38194784
Performance of capillary discharge guided laser plasma wakefield accelerator
A GeV-class laser-driven plasma-based wakefield accelerator has been realized at the Lawrence Berkeley National Laboratory (LBNL). The device consists of the 40 TW high repetition rate Ti:sapphire LOASIS laser system at LBNL and a gas-filled capillary discharge waveguide developed at Oxford University. The operation of the capillary discharge guided laser plasma wakefield accelerator with a capillary of 225 mum diameter and 33 mm in length was analyzed in detail. The input intensity dependence suggests that excessive self-injection causes increased beam loading leading to broadband lower energy electron beam generation. The trigger versus laser arrival timing dependence suggests that the plasma channel parameters can be tuned to reduce beam divergence.
9545680
Long-range persistence of femtosecond modulations on laser-plasma-accelerated electron beams.
Laser plasma accelerators have produced femtosecond electron bunches with a relative energy spread ranging from 100% to a few percent. Simulations indicate that the measured energy spread can be dominated by a correlated spread, with the slice spread significantly lower. Measurements of coherent optical transition radiation are presented for broad-energy-spread beams with laser-induced density and momentum modulations. The long-range (meter-scale) observation of coherent optical transition radiation indicates that the slice energy spread is below the percent level to preserve the modulations.
55045125
Design considerations for a laser‐plasma linear collider
Design considerations for a next‐generation electron‐positron linear collider based on laser‐plasma‐accelerators are discussed. Several of the advantages and challenges of laser‐plasma‐based accelerator technology are addressed. An example of the parameters for a 1 TeV laser‐plasma‐based collider is presented.
21248438
Mono-Energetic Beams from Laser Plasma Interactions
A laser driven wakefield accelerator has been tuned to produce high energy electron bunches with low emittance and energy spread by extending the interaction length using a plasma channel. Wakefield accelerators support gradients thousands of times those achievable in RF accelerators, but short acceleration distance, limited by diffraction, has resulted in low energy beams with 100% electron energy spread. In the present experiments on the L’OASIS laser, the relativistically intense drive pulse was guided over 10 diffraction ranges by a plasma channel. At a drive pulse power of 9 TW, electrons were trapped from the plasma and beams of percent energy spread containing > 200 pC charge above 80 MeV and with normalized emittance estimated at < 2 π-mm-mrad were produced. Data and simulations (VORPAL code) show the high quality bunch was formed when beam loading turned off injection after initial trapping, and when the particles were extracted as they dephased from the wake. Up to 4 TW was guided without trapping, potentially providing a platform for controlled injection. The plasma channel technique forms the basis of a new class of accelerators, with high gradients and high beam quality.
118397655
High Quality Electron Bunches up to 1 GeV from Laser Wakefield Acceleration at LBNL
Experiments at the LOASIS laboratory of LBNL have demonstrated production of 100 MeV to 1 GeV electron bunches with low energy spread and low divergence from laser wakefield acceleration. The radiation pressure of a 10 TW laser pulse, guided over 10 diffraction ranges by a few‐mm long plasma density channel, was used to drive an intense plasma wave (wakefield), producing electron bunches with energies on the order of 100 MeV and acceleration gradients on the order of 100 GV/m. Beam energy was increased from 100 MeV to 1 GeV by using a few‐cm long guiding channel at lower density, driven by a 40 TW laser, demonstrating the anticipated scaling to higher beam energies. Particle simulations indicate that the low energy spread beams were produced from self‐trapped electrons through the interplay of trapping, loading, and dephasing. Other experiments and simulations are also underway to control injection of particles into the wake, and hence improve beam quality and stability further.
56420210
Generation of single pulse particle beams in a plasma channel by laser injection in laser wakefield accelerators
A laser injection mechanism that generates a single pulse, high quality beam is described. In the past, different all-optical injection schemes for the generation of ultrashort electron bunches were proposed. A very promising scheme proposed by E. Esarey [E. Esarey, R.F. Hubbard, W.P. Leemans A. Ting and P. Sprangle," Phys. Rev. Lett 79, 2682 (1997)] uses the collision of two counterpropagation laser pulses to inject particles. However, the results of ours 2D particle-in-cell (PIC) simulations have shown that in addition to the bunch created by pulse collision, a train of pulses is also generated by a different mechanism. In this paper we show that is possible to achieve a single pulse, high quality beam if the generation of the plasma wakefield takes place in a channel and particles are injected by a phase-kick mechanism [J. Cary at this conference]. We have performed 2D PIC simulations of our proposed injection scheme using the code VORPAL [C. Nieter at this conference]. We have obtained a high quality 11 MeV., 6 fs. single electron bunch with energy spread of 4% and emittance of 0.01/spl pi/ - mm - mrad.
