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2 pages, 164 KiB

Open AccessEditorial

Preface to “Oscillator-Amplifier Free Electron Lasers an Outlook to Their Feasibility and Performances”

by Giuseppe Dattoli, Alessandro Curcio and Danilo Giulietti

Appl. Sci. 2022, 12(19), 9444; https://doi.org/10.3390/app12199444 - 21 Sep 2022

Viewed by 722

Abstract

Free Electron Lasers (FELs) are certainly among the most interesting devices, belonging to the realm of coherent radiation sources [...] Full article

(This article belongs to the Special Issue Oscillator-Amplifier Free Electron Lasers an Outlook to Their Feasibility and Performances)

Research

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17 pages, 1304 KiB

Open AccessArticle

Radio-Frequency Undulators, Cyclotron Auto Resonance Maser and Free Electron Lasers

by Emanuele Di Palma, Silvio Ceccuzzi, Gian Luca Ravera, Elio Sabia, Ivan Spassovsky and Giuseppe Dattoli

Appl. Sci. 2021, 11(20), 9499; https://doi.org/10.3390/app11209499 - 13 Oct 2021

Cited by 3 | Viewed by 2033

Abstract

We discuss a hybrid Free Electron Laser (FEL) architecture operating with a RF undulator provided by a powerful Cyclotron Auto-Resonance Maser (CARM). We outline the design elements to operate a compact X-ray device. We review the essential aspects of wave undulator FEL theory [...] Read more.

We discuss a hybrid Free Electron Laser (FEL) architecture operating with a RF undulator provided by a powerful Cyclotron Auto-Resonance Maser (CARM). We outline the design elements to operate a compact X-ray device. We review the essential aspects of wave undulator FEL theory and of CARM devices. Full article

(This article belongs to the Special Issue Oscillator-Amplifier Free Electron Lasers an Outlook to Their Feasibility and Performances)

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9 pages, 697 KiB

Open AccessArticle

Two-Color TeraHertz Radiation by a Multi-Pass FEL Oscillator

by Michele Opromolla and Vittoria Petrillo

Appl. Sci. 2021, 11(14), 6495; https://doi.org/10.3390/app11146495 - 14 Jul 2021

Cited by 4 | Viewed by 1655

Abstract

In this paper, we show that an electron beam produced by a super-conducting linac, driven in a sequence of two undulator modules of different periods, can generate two-color Terahertz radiation with wavelengths ranging from 100

μ

m to 2

μ

m. The generated [...] Read more.

In this paper, we show that an electron beam produced by a super-conducting linac, driven in a sequence of two undulator modules of different periods, can generate two-color Terahertz radiation with wavelengths ranging from 100

μ

m to 2

μ

m. The generated pulses are synchronized, both MW-class, and highly coherent. Their specific properties and generation will be discussed in detail. Besides the single-spike pulse structure, usually observed in oscillators, we show that both the THz pump and probe can be modulated in a coherent comb of pulses, enabling periodic excitation and stroboscopic measurements. Full article

(This article belongs to the Special Issue Oscillator-Amplifier Free Electron Lasers an Outlook to Their Feasibility and Performances)

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16 pages, 885 KiB

Open AccessFeature PaperArticle

Two-Beam Free-Electron Lasers and Self-Injected Nonlinear Harmonic Generation

by Elio Sabia, Emanuele Di Palma and Giuseppe Dattoli

Appl. Sci. 2021, 11(14), 6462; https://doi.org/10.3390/app11146462 - 13 Jul 2021

Cited by 3 | Viewed by 1419

Abstract

The possibility of extending the tunability of Free-Electron Lasers towards short wavelengths has been explored through the design of devices conceived to enhance the mechanisms of nonlinear harmonic generation. In this respect, different schemes of operation have been suggested in the past, such [...] Read more.

