444 research outputs found
Особенности выполнения сварочных работ на предприятии ООО "РСП-М"
В данной статье рассмотрены особенности выполнения сварочных работ на предприятии ООО "РСП-М"
Bright betatron x-ray radiation from a laser-driven-clustering gas target
Hard X-ray sources from femtosecond (fs) laser-produced plasmas, including the betatron X-rays from laser wakefield-accelerated electrons, have compact sizes, fs pulse duration and fs pump-probe capability, making it promising for wide use in material and biological sciences. Currently the main problem with such betatron X-ray sources is the limited average flux even with ultra-intense laser pulses. Here, we report ultra-bright betatron X-rays can be generated using a clustering gas jet target irradiated with a small size laser, where a ten-fold enhancement of the X-ray yield is achieved compared to the results obtained using a gas target. We suggest the increased X-ray photon is due to the existence of clusters in the gas, which results in increased total electron charge trapped for acceleration and larger wiggling amplitudes during the acceleration. This observation opens a route to produce high betatron average flux using small but high repetition rate laser facilities for applications
Self-guided wakefield experiments driven by petawatt class ultra-short laser pulses
We investigate the extension of self-injecting laser wakefield experiments to
the regime that will be accessible with the next generation of petawatt class
ultra-short pulse laser systems. Using linear scalings, current experimental
trends and numerical simulations we determine the optimal laser and target
parameters, i.e. focusing geometry, plasma density and target length, that are
required to increase the electron beam energy (to > 1 GeV) without the use of
external guiding structures.Comment: 15 pages, 8 figure
Probing electron acceleration and X-ray emission in laser-plasma accelerator
While laser-plasma accelerators have demonstrated a strong potential in the
acceleration of electrons up to giga-electronvolt energies, few experimental
tools for studying the acceleration physics have been developed. In this paper,
we demonstrate a method for probing the acceleration process. A second laser
beam, propagating perpendicular to the main beam is focused in the gas jet few
nanosecond before the main beam creates the accelerating plasma wave. This
second beam is intense enough to ionize the gas and form a density depletion
which will locally inhibit the acceleration. The position of the density
depletion is scanned along the interaction length to probe the electron
injection and acceleration, and the betatron X-ray emission. To illustrate the
potential of the method, the variation of the injection position with the
plasma density is studied
Tuning the electron energy by controlling the density perturbation position in laser plasma accelerators
A density perturbation produced in an underdense plasma was used to improve
the quality of electron bunches produced in the laser-plasma wakefield
acceleration scheme. Quasi-monoenergetic electrons were generated by controlled
injection in the longitudinal density gradients of the density perturbation. By
tuning the position of the density perturbation along the laser propagation
axis, a fine control of the electron energy from a mean value of 60 MeV to 120
MeV has been demonstrated with a relative energy-spread of 15 +/- 3.6%,
divergence of 4 +/- 0.8 mrad and charge of 6 +/- 1.8 pC.Comment: 7 pages, 8 figure
Influence of realistic parameters on state-of-the-art LWFA experiments
We examine the influence of non-ideal plasma-density and non-Gaussian
transverse laser-intensity profiles in the laser wakefield accelerator
analytically and numerically. We find that the characteristic amplitude and
scale length of longitudinal density fluctuations impacts on the final energies
achieved by electron bunches. Conditions that minimize the role of the
longitudinal plasma density fluctuations are found. The influence of higher
order Laguerre-Gaussian laser pulses is also investigated. We find that higher
order laser modes typically lead to lower energy gains. Certain combinations of
higher order modes may, however, lead to higher electron energy gains.Comment: 16 pages, 6 figures; Accepted for publication in Plasma Physics and
Controlled Fusio
Demonstration of the synchrotron-type spectrum of laser-produced Betatron radiation
Betatron X-ray radiation in laser-plasma accelerators is produced when
electrons are accelerated and wiggled in the laser-wakefield cavity. This
femtosecond source, producing intense X-ray beams in the multi kiloelectronvolt
range has been observed at different interaction regime using high power laser
from 10 to 100 TW. However, none of the spectral measurement performed were at
sufficient resolution, bandwidth and signal to noise ratio to precisely
determine the shape of spectra with a single laser shot in order to avoid shot
to shot fluctuations. In this letter, the Betatron radiation produced using a
80 TW laser is characterized by using a single photon counting method. We
measure in single shot spectra from 8 to 21 keV with a resolution better than
350 eV. The results obtained are in excellent agreement with theoretical
predictions and demonstrate the synchrotron type nature of this radiation
mechanism. The critical energy is found to be Ec = 5.6 \pm 1 keV for our
experimental conditions. In addition, the features of the source at this energy
range open novel perspectives for applications in time-resolved X-ray science.Comment: 5 pages, 4 figure
Single shot phase contrast imaging using laser-produced Betatron x-ray beams
Development of x-ray phase contrast imaging applications with a laboratory
scale source have been limited by the long exposure time needed to obtain one
image. We demonstrate, using the Betatron x-ray radiation produced when
electrons are accelerated and wiggled in the laser-wakefield cavity, that a
high quality phase contrast image of a complex object (here, a bee), located in
air, can be obtained with a single laser shot. The Betatron x-ray source used
in this proof of principle experiment has a source diameter of 1.7 microns and
produces a synchrotron spectrum with critical energy E_c=12.3 +- 2.5 keV and
10^9 photons per shot in the whole spectrum.Comment: 3 pages, 3 figure
Synchrotron x-ray radiation from laser wakefield accelerated electron beams in a plasma channel
Synchrotron x-ray radiation from laser wakefield accelerated electron beams was characterized at the HERCULES facility of the University of Michigan. A mono-energetic electron beam with energy up to 400 MeV was observed in the interaction of an ultra-short laser pulse with a super-sonic gas jet target. The experiments were performed at a peak intensity of 5×1019 W/cm2 by using an adaptive optic. The accelerated electron beam undergoes a so called "betatron" oscillation in an ion channel, where plasma electrons have been expelled by the laser ponderomotive force, and, therefore, emits synchrotron radiation. We observe broad synchrotron x-ray radiation extending up to 30 keV. We find that this radiation is emitted in a beam with a divergence angle as small as 12×4 mrad2 and can have a source size smaller than 3 microns and a peak brightness of 1022 photons/mm2/mrad2/second/0.1% bandwidth, which is comparable to currently existing 3rd generation conventional light sources. This opens up the possibility of using laser-produced "betatron" sources for many applications that currently require conventional synchrotron sources.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85402/1/jpconf10_244_042026.pd
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