366 research outputs found
Relativistic spherical plasma waves
Tightly focused laser pulses as they diverge or converge in underdense plasma
can generate wake waves, having local structures that are spherical waves. Here
we report on theoretical study of relativistic spherical wake waves and their
properties, including wave breaking. These waves may be suitable as particle
injectors or as flying mirrors that both reflect and focus radiation, enabling
unique X-ray sources and nonlinear QED phenomena.Comment: 6 pages; 4 figure
Laser acceleration of protons from near critical density targets for application to radiation therapy
Laser accelerated protons can be a complimentary source for treatment of
oncological diseases to the existing hadron therapy facilities. We demonstrate
how the protons, accelerated from near-critical density plasmas by laser pulses
having relatively small power, reach energies which may be of interest for
medical applications. When an intense laser pulse interacts with near-critical
density plasma it makes a channel both in the electron and then in the ion
density. The propagation of a laser pulse through such a self-generated channel
is connected with the acceleration of electrons in the wake of a laser pulse
and generation of strong moving electric and magnetic fields in the propagation
channel. Upon exiting the plasma the magnetic field generates a quasi-static
electric field that accelerates and collimates ions from a thin filament formed
in the propagation channel. Two-dimensional Particle-in-Cell simulations show
that a 100 TW laser pulse tightly focused on a near-critical density target is
able to accelerate protons up to energy of 250 MeV. Scaling laws and optimal
conditions for proton acceleration are established considering the energy
depletion of the laser pulse.Comment: 25 pages, 8 figure
Formation of Luminescence Centers in Oxygen-Deficient Cerium Oxide Nanocrystals
In this work the peculiarities of oxygen vacancies formation in cerium oxide nanoparticles for different
external influences have been investigated by spectroscopic methods.
The features of oxygen vacancies and therefore non-stoichiometric cerium oxide formation in CeO2
nanocrystals depending on the atmosphere of high temperature treatment were investigated. Stimulation
of oxygen vacancies formation in reducing and neutral atmospheres was revealed. Occurrence of two different
luminescence centers (viz. the charge-transfer complexes formed by Ce4+ and O2- ions, and Ce3+ ions
stabilized by vacancies) after cerium oxide nanoparticles annealing in a neutral atmosphere has been observed.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3544
Adjustment accuracy parameters of face mills
The variants of customization mechanisms design for setting adjustable face mills in the radial and face directions are presented
High Flux Femtosecond X-ray Emission from the Electron-Hose Instability in Laser Wakefield Accelerators
Bright and ultrashort duration X-ray pulses can be produced by through
betatron oscillations of electrons during Laser Wakefield Acceleration (LWFA).
Our experimental measurements using the \textsc{Hercules} laser system
demonstrate a dramatic increase in X-ray flux for interaction distances beyond
the depletion/dephasing lengths, where the initial electron bunch injected into
the first wake bucket catches up with the laser pulse front and the laser pulse
depletes. A transition from an LWFA regime to a beam-driven plasma wakefield
acceleration (PWFA) regime consequently occurs. The drive electron bunch is
susceptible to the electron-hose instability and rapidly develops large
amplitude oscillations in its tail, which leads to greatly enhanced X-ray
radiation emission. We measure the X-ray flux as a function of acceleration
length using a variable length gas cell. 3D particle-in-cell (PIC) simulations
using a Monte Carlo synchrotron X-ray emission algorithm elucidate the
time-dependent variations in the radiation emission processes.Comment: 6 pages, 4 figures, accepted for publication in Phys. Rev. Accel.
Beam
Formation of Block-Modular Face Milling Cutters with Adjustment of Geometric Blade Parameters
Design variants of adjustment models for adjusting cutting blocks in block-modular cutting tools and adjustment variants of face milling cutter in the radial and axial directions are considered. Possible variants for adjusting mechanisms and forming scheme of block modular face milling cutters with adjustment of the geometric blades parameters are proposed
Application of a picosecond soft x-ray source to time-resolved plasma dynamics
We demonstrate the application of an ultrashort x-ray source as an external probe to measure plasma dynamics. The plasma is generated by a 100-fs Ti:sapphire laser focused onto thin metallic films. Time-resolved spectroscopy of the gold x-ray probe transmission through a perturbed 1000 Å aluminum film reveals redshifts of the LL-shell photoabsorption edge. We show that the dynamic behavior of this shift is consistent with the relaxation of the aluminum following the compression generated by a shock wave traveling through the film. An analytic plasma model, with comparison to a numerical hydrodynamics model, indicates compression up to 1.4 times solid density. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69766/2/APPLAB-70-3-312-1.pd
Improving of fixing system of cutting plates in block-modular cutting tools
The paper present research system of fixing cutting plates and blocks in block-modular cutting tool
Improving of fixing system of cutting plates in block-modular cutting tools
The paper present research system of fixing cutting plates and blocks in block-modular cutting tool
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