120002962
Numerical simulations of LWFA for the next generation of laser systems
The development of new laser systems based on OPCPA will push Laser Wakefield Accelerators (LWFA) to a qualitatively new energy range. As in the past, numerical simulations will play a critical role in testing, probing and optimizing the physical parameters and setup of these upscale experiments. Based on the prospective design parameters for the future Vulcan 10 PW OPCPA laser system, we have determined the optimal parameters for a single LWFA stage from theoretical scalings for such system, which predict accelerations to the energy frontier, with self‐injected electrons in excess of 10 GeV for a self‐guided configuration, and above 50 GeV bunches with externally‐injected electrons in a laser‐guided configuration. These parameters were then used as a baseline for 3D full scale simulations with OSIRIS and QuickPIC. A 12 GeV self‐injected beam was obtained with both codes, in agreement with theoretical predictions for the maximum energy gain and the injected charge. Preliminary results on the laser‐guided configuration already confirm the accelerating gradients and the stability of the laser guided propagation for long distances required to reach the higher energies predicted by the theoretical scalings for this scenario.
121799036
Modeling of laser wakefield acceleration in the Lorentz boosted frame using OSIRIS and UPIC framework
We examine numerical issues related to modeling laser wakefield acceleration (LWFA) in a Lorentz boosted frame. We present some theoretical results on a numerical instability that results from a relativistic plasma drift on a grid. We compare these predictions with results obtained from a finite difference time domain (FDTD) code OSIRIS and a spectral (FFT) time domain code UPIC. Consistent with the theoretical predictions, it is found that the spectral solver has advantages for mitigating the numerical instability when compared against some prevailing (FDTD) solvers. We also compared using finite difference or spectral field solvers in simplified 2D LWFA simulations using a plane wave for the laser. We find that the use of the spectral solver has advantages for mitigating the numerical instability induced by the relativistically drifting plasma.
12875278
Near-GeV-energy laser-wakefield acceleration of self-injected electrons in a centimeter-scale plasma channel.
The first three-dimensional, particle-in-cell (PIC) simulations of laser-wakefield acceleration of self-injected electrons in a 0.84 cm long plasma channel are reported. The frequency evolution of the initially 50 fs (FWHM) long laser pulse by photon interaction with the wake followed by plasma dispersion enhances the wake which eventually leads to self-injection of electrons from the channel wall. This first bunch of electrons remains spatially highly localized. Its phase space rotation due to slippage with respect to the wake leads to a monoenergetic bunch of electrons with a central energy of 0.26 GeV after 0.55 cm propagation. At later times, spatial bunching of the laser enhances the acceleration of a second bunch of electrons to energies up to 0.84 GeV before the laser pulse intensity is significantly reduced.
2877366
Very high Mach-number electrostatic shocks in collisionless plasmas.
The kinetic theory of collisionless electrostatic shocks resulting from the collision of plasma slabs with different temperatures and densities is presented. The theoretical results are confirmed by self-consistent particle-in-cell simulations, revealing the formation and stable propagation of electrostatic shocks with very high Mach numbers (M>>10), well above the predictions of the classical theories for electrostatic shocks.
118459210
A Bright Spatially-Coherent Compact X-ray Synchrotron Source
Author(s): Kneip, S; McGuffey, C; Martins, JL; Martins, SF; Bellei, C; Chvykov, V; Dollar, F; Fonseca, R; Huntington, C; Kalintchenko, G; Maksimchuk, A; Mangles, SPD; Matsuoka, T; Nagel, SR; Palmer, C; Schreiber, J; Phuoc, K Ta; Thomas, AGR; Yanovsky, V; Silva, LO; Krushelnick, K; Najmudin, Z | Abstract: Each successive generation of x-ray machines has opened up new frontiers in science, such as the first radiographs and the determination of the structure of DNA. State-of-the-art x-ray sources can now produce coherent high brightness keV x-rays and promise a new revolution in imaging complex systems on nanometre and femtosecond scales. Despite the demand, only a few dedicated synchrotron facilities exist worldwide, partially due the size and cost of conventional (accelerator) technology. Here we demonstrate the use of a recently developed compact laser-plasma accelerator to produce a well-collimated, spatially-coherent, intrinsically ultrafast source of hard x-rays. This method reduces the size of the synchrotron source from the tens of metres to centimetre scale, accelerating and wiggling a high electron charge simultaneously. This leads to a narrow-energy spread electron beam and x-ray source that is g1000 times brighter than previously reported plasma wiggler and thus has the potential to facilitate a myriad of uses across the whole spectrum of light-source applications.
