Analysis of Čerenkov free-electron lasers

Kalkal, Yashvir; Kumar, Vinay

doi:10.1103/physrevstab.18.030707

Cited by 14 publications

(45 citation statements)

References 44 publications

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“…We observe that the above expression is similar to the expression for the gain derived for the case of CFEL without any side wall in Ref. [2], with some notable differences. First, the parameter w appearing in the denominator of the above equation appears as ∆y e = πβ p λL/4 in the corresponding equation for the case of CFEL without any side wall.…”

Section: B Coupled Maxwell-lorentz Equations and Gain Calculationsupporting

confidence: 81%

“…given in Ref. [2] for the case of CFEL without any side wall, we observe that the value of U/E 2 z is reduced nearly by a factor of 2 due to the presence of side walls. Thus the effective mode width for the case of CFEL with side walls can be taken as w/2.…”

Section: B Coupled Maxwell-lorentz Equations and Gain Calculationsupporting

confidence: 57%

“…The phase velocity of the surface mode is here taken as equal to the electron velocity v. As it is seen in the above equation, the guided surface mode is a combination of two plane evanescent waves travelling in different directions in the (y, z) plane, each having frequency ω and wave vector k 0 = k 2 y + k 2 z . Each of these two plane evanescent waves is a solution of the wave equation for the case of CFEL without side walls, and should therefore satisfy the corresponding dispersion relation k 0 = tan −1 (1/a)/b for that case [2,15,19].…”

Section: A Formula For the Resonant Wavelengthmentioning

confidence: 99%

“…where, v g is group velocity of the surface mode, which is equal to P/wU for the CFEL [2], P is total power contained in the surface mode, and U is electromagnetic energy stored in the fields per unit mode width w, and per unit length in the z-direction. The current density of the flat beam propagating at a height h from the dielectric surface is given by 8), and performing the integral, we obtain the following time dependent differential equation for E z :…”

Section: B Coupled Maxwell-lorentz Equations and Gain Calculationmentioning

confidence: 99%

“…Electrons will see the maximum field at y = 0 while propagating along the z-direction. For the parameters of CFEL discussed earlier, the ac space charge field does not have any significant effect on the dynamics of the electron beam [2], and we have therefore neglected it in our calculations. Equations (10)(11)(12) can be expressed in a more elegant form by defining the following dimensionless variables [2,32]:…”

Section: B Coupled Maxwell-lorentz Equations and Gain Calculationmentioning

confidence: 99%

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Čerenkov free-electron laser with side walls

Kalkal¹,

Kumar²

2016

Nuclear Instruments and Methods in Physics Research Section A:

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In this paper, we have proposed aČerenkov free-electron laser (CFEL) with metallic side walls, which are used to confine an electromagnetic surface mode supported by a thin dielectric slab placed on top of a conducting surface. This leads to an enhancement in coupling between the optical mode and the co-propagating electron beam, and consequently, performance of the CFEL is improved.We set up coupled Maxwell-Lorentz equations for the system, in analogy with an undulator based conventional FEL, and obtain formulas for the small-signal gain and growth rate. It is shown that small signal gain and growth rate in this configuration are larger compared to the configuration without the side walls. In the nonlinear regime, we solve the coupled Maxwell-Lorentz equations numerically and study the saturation behaviour of the system. It is found that theČerenkov FEL with side walls saturates quickly, and produces powerful coherent terahertz radiation.

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Section: B Coupled Maxwell-lorentz Equations and Gain Calculationsupporting

confidence: 81%

Section: B Coupled Maxwell-lorentz Equations and Gain Calculationsupporting

confidence: 57%

Section: A Formula For the Resonant Wavelengthmentioning

confidence: 99%

Section: B Coupled Maxwell-lorentz Equations and Gain Calculationmentioning

confidence: 99%

Section: B Coupled Maxwell-lorentz Equations and Gain Calculationmentioning

confidence: 99%

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Čerenkov free-electron laser with side walls

Kalkal¹,

Kumar²

2016

Nuclear Instruments and Methods in Physics Research Section A:

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High‐Q Metallic Fano Metamaterial for Highly Efficient Cerenkov Lasing

Kim

Baek

Bhattacharya

et al. 2018

Advanced Optical Materials

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development of such CR-based applications is limited by thermal and dielectric breakdown issues. [3,4] Another limitation is that, due to the velocity threshold, large facilities are required to generate highly energetic particles. These limitations restrict the upper and lower size and performance boundaries in vital applications. Nowadays, metallic metamaterial devices have been proposed, which overcome the limitations of conventional Cerenkov devices to realize reversed CR from the negative-refractive index, [5] the ultralow threshold of kinetic energy in hyperbolic metamaterials, [6] and various metallic metamaterials comprised of subwavelength slits. [7][8][9] However, the realization of a high quality factor (Q) is still an outstanding roadblock for practical Cerenkov devices. Previous works on Cerenkov lasing (CL) using mirrors were limited by a lower electron beam impedance due to the interaction device and the radio-frequency (RF) coupling mechanism. [4,10] Here, to achieve a high Q for highly efficient CL, we focus on maximally trapping the electromagnetic Cerenkov radiation wave to extend its interaction with the electron beam and on controlling the radiation damping, as has been described in Rayleigh scattering to maximize the efficiency of CL. In this paper, we demonstrate that the interplay between an extremely low group velocity from the infinite transverse permittivity of the anisotropic metamaterials and the subradiant A high-quality-factor (high-Q) metallic Fano metamaterial is demonstrated both experimentally and theoretically. This material is suitable for highly efficient Cerenkov lasing in which subwavelength metallic slits are arranged to form asymmetric unit cells. In contrast to conventional dielectric Cerenkov or Smith-Purcell devices, in the proposed device, convection electrons traverse the high-Q metallic metamaterial. The interplay between an extremely low group velocity from the infinite transverse permittivity of the anisotropic metamaterial and the subradiant damping from a Fano-type slit mode is shown to be responsible for the high-Q value, which is measured to be unprecedented at 700. The resulting improvement in the Cerenkov lasing efficiency is estimated to be more than two orders of magnitude using a particle-in-cell simulation.

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Terahertz radiation source using a high-power industrial electron linear accelerator

Kalkal

Kumar

2017

Pramana - J Phys

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High power (∼ 100 kW) industrial electron linear accelerators (linacs) are used for irradiation applications e.g., for pasteurization of food products, disinfection of medical waste, etc. We propose that high power electron beam from such an industrial linac can be first passed through an undulator to generate powerful terahertz (THz) radiation, and the spent electron beam coming out of the undulator can still be used for industrial applications. This will enhance the utilisation of a high power industrial linac. We have performed calculation of spontaneous emission in the undulator to show that for typical parameters, continuous terahertz radiation having power of the order of µW can be produced, which may be useful for many scientific applications.

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Analysis of Čerenkov free-electron lasers

Cited by 14 publications

References 44 publications

Čerenkov free-electron laser with side walls

Čerenkov free-electron laser with side walls

High‐Q Metallic Fano Metamaterial for Highly Efficient Cerenkov Lasing

Terahertz radiation source using a high-power industrial electron linear accelerator

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