53 research outputs found
Nonlinear wakefields and electron injection in cluster plasma
Laser and beam driven wakefields promise orders of magnitude increases in
electric field gradients for particle accelerators for future applications. Key
areas to explore include the emittance properties of the generated beams and
overcoming the dephasing limit in the plasma. In this paper, the first in-depth
study of the self-injection mechanism into wakefield structures from
non-homogeneous cluster plasmas is provided using high-resolution two
dimensional particle-in-cell simulations. The clusters which are typical
structures caused by ejection of gases from a high-pressure gas jet have a
diameter much smaller than the laser wavelength. Conclusive evidence is
provided for the underlying mechanism that leads to particle trapping,
comparing uniform and cluster plasma cases. The accelerated electron beam
properties are found to be tunable by changing the cluster parameters. The
mechanism explains enhanced beam charge paired with large transverse momentum
and energy which has implications for the betatron x-ray flux. Finally, the
impact of clusters on the high-power laser propagation behavior is discussed
Generation of GeV protons from 1 PW laser interaction with near critical density targets
The propagation of ultra intense laser pulses through matter is connected
with the generation of strong moving magnetic fields in the propagation channel
as well as the formation of a thin ion filament along the axis of the channel.
Upon exiting the plasma the magnetic field displaces the electrons at the back
of the target, generating a quasistatic electric field that accelerates and
collimates ions from the filament. Two-dimensional Particle-in-Cell simulations
show that a 1 PW laser pulse tightly focused on a near-critical density target
is able to accelerate protons up to an energy of 1.3 GeV. Scaling laws and
optimal conditions for proton acceleration are established considering the
energy depletion of the laser pulse.Comment: 26 pages, 8 figure
Laser-ion acceleration through controlled surface contamination
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98750/1/PhysPlasmas_18_040702.pd
X-ray phase contrast imaging of biological specimens with tabletop synchrotron radiation
Since their discovery in 1896, x-rays have had a profound impact on science, medicine and technology. Here we show that the x-rays from a novel tabletop source of bright coherent synchrotron radiation can be applied to phase contrast imaging of biological specimens, yielding superior image quality and avoiding the need for scarce or expensive conventional sources
Accelerating Protons to Therapeutic Energies with Ultra-Intense Ultra-Clean and Ultra-Short Laser Pulses
Proton acceleration by high-intensity laser pulses from ultra-thin foils for
hadron therapy is discussed. With the improvement of the laser intensity
contrast ratio to 10-11 achieved on Hercules laser at the University of
Michigan, it became possible to attain laser-solid interactions at intensities
up to 1022 W/cm2 that allows an efficient regime of laser-driven ion
acceleration from submicron foils. Particle-In-Cell (PIC) computer simulations
of proton acceleration in the Directed Coulomb explosion regime from ultra-thin
double-layer (heavy ions / light ions) foils of different thicknesses were
performed under the anticipated experimental conditions for Hercules laser with
pulse energies from 3 to 15 J, pulse duration of 30 fs at full width half
maximum (FWHM), focused to a spot size of 0.8 microns (FWHM). In this regime
heavy ions expand predominantly in the direction of laser pulse propagation
enhancing the longitudinal charge separation electric field that accelerates
light ions. The dependence of the maximum proton energy on the foil thickness
has been found and the laser pulse characteristics have been matched with the
thickness of the target to ensure the most efficient acceleration. Moreover the
proton spectrum demonstrates a peaked structure at high energies, which is
required for radiation therapy. 2D PIC simulations show that a 150-500 TW laser
pulse is able to accelerate protons up to 100-220 MeV energies.Comment: 26 pages, 6 figure
Quasimonoenergetic electron beams with relativistic energies and ultrashort duration from laser-solid interactions at 0.5 kHz
International audienceWe investigate the production of electron beams from the interaction of relativistically-intense laser pulses with a solid-density SiO2 target in a regime where the laser pulse energy is -mJ and the repetition rate -kHz. The electron beam spatial distribution and spectrum were investigated as a function of the plasma scale length, which was varied by deliberately introducing a moderate-intensity prepulse. At the optimum scale length of λ/2, the electrons are emitted in a collimated beam having a quasimonoenergetic distribution that peaked at -0.8MeV. A highly reproducible structure in the spatial distribution exhibits an evacuation of electrons along the laser specular direction and suggests that the electron beam duration is comparable to that of the laser pulse. Particle-in-cell simulations which are in good agreement with the experimental results offer insights on the acceleration mechanism by the laser field. © 2009 The American Physical Society
Electron acceleration using laser produced plasmas
Low density plasmas have long been of interest as a potential medium for particle acceleration since relativistic plasma waves are capable of supporting electric fields greater than 100 GeV/m. The physics of particle acceleration using plasmas will be reviewed, and new results will be discussed which have demonstrated that relatively narrow energy spread (<3%) beams having energies greater than 100 MeV can be produced from femtosecond laser plasma interactions. Future experiments and potential applications will also be discussed
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