Free-electron-laser oscillator with a linear taper

Christodoulou, A.; Lampiris, D.; Polykandriotis, K.; Colson, W.B.; Crooker, P. P.; Benson, S.V.; Gubeli, J.; Neil, George

doi:10.1103/physreve.66.056502

Cited by 7 publications

(8 citation statements)

References 11 publications

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“…Motivated by their observation, we present the exact analytic solution for optimal FM, recovering the low-field linewidth even in the high-field regime. The narrowing of the scattered pulse is Fourier-limited only by the duration of the incident pulse.The essence of laser pulse chirping is analogous to free electron laser (FEL) undulator tapering [12][13][14][15][16]. In tapering, as deceleration occurs due to the FEL emis-sion, the field strength is adjusted to preserve the same FEL emission frequency.…”

mentioning

confidence: 99%

Narrow-Band Emission in Thomson Sources Operating in the High-Field Regime

Terzić¹,

Deitrick

Hofler

et al. 2014

Phys. Rev. Lett.

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We present a novel and quite general analysis of the interaction of a high-field chirped laser pulse and a relativistic electron, in which exquisite control of the spectral brilliance of the upshifted Thomson-scattered photon is shown to be possible. Normally, when Thomson scattering occurs at high field strengths, there is ponderomotive line broadening in the scattered radiation. This effect makes the bandwidth too large for some applications and reduces the spectral brilliance. We show that such broadening can be corrected and eliminated by suitable frequency modulation of the incident laser pulse. Further, we suggest a practical realization of this compensation idea in terms of a chirped-beam driven free electron laser oscillator configuration and show that significant compensation can occur, even with the imperfect matching to be expected in these conditions. PACS numbers: 29.20.Ej, 29.25.Bx, 29.27.Bd, 07.85.Fv Sources of electromagnetic radiation relying upon Thomson scattering are increasingly being applied in fundamental physics research [1], and compact acceleratorbased sources specifically designed for potential user facilities have been built [2]. One remarkable feature of the radiation emerging from such sources, compared to bremsstrahlung sources, is the narrowband nature of the radiation produced. For example, applications to Xray structure determination [3], dark-field imaging [4,5], phase contrast imaging [6], and computed tomography [7] have been demonstrated experimentally and take full advantage of the narrow bandwidth of the Thomson source.Given that narrow bandwidth is desired, it is important to know and understand the sources of bandwidth of the scattered radiation and the limitations imposed on the performance of Thomson sources. For applications where the normalized vector potential of the incident laser pulse is much less than one (the low-field regime), the line width of the radiation from a scattering event reproduces the line width of the incident laser pulse. Unfortunately, when the normalized vector potential increases, as is desired for stronger sources, a detuning red-shift arises during the scattering events that tends to spread out the spectrum [8][9][10]. Physically, the scattering electron slows down, by a varying amount, as the incident pulse is traversed.In a recent paper, Ghebregziabher, Shadwick, and Umstadter (GSU) observed that frequency modulation (FM), or "chirping", of the scattering laser pulse can compensate for such ponderomotive line broadening, and suggested a form for this modulation [11]. Motivated by their observation, we present the exact analytic solution for optimal FM, recovering the low-field linewidth even in the high-field regime. The narrowing of the scattered pulse is Fourier-limited only by the duration of the incident pulse.The essence of laser pulse chirping is analogous to free electron laser (FEL) undulator tapering [12][13][14][15][16]. In tapering, as deceleration occurs due to the FEL emission, the field strength is adjusted to preserve the...

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mentioning

confidence: 99%

Narrow-Band Emission in Thomson Sources Operating in the High-Field Regime

Terzić¹,

Deitrick

Hofler

et al. 2014

Phys. Rev. Lett.

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“…An analytic theory for this regime predicts a scaling of the optical pulse energy E L with the bunch charge q as E L ∝ q 3/2 and a scaling of the temporal width τ L of the optical pulse as τ L ∝ q −1/2 [138], which has been experimentally confirmed [139], although higher extraction efficiencies have also been observed for a perfectly synchronized cavity length, where the analytic theory breaks down [92,132]. Furthermore, short pulse FEL oscillators operating in the large-slippage regime also show a stable oscillation in the macropulse power, known as limit-cycle oscillations, for certain cavity lengths detuned from perfect synchronization, which has been observed both experimentally [102,137,[143][144][145][146] and in numerical simulations [136,138,[147][148][149].…”

Section: Introductionmentioning

confidence: 60%

“…Superconducting energy recovery linacs are the primary drivers for high average power FEL oscillators [64][65][66][67][68][69][70]; however, other types of FEL oscillators have used various techniques to increase the output pulse energy including, but not limited to, optical klystrons [34,36,48,57,58,60,63,[71][72][73][74][75][76], cavity dumping [77][78][79][80][81], pulse stacking in an external cavity [82][83][84], electron beam energy ramping [85,86] or dynamic cavity desynchronization [87][88][89][90][91][92]. Tapering of the undulator [93][94][95] has also been used to improve the peak power in the pulse [96][97][98][99][100], however, tapering of the undulator in FEL oscillators leads to complicated dynamics and a strong dependence on system parameters [101]…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional, Time-Dependent Analysis of High- and Low-Q Free-Electron Laser Oscillators

Slot

Freund

2021

Applied Sciences

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Free-electron lasers (FELs) have been designed to operate over virtually the entire electromagnetic spectrum, from microwaves through to X-rays, and in a variety of configurations, including amplifiers and oscillators. Oscillators can operate in both the low and high gain regime and are typically used to improve the spatial and temporal coherence of the light generated. We will discuss various FEL oscillators, ranging from systems with high-quality resonators combined with low-gain undulators, to systems with a low-quality resonator combined with a high-gain undulator line. The FEL gain code MINERVA and wavefront propagation code OPC are used to model the FEL interaction within the undulator and the propagation in the remainder of the oscillator, respectively. We will not only include experimental data for the various systems for comparison when available, but also present, for selected cases, how the two codes can be used to study the effect of mirror aberrations and thermal mirror deformation on FEL performance.

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“…This concluding section is not dedicated to the efficiency problem but to the phenomenology emerging from the inclusion of pulse propagation effects in a tapered FEL oscillator [9]. It is particularly interesting because, as we will see in the following, new interesting dynamical features emerge which make the uniform tapering an additional tool to control the laser beam quality.…”

Section: Pulse Propagation Effectsmentioning

confidence: 99%

Free electron laser oscillators with tapered undulators: Inclusion of harmonic generation and pulse propagation

Dattoli

Pagnutti²,

Ottaviani³

et al. 2012

Phys. Rev. ST Accel. Beams

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We review the theory of free-electron laser (FEL) oscillators operating with tapered undulators. We have considered the case of a uniform tapering and introduced a parameter which characterizes the effect of the tapering on the gain and the saturation intensity. We have analyzed the effect of the tapering on the FEL dynamics by including the pulse propagation effects. We further analyze the importance of tapering as a tool to model the optical pulse shapes and to control the higher harmonic intensities.

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Free-electron-laser oscillator with a linear taper

Cited by 7 publications

References 11 publications

Narrow-Band Emission in Thomson Sources Operating in the High-Field Regime

Narrow-Band Emission in Thomson Sources Operating in the High-Field Regime

Three-Dimensional, Time-Dependent Analysis of High- and Low-Q Free-Electron Laser Oscillators

Free electron laser oscillators with tapered undulators: Inclusion of harmonic generation and pulse propagation

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