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39 papers
| title: | Production of High Harmonic X-ray Radiation from Non-linear Thomson Scattering at LLNL PLEIADES |
| format: | conference procceeding |
| conference: | 2005 Particle Accelerator Conference |
| year: | 2005 |
| 11 authors: | | | | | | | | | | | |
| abstract: | We describe an experiment for production of high harmonic x-ray radiation from Thomson backscattering of an ultra-short high power density laser by a relativistic electron beam at the PLEIADES facility at LLNL. In this scenario, electrons execute a ``figure-8'' motion under the influence of the high-intensity laser field, where the constant characterizing the field strength is expected to exceed unity: $a_{L}=eE_{L}/m_{e}c\omega_{L}\geq1$. With large $a_{L}$ this motion produces high harmonic x-ray radiation and significant broadening of the spectral peaks. This paper is intended to give a layout of the PLEIADES experiment, along with progress towards experimental goals. |
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| title: | Free-Electron Lasers as Pumps for High-Energy Solid-State Lasers |
| format: | conference procceeding |
| conference: | 25th International Free Electron Laser Conference |
| year: | 2004 |
| 3 authors: | | | |
| abstract: | High average-power free-electron lasers may be useful for pumping high peak-power solid-state laser-amplifiers. At very high peak-powers, the pump source for solid-state lasers is non-trivial: flash lamps produce thermal problems and are unsuitable for materials with short florescence-times, while diodes can be expensive and are only available at select wavelengths. FELs can provide pulse trains of light tuned to a laser material's absorption peak, and florescence lifetime. An FEL pump can thus minimize thermal effects anad potentially allow for new laser materials to be used. This paper examines the design of a high average-power, effecient high-gain FEL for use as a pump source. Specifically, the cases of a 100 J class pump, and a 100 TW-class laser at a planned fourth-generation light-source are considered. |
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| title: | Properties of the ultrashort gain length, self-amplified spontaneous emission free-electron laser in the linear regime and saturation |
| format: | journal article |
| year: | 2003 |
| 26 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | VISA (Visible to Infrared SASE Amplifier) is a high-gain self-amplified spontaneous emission (SASE) free-electron laser (FEL), which achieved saturation at 840 nm within a single-pass 4-m undulator. The experiment was performed at the Accelerator Test Facility at BNL, using a high brightness 70-MeV electron beam. A gain length shorter than 18 cm has been obtained, yielding a total gain of 2x10(8) at saturation. The FEL performance, including the spectral, angular, and statistical properties of SASE radiation, has been characterized for different electron beam conditions. Results are compared to the three-dimensional SASE FEL theory and start-to-end numerical simulations of the entire injector, transport, and FEL systems. An agreement between simulations and experimental results has been obtained at an unprecedented level of detail. |
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| title: | An Adjustable Permanent Magnet Quadrupole Final Focus System for Low Energy Experiments |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 7 authors: | | | | | | | |
| abstract: | The final focus system for the Thomson X-ray scattering experiment termed PLEIADES (Picosecond Laser-Electron InterAction for Dynamic Evaluation of Structures) at LLNL demands ultra-high field gradient quadrupoles in order to focus initially small beams to 10-20 micron spot sizes. This scheme circumvents limitations due to chromatic aberrations and space-charge effects in this relatively low energy (<100 Mev) system. The final focus scheme is based on an ultra-high gradient (300T/m) quadrupole which employs the Halbach 16-piece, permanent magnet design. Use of this optimized goemetry, NdFeB material, and a small (4 mm) bore allows the desired field gradient, and few cm focal length, to be achieved. The adjustability of the focusing system is obtained by changing the relative longitudinal positions of sub-component focusing and defocusing magnets on precision movers. We present the results of RADIA 3D design simulations, and measurement of prototype magnets. We also discuss the results of beam dynamics simulations of the PLEIADES system using both envelope and tracking codes. |
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| title: | Generation of High Brightness X-Rays with the PLEIADES Thomson X-Ray Source |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 14 authors: | | | | | | | | | | | | | | |
