| 1. |
- Hines, C J, et al.
(författare)
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Characterization of endotoxin and 3-hydroxy fatty acid levels in air and settled dust from commercial aircraft cabins.
- 2003
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Ingår i: Indoor Air. - : Hindawi Limited. - 0905-6947. ; 13:2, s. 166-173
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Tidskriftsartikel (refereegranskat)abstract
- Endotoxin was measured in air and dust samples collected during four commercial aircraft flights. Samples were analyzed for endotoxin biological activity using the Limulus assay. 3-hydroxy fatty acids (3-OH FA) of carbon chain lengths C10:0-C18:0 were determined in dust by gas chromatography-ion trap tandem mass spectrometry. The geometric mean (geometric standard deviation) endotoxin air level was 1.5 EU/m3 (1.9, n = 28); however, significant differences were found by flight within aircraft type. Mean endotoxin levels were significantly higher in carpet dust than in seat dust (140 ± 81 vs. 51 ± 25 EU/mg dust, n = 32 each, P < 0.001). Airborne endotoxin levels were not significantly related to either carpet or seat dust endotoxin levels. Mean 3-OH FA levels were significantly higher in carpet dust than in seat dust for C10:2, C12:0, and C14:0 (P < 0.001 for each), while the mean level of C16:0 was significantly higher in seat dust than in carpet dust (P < 0.01). Carpet dust endotoxin was significantly, but moderately, correlated with 3-OH-C12:0 and 3-OH-C14:0 (Pearson r = 0.52 and 0.48, respectively), while correlation of seat dust endotoxin with individual 3-OH FAs depended on the test statistic used. Mean endotoxin potency was significantly higher for carpet dust than for seat dust (6.3 ± 3.0 vs. 3.0 ± 1.4 EU/pmol LPS, P < 0.0001). Mean endotoxin levels in the air and dust of commercial aircraft cabins were generally higher than mean levels reported in homes and office buildings. These results suggest that exposure route and dust source are important considerations when relating endotoxin exposure to specific health outcomes.
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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
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| 8. |
- 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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| 9. |
- Lumpkin, A. H., et al.
(författare)
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Evidence for microbunching "sidebands" in a saturated free-electron laser using coherent optical transition radiation
- 2002
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Ingår i: Physical Review Letters. - 1079-7114. ; 88:23, s. 4-4
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Tidskriftsartikel (refereegranskat)abstract
- We report the first measurements of z -dependent coherent optical transition radiation (COTR) due to electron-beam microbunching at high gains (>10(4) ) including saturation of a self-amplified spontaneous emission free-electron laser (FEL). In these experiments the fundamental wavelength was near 530 nm, and the COTR spectra exhibit the transition from simple spectra to complex spectra (5% spectral width) after saturation. The COTR intensity growth and angular distribution data are reported as well as the evidence for transverse spectral dependencies and an "effective" core of the beam being involved in microbunching.
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| 10. |
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