7737409
Two-color gauge theory with novel infrared behavior.
Using lattice simulations, we study the infrared behavior of a particularly interesting SU(2) gauge theory, with six massless Dirac fermions in the fundamental representation. We compute the running gauge coupling derived nonperturbatively from the Schrödinger functional of the theory, finding no evidence for an infrared fixed point up through gauge couplings g(2) of order 20. This implies that the theory either is governed in the infrared by a fixed point of considerable strength, unseen so far in nonsupersymmetric gauge theories, or breaks its global chiral symmetries producing a large number of composite Nambu-Goldstone bosons relative to the number of underlying degrees of freedom. Thus either of these phases exhibits novel behavior.
121056309
Lattice QCD thermodynamics in the presence of the charm quark
Abstract We present an update on the 2 + 1 flavor QCD equation of state of the Wuppertal–Budapest Collaboration, extending our previous studies to finer lattice spacings and providing a continuum extrapolation of the trace anomaly. A Symanzik improved gauge and a stout-link improved staggered fermion action is utilized. We also present preliminary results for the fully dynamical charmed equation of state.
54915805
The QCD equation of state and the effects of the charm
Szabolcs Borsanyia, Gergely Endrodib, Zoltan Fodora,c,d , Sandor D. Katza,d , Stefan Krieg∗a,c, Claudia Rattie, Chris Schroedera, f , Kalman K. Szaboa aBergische Universitat Wuppertal, D-42119 Wuppertal, Germany bUniversitat Regensburg, D-93040 Regensburg, Germany cIAS, Julich Supercomputing Centre, Forschungszentrum Julich, D-52425 Julich, Germany dInstitute for Theoretical Physics, Eotvos University, H-1117 Budapest, Hungary eUniversita degli Studi di Torino and INFN, Sezione di Torino, I-10125 Torino, Italy f Lawrence Livermore National Laboratory, Livermore, California 94550, USA E-mail: s.krieg@fz-juelich.de
116984453
Equation of state in ( 2+1 )-flavor QCD
We present results for the equation of state in (2 + 1)-flavor QCD using the highly improved staggered quark action and lattices with temporal extent N tau = 6, 8, 10, and 12. We show that these data can be reliably extrapolated to the continuum limit and obtain a number of thermodynamic quantities and the speed of sound in the temperature range 130-400 MeV. We compare our results with previous calculations and provide an analytic parameterization of the pressure, from which other thermodynamic quantities can be calculated, for use in phenomenology. We show that the energy density in the crossover region, 145 MeV <= T <= 163 MeV, defined by the chiral transition, is epsilon(c) = (0.18-0.5) GeV/fm(3), i.e., (1.2-3.1) epsilon(nuclear). At high temperatures, we compare our results with resummed and dimensionally reduced perturbation theory calculations. As a byproduct of our analyses, we obtain the values of the scale parameters r(0) from the static quark potential and w(0) from the gradient flow.
119017493
Composite bosonic baryon dark matter on the lattice: SU(4) baryon spectrum and the effective Higgs interaction
We present the spectrum of baryons in a new SU(4) gauge theory with fundamental fermion constituents. The spectrum of these bosonic baryons is of significant interest for composite dark matter theories. Here, we compare the spectrum and properties of SU(3) and SU(4) baryons, and then compute the dark-matter direct detection cross section via Higgs boson exchange for TeV-scale composite dark matter arising from a confining SU(4) gauge sector. Comparison with the latest LUX results leads to tight bounds on the fraction of the constituent-fermion mass that may arise from electroweak symmetry breaking. Lattice calculations of the dark matter mass spectrum and the Higgs-dark matter coupling are performed on quenched $16^{3} \times 32$, $32^{3} \times 64$, $48^{3} \times 96$, and $64^{3} \times128$ lattices with three different lattice spacings, using Wilson fermions with moderate to heavy pseudoscalar meson masses. Our results lay a foundation for future analytic and numerical study of composite baryonic dark matter.