| abstract: | The use of short laser pulses to generate high peak intensity, ultra-short x-ray pulses enables exciting new experimental capabilities, such as femtosecond pump-probe experiments used to temporally resolve material structural dynamics on atomic time scales. PLEIADES (Picosecond Laser Electron InterAction for the Dynamic Evaluation of Structures) is a next generation Thomson scattering x-ray source being developed at Lawrence Livermore National Laboratory (LLNL). Ultra-fast picosecond x-rays (10-200 keV) are generated by colliding an energetic electron beam (20-100 MeV) with a high intensity, sub-ps, 800 nm laser pulse. The peak brightness of the source is expected to exceed 1020 photons/s/0.1 bandwidth/mm2/mrad2. Simulations of the electron beam production, transport, and final focus are presented. Electron beam measurements, including emittance and final focus spot size are also presented and compared to simulation results. Measurements of x-ray production are also reported and compared to theoretical calculations. |
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| title: | Results of the VISA SASE FEL Experiment at 840 nm |
| format: | conference procceeding |
| conference: | 24th International Free Electron Laser Conference |
| year: | 2003 |
| 26 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | VISA (Visible to Infrared SASE Amplifier) is a high-gain self-amplified spontaneous emission (SASE) free-electron laser (FEL), which achieved saturation at 840 nm within a single-pass 4-m undulator. A gain length shorter than 18 cm has been obtained, yielding the gain of 2x10(8) at saturation. The FEL performance, including the spectral, angular, and statistical properties of SASE radiation, has been characterized for different electron beam conditions. The results are compared to 3-D SASE FEL theory and start-to-end numerical simulations of the entire injector, transport, and FEL system. Detailed agreement between simulations and experimental results is obtained over the wide range of the electron beam parameters. |
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| title: | Measurements of nonlinear harmonic radiation and harmonic microbunching in a visible SASE FEL |
| format: | conference procceeding |
| conference: | 24th International Free Electron Laser Conference |
| year: | 2003 |
| 13 authors: | | | | | | | | | | | | | |
| abstract: | The experimental characterization of nonlinear harmonic generation (NHG) and electron beam microbunching at saturation from a visible SASE FEL are presented in this report. The gain lengths, spectra and energies of NHG were experimentally measured up to the third harmonic, and agree with theoretical predictions. Electron beam microbunching in both the fundamental and the second harmonic as the function of the SASE output were experimentally observed over the full range of SASE gain. The bunching factors for both the fundamental (b(1)) and second harmonic (b(2)) were experimentally characterized at saturation. The microbunching data provides another test of SASE saturation as well as correlating the NHG and electron beam microbunching modes to the fundamental SASE. |
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| title: | Ultrafast materials probing with the LLNL Thomson X-ray source |
| format: | conference procceeding |
| conference: | 2002 Linear Accelerator Conference |
| year: | 2002 |
| 24 authors: | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The use of short laser pulses to generate very high brightness, ultra short (fs to ps) x-ray pulses is a topic of great interest. In principle, femtosecond-scale pump-probe experiments can be used to temporally resolve structural dynamics of materials on the time scale of atomic motion. The development of sub?ps x-ray pulses will make possible a wide range of materials and plasma physics studies with unprecedented time resolution. PLEIADES (Picosecond Laser Electron Interaction for Dynamic Evaluation of Structures), the Thomson scattering project at LLNL, will provide such a novel x-ray source of high power using short laser pulses and a high brightness, relativistic electron bunch. The system is based on a 5 mm-mrad normalized emittance photoinjector, 100 MeV electron RF linac, and a 300 mJ, 35 fs solid-state laser system. PLEIADES will produce ultra fast pulses with x-ray energies (60 keV) capable of probing into high-Z metals. |
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| title: | Properties of an Ultra-Short Gain Length, Saturated, Self-Amplified Spontaneous Emission FEL |
| format: | preprint |
| year: | 2002 |
| 26 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The VISA experiment, conducted at the BNL Accelerator Test Facility (ATF), has studied the properties of SASE FEL process in a saturating system. The experiment utilized a high brightness electron beam and a strong focusing undulator. Saturated gain greater than 108, with a power gain length below 18 cm, was obtained at 840 nm. Measurements of FEL gain, spectral and angular properties of SASE radiation are reported, and the results are compared to theory and to start-to-end simulations of the system. FEL performance was found critically dependent on the compression of the electron beam. |
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| title: | Experimental characterization of nonlinear harmonic radiation from a visible self-amplified spontaneous emission free-electron laser at saturation |
| format: | unknown |
| year: | 2002 |
| 12 authors: | | | | | | | | | | | | |
