. in various ecotopes of Southern European Russia
The article contains the results of the study of the environmental and biological features of Ph. tanacetifolia in four natural and territorial complexes of the Belgorod region. In all natural-territorial complexes Ph. tanacetifolia accompanied by dominant species such as: M. albus Medik., Ch. album L., E. canadensis L., E. repens (L.) Nevski, S. pumila (Poir.) Roem. & Schult., C. xanthiifolia (Nutt.
- …