2,632 research outputs found
Quasi-monoenergetic femtosecond photon sources from Thomson Scattering using laser plasma accelerators and plasma channels
Narrow bandwidth, high energy photon sources can be generated by Thomson
scattering of laser light from energetic electrons, and detailed control of the
interaction is needed to produce high quality sources. We present analytic
calculations of the energy-angular spectra and photon yield that parametrize
the influences of the electron and laser beam parameters to allow source
design. These calculations, combined with numerical simulations, are applied to
evaluate sources using conventional scattering in vacuum and methods for
improving the source via laser waveguides or plasma channels. We show that the
photon flux can be greatly increased by using a plasma channel to guide the
laser during the interaction. Conversely, we show that to produce a given
number of photons, the required laser energy can be reduced by an order of
magnitude through the use of a plasma channel. In addition, we show that a
plasma can be used as a compact beam dump, in which the electron beam is
decelerated in a short distance, thereby greatly reducing radiation shielding.
Realistic experimental errors such as transverse jitter are quantitatively
shown to be tolerable. Examples of designs for sources capable of performing
nuclear resonance fluorescence and photofission are provided
Laser-heater assisted plasma channel formation in capillary discharge waveguides
A method of creating plasma channels with controllable depth and transverse
profile for the guiding of short, high power laser pulses for efficient
electron acceleration is proposed. The plasma channel produced by the
hydrogen-filled capillary discharge waveguide is modified by a ns-scale laser
pulse, which heats the electrons near the capillary axis. This interaction
creates a deeper plasma channel within the capillary discharge that evolves on
a ns-time scale, allowing laser beams with smaller spot sizes than would
otherwise be possible in the unmodified capillary discharge.Comment: 5 pages, 3 figure
Laminar flow of two miscible fluids in a simple network
When a fluid comprised of multiple phases or constituents flows through a
network, non-linear phenomena such as multiple stable equilibrium states and
spontaneous oscillations can occur. Such behavior has been observed or
predicted in a number of networks including the flow of blood through the
microcirculation, the flow of picoliter droplets through microfluidic devices,
the flow of magma through lava tubes, and two-phase flow in refrigeration
systems. While the existence of non-linear phenomena in a network with many
inter-connections containing fluids with complex rheology may seem
unsurprising, this paper demonstrates that even simple networks containing
Newtonian fluids in laminar flow can demonstrate multiple equilibria.
The paper describes a theoretical and experimental investigation of the
laminar flow of two miscible Newtonian fluids of different density and
viscosity through a simple network. The fluids stratify due to gravity and
remain as nearly distinct phases with some mixing occurring only by diffusion.
This fluid system has the advantage that it is easily controlled and modeled,
yet contains the key ingredients for network non-linearities. Experiments and
3D simulations are first used to explore how phases distribute at a single
T-junction. Once the phase separation at a single junction is known, a network
model is developed which predicts multiple equilibria in the simplest of
networks. The existence of multiple stable equilibria is confirmed
experimentally and a criteria for their existence is developed. The network
results are generic and could be applied to or found in different physical
systems
Computational accelerator science needs towards laser-plasma accelerators for future colliders
Laser plasma accelerators have the potential to reduce the size of future
linacs for high energy physics by more than an order of magnitude, due to their
high gradient. Research is in progress at current facilities, including the
BELLA PetaWatt laser at LBNL, towards high quality 10 GeV beams and staging of
multiple modules, as well as control of injection and beam quality. The path
towards high-energy physics applications will likely involve hundreds of such
stages, with beam transport, conditioning and focusing. Current research
focuses on addressing physics and R&D challenges required for a detailed
conceptual design of a future collider. Here, the tools used to model these
accelerators and their resource requirements are summarized, both for current
work and to support R&D addressing issues related to collider concepts
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Design of 10 GeV laser wakefield accelerator stages with shaped laser modes
We present particle-in-cell simulations, using the VORPAL framework, of 10 GeV laser plasma wakefield accelerator stages. Scaling of the physical parameters with the plasma density allows us to perform these simulations at reasonable cost and to design high performance stages. In particular we show that, by choosing to operate in the quasi-linear regime, we can use higher order laser modes to tailor the focusing forces. This makes it possible to increase the matched electron beam radius and hence the total charge in the bunch while preserving the low bunch emittance required for applications
Tradeoffs in jet inlet design: a historical perspective
The design of the inlet(s) is one of the most demanding tasks of the development process of any gas turbine-powered aircraft. This is mainly due to the multi-objective and multidisciplinary nature of the exercise. The solution is generally a compromise between a number of conflicting goals and these conflicts are the subject of the present paper. We look into how these design tradeoffs have been reflected in the actual inlet designs over the years and how the emphasis has shifted from one driver to another. We also review some of the relevant developments of the jet age in aerodynamics and design and manufacturing technology and we examine how they have influenced and informed inlet design decision
Spatial correlations in hexagons generated via a Kerr nonlinearity
We consider the hexagonal pattern forming in the cross-section of an optical
beam produced by a Kerr cavity, and we study the quantum correlations
characterizing this structure. By using arguments related to the symmetry
broken by the pattern formation, we identify a complete scenario of six-mode
entanglement. Five independent phase quadratures combinations, connecting the
hexagonal modes, are shown to exhibit sub-shot-noise fluctuations. By means of
a non-linear quantum calculation technique, quantum correlations among the mode
photon numbers are demonstrated and calculated.Comment: ReVTeX file, 20 pages, 7 eps figure
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