5,009 research outputs found
Design considerations for the use of laser-plasma accelerators for advanced space radiation studies
We present design considerations for the use of laser-plasma accelerators for mimicking space radiation and testing space-grade electronics. This novel application takes advantage of the inherent ability of laser-plasma accelerators to produce particle beams with exponential energy distribution, which is a characteristic shared with the hazardous relativistic electron flux present in the radiation belts of planets such as Earth, Saturn and Jupiter. Fundamental issues regarding laser-plasma interaction parameters, beam propagation, flux development, and experimental setup are discussed
Energy Loss of a High Charge Bunched Electron Beam in Plasma
There has been much interest in the blowout regime of plasma wakefield
acceleration (PWFA), which features ultra-high fields and nonlinear plasma
motion. Using an exact analysis, we examine here a fundamental limit of
nonlinear PWFA excitation, by an infinitesimally short, relativistic electron
beam. The beam energy loss in this case is shown to be linear in charge even
for nonlinear plasma response, where a normalized, unitless charge exceeds
unity. The physical basis for this effect is discussed, as are deviations from
linear behavior observed in simulations with finite length beams.Comment: Submitted to Physical Review Letter
Horizontal cooling towers: riverine ecosystem services and the fate of thermoelectric heat in the contemporary Northeast US
The electricity sector is dependent on rivers to provide ecosystem services that help regulate excess heat, either through provision of water for evaporative cooling or by conveying, diluting and attenuating waste heat inputs. Reliance on these ecosystem services alters flow and temperature regimes, which impact fish habitat and other aquatic ecosystem services. We demonstrate the contemporary (2000–2010) dependence of the electricity sector on riverine ecosystem services and associated aquatic impacts in the Northeast US, a region with a high density of thermoelectric power plants. We quantify these dynamics using a spatially distributed hydrology and water temperature model (the framework for aquatic modeling in the Earth system), coupled with the thermoelectric power and thermal pollution model. We find that 28.4% of thermoelectric heat production is transferred to rivers, whereas 25.9% is directed to vertical cooling towers. Regionally, only 11.3% of heat transferred to rivers is dissipated to the atmosphere and the rest is delivered to coasts, in part due to the distribution of power plants within the river system. Impacts to the flow regime are minimal, while impacts to the thermal regime include increased river lengths of unsuitable habitats for fish with maximum thermal tolerances of 24.0, 29.0, and 34.0 ° C in segments downstream of plants by 0.6%, 9.8%, and 53.9%, respectively. Our analysis highlights the interactions among electricity production, cooling technologies, aquatic impacts, and ecosystem services, and can be used to assess the full costs and tradeoffs of electricity production at regional scales
Analytical treatment of the wakefields driven by transversely shaped beams in a planar slow-wave structure
The suppression of transverse wakefield effects using transversely elliptical
drive beams in a planar structure is studied with a simple analytical model
that unveils the geometric nature of this phenomenon. By analyzing the
suggested model we derive scaling laws for the amplitude of the longitudinal
and transverse wake potentials as a function of the Gaussian beam ellipticity -
. We explicitly show that in a wakefield accelerator application it
is beneficial to use highly elliptical beams for mitigating transverse forces
while maintaining the accelerating field. We consider two scaling strategies:
1) aperture scaling, where we keep a constant charge to have the same
accelerating gradient as in a cylindrical structure and 2) charge scaling,
where aperture is the same as in the cylindrical structure and charge is
increased to match the gradient.Comment: 10 pages, 6 figure
On the Theory of Relativistic Strong Plasma Waves
The influence of motion of ions and electron temperature on nonlinear
one-dimensional plasma waves with velocity close to the speed of light in
vacuum is investigated. It is shown that although the wavebreaking field weakly
depends on mass of ions, the nonlinear relativistic wavelength essentially
changes. The nonlinearity leads to the increase of the strong plasma
wavelength, while the motion of ions leads to the decrease of the wavelength.
Both hydrodynamic approach and kinetic one, based on Vlasov-Poisson equations,
are used to investigate the relativistic strong plasma waves in a warm plasma.
The existence of relativistic solitons in a thermal plasma is predicted.Comment: 13 pages, 8 figure
Progress on the hybrid gun project at UCLA
UCLA/INFN-LNF/Univ. Rome has been developing the hybrid gun which has an RF gun and a short linac for velocity bunching in one structure. After the cavity was manufactured at INFN-LNF in 2012, tests of the gun was carried out at UCLA. The field in the standing wave part was 20 % smaller than the simulation but the phase advance was fine. The cavity was commissioned successfully up to 13 MW. The beam test was performed at 11.5 MW and demonstrated the bunch compression
Tunable Electron Multibunch Production in Plasma Wakefield Accelerators
Synchronized, independently tunable and focused J-class laser pulses are
used to release multiple electron populations via photo-ionization inside an
electron-beam driven plasma wave. By varying the laser foci in the laboratory
frame and the position of the underdense photocathodes in the co-moving frame,
the delays between the produced bunches and their energies are adjusted. The
resulting multibunches have ultra-high quality and brightness, allowing for
hitherto impossible bunch configurations such as spatially overlapping bunch
populations with strictly separated energies, which opens up a new regime for
light sources such as free-electron-lasers
Topological String Defect Formation During the Chiral Phase Transition
We extend and generalize the seminal work of Brandenberger, Huang and Zhang
on the formation of strings during chiral phase transitions(berger) and discuss
the formation of abelian and non-abelian topological strings during such
transitions in the early Universe and in the high energy heavy-ion collisions.
Chiral symmetry as well as deconfinement are restored in the core of these
defects. Formation of a dense network of string defects is likely to play an
important role in the dynamics following the chiral phase transition. We
speculate that such a network can give rise to non-azimuthal distribution of
transverse energy in heavy-ion collisions.Comment: 10 pages, 4 figures, minor correction
Photoinjector-generation of a flat electron beam with transverse emittance ratio of 100
The generation of a flat electron beam directly from a photoinjector is an
attractive alternative to the electron damping ring as envisioned for linear
colliders. It also has potential applications to light sources such as the
generation of ultra-short x-ray pulses or Smith-Purcell free electron lasers.
In this Letter, we report on the experimental generation of a flat-beam with a
measured transverse emittance ratio of for a bunch charge of
nC; the smaller measured normalized root-mean-square emittance is
m and is limited by the resolution of our experimental setup.
The experimental data, obtained at the Fermilab/NICADD Photoinjector
Laboratory, are compared with numerical simulations and the expected scaling
laws.Comment: 5 pages, 3 figure
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