| 1. |
- Biedron, Sandra G., et al.
(författare)
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Evolution of transverse modes in a high-gain free-electron laser
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 528:1-2, s. 443-447
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Tidskriftsartikel (refereegranskat)abstract
- At the point of saturation in a high-gain free-electron laser (FEL) the light is fully transversely coherent. The number and evolution of the transverse modes is important for the effective tune-up and subsequent operation of FELs based on the photon beam characterization and in designing multi-module devices that rely on relatively stable saturation distances in each module. In the latter, this is particularly critical since each section will seed another module. Overall, in a single- or multi-module device, experimental users will desire stability in power and in photon beam quality. Using a numerical simulation code, the evolution of the transverse modes in the high-gain free-electron laser (FEL) is examined and is discussed. In addition, the transverse modes in the first few higher nonlinear harmonics are investigated.
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| 2. |
- Biedron, Sandra G., et al.
(författare)
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Impact of electron beam quality on nonlinear harmonic generation in high-gain free-electron lasers
- 2002
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Ingår i: Physical Review Special Topics. Accelerators and Beams. - 1098-4402. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear harmonic generation can be a very useful and important phenomenon for single-pass free-electron lasers (FELs) operating in the high-gain regime. Strong bunching at the fundamental wavelength and its associated higher harmonic content allow significant radiation at shorter wavelengths to be emitted without serious effects upon the output power at the fundamental. Here, we analyze the relative sensitivities to beam quality variations of the output fundamental and harmonic powers for a visible-wavelength FEL operating in the high-gain regime.
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| 3. |
- Biedron, Sandra G., et al.
(författare)
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Measurements of nonlinear harmonic generation at the Advanced Photon Source's SASE FEL
- 2002
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 483:1-2, s. 94-100
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Tidskriftsartikel (refereegranskat)abstract
- SASE saturation was recently achieved at the Advanced Photon Source's SASE FFL in the low-energy undulator test line at 530 nm and 385 urn. The electron beam microbunching becomes more and more prominent until saturation is achieved. This bunching causes nonlinear harmonic emission that extends the usefulness of a SASE system in achieving shorter FEL wavelengths for the same electron beam energy. We have investigated the intensity of the fundamental and second harmonic undulator radiation as a function of distance along the undulator line and present the experimental results and compare them to numerical simulations. In addition, we have measured the single-shot second harmonic spectra as well as the simultaneous fundamental and second harmonic spectra and present the experimental results. (C) 2002 Elsevier Science B.V. All riudits reserved.
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| 4. |
- Biedron, Sandra G., et al.
(författare)
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The sensitivity of nonlinear harmonic generation to electron beam quality in free electron lasers
- 2002
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 483:1-2, s. 101-106
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Tidskriftsartikel (refereegranskat)abstract
- The generation of harmonics through a nonlinear mechanism driven by bunching at the fundamental has sparked interest as a path toward enhancing and extending the usefulness of an X-ray free-electron laser (FEL) facility. The sensitivity of the nonlinear harmonic generation to undulator imperfections, electron beam energy spread, peak current, and emittance is important in an evaluation of the process. Typically, linear instabilities in FELs are characterized by increased sensitivity to both electron beam and undulator quality with increasing harmonic number. However, since the nonlinear harmonic generation mechanism is driven by the growth of the fundamental, the sensitivity of the nonlinear harmonic mechanism is not expected to be significantly greater than that of the fundamental. In this paper, we study the effects of electron beam quality, more specifically, emittance, energy spread, and peak current, on the nonlinear harmonics in a 1.5-Angstrom FEL, and show that the decline in the harmonic emission roughly follows that of the fundamental. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 5. |
- Dattoli, G, et al.
(författare)
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A compact free electron laser device operating in the UV-soft X-ray region
- 2004
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Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018. ; 232:1-6, s. 319-326
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the design elements of a compact free electron laser device, operating, in an oscillator-amplifier configuration, up to the soft X-ray region. We show that, the source can provide radiation from extreme UV to soft X-ray region, with significantly large output peak and average laser power with undulator lengths not exceeding 7 in.
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| 6. |
- Lewellen, JW, et al.