| abstract: | Nonlinear harmonic radiation was observed using the VISA self-amplified, spontaneous emission (SASE) free-electron laser (FEL) at saturation. The gain lengths, spectra, and energies of the three lowest SASE FEL modes were experimentally characterized. The measured nonlinear harmonic gain lengths and center spectral wavelengths decrease with harmonic number, n, which is consistent with nonlinear harmonic theory. Both the second and third nonlinear harmonics energies are about 1% of the fundamental energy. These experimental results demonstrate for the first time the feasibility of using nonlinear harmonic SASE FEL radiation to produce coherent, femtosecond X-rays. (33 References). |
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| title: | Electron Beam Production and Characterization for the PLEIADES Thomson X-Ray Source |
| format: | conference procceeding |
| conference: | 10th Advanced Accelerator Concepts Workshop |
| year: | 2002 |
| 13 authors: | | | | | | | | | | | | | |
| abstract: | We report on the performance of an S-band RF photocathode electron gun and accelerator for operation with the PLEIADES Thomson x-ray source at LLNL. Simulations of beam production, transport, and focus are presented. It is shown that a 1 ps, 500 pC electron bunch with a normalized emittance of less than 5 Tcmm-mrad can be delivered to the interaction point. Initial electron measurements are presented. Calculations of expected x-ray flux are also performed, demonstrating an expected peak spectral brightness of 1020 photons/s/mm2/mrad2/0.1% bandwidth. Effects of RF phase jitter are also presented, and planned phase measurements and control methods are discussed. |
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| title: | Fundamental and Harmonic Microbunching Measurements in a High-Gain, Self-Amplified, Spontaneous Emission Free-Electron Laser |
| format: | preprint |
| year: | 2002 |
| 13 authors: | | | | | | | | | | | | | |
| abstract: | The self-amplified, spontaneous emission free-electron laser (SASE-FEL) gain process is a collective instability which induces microbunching in the electron beam. Micro-bunching approaching unity at the fundamental FEL wavelength (845 nm), and its second harmonic, have been measured at the VISA FEL, at or near saturation. These measurements, which use the beam's coherent transition radiation (CTR) spectrum, are sompared to the predictions of FEL simulations. Comparison of shot-by-shot SASE and CTR signals firmly establishes the role of SASE in the development of microbunching harmonics. |
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| title: | Fundamental and harmonic microbunching in a high-gain self-amplified spontaneous-emission free-electron laser |
| format: | unknown |
| year: | 2002 |
| 13 authors: | | | | | | | | | | | | | |
| abstract: | Electron beam microbunching in both the fundamental and second harmonic in a high-gain self-amplified spontaneous emission free-electron laser (SASE FEL) was experimentally characterized using coherent transition radiation. The microbunching factors for both modes (b1 and b2) approach unity, an indication of FEL saturation. These measurements are compared to the predictions of FEL simulations. The simultaneous capture of the microbunching and SASE radiation for individual micropulses correlate the longitudinal electron beam structure with the FEL gain. |
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| title: | Characterization of an 800 nm SASE FEL at saturation |
| format: | conference procceeding |
| conference: | 23rd International Free Electron Laser Conference |
| year: | 2002 |
| 24 authors: | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | Visible to Infrared SASE Amplifier is a free electron laser (FEL) designed to saturate at a radiation wavelength of 800 nm within a 4 m long, strong focusing undulator. A large gain is achieved by driving the FEL with 72 MeV, high brightness beam of BNL's accelerator test facility. We present measurements that demonstrate saturation in addition to the frequency spectrum of the FEL radiation. Energy, gain length and spectral characteristics are compared and shown to agree with simulation and theoretical predictions. (16 References). |
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| title: | Measuring FEL radiation properties at VISA-FEL |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 25 authors: | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The VISA (Visible to Infrared SASE Amplifier) SASE free electron laser has been successfully operated at the Accelerator Test Facility (ATF) at BNL. High gain and saturation were observed at 840 nm. We describe here the diagnostic system, experimental procedures and data reduction algorithms, as the FEL performance was measured along the length of the undulator. We also discuss selected spectral radiation measurements. (10 References). |
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| title: | Saturation measurements of a visible SASE FEL |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 14 authors: | | | | | | | | | | | | | | |
| abstract: | VISA (visible to infrared SASE amplifier) is an FEL designed to obtain high gain at a radiation wavelength of 800 nm. Large gain is achieved by driving the FEL with the 71 MeV, high brightness beam of the Accelerator Test Facility (ATF) and using a novel, strong focusing, 4 m long undulator with a gap of 6 mm and a period of 1.8 cm. We report measurements of exponential gain, saturation, and spectra of the FEL radiation intensity. (11 References). |
