First Name: J.
Middle Name: W.
Last Name: Lewellen
Full Name: J. W. Lewellen
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9 papers
| title: | Self-amplified spontaneous emission saturation at the Advanced Photon Source free-electron laser |
| format: | journal article |
| year: | 2002 |
| 29 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | Today, many bright photon beams in the ultraviolet and x-ray wavelength range are produced by insertion devices installed in specially designed third-generation storage rings. There is the possibility of producing photon beams that are orders of magnitude brighter than presently achieved at synchrotron sources, by using self-amplified spontaneous emission (SASE). At the Advanced Photon Source (APS), the low-energy undulator test line (LEUTL) free-electron laser (FEL) project was built to explore the SASE process in the visible through vacuum ultraviolet wavelength range. While the understanding gained in these experiments will guide future work to extend SASE FELs to shorter wavelengths, the APS FEL itself will become a continuously tunable, bright light source. Measurements of the SASE process to saturation have been made at 530 and 385 nm. A number of quantities were measured to confirm our understanding of the SASE process and to verify that saturation was reached. The intensity of the FEL light was measured versus distance along the FEL, and was found to flatten out at saturation. The statistical variation of the light intensity was found to be wide in the exponential gain region where the intensity is expected to be noisy, and narrower once saturation was reached. Absolute power measurements compare well with GINGER simulations. The FEL light spectrum at different distances along the undulator line was measured with a high-resolution spectrometer, and the many sharp spectral spikes at the beginning of the SASE process coalesce into a single peak at saturation. The energy spread in the electron beam widens markedly after saturation due to the number of electrons that transfer a significant amount of energy to the photon beam. Coherent transition radiation measurements of the electron beam as it strikes a foil provide additional confirmation of the microbunching of the electron beam. The quantities measured confirm that saturation was indeed reached. Details are given in Milton et al., Science 292, 2037 (2001) (also online at www.sciencexpress.org as 10.1126/science. 1059955, 17 May 2001), and Lewellen et al., "Present Status and Recent Results from the APS SASE FEL," to be published in the Proceedings of the 23rd International Free-Electron Laser Conference, Darmstadt, Germany, 20?24 August 2001. |
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| title: | Exponential gain and saturation of a self-amplified spontaneous emission free-electron laser |
| format: | journal article |
| year: | 2001 |
| 32 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent X-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational X-ray free-electron laser. (30 References). |
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| title: | Observation and analysis of self-amplified spontaneous emission at the APS low-energy undulator test line |
| format: | conference procceeding |
| conference: | 22nd International Free Electron Laser Conference |
| year: | 2001 |
| 153 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | Exponential growth of self-amplified spontaneous emission at 530 nm was first experimentally observed at the Advanced Photon Source low-energy undulator test line in December 1999. Since then, further detailed measurements and analysis of the results have been made. Here, we present the measurements and compare these with calculations based on measured electron beam properties and theoretical expectations. (31 References). |
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| title: | Observation of self-amplified spontaneous emission and exponential growth at 530 nm |
| format: | journal article |
| year: | 2000 |
| 50 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | Experimental evidence for self-amplified spontaneous emission (SASE) at 530 nm is reported. The measurements were made at the low-energy undulator test line facility at the Advanced Photon Source, Argonne National Laboratory. The experimental setup and details of the experimental results are presented, as well as preliminary analysis. This experiment extends to shorter wavelengths the operational knowledge of a linac-based SASE free-electron laser and explicitly shows the predicted exponential growth in intensity of the optical pulse as a function of length along the undulator. (20 References). |
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| title: | Characterizing The Electron Beam For The Aps Leutl Free Electron Laser |
| format: | conference procceeding |
| conference: | 2nd ICFA Advanced Accelerator Workshop on the Physics of High Brightness Beams |
| year: | 2000 |
| 3 authors: | | | |
| abstract: | The Advanced Photon Source (APS) Low-Energy Undulator Test Line (LEUTL) project was originally intended to test and characterize advanced undulator designs via electron beambased diagnostics technique. It is presently being used to conduct free electron laser (FEL) research for a future fourth-generation light source. The APS injector linac has been upgraded to deliver a beam suitable for these FEL tests. The project has as an initial goal the operation of a self amplified spontaneous emission (SASE) device operating in the visible at 530 nm (green light). The visible FEL requires a 217 MeV moderately high brightness beam with a peak current of 100 A or greater, a normalized rms emittance of 5 ?m or less, and an energy spread of 0.1% or better. Beam characterization is fundamental to being able to match experimental results with theoretical models. This paper describes the LEUTL FEL, lists the major goals, the beam diagnostics, and presents the initial electron beam measured properties. Future plans are also discussed. |
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| title: | The APS SASE FEL: status and commissioning results |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 7 authors: | | | | | | | |
| abstract: | A self-amplified spontaneous emission (SASE) free-electron laser (FEL) is under construction at the Advanced Photon Source (APS). Three gun systems, an rf-test area, laser room, numerous diagnostics, a transfer line at the end of the linac and a new building, which will serve as the experimental hall, have been added. The only remaining items to be installed are the undulators into the beamline. Here, the additions to the APS in support of this project as well as commissioning results and future plans will be discussed. (9 References). |
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| title: | The operation of the BNL/ATF GUN-IV photocathode RF gun at the Advanced Photon Source |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 18 authors: | | | | | | | | | | | | | | | | | | |
| abstract: | At the Advanced Photon Source (APS) at Argonne National Laboratory (ANL), a free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) process is nearing completion. Recently, an RF photoinjector gun system was made available to the APS by Brookhaven National Laboratory/Accelerator Test Facility (BNL/ATF). It will be used to provide the high-brightness, low-emittance, and low-energy spread electron beam required by the SASE FEL theory. A Nd:Glass laser system, capable of producing a maximum of 500 mu J of UV in a 1-10 ps pulse at up to a 10-Hz repetition rate, serves as the photoinjector's drive laser. Here, the design, commissioning, and integration of this gun with the APS are discussed. (8 References). |
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| title: | The FEL development at the Advanced Photon Source |
| format: | conference procceeding |
| conference: | Free-Electron Laser Challenges II |
| year: | 1999 |
| 46 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | Construction of a single-pass free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) mode of operation is nearing completion at the Advanced Photon Source (APS) with initial experiments imminent. The APS SASE FEL is a proof-of-principle fourth-generation light source. As of January 1999 the undulator hall, end-station building, necessary transfer lines, electron and optical diagnostics, injectors, and initial undulators have been constructed and, with the exception of the undulators, installed. All preliminary code development and simulations have also been completed. The undulator hall is now ready to accept first beam for characterization of the output radiation. It is the project goal to push towards full FEL saturation, initially in the visible, but ultimately to UV and VUV, wavelengths. (10 References). |
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| title: | Operation of the APS RF Gun |
| format: | conference procceeding |
| conference: | 1998 Linear Accelerator Conference |
| year: | 1998 |
| 8 authors: | | | | | | | | |
| abstract: | The Advanced Photon Source (APS) has a thermioniccathode rf gun system capable of providing beam to the APS linac. The gun system consists of a 1.6-cell thermionic-cathode rf gun, a fast kicker for beam current control, and an alpha magnet for bunch compression and injection into the APS linac line. This system is intended for use both as an injector for positron creation, and as a first beam source for the Low-Energy Undulator Test Line (LEUTL) project [1]. The first measured performance characteristics of the gun are presented. |
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