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18 papers
| title: | Current-Enhanced SASE Using an Optical Laser and its Application to the LCLS |
| format: | journal article |
| year: | |
| 6 authors: | | | | | | |
| abstract: | We propose a significant enhancement of the electron peak current entering a SASE undulator by inducing an en- ergy modulation in an upstream wiggler magnet via res- onant interaction with an optical laser, followed by mi- crobunching of the energy-modulated electrons at the ac- celerator exit. This current enhancement allows a reduc- tion of the FEL gain length. The x-ray output consists of a series of uniformly spaced spikes, each spike being tem- porally coherent. The duration of this series is controlled by the laser pulse and in principle can be narrowed down to just a single, -attosecond spike. Given potentially absolute temporal synchronization of the x-ray spikes to the energy-modulating laser pulse, this scheme naturally makes pump-probe experiments available to SASE FEL’s. We also study various detrimental effects related to the high electron peak current . |
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| title: | Pulse Length Control in an X-Ray FEL by Using Wakefields |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 3 authors: | | | |
| abstract: | For the users of the high-brightness radiation sources of free-electron lasers it is necessary to reduce the FEL pulse length to 10 fs and below for time-resolving pump and probe experiments. Although it can be achieved by conventional compression methods for the electron beam or the chirped FEL pulse, the technical realization is demanding. In this presentation we study the impact of undulator wakefields and how their properties can be used to reduced the amplifying part of the bunch to the desired length. Methods of actively controlling the wakefields are presented. |
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| title: | Theoretical evaluation of the LCLS X-Ray Free-Electron Laser performance |
| format: | conference procceeding |
| conference: | 25th International Free Electron Laser Conference |
| year: | 2003 |
| 4 authors: | | | | |
| abstract: | In this paper we evaluate the performance of the LCLS FEL, including all known physical effects from the electron source to the undulator exit which determine the X-ray pulse characteristics. The wavelength range considered is from the 15 to 1.5 Angstrom, with an extension to 0.5 Angstrom using the third harmonic. The results of this work have been useful to identify areas in the LCLS design where improvements could be made, thus optimizing the system performance. |
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| title: | Start-to-End Simulations for the LCLS X-Ray Free-Electron Laser |
| format: | conference procceeding |
| conference: | 25th International Free Electron Laser Conference |
| year: | 2003 |
| 7 authors: | | | | | | | |
| abstract: | The LCLS Free-Electron Lasers operates in the wavelength range of 1.5-15 Angstrom, using an electron beam with an energy between 4.5 and 14.5 GeV. The generation of the electron beam, the preservation of its brightness during acceleration and compression, and the amplififcation of the spontaneous radiation within the FEL can only be described by a consistent set of simulation codes. We preset the change in the FEL performance with respect to the LCLS design case, when various effects are included, altering the electron beam distribution and motion (e.g. wake fields, CSR, magnet misalignment or field errors of the undulator field). To distinguish the individual contribution of each effect, multiple start-end simulations are performed, including step by step additional effects and, thus, approaching a more and more realistic model of the LCLS FEL. |
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| title: | Start to End Simulations for the SPARX Proposal |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 18 authors: | | | | | | | | | | | | | | | | | | |
| abstract: | The resource allocation in the Italian National Research Plan (PNR) for the development of a coherent ultra-brilliant X-ray source, based on a SASE Free Electron Laser, brought about the formation of a CNR-ENEA-INFN- University of Roma "Tor Vergata" study group. A conceptual design study has been developed and possible schemes for linac sources have been investigated leading to the SPARX proposal. We report in this paper the results of start to end simulations concerning the option based on an S-band normal conducting linac. Saturation at 1-10 nm can be achieved in a 40 m long undulator provided the peak current delivered by the linac is 2.5 kA at 2.5 GeV with rms normalized slice emittance of the order of 1 _m and the energy spread less than 0.1%. One of the most critical systems is the bunch compressor. The effects on beam dynamics of a magnetic chicane system and a rectilinear RF compressor (based on velocity bunching), integrated in a high brightness photoinjector, are analyzed and compared in this paper. |
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| title: | Pulse length control in an X-ray FEL by using wakefields |
| format: | conference procceeding |
| conference: | 24th International Free Electron Laser Conference |
| year: | 2003 |
| 3 authors: | | | |
| abstract: | For the users of the high-brightness radiation sources of free-electron lasers it is desirable to reduce the FEL pulse length to 10 fs and below for time-resolving pump and probe experiments. Although it can be achieved by conventional compression methods for the electron beam or the chirped FEL pulse, the technical realization is demanding. In this presentation we study the impact of longitudinal wakefields in the undulator and how their properties can be used to reduced the amplifying part of the bunch to the desired length. Methods of actively controlling the wakefields are presented. |