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| title: | Visible-infrared self-amplified spontaneous emission amplifier free electron laser undulator |
| format: | unknown |
| year: | 2001 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | The visible-infrared self-amplified spontaneous emission amplifier (VISA) free electron laser (FEL) is an experimental device designed to show self-amplified spontaneous emission (SASE) to saturation in the near infrared to visible light energy range. It generates a resonant wavelength output from 800?600 nm, so that silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is designed to show how SASE FEL theory corresponds with experiment in this wavelength range, using an electron beam with emittance close to that planned for the future Linear Coherent Light Source at SLAC. VISA comprises a 4 m pure permanent magnet undulator with four 99 cm segments, each of 55 periods, 18 mm long. The undulator has distributed focusing built into it, to reduce the average beta function of the 70?85 MeV electron beam to about 30 cm. There are four FODO cells per segment. The permanent magnet focusing lattice consists of blocks mounted on either side of the electron beam, in the undulator gap. The most important undulator error parameter for a free electron laser is the trajectory walk-off, or lack of overlap of the photon and electron beams. Using pulsed wire magnet measurements and magnet shimming, we were able to control trajectory walk-off to less than |
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| title: | Initial gain measurements of an 800 nm SASE FEL, VISA |
| format: | conference procceeding |
| conference: | 22nd International Free Electron Laser Conference |
| year: | 2001 |
| 26 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The visible to infrared SASE amplifier (VISA) FEL is designed to obtain high gain at a radiation wavelength of 800 nm. The FEL uses the high brightness electron beam of the accelerator test facility (ATF), with energy of 72 MeV. VISA uses a novel, 4 m long, strong focusing undulator with a gap of 6 mm and a period of 1.8 cm. To obtain large gain the beam and undulator axis have to be aligned to better than 5 mu m. Results from initial measurements on the alignment, gain, and spectrum will be presented and compared to theoretical calculations and simulations. (10 References). |
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| title: | Intra-undulator measurements at VISA FEL |
| format: | conference procceeding |
| conference: | 22nd International Free Electron Laser Conference |
| year: | 2001 |
| 11 authors: | | | | | | | | | | | |
| abstract: | We describe a diagnostics system developed, to measure exponential gain properties and the electron beam dynamics inside the strong focusing 4-m long undulator for the VISA (Visible to Infrared SASE Amplifier) FEL. The technical challenges included working inside the small undulator gap, optimising the electron beam diagnostics in the high background environment of the spontaneous undulator radiation, multiplexing and transporting the photon beam. Initial results are discussed. |
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| title: | A diagnostic system to measure SASE-FEL radiation properties along the 4-meter VISA undulator |
| format: | conference procceeding |
| conference: | 21st International Free Electron Laser Conference |
| year: | 2000 |
| 4 authors: | | | | |
| abstract: | |
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| title: | Status and initial commissioning of a high gain 800 nm SASE FEL |
| format: | conference procceeding |
| conference: | 21st International Free Electron Laser Conference |
| year: | 2000 |
| 22 authors: | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | We describe the status and initial commissioning of the visible to infrared SASE amplifier (VISA) experiment. VISA uses a strong focusing 4 m undulator, the Brookhaven National Laboratory ATF linac with an energy of 72 MeV, and a photoinjector electron source. The VISA fundamental radiation wavelength is near 800 nm and the power expected at saturation is near 60 MW. Power, angular and spectral measurements are planned for the VISA radiation and these results will be analyzed and compared with SASE FEL theory and computer simulation. In addition, the induced electron beam micro-bunching will be measured using coherent transition radiation. (12 References). |
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| title: | A measurement of high gain SASE FEL induced electron beam micro-bunching using coherent transition radiation |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 9 authors: | | | | | | | | | |
| abstract: | Coherent transition radiation (CTR) was used to study the longitudinal modulations of an electron beam exiting the UCLA/LANL high gain SASE FEL. The induced longitudinal micro-bunching of the electron beam at the exit of the undulator was measured with a frequency domain technique using the CTR emitted when this beam strikes a thin conducting foil. Formalisms for both CTR and SASE theories are related using the simulation code GINGER in which the SASE FEL gain of the output radiation and the micro-bunching of the electron beam are given. Experimental results from the CTR measurement will show the limit of standard transition radiation theory is being approached and new analysis is needed. (8 References). |
