167 research outputs found
Probing the quantum vacuum with ultra intense laser pulses
This article presents: 1) The theoretical background of strong field physics
and vacuum structure and stability; 2) The instrumental developments in the
area of pulse lasers and considers the physics case for ultra intense laser
facilities; and 3) Discussion of the applied and fundamental uses of
ultra-intense lasers.Comment: Contribution in Special Topics issue for IZEST, 12 pages incl 1
figure. Contains extended citation list compared to published versio
Fast ignition driven by quasi-monoenergetic ions: Optimal ion type and reduction of ignition energies with an ion beam array
Fast ignition of inertial fusion targets driven by quasi-monoenergetic ion
beams is investigated by means of numerical simulations. Light and intermediate
ions such as lithium, carbon, aluminium and vanadium have been considered.
Simulations show that the minimum ignition energies of an ideal configuration
of compressed Deuterium-Tritium are almost independent on the ion atomic
number. However, they are obtained for increasing ion energies, which scale,
approximately, as Z^2, where Z is the ion atomic number. Assuming that the ion
beam can be focused into 10 {\mu}m spots, a new irradiation scheme is proposed
to reduce the ignition energies. The combination of intermediate Z ions, such
as 5.5 GeV vanadium, and the new irradiation scheme allows a reduction of the
number of ions required for ignition by, roughly, three orders of magnitude
when compared with the standard proton fast ignition scheme
Fast ignition of inertial fusion targets by laser-driven carbon beams
Two-dimensional simulations of ion beam driven fast ignition are presented.
Ignition energies of protons with Maxwellian spectrum and carbon ions with
quasimonoenergetic and Maxwellian energy distributions are evaluated. The
effect of the coronal plasma surrounding the compressed deuterium-tritium is
studied for three different fuel density distributions. It is found that quasi-
monoenergetic ions have better coupling with the compressed deuterium-tritium
and substantially lower ignition energies. Comparison of quasimonoenergetic
carbon ions and relativistic electrons as ignitor beams shows similar laser
energy requirements, provided that a laser to quasimonoenergetic carbon ion
conversion efficiency around 10% can be achieved.Comment: 8 pages, 10 figures, published in Physics of Plasma
Laser-like X-ray Sources Based on Optical Reflection from Relativistic Electron Mirror
A novel scheme is proposed to generate uniform relativistic electron layers
for coherent Thomson backscattering. A few-cycle laser pulse is used to produce
the electron layer from an ultra-thin solid foil. The key element of the new
scheme is an additional foil that reflects the drive laser pulse, but lets the
electrons pass almost unperturbed. It is shown by analytic theory and by 2D-PIC
simulation that the electrons, after interacting with both drive and reflected
laser pulse, form a very uniform flyer freely cruising with high relativistic
gamma-factor exactly in drive laser direction (no transverse momentum). It
backscatters probe light with a full Doppler shift factor of 4*gamma^2. The
reflectivity and its decay due to layer expansion is discussed.Comment: 5 pages, 3 figures, submitted, invited talk on the workshop of
Frontiers in Intense Laser-Matter Interaction Theory, MPQ, March 1-3, 2010
Photon and neutron production as in-situ diagnostics of proton-boron fusion
Short-pulse, ultra high-intensity lasers have opened new regimes for studying
fusion plasmas and creating novel ultra-short ion beams and neutron sources.
Diagnosing the plasma in these experiments is important for optimizing the
fusion yield but difficult due to the picosecond time scales, 10s of
micron-cubed volumes and high densities. We propose to use the yields of
photons and neutrons produced by parallel reactions involving the same
reactants to diagnose the plasma conditions and predict the yields of specific
reactions of interest. In this work, we focus on verifying the yield of the
high-interest aneutronic proton-boron fusion reaction
, which is difficult to measure directly due to
the short stopping range of the produced s in most materials. We
identify promising photon-producing reactions for this purpose and compute the
ratios of the photon yield to the yield as a function of plasma
parameters. In beam fusion experiments, the yield is an
easily-measurable observable to verify the yield. In light of our
results, improving and extending measurements of the cross sections for these
parallel reactions are important steps to gaining greater control over these
laser-driven fusion plasmas.Comment: 23 pages, 7 figures, revtex forma
En-route to the fission-fusion reaction mechanism: a status update on laser-driven heavy ion acceleration
The fission-fusion reaction mechanism was proposed in order to generate
extremely neutron-rich nuclei close to the waiting point N = 126 of the rapid
neutron capture nucleosynthesis process (r-process). The production of such
isotopes and the measurement of their nuclear properties would fundamentally
help to increase the understanding of the nucleosynthesis of the heaviest
elements in the universe. Major prerequisite for the realization of this new
reaction scheme is the development of laser-based acceleration of ultra-dense
heavy ion bunches in the mass range of A = 200 and above. In this paper, we
review the status of laser-driven heavy ion acceleration in the light of the
fission-fusion reaction mechanism. We present results from our latest
experiment on heavy ion acceleration, including a new milestone with
laser-accelerated heavy ion energies exceeding 5 MeV/u
Luminosity for laser-electron colliders
High intensity laser facilities are expanding their scope from laser and
particle-acceleration test beds to user facilities and nuclear physics
experiments. A basic goal is to confirm long-standing predictions of
strong-field quantum electrodynamics, but with the advent of high-repetition
rate laser experiments producing GeV-scale electrons and photons, novel
searches for new high-energy particle physics also become possible. The common
figure of merit for these facilities is the invariant describing the electric field strength in
the electron rest frame relative to the ``critical'' field strength of quantum
electrodynamics where the vacuum decays into electron-positron pairs. However,
simply achieving large is insufficient; discovery or validation requires
statistics to distinguish physics from fluctuations. The number of events
delivered by the facility is therefore equally important. In high-energy
physics, luminosity quantifies the rate at which colliders provide events and
data. We adapt the definition of luminosity to high-intensity laser-electron
collisions to quantify and thus optimize the rate at which laser facilities can
deliver strong-field QED and potentially new physics events. Modeling the
pulsed laser field and electron bunch, we find that luminosity is maximized for
laser focal spot size equal or slightly larger than the diameter of the dense
core of the electron bunch. Several examples show that luminosity can be
maximized for parameters different from those maximizing the peak value of
in the collision. The definition of luminosity for electron-laser
collisions is straightforwardly extended to photon-laser collisions and lepton
beam-beam collisions
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