(författare)
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Present status and recent results from the APS SASE FEL
- 2002
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 483:1-2, s. 40-45
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Tidskriftsartikel (refereegranskat)abstract
- The Low-Energy Undulator Test Line (LEUTL) at the Advanced Photon Source, Argonne National Laboratory, is intended to demonstrate the basic operation of a SASE-based free-electron laser. Goals include comparison of experimental results With theoretical predictions and scaling laws, identification of problems relevant to fourth-generation light source construction and operation and the means of addressing them, the development of operational and diagnostic techniques to optimize SASE FEL performance and increase repeatability from run to run. and performance of initial pioneering experiments capable of exploiting the unique properties of the laser. The basic layout and operational philosophy of the LEUTL experiment is presented. A summary of past results, including saturation, is reviewed, and a description of recent results is presented. We conclude with future plans, which include pressing to shorter wavelengths and incorporating user experiments into the LEUTL experimental program.
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| 7. |
- Biedron, Sandra G.
(författare)
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Toward Creating a Coherent, Next-Generation Light Source with special emphasis on nonlinear harmonic generation in single-pass, high-gain free-electron lasers
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There is a strong desire for short wavelength (~1 Å), short pulsewidth (<100 fs), high-brightness, transverse and longitudinally coherent light pulses for use by the synchrotron radiation community. These requirements exceed the limits achievable by existing, so-called, "third-generation" light sources, such as the Advanced Photon Source (APS) at Argonne National Laboratory (ANL), USA, the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, and SPring-8 in Harima Science Garden City, Japan. Single-pass, high-gain free-electron laser (FEL) methods have the ability to fulfill these requirements and have been proposed as the next-generation light source. Such arrangements include, but are not limited to, straight amplifier configurations, self-amplified spontaneous emission (SASE), the two-undulator harmonic generation amplifier scheme (TUHGS), and high-gain harmonic generation (HGHG). These single-pass, high-gain FELs typically employ planar undulators and can all generate nonlinear spectral harmonics with significant power levels. Of notable interest is the combination of the accelerator and traditional lasers, since existing laser technologies may be used for seeding the amplifier, TUHGS, and HGHG cases. This work examines single-pass, high-gain free-electron lasers analytically, via numerical simulations, and experimentally. An existing code, MEDUSA, was further developed to simulate relevant mechanisms as will be described. Along with a review of the respective theories, a three-step SASE FEL experiment at the APS, a two-step FEL experiment at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory (BNL) involving both the SASE and HGHG methods, and the characteristics of nonlinear harmonic generation in both of these experiments are discussed. Finally, a modular approach to the next-generation light source is described. The above proof-of-principle experiments represent necessary steps toward achieving the next-generation light source. The ATF experiment tests the SASE and HGHG theories at a mid-infrared wavelength, while the APS experiment examines the SASE theory first at visible and then at ultraviolet wavelengths. The extension from the visible/ultraviolet wavelengths to the x-ray wavelength regime is not trivial, and there still remains much work before achieving the final goal based on the single-pass, high-gain free-electron laser theories and experiments. Of the topics elucidated within this manuscript, nonlinear harmonic generation in single-pass, high-gain FELs is perhaps the most significant. Although there is a reduction, compared to the fundamental wavelength, in the resultant output photon power when using the nonlinear harmonics to achieve shorter wavelengths, the harmonics do permit the use of an electron bunch of both lower energy and lesser quality. Therefore, smaller, less expensive machines could be developed, allowing many more facilities to be constructed and ultimately benefit from these bright, coherent, next-generation light sources.
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| 8. |
- Freund, HP, et al.
(författare)
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Nonlinear harmonic generation in free-electron laser oscillators
- 2004
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Ingår i: Proceedings of the 25th International Free Electron Laser Conference, and the 10th FEL Users Workshop (Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment). - : Elsevier BV. - 0168-9002. ; 528:1-2, s. 44-47
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Konferensbidrag (refereegranskat)abstract
- Nonlinear harmonic generation has been described theoretically, and observed, in free-electron laser (FEL) amplifiers. The mechanism relies on the nonlinear, higher-order bunching when the fundamental reaches high intensities, and can also be expected in high-power FEL oscillators. We use the 3D polychromatic simulation code MEDUSA to study the nonlinear harmonic generation in FEL oscillators. Strong harmonic growth is, indeed, found when an oscillator is near saturation, and the third (fifth) harmonic can reach power levels approaching 1% (0.1%) that of the fundamental. (C) 2004 Elsevier B.V. All rights reserved.
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