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| title: | Coherent Radiation Diagnosis of Self Amplified Spontaneous Emission free Electron Laser-Derived Electron beam Microbunching |
| format: | thesis |
| year: | 1999 |
| 1 author: | |
| abstract: | This thesis presents an experiment in which the longitudinal profile of an electron beam was measured by studying the coherrent transition radiation (CTR) emitted when the beam strikes a thin conducting foil. A high gain Self Amplified Spontaneous Emission (SASE) Free Electron laser (FEL) was implemented and the source fo the longitudinal beam profile modulation. Diagnostics measuring very short periodic electron beam modulation will be necessary for future experiments in which the modulating wavelength will be several microns. Up to this point, there have been reliable tools used for such longitudinal beam profile measurements. However, the limits of resolution in these devices are being approached and new and less expensive methods are needed. Transition radiation from an electron beam striking a metallic surface is an easily emplementable and inexpensive diagnostic and is shown to be a reliable diagnostic for the future. This thesis presents the theoretical calculation of the expected CTR photon spectrums and compares the analysis with an experiment recently done on an electron beam which has been longitudinally modulated by SASE FEL. The accelerator beamline and its parameters important to the experiment are described. Also, discussed, are the requirements on the system needed for the best CTR emission possible and the importance in choosing a good metallic radiating foil. Results from the data are compared with computer simulation in which these issues are taken into account. Also, the experimental results point out approximations used in traditional transition radiation modeling that will not be valid in future CTR experiemnts and more rigorous theorectical analysis will be needed. |
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| title: | The development of S-band plane wave transformer photoinjector |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 11 authors: | | | | | | | | | | | |
| abstract: | An integrated S-band RF photoinjector based on the plane wave transformer (PWT) is being built in the Particle Beam Physics Laboratory at UCLA in collaboration with DULY Research. This novel structure integrates a photocathode directly into a PWT linac making the structure simple and compact. Due to the strong coupling between each adjacent cell, this structure is relatively easy to fabricate and operate. This photoinjector can provide high brightness beams at energies of 15 to 20 MeV, with emittance less than 1 mm-mrad at charge of 1 nC. These short-pulse beams can be used in various applications: space charge dominated beam physics studies, plasma lenses, plasma accelerators, free-electron laser microbunching techniques, and SASEFEL physics studies. It will also provide commercial opportunities in chemistry, biology and medicine. The present status of the PWT photoinjector including fabrication and cold test to characterise the structure is described. RF system and photocathode drive laser system are also discussed. |
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| title: | Photon beam diagnostics for VISA FEL |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | The VISA (Visible to Infrared SASE Amplifier) project is designed to be a SASE-FEL driven to saturation in the sub-micron wavelength region. Its goal is to test various aspects of the existing theory of self-amplified spontaneous emission, as well as numerical codes. Measurements include: angular and spectral distribution of the FEL light at the exit and inside of the undulator; electron beam micro-bunching using CTR; single-shot time resolved measurements of the pulse profile, using an auto-correlation technique and FROG algorithm. The diagnostics are designed to provide maximum information on the physics of the SASE-FEL process, to ensure a close comparison of the experimental results with theory and simulations. (9 References). |
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| title: | Commissioning of the Neptune photoinjector |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 21 authors: | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The status of the commissioning of the RF photoinjector in the Neptune advanced accelerator laboratory is discussed. The component parts of the photoinjector, the RF gun, photocathode drive laser system, booster linac, RF system, chicane compressor, beam diagnostics systems, and control system are described. This injector is designed to produce short pulse length, high brightness electron beams. Experiments planned for the immediate future are described. Initial measurements of various beam parameters are presented. (10 References). |
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| title: | Measured free-electron laser microbunching using coherent transition radiation |
| format: | conference procceeding |
| conference: | 20th International Free Electron Laser Conference |