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| title: | Chirped-beam two-stage free-electron laser for high-power femtosecond x-ray pulse generation |
| format: | journal article |
| year: | 2002 |
| 5 authors: | | | | | |
| abstract: | A method for generating femtosecond-duration x-ray pulses with a free-electron laser is presented. This method uses an energy-chirped electron beam propagating through an undulator to produce a frequency-chirped x-ray pulse by self-amplified spontaneous emission. A short temporal pulse is created by use of a monochromator to select a narrow radiation bandwidth. A second undulator is used to amplify the short-duration radiation. The radiation characteristics produced by a chirped-beam two-stage free-electron laser are calculated, and the performance of the chirped-beam two-stage option for the Linac Coherent Light Source is considered. |
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| title: | Two-Stage Chirped-Beam SASE-FEL for High Power Femtosecond X-Ray Pulse Generation |
| format: | preprint |
| year: | December 10, 2001 |
| 5 authors: | | | | | |
| abstract: | |
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| title: | Chirped-beam two-stage SASE-FEL for high power femtosecond X-ray pulse generation |
| format: | conference procceeding |
| conference: | 23rd International Free Electron Laser Conference |
| year: | 2002 |
| 5 authors: | | | | | |
| abstract: | A method for generating femtosecond duration X-ray pulses using a single-pass free-electron laser (FEL) is presented. This method uses an energy-chirped electron beam propagating through an undulator to produce a frequency-chirped X-ray pulse through self-amplified spontaneous emission (SASE). After the undulator, we consider passing the radiation through a monochromator. The frequency is correlated to the longitudinal position within the pulse; therefore, by selecting a narrow bandwidth, a short temporal pulse will be transmitted. The short pulse radiation is used to seed a second undulator, where the radiation is amplified to saturation. In addition to short pulse generation, this scheme has the ability to control shot-to-shot fluctuations in the central wavelength due to electron beam energy jitter. We present calculations of the radiation characteristics produced by a chirped-beam two-stage SASE?FEL, and consider the performance of the chirped-beam two-stage option for the Linac Coherent Light Source. |
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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: | Start-to-end simulation for the LCLS X-ray FEL |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 5 authors: | | | | | |
| abstract: | X-ray FELs, such as the LCLS and TESLA FEL, require electron beams with large peak current and very small emittance. The X-ray peak power, temporal and spectral properties, depend significantly on details of the electron beam phase space distribution. The electron beam distribution is determined by many effects, as the emission process at the gun photo-cathode, bunch compression, acceleration and wakefields within the undulator. Although analytical results can give an estimate of the expected performance, the complexity of the electron beam generation, acceleration and compression can only be evaluated using a numerical simulation of all these processes, a start-to-end simulation. In this presentation we discuss the LCLS X-Ray FEL performance estimated by a start-to-end simulation, and we compare the results with those obtained using a simpler model. (19 References). |
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| title: | Chirped-beam two-stage SASE-FEL for high power femtosecond x-ray pulse generation |
| format: | conference procceeding |
| conference: | Conference on Optics for Fourth-Generation X-Ray Sources |
| year: | 2001 |
| 5 authors: | | | | | |
| abstract: | We present a method for generating femtosecond duration x-ray pulses using a single-pass free-electron laser (FEL). This method uses an energy-chirped electron beam to produce a frequency-chirped x-ray pulse through self-amplified spontaneous emission (SASE). After the undulator we consider passing the radiation through a monochromator. The frequency is correlated to the longitudinal position within the pulse, and therefore, by selecting a narrow bandwidth, a short temporal pulse will be transmitted. The short pulse radiation is used to seed a second undulator, where the radiation is amplified to saturation. In addition to short pulse generation, this scheme has the ability to control shot-to-shot fluctuations in the central wavelength due to electron beam energy jitter. We present calculations of the radiation characteristics produced by a chirped-beam two-stage SASE-FEL, and consider the performance of the chirped-beam two-stage option for the Linac Coherent Light Source (LCLS). |
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| title: | The design for the LCLS RF photoinjector |
| format: | conference procceeding |
| conference: | 20th International Free Electron Laser Conference |
| year: | 1999 |
| 16 authors: | | | | | | | | | | | | | | | | |
| abstract: | We report on the design of the RF photoinjector of the Linac Coherent Light Source. The RF photoinjector is required to produce a single 150 MeV bunch of similar to 1 nC and similar to 100 A peak current at a repetition rate of 120 Hz with a normalized rms transverse emittance of similar to 1 pi mm-mrad. The design employs a 1.6-cell S-band RF gun with an optical spot size at the cathode of a radius of similar to 1 mm and a pulse duration with an rms sigma of similar to 3 ps. The peak RF field at the cathode is 150 MV/m with extraction 57 degrees ahead of the RF peak. A solenoidal field near the cathode allows the compensation of the initial emittance growth by the end of the injection linac. Spatial and temporal shaping of the laser pulse striking the cathode will reduce the compensated emittance even further. Also, to minimize the contribution of the thermal emittance from the cathode surface, while at the same time optimizing the quantum efficiency, the laser wavelength for a Cu cathode should be tunable around 260 nm. Following the injection linac the geometric emittance simply damps linearly with energy growth. PARMELA simulations show that this design will produce the desired normalized emittance, which is about a factor of two lower than has been achieved to date in other systems. In addition to low emittance, we also aim for laser amplitude stability of 1% in the UV and a timing jitter in the electron beam of 0.5 ps rms, which will lead to less than 10% beam intensity fluctuation after the electron bunch is compressed in the main linac. |
