Observation of coherent Smith-Purcell radiation using an initially continuous flat beam

Gardelle, J.; Courtois, L.; Modin, P.; Donohue, J.T.

doi:10.1103/physrevstab.12.110701

Cited by 31 publications

(22 citation statements)

References 23 publications

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“…The Vanderbilt-Vermont Photonics collaboration [10] observed the evanescent wave, but they used a grating equipped with sidewalls at the groove ends, which is not strictly 2D. At CEA-CESTA a demonstration experiment in the microwave domain without sidewalls has found results in agreement with the scenario of AB [11]. In the latter the width of both the grating and the beam, w, was 10 cm.…”

Section: Introductionsupporting

confidence: 70%

“…In support of our theory we show the results of 3D MAGIC simulations as well as measurements of the transmission coefficient of the grating used in the experiment described in Ref. [11]. Extremely good agreement is found among theory, simulation, and measurements carried out at loops and nodes of the transverse waves.…”

Section: Introductionsupporting

confidence: 64%

“…10 we show the results of 3D simulations performed for our grating without sidewalls, as was the case in the experiment reported in Ref. [11]. Here the current driver placed at x ¼ 0 was used at several discrete frequencies, and the ''range'' command of MAGIC was used to obtain the z dependence of B x along the line x ¼ 0, y ¼ 2 mm.…”

Section: B Results With Monochromatic Current Drivermentioning

confidence: 99%

“…However, in the experiment of Ref. [11], the grating had no sidewalls, and it is of interest to ask how the fields vary in the transverse direction. We have performed simulations with no sidewalls, and a selection of our results is shown in Fig.…”

Section: A Response Of Grating To a Ping In Simulationsmentioning

confidence: 99%

“…In addition, since the grating used in Ref. [11] is well suited to the microwave frequency range, measurements of the transmission coefficient between any two points just above the top of the grating may be performed using a standard network analyzer. Typically the network analyzer measures the transmission coefficient as a function of frequency, for frequencies up to 10 GHz.…”

Section: Computations Of Fieldsmentioning

confidence: 99%

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Dispersion relation for a three-dimensional lamellar grating

Donohue

Gardelle

2011

Phys. Rev. ST Accel. Beams

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A few years ago, Andrews and Brau (AB) presented the dispersion relation for a lamellar grating in two dimensions (2D) as a step in understanding coherent Smith-Purcell radiation. This involved solving Maxwell's equations both in the grooves and in the region above the grooves, where Floquet theory was used. The coupling with an electron beam was studied, and an expression for the gain as a function of current was derived. Their approach has been supported by 2D simulations using particle-in-cell (PIC) codes, and more recently by a demonstration experiment that used a wide grating. We present here the dispersion relation (in the absence of beam) of a grating in three dimensions, which turns out to be a relatively straightforward extension of the AB results. The predictions of this theory are compared with PIC simulations, and also with measurements of the transmission coefficient as a function of frequency. Extremely good agreement is observed.

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Section: Introductionsupporting

confidence: 70%

Section: Introductionsupporting

confidence: 64%

Section: B Results With Monochromatic Current Drivermentioning

confidence: 99%

Section: A Response Of Grating To a Ping In Simulationsmentioning

confidence: 99%

Section: Computations Of Fieldsmentioning

confidence: 99%

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Dispersion relation for a three-dimensional lamellar grating

Donohue

Gardelle

2011

Phys. Rev. ST Accel. Beams

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Super-radiant Smith–Purcell radiation from periodic line charges

Hangyo

Tsunawaki

et al. 2012

Nuclear Instruments and Methods in Physics Research Section A:

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Numerical modeling of a table-top tunable Smith–Purcell terahertz free-electron laser operating in the super-radiant regime

Prokop

Piot

Lin

et al. 2010

Applied Physics Letters

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Terahertz (THz) radiation occupies a very large portion of the electromagnetic spectrum and has generated much recent interest due to its ability to penetrate deep into many organic materials without the damage associated with ionizing radiation such as x-rays. One path for generating copious amount of tunable narrow-band THz radiation is based on the Smith-Purcell free-electron laser (SPFEL) effect. In this Letter we propose a simple concept for a compact two-stage tunable SPFEL operating in the superradiant regime capable of radiating at the grating's fundamental bunching frequency. We demonstrate its capabilities and performances via computer simulation using the conformal finite-difference time-domain electromagnetic solver vorpal. [5,6]. THz sources based on SPFELs are foreseen to have table-top footprint and can operate in a continuous wave mode, enabling the production of moderate average output power (on the order of Watts).In an SPFEL, a low energy (∼ 50 keV) sheet DC electron beam is propagated close to a metallic grating with velocity v ≡ cβŷ . The beam excites evanescent surface waves with axial field of the form E y,e (x, y) = E 0,e exp(αx) where α ≡ 2π/(βγλ e ) and γ ≡ (1 − β 2 ) −1/2 is the Lorentz factor. The evanescent wave can, under certain circumstances, have a negative group velocity [2]. In such a case the wave counter-streams the electron beam direction and can couple to the beam, thereby giving rise to an energy modulation. Due to the non-relativistic nature of the beam (γ ≃ 1), the impressed energy modulation eventually transforms into a density modulation at wavelength λ e . The produced microbunches will result in strongly enhanced radiation at harmonic frequencies of the microbunching frequency f e ≡ c/λ e . In an SPFEL the radiative mechanism is the Smith-Purcell (SP) effect [7]. If instead of a DC electron beam, a beam consisting of a train of microbunches is used the SP radiation is emitted in the super-radiant regime [8][9][10] in which the radiation rate goes as th number of electrons in each microbunch squared. Prebunching the electron beam in a way that satisfies emission of super-radiant radiation is however challenging and a possible solution discussed in, e.g., Ref.[11] significantly decreases the average power capability of the SPFEL.In this Letter we consider and present detailed numerical simulations of a "two-stage" SPFEL; see Fig. 1. In such a configuration a first stage, referred to as a "buncher", is optimized to enhance the beam-evanescent wave interaction, thereby resulting in faster bunching than in the configuration analyzed in previous papers [2,3,12]. A second stage, referred to as a "radiator", consists of a grating with parameters tuned to produce coherent SP radiation at frequencies nf e (n is an integer). The numerical simulations were performed using vorpal, a conformal finite-difference time-domain (CFDTD) particle-in-cell electromagnetic solver [13]. vorpal is a parallel, object-oriented framework for three dimensional relativistic electrostatic and elec...

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Observation of coherent Smith-Purcell radiation using an initially continuous flat beam

Cited by 31 publications

References 23 publications

Dispersion relation for a three-dimensional lamellar grating

Dispersion relation for a three-dimensional lamellar grating

Super-radiant Smith–Purcell radiation from periodic line charges

Numerical modeling of a table-top tunable Smith–Purcell terahertz free-electron laser operating in the super-radiant regime

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