The possibility of extending the tunability of Free-Electron Lasers towards short wavelengths has been explored through the design of devices conceived to enhance the mechanisms of nonlinear harmonic generation. In this respect, different schemes of operation have been suggested in the past, such as harmonic seeding, bi-harmonic undulators, and two-beam self-seeding devices. In this paper, we discuss how these methods can be merged into a tool, extending the performance of FEL devices. Full article

(This article belongs to the Special Issue Oscillator-Amplifier Free Electron Lasers an Outlook to Their Feasibility and Performances)

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21 pages, 1613 KiB

Open AccessArticle

Advanced Scheme to Generate MHz, Fully Coherent FEL Pulses at nm Wavelength

by Georgia Paraskaki, Sven Ackermann, Bart Faatz, Gianluca Geloni, Tino Lang, Fabian Pannek, Lucas Schaper and Johann Zemella

Appl. Sci. 2021, 11(13), 6058; https://doi.org/10.3390/app11136058 - 29 Jun 2021

Cited by 5 | Viewed by 1846

Abstract

Current FEL development efforts aim at improving the control of coherence at high repetition rate while keeping the wavelength tunability. Seeding schemes, like HGHG and EEHG, allow for the generation of fully coherent FEL pulses, but the powerful external seed laser required limits [...] Read more.

Current FEL development efforts aim at improving the control of coherence at high repetition rate while keeping the wavelength tunability. Seeding schemes, like HGHG and EEHG, allow for the generation of fully coherent FEL pulses, but the powerful external seed laser required limits the repetition rate that can be achieved. In turn, this impacts the average brightness and the amount of statistics that experiments can do. In order to solve this issue, here we take a unique approach and discuss the use of one or more optical cavities to seed the electron bunches accelerated in a superconducting linac to modulate their energy. Like standard seeding schemes, the cavity is followed by a dispersive section, which manipulates the longitudinal phase space of the electron bunches, inducing longitudinal density modulations with high harmonic content that undergo the FEL process in an amplifier placed downstream. We will discuss technical requirements for implementing these setups and their operation range based on numerical simulations. Full article

(This article belongs to the Special Issue Oscillator-Amplifier Free Electron Lasers an Outlook to Their Feasibility and Performances)

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12 pages, 5140 KiB

Open AccessArticle

Hybrid (Oscillator-Amplifier) Free Electron Laser and New Proposals

by Andrea Doria

Appl. Sci. 2021, 11(13), 5948; https://doi.org/10.3390/app11135948 - 26 Jun 2021

Cited by 1 | Viewed by 1593

Abstract

The present work analyses a hybrid free electron laser (FEL) scheme where the oscillator is based on a radiation source operating with a slow-wave guiding structure as, for instance, a Cerenkov FEL or a Smith–Purcell FEL. Such devices, often running in transverse magnetic [...] Read more.

The present work analyses a hybrid free electron laser (FEL) scheme where the oscillator is based on a radiation source operating with a slow-wave guiding structure as, for instance, a Cerenkov FEL or a Smith–Purcell FEL. Such devices, often running in transverse magnetic (TM) modes, present a longitudinal electric field which can easily affect the longitudinal electrons’ velocities, inducing an energy modulation on the beam. Such a modulation, properly controlled, can induce a strong radiation emission in a magnetic undulator properly designed to operate as a radiator. General considerations will be exposed together with a practical numerical example in the far infrared region of the spectrum. Full article

(This article belongs to the Special Issue Oscillator-Amplifier Free Electron Lasers an Outlook to Their Feasibility and Performances)

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14 pages, 637 KiB

Open AccessArticle

Recirculated Wave Undulators for Compact FELs

by Alessandro Curcio

Appl. Sci. 2021, 11(13), 5936; https://doi.org/10.3390/app11135936 - 25 Jun 2021

Cited by 2 | Viewed by 1510

Abstract

Particular schemes of Free Electron Lasers (FELs) are designed to exploit wave undulators. We consider a system employing a recirculated electromagnetic undulator provided by a high-power laser in a resonator cavity. The aim is to establish from calculations a set of realizable parameters [...] Read more.