1541538
Weibel-instability-mediated collisionless shocks in the laboratory with ultraintense lasers.
The formation of nonrelativistic collisionless shocks in the laboratory with ultrahigh intensity lasers is studied via ab initio multidimensional particle-in-cell simulations. The microphysics behind shock formation and dissipation and the detailed shock structure are analyzed, illustrating that the Weibel instability plays a crucial role in the generation of strong subequipartition magnetic fields that isotropize the incoming flow and lead to the formation of a collisionless shock, similar to what occurs in astrophysical scenarios. The possibility of generating such collisionless shocks in the laboratory opens the way to the direct study of the physics associated with astrophysical shocks.
31040253
Calculating the renormalisation group equations of a SUSY model with Susyno
Susyno is a Mathematica package dedicated to the computation of the 2-loop renormalisation group equations of a supersymmetric model based on any gauge group (the only exception being multiple U(1) groups) and for any field content. Supersymmetry (SUSY) is an elegant and well known extension of the Standard Model (SM) which aims at solving or softening some of the SM theoretical and experimental shortcomings. Supersymmetric models based on Grand Unified Theories (GUTs) offer the appealing feature of being described by a unique gauge group and coupling constant; furthermore, the potential new superfields, as well as their dynamics, can provide answers to fundamental problems. For example SO(10) based models offer a natural explanation for neutrino masses and mixings via a type-I seesaw. This occurs since the spinor representation of the group contains a SM singlet superfield (with the appropriate quantum numbers). Even larger and/or more complex groups are often considered, for example E6 in string inspired models. The analysis of the theoretical and phenomenological implications of SUSY GUT models requires a careful study of the evolution of the fundamental parameters from the high-energy scale down to the electroweak scale, at which observables are computed and constraints applied. As such, knowledge of the renormalisation group equations (RGEs) is necessary. Although the RGEs of several models (e.g., MSSM, NMSSM) are already known [1, 3], for other SUSY extensions of the SM complicated general equations must be used [1, 2]. Here we describe Susyno, a Mathematica-based package that addresses this issue. The program takes as input the gauge group, the representations (i.e., the chiral superfield content), the number of flavours/copies 1 of each representation, and any abelian discrete symmetries (e.g., R-parity). Susyno then constructs the most general superpotential and soft SUSY breaking Lagrangian consistent with the field content and symmetries imposed. Once these elements have been derived, Susyno then computes the 2-loop �-functions of all the parameters of the model, which is its main output.
199681250
Running soft parameters in SUSY models with multiple U(1) gauge factors
The two-loop renormalization group equations for the parameters of softly broken supersymmetric gauge theories given in the literature are generalized to the case when the gauge group contains more than a single abelian factor. This contribution to the proceedings of the DISCRETE 2012 symposium is based on reference [1].
119235558
Renormalization group equations and matching in a general quantum field theory with kinetic mixing
Abstract We work out a set of simple rules for adopting the two-loop renormalization group equations of a generic gauge field theory given in the seminal works of Machacek and Vaughn to the most general case with an arbitrary number of Abelian gauge factors and comment on the extra subtleties possibly encountered upon matching a set of effective gauge theories in such a framework.
118530599
Running soft parameters in SUSY models with multiple U(1) gauge factors
Abstract We generalize the two-loop renormalization group equations for the parameters of the softly broken SUSY gauge theories given in the literature to the most general case when the gauge group contains more than a single Abelian gauge factor. The complete method is illustrated at two-loop within a specific example and compared to some of the previously proposed partial treatments.
118698479
Supersymmetric SO(10)-inspired GUTs with sliding scales
This work has been supported in part by EU Network Grant No. UNILHC PITN-GA-2009-237920. M. H. also acknowledges support from the Spanish MICINN Grants No. FPA2011-22975, No. MULTIDARK CSD2009-00064 and by the Generalitat Valenciana Grant No. Prometeo/2009/091. The work of R. M. F has been supported by Fundacao para a Ciencia e a Tecnologia through the fellowship SFRH/BD/47795/2008. R. M. F. and J. C. R. also acknowledge the financial support from Grants No. CFTP-FCT UNIT 777, No. CERN/FP/123580/2011 and No. PTDC/FIS/102120/2008.