1,734 research outputs found
Electromagnetic cascade in high energy electron, positron, and photon interactions with intense laser pulses
The interaction of high energy electrons, positrons, and photons with intense
laser pulses is studied in head-on collision geometry. It is shown that
electrons and/or positrons undergo a cascade-type process involving multiple
emissions of photons. These photons can consequently convert into
electron-positron pairs. As a result charged particles quickly lose their
energy developing an exponentially decaying energy distribution, which
suppresses the emission of high energy photons, thus reducing the number of
electron-positron pairs being generated. Therefore, this type of interaction
suppresses the development of the electromagnetic avalanche-type discharge,
i.e., the exponential growth of the number of electrons, positrons, and photons
does not occur in the course of interaction. The suppression will occur when 3D
effects can be neglected in the transverse particle orbits, i.e., for
sufficiently broad laser pulses with intensities that are not too extreme. The
final distributions of electrons, positrons, and photons are calculated for the
case of a high energy e-beam interacting with a counter-streaming, short
intense laser pulse. The energy loss of the e-beam, which requires a
self-consistent quantum description, plays an important role in this process,
as well as provides a clear experimental observable for the transition from the
classical to quantum regime of interaction.Comment: 13 pages, 7 figure
Optimized laser pulse profile for efficient radiation pressure acceleration of ions
The radiation pressure acceleration regime of laser ion acceleration requires
high intensity laser pulses to function efficiently. Moreover the foil should
be opaque for incident radiation during the interaction to ensure maximum
momentum transfer from the pulse to the foil, which requires proper matching of
the target to the laser pulse. However, in the ultrarelativistic regime, this
leads to large acceleration distances, over which the high laser intensity for
a Gaussian laser pulse must be maintained. It is shown that proper tailoring of
the laser pulse profile can significantly reduce the acceleration distance,
leading to a compact laser ion accelerator, requiring less energy to operate.Comment: 10 pages, 4 figure
Expression of Interest ICES/KIS-3 : Thema 4: Hoogwaardig Ruimtegebruik Speerpunt 6
Hoofddoel van dit speerpunt is om zowel de Nederlandse overheid als het bedrijfsleven uit te rusten met een operationele kennisinfrastructuur die toegesneden is op de relatie tussen (antropogene en natuurlijke) klimaatverandering en meervoudig ruimtegebrui
Helium-3 and Helium-4 acceleration by high power laser pulses for hadron therapy
The laser driven acceleration of ions is considered a promising candidate for
an ion source for hadron therapy of oncological diseases. Though proton and
carbon ion sources are conventionally used for therapy, other light ions can
also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the
same penetration depth as 250 MeV protons, helium ions require only 250 MeV per
nucleon, which is the lowest energy per nucleon among the light ions. This fact
along with the larger biological damage to cancer cells achieved by helium
ions, than that by protons, makes this species an interesting candidate for the
laser driven ion source. Two mechanisms (Magnetic Vortex Acceleration and
hole-boring Radiation Pressure Acceleration) of PW-class laser driven ion
acceleration from liquid and gaseous helium targets are studied with the goal
of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy
requirements. We show that He3 ions, having almost the same penetration depth
as He4 with the same energy per nucleon, require less laser power to be
accelerated to the required energy for the hadron therapy.Comment: 8 pages, 3 figures, 1 tabl
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
On Retardation Effects in Space Charge Calculations Of High Current Electron Beams
Laser-plasma accelerators are expected to deliver electron bunches with high
space charge fields. Several recent publications have addressed the impact of
space charge effects on such bunches after the extraction into vacuum.
Artifacts due to the approximation of retardation effects are addressed, which
are typically either neglected or approximated. We discuss a much more
appropriate calculation for the case of laser wakefield acceleration with
negligible retardation artifacts due to the calculation performed in the mean
rest frame. This presented calculation approach also aims at a validation of
other simulation approaches
Enhancing proton acceleration by using composite targets
Efficient laser ion acceleration requires high laser intensities, which can
only be obtained by tightly focusing laser radiation. In the radiation pressure
acceleration regime, where the tightly focused laser driver leads to the
appearance of the fundamental limit for the maximum attainable ion energy, this
limit corresponds to the laser pulse group velocity as well as to another limit
connected with the transverse expansion of the accelerated foil and consequent
onset of the foil transparency. These limits can be relaxed by using composite
targets, consisting of a thin foil followed by a near critical density slab.
Such targets provide guiding of a laser pulse inside a self-generated channel
and background electrons, being snowplowed by the pulse, compensate for the
transverse expansion. The use of composite targets results in a significant
increase in maximum ion energy, compared to a single foil target case.Comment: 16 pages, 9 figure
Radiation Pressure Acceleration: the factors limiting maximum attainable ion energy
Radiation pressure acceleration (RPA) is a highly efficient mechanism of
laser-driven ion acceleration, with with near complete transfer of the laser
energy to the ions in the relativistic regime. However, there is a fundamental
limit on the maximum attainable ion energy, which is determined by the group
velocity of the laser. The tightly focused laser pulses have group velocities
smaller than the vacuum light speed, and, since they offer the high intensity
needed for the RPA regime, it is plausible that group velocity effects would
manifest themselves in the experiments involving tightly focused pulses and
thin foils. However, in this case, finite spot size effects are important, and
another limiting factor, the transverse expansion of the target, may dominate
over the group velocity effect. As the laser pulse diffracts after passing the
focus, the target expands accordingly due to the transverse intensity profile
of the laser. Due to this expansion, the areal density of the target decreases,
making it transparent for radiation and effectively terminating the
acceleration. The off-normal incidence of the laser on the target, due either
to the experimental setup, or to the deformation of the target, will also lead
to establishing a limit on maximum ion energy.Comment: 17 pages, 6 figure
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