1,721,473 research outputs found
Two-color free-electron laser via two orthogonal undulators
No full textAn amplifier Free electron Laser (FEL) including two orthogonal polarized undulators with different periods and field intensities is able to emit two color radiations with different frequency and polarization while the total length of device does not change respect to usual single color FELs. The wavelengths of two different colors can be changed by choosing different periods, while variation in the magnetic strengths can be used to modify the gain lengths and saturation powers
Simulation and analysis of laser/electron beam interaction for use as a free electron laser
No full textThrough the use of simulation tools and theoretical analysis techniques, the Free Electron Laser process is investigated for a wiggler that is generated by an ultrafast laser system. The development and availability of such systems allows for novel FEL designs due to the high peak power of such lasers. Even though such high powers are possible, difficulties arise due to inhomogeneity in the laser pulse. This project looks at simulation results for a system with a realistic laser pulse profile and looks in to the pulse-shape effects on various system parameters. Models are presented for the expected behavior with important parameters noted, as well as highlighting possible difficulties that might occur experimentally. While head-on interaction has been proven experimentally for the short wavelength regime [1], we believe that using a co-propagating laser can provide benefits that have currently been untested. This experimental setup is outlined in Lawler, J et al [2], and we are currently simulating how the use of an ultrashort laser pulse as an electromagnetic wiggler will affect characteristics of the output radiation. Copyright © 2015 CC-BY-3.0 and by the respective authors
Transport matrix of a solenoid with linear fringe field
No full textThe problem of the transport matrix through a solenoid with a linear fringe field is solved exactly. The mathematical problem is simplified by the introduction of a new set of functions that generalize the ordinary hyperbolic functions. The results are used to characterize the physical properties of a solenoid exploited as magnetic lens. In particular it is shown that the role of a solenoid, with a linear fringe, in the transport of an electron beam is equivalent to the combined effect of a thin lens, a drift section and a beam expander. © Società Italiana di Fisica
The spherical Bessel and Struve functions and operational methods
No full textWe review some aspects of the theory of spherical Bessel functions and Struve functions by means of an operational procedure essentially of umbral nature, capable of providing the straightforward evaluation of their definite integrals and of successive derivatives. The method we propose allows indeed the formal reduction of these family of functions to elementary ones of Gaussian type. We study the problem in general terms and present a formalism capable of providing a unifying point of view including Anger and Weber functions too. The link to the multi-index Bessel functions is also briefly discussed. © 2014 Elsevier B.V. All rights reserved
Generating functions involving arbitrary products
No full textWe show that the use of operational methods and of multi-index Bessel functions allow the derivation of generating functions, involving the product of an arbitrary number of Laguerre polynomials
Repeated derivatives of composite functions and generalizations of the Leibniz rule
No full textWe use the properties of Hermite and Kampé de Fériet polynomials to get closed forms for the repeated derivatives of functions whose argument is a quadratic or higher-order polynomial. These results are extended to product of functions of the above argument, thus giving rise to expressions which can formally be interpreted as generalizations of the familiar Leibniz rule. Finally, examples of practical interest are discussed. © 2014 Elsevier Inc. All rights reserved
Resonant interaction between laser and electrons undergoing betatron oscillations in the bubble regime
No full textThe betatron radiation in the bubble regime is studied in the presence of resonant interaction between the accelerated electrons and the driver laser pulse tail. The calculations refer to experimental parameters available at the FLAME laser facility at the National Laboratories of Frascati (LNF), and represent the radiation spectra and spatial distributions to be expected in forthcoming experiments. © 2015 Cambridge University Press
Symbolic methods for the evaluation of sum rules of Bessel functions
No full textThe use of the umbral formalism allows a significant simplification of the derivation of sum rules involving products of special functions and polynomials. We rederive in this way known sum rules and addition theorems for Bessel functions. Furthermore, we obtain a set of new closed form sum rules involving various special polynomials and Bessel functions. The examples we consider are relevant for applications ranging from plasma physics to quantum optics. © 2013 AIP Publishing LLC
Photoluminescence decay of silicon nanocrystals and Lévy stable distributions
No full textWe incorporate the tools of Lévy processes and distributions to describe the photoluminescence of silicon nanocrystals. The method relies on two novel features: first we use exact forms of one-sided Lévy distributions to get an excellent reproduction of experimental data. Then we show that the dynamics leading to photoluminescence decay can be modelled in terms of fractional Fokker-Planck equation. © 2014 Elsevier B.V
Mittag-Leffler function and fractional differential equations
No full textWe adopt a procedure of operational-umbral type to solve the (1 + 1)-dimensional fractional Fokker-Planck equation in which time fractional derivative of order α (0 < α < 1) is in the Riemann-Liouville sense. The technique we propose merges well documented operational methods to solve ordinary FP equation and a redefinition of the time by means of an umbral operator. We show that the proposed method allows significant progress including the handling of operator ordering. © 2018 Diogenes Co., Sofia
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