Particular schemes of Free Electron Lasers (FELs) are designed to exploit wave undulators. We consider a system employing a recirculated electromagnetic undulator provided by a high-power laser in a resonator cavity. The aim is to establish from calculations a set of realizable parameters for such a device. Indeed, novel generation electron accelerators push forward the limits on the accelerating fields, reducing to the sub-meter scale the length over which the electrons can gain enough energy for lasing in the VUV/X-ray region of the electromagnetic spectrum. On the other hand, these innovative technologies do not solve yet the problem associated with the saturation length and therefore of the undulator length, which can be as long as several tens of meters. The option of a FEL based on a wave undulator might provide a valid solution in this respect. Full article

(This article belongs to the Special Issue Oscillator-Amplifier Free Electron Lasers an Outlook to Their Feasibility and Performances)

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10 pages, 5289 KiB

Open AccessFeature PaperArticle

High Repetition Rate and Coherent Free-Electron Laser Oscillator in the Tender X-ray Range Tailored for Linear Spectroscopy

by Michele Opromolla, Alberto Bacci, Marcello Rossetti Conti, Andrea Renato Rossi, Giorgio Rossi, Luca Serafini, Alberto Tagliaferri and Vittoria Petrillo

Appl. Sci. 2021, 11(13), 5892; https://doi.org/10.3390/app11135892 - 24 Jun 2021

Cited by 10 | Viewed by 1779

Abstract

Fine time-resolved analysis of matter—that is, spectroscopy and photon scattering—in the linear response regime requires fs-scale pulsed, high repetition rate, fully coherent X-ray sources. A seeded Free-Electron Laser, driven by a linac based on Super Conducting cavities, generating

10^{8}

–

10^{10}

[...] Read more.

Fine time-resolved analysis of matter—that is, spectroscopy and photon scattering—in the linear response regime requires fs-scale pulsed, high repetition rate, fully coherent X-ray sources. A seeded Free-Electron Laser, driven by a linac based on Super Conducting cavities, generating

10^{8}

–

10^{10}

coherent photons at 2–5 keV with 0.2–1 MHz of repetition rate, can address this need. The scheme proposed is a Free-Electron Laser Oscillator at 3 keV, working with a cavity based on X-ray mirrors. The whole chain of the X-ray generation is here described by means of start-to-end simulations. Full article

(This article belongs to the Special Issue Oscillator-Amplifier Free Electron Lasers an Outlook to Their Feasibility and Performances)

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22 pages, 2454 KiB

Open AccessArticle

Free Electron Laser High Gain Equation and Harmonic Generation

by Giuseppe Dattoli, Emanuele Di Palma, Silvia Licciardi and Elio Sabia

Appl. Sci. 2021, 11(1), 85; https://doi.org/10.3390/app11010085 - 24 Dec 2020

Cited by 10 | Viewed by 2159

Abstract

The

F E L

integral equation is reviewed here and is studied under different contexts, accounting for diverse physical regimes. We include higher order harmonics and saturation effects, and explain the origin of scaling relations, widely exploited to describe either

F E L

[...] Read more.

The

F E L

integral equation is reviewed here and is studied under different contexts, accounting for diverse physical regimes. We include higher order harmonics and saturation effects, and explain the origin of scaling relations, widely exploited to describe either

F E L

dynamics or nonnlinear harmonic generation. Full article

(This article belongs to the Special Issue Oscillator-Amplifier Free Electron Lasers an Outlook to Their Feasibility and Performances)

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Review

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47 pages, 1536 KiB

Open AccessFeature PaperReview

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

by Peter J. M. van der Slot and Henry P. Freund

Appl. Sci. 2021, 11(11), 4978; https://doi.org/10.3390/app11114978 - 28 May 2021

Cited by 6 | Viewed by 2906

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Oscillator-Amplifier Free Electron Lasers an Outlook to Their Feasibility and Performances)

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