| year: | 1999 |
| 9 authors: | | | | | | | | | |
| abstract: | The microbunch distribution of an electron beam exiting a SASE free-electron laser has been measured using the emitted coherent transition radiation (CTR) produced from a thin aluminum foil placed at the end of the undulator. The wavelength of the coherent transition radiation is shown to be the same as the FEL wavelength, and thus a measure of the beam microbunch spacing. Also, the study of the CTR linewidth and angular acceptance of the radiation captured are shown to be derived from this coherent radiative process. Scattering effects on the forward emitted transition radiation from the electron beam traversing an aluminum foil are also considered. (11 References). |
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| title: | Coherent transition radiation-based diagnosis of electron beam pulse shape |
| format: | conference procceeding |
| conference: | 8th Advanced Accelerator Concepts Workshop |
| year: | 1999 |
| 3 authors: | | | |
| abstract: | The bunch shapes of an electron beams is increasingly difficult to measure, as the time-scales of interest are now sub-picosecond. We discuss here the use of coherent transition radiation (CTR) for such measurements. Two types of measurements are presented: the deduction of macroscopic (0.3 psec resolution) pulse profile using interferometry, and the examination of microbunch (50 fsec) structure from an FEL-bunched beam using spectral characteristics of the CTR. For the macrobunch measurement we discuss the problem of missing low frequency radiation and one solution for extracting meaningful data with this problem are presented. For microbunch CTR, we examining initial spectrally-resolved measurements, and some interesting deviations in the CTR spectrum from the standard theoretical predictions. (23 References). |
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| title: | Measurements of gain larger than 10(5) at 12 mu m in a self-amplified spontaneous-emission free-electron laser |
| format: | unknown |
| year: | 1998 |
| 14 authors: | | | | | | | | | | | | | | |
| abstract: | We report measurements of very large output intensities corresponding to a gain larger than 10/sup 5/ for a single pass free-electron laser operating in the self-amplified spontaneous emission (SASE) mode at 12 mu m. We also report the observation and analysis of intensity fluctuations of the SASE radiation intensity in the high-gain regime. The results are compared with theoretical predictions and simulations. (18 References). |
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| title: | Observation of Self-Amplified Spontaneous-Emission-Induced Electron-Beam Microbunching Using Coherent Transition Radiation |
| format: | unknown |
| year: | 1998 |
| 9 authors: | | | | | | | | | |
| abstract: | We report the measurement of electron-beam microbunching at the exit of a self-amplified spontaneous-emission free-electron laser (SASE FEL), by observation of coherent transition radiation (CTR). The CTR was found to have an angular spectrum much narrower than spontaneous transition radiation and a narrow-band frequency spectrum. The central frequency of the fundamental CTR spectrum is found to differ slightly from that of the SASE, a finding in disagreement with previously invoked CTR theory. The CTR measurement establishes the uniformity of microbunching in the transverse dimension, indicating the SASE FEL operates in a dominant transverse mode. |
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| title: | Measurements of High Gain and Intensity Fluctuations in a Self-Amplified, Spontaneous-Emission Free-Electron Laser |
| format: | journal article |
| year: | 1998 |
| 12 authors: | | | | | | | | | | | | |
| abstract: | We report measurements of large gain for a single pass free-electron laser operating in self-amplified spontaneous emission (SASE) at 16 mm starting from noise. We also report the first observation and analysis of intensity fluctuations of the SASE radiation intensity in the high gain regime. The results are compared with theoretical predictions and simulations. |
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| title: | The Neptune photoinjector |
| format: | conference procceeding |
| conference: | ICFA Second Generation Plasma Acceleration Workshop |
| year: | 1998 |
| 12 authors: | | | | | | | | | | | | |
| abstract: | The RF photoinjector in the Neptune advanced accelerator laboratory, along with associated beam diagnostics, transport and phase-space manipulation techniques are described. This versatile injector has been designed to produce short-pulse electron beams for a variety of uses: ultra-short bunches for injection into a next-generation plasma beatwave acceleration experiment, space-charge dominated beam physics studies, plasma wake-field acceleration driver, plasma lensing, and free-electron laser microbunching techniques. The component parts of the photoinjector, the RF gun, photocathode drive laser systems, booster linac, RF system, chicane compressor, beam diagnostic systems, and control system, are discussed. The present status of photoinjector commissioning at Neptune is reviewed, and proposed experiments are detailed. (33 References). |
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