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| title: | The VISA FEL Undulator |
| format: | conference procceeding |
| conference: | 20th International Free Electron Laser Conference |
| year: | 1999 |
| 14 authors: | | | | | | | | | | | | | | |
| abstract: | The Visible-Infrared SASE Amplifier (VISA) FEL is an experimental device designed to show self amplified spontaneous emission (SASE) to saturation in the 800-600 nm range, where silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is the first SASE FEL designed to saturate, and its diagnostics will provide important checks of theory. |
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| title: | Status of the SPARC-X Project |
| format: | journal article |
| year: | 2007 |
| 97 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | SPARC-X is a two branch project consisting in the SPARC test facility dedicated to the development and test of critical subsystems such as high brightness photoinjector and a modular expandable undulator for SASE-FEL experiments at 500 nm with seeding, and the SPARX facility aiming at generation of high brilliance coherent radiation in the 1.5-13 nm range, based on the achieved expertise. The projects are supported by MIUR (Research Department of Italian Government) and Regione Lazio. SPARC has completed the commissioning phase of the photoinjector in November 2006. The achieved experimental results are here summarized together with the status of the second phase commissioning plans. The SPARX project is based on the generation of ultra high peak brightness electron beams at the energy of 1 and 2 GeV generating radiation in the 1.5-13 nm range. The construction is at the moment planned in two steps starting with a 1 GeV Linac. The project layout including both RF-compression and magnetic chicane techniques has been studied. |
| keywords: | pbpl |
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| title: | Status of the SPARX FEL Project |
| format: | journal article |
| year: | 2006 |
| 67 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The SPARX project consists in an X-ray-FEL facility jointly supported by MIUR (Research Department of Italian Government), Regione Lazio, CNR, ENEA, INFN and Rome University Tor Vergata. It is the natural extension of the ongoing activities of the SPARC collaboration. The aim is the generation of electron beams characterized by ultra-high peak brightness at the energy of 1 and 2 GeV, for the first and the second phase respectively. The beam is expected to drive a single pass FEL experiment in the range of 13.5÷6 nm and 6÷1.5 nm, at 1 GeV and 2 GeV respectively, both in SASE and SEEDED FEL configurations. A hybrid scheme of RF and magnetic compression will be adopted, based on the expertise achieved at the SPARC high brightness photoinjector presently under commissioning at Frascati INFN-LNF Laboratories [1,2]. The use of superconducting and exotic undulator sections will be also exploited. In this paper we report the progress of the collaboration together with start to end simulation results based on a combined scheme of RF compression techniques. |
| keywords: | pbpl |
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| title: | Status Report on SPARC Project |
| format: | journal article |
| year: | |
| 96 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | We review the status of FEL source activity of the ongoing SPARC FEL experiment, developed within the framework of a collaboration among ENEA, CNR, INFN, INFM, Sincrotrone Trieste and University of Rome Tor Vergata. The project is aimed at realising a SASE-FEL source, operating in the visible (around 500 nm), with an extended range of tunability down to the VUV (100 nm) by the use of the mechanism of non-linear harmonic generation. The development of the relevant activities foresees the realisation of an advanced 150 MeV photo- injector source, aimed at producing a high brightness electron beams, needed to drive a SASE-FEL experiment, and a 14 m long undulator. We present the status of the design and construction of SPARC FEL device. In particular we discuss the choice of the project parameters, their optimisation and the sensitivity of the SPARC performance to any parameter variation. We will show, using start-to-end simulations, what is the impact of the e- beam and of the undulator parameters on the characteristics of the output laser field and in particular on the amount of the non-linearly generated power at higher harmonics. |
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| title: | The SPARX project: R & D Activity towards X-Ray Sources |
| format: | journal article |
| year: | |
| 79 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | SPARX is an evolutionary project proposed by a collaboration among ENEA-INFN-CNR-Universita` di Roma Tor Vergata aiming at the construction of a FEL- SASE X-ray source in the Tor Vergata Campus. The first phase of the SPARX project, funded by Government Agencies, will be focused on R&D activity on critical components and techniques for future X-ray facilities as described in this paper. |
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