Laser-driven plasma waves in capillary tubes

The excitation of plasma waves over a length of up to 8 centimeters is, for the first time, demon- strated using laser guiding of intense laser pulses through hydrogen filled glass capillary tubes. The plasma waves are diagnosed by spectral analysis of the transmitted laser radiation. The dependence of the spectral redshift, measured as a function of filling pressure, capillary tube length and incident laser energy, is in excellent agreement with simulation results. The longitudinal accelerating field inferred from the simulations is in the range 1 -10 GV/m

Charge Fluctuation Forces Between Stiff Polyelectrolytes in Salt Solution: Pairwise Summability Re-examined

We formulate low-frequency charge-fluctuation forces between charged cylinders - parallel or skewed - in salt solution: forces from dipolar van der Waals fluctuations and those from the correlated monopolar fluctuations of mobile ions. At high salt concentrations forces are exponentially screened. In low-salt solutions dipolar energies go as $R^{-5}$ or $R^{-4}$; monopolar energies vary as $R^{-1}$ or $\ln{R}$, where $R$ is the minimal separation between cylinders. However, pairwise summability of rod-rod forces is easily violated in low-salt conditions. Perhaps the most important result is not the derivation of pair potentials but rather the demonstration that some of these expressions may not be used for the very problems that originally motivated their derivation.Comment: 8 pages and 1 fig in ps forma

Study of electron acceleration and X-ray radiation as a function of plasma density in capillary-guided laser wakefield accelerators

Laser wakefield electron acceleration in the blow-out regime and the associated betatron X-rayradiation were investigated experimentally as a function of the plasma density in a configuration where the laser is guided. Dielectric capillary tubes were employed to assist the laser keeping self-focused over a long distance by collecting the laser energy around its central focal spot. With a 40 fs, 16 TW pulsed laser, electron bunches with tens of pC charge were measured to be accelerated to an energy up to 300 MeV, accompanied by X-ray emission with a peak brightness of the order of 10 21 ph/s/mm 2 / mrad 2 /0.1%BW. Electron trapping and acceleration were studied using the emitted X-ray beamdistribution to map the acceleration process; the number of betatron oscillations performed by theelectrons was inferred from the correlation between measured X-ray fluence and beam charge. A studyof the stability of electron and X-ray generation suggests that the fluctuation of X-ray emission can be reduced by stabilizing the beam charge. The experimental results are in good agreement with 3D particle-in-cell (PIC) simulation.Fil: Ju, L.. Universite de Paris Xi; Francia;Fil: Svensson, K.. Lund University; SueciaFil: Ferrari, Hugo Emilio. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Döpp, A.. Universite de Paris Xi; Francia;Fil: Cassou, K.. Universite de Paris Xi; Francia;Fil: Genoud, G.. Lund University; Suecia;Fil: Wojda, F.. Lund University; Suecia;Fil: Burza, M.. Lund University; Suecia;Fil: Persson, A.. Lund University; Suecia;Fil: Lundh, O.. Lund University; Suecia;Fil: Wahlström, C. G.. Lund University; Suecia;Fil: Cros, B.. Universite de Paris Xi; Francia

On the non-abelian Brumer-Stark conjecture and the equivariant Iwasawa main conjecture

We show that for an odd prime p, the p-primary parts of refinements of the (imprimitive) non-abelian Brumer and Brumer-Stark conjectures are implied by the equivariant Iwasawa main conjecture (EIMC) for totally real fields. Crucially, this result does not depend on the vanishing of the relevant Iwasawa mu-invariant. In combination with the authors' previous work on the EIMC, this leads to unconditional proofs of the non-abelian Brumer and Brumer-Stark conjectures in many new cases.Comment: 33 pages; to appear in Mathematische Zeitschrift; v3 many minor updates including new title; v2 some cohomological arguments simplified; v1 is a revised version of the second half of arXiv:1408.4934v

Numerical evidence toward a 2-adic equivariant ''Main Conjecture''

International audienceWe test a conjectural non abelian refinement of the classical 2-adic Main Conjecture of Iwasawa theory. In the first part, we show how, in the special case that we study, the validity of this refinement is equivalent to a congruence condition on the coefficients of some power series. Then, in the second part, we explain how to compute the first coefficients of this power series and thus numerically check the conjecture in that setting

Laser frequency stabilization using folded cavity and mirror reflectivity tuning

International audienceA new method of laser frequency stabilization using polarization property of an optical cavity is proposed. In a standard Fabry–Perot cavity, the coating layers thickness of cavity mirrors is calculated to obtain the same phase shift for sand p-wave but a slight detuning from the nominal thickness can produce sand p-wave phase detuning. As a result, each wave accumulates a different round-trip phase shift and resonates at a different frequency. Using this polarization property, an error signal is generated by a simple setup consisting of a quarter wave-plate rotated at 45°, a polarizing beam splitter and two photodiodes. This method exhibits similar error signal as the Pound–Drever–Hall technique but without need for any frequency modulation. Lock theory and experimental results are presented in this paper.

Population inversion of a NAHS mixture adsorbed into a cylindrical pore

A cylindrical nanopore immersed in a non-additive hard sphere binary fluid is studied by means of integral equation theories and Monte Carlo simulations. It is found that at low and intermediate values of the bulk total number density the more concentrated bulk species is preferentially absorbed by the pore, as expected. However, further increments of the bulk number density lead to an abrupt population inversion in the confined fluid and an entropy driven prewetting transition at the outside wall of the pore. These phenomena are a function of the pore size, the non-additivity parameter, the bulk number density, and particles relative number fraction. We discuss our results in relation to the phase separation in the bulk.Comment: 7 pages, 8 Figure