Paper | Title | Other Keywords | Page |
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MOP042 | All-Fiber Approach to Long-Term Stable Timing Distribution System | timing, laser, polarization, optics | 122 |
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High precision timing distribution systems are critical for free-electron lasers (FELs). Real facilities such as FLASH and the European XFEL need fiber networks consisting of 20 or more timing links, which require tremendous attention to the alignment and stability of the free-space optics to minimize timing-drifts induced by beam pointing instabilities. This situation also necessitates preamplification of the master laser output to overcome excessive free-space to fiber coupling losses to provide adequate power for all timing links. Recently, we have developed integrated, fiber-coupled balanced optical cross-correlators (FC-BOC) using periodically-poled KTiOPO4 (PPKTP) waveguides. These waveguides exhibit second harmonic conversion efficiencies 20 times higher than the bulk optical devices, which will decrease the power demand from the master laser and consequently support more timing links. Furthermore, the robustness and ease of implementation of these fiber-coupled devices will eliminate alignment-related problems observed in free-space optics. In this paper, we present an all-fiber implementation of a 3.5-km timing distribution system using FC-BOCs, over 200 hours operation without interruption. The remaining drift (<1 Hz) is only 3.3 fs RMS, and the integrated jitter above 1 Hz is kept below 0.7 fs, which is more than sufficient for an efficient FEL synchronization. | |||
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TUP040 | Simulation and Design of Low Emittance RF Electron Gun | electron, emittance, gun, cavity | 455 |
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Funding: This work has been supported by the CMU Junior Research Fellowship Program and the Department of Physics and Materials Science, Faculty of Science, Chiang Mai University. Generation of high-brightness electron beam is one of the most critical issues in development of advanced electron accelerators and light sources. At the Plasma and Beam Physics (PBP) Research Facility, Chiang Mai University, a low emittance RF electron gun is under the development. This RF-gun is planned to be used as an electron source for a future IR/THz FEL facility. An extra resonant cavity is added to the modified design of the existing PBP-CMU RF-gun in order to reduce the transverse sliced emittance. This cell is coupled to the main full-cell via a side-coupling cavity. The electromagnetic field distributions inside the cavities are simulated by using the CST Microwave Studio 2012. Then, beam dynamic simulations utilizing the program PARMELA are performed. Both RF and beam dynamic simulation results are reported and discussed in this contribution. The authors would like to acknowledge the financial support to participate this conference by the Department of Physics and Materials Science and the Graduate School, Chiang Mai University. |
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Poster TUP040 [2.140 MB] | ||
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TUP069 | THz Based Phase-Space Manipulation in a Guided IFEL | electron, laser, simulation, undulator | 519 |
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Funding: This work has been supported by DOE grant DE-FG02-92ER40693, and NSF grant PHY-1415583. We propose a guided IFEL interaction driven by a broadband THz source to compress a relativistic electron bunch and synchronize it with an external laser pulse. A high field single-cycle THz pulse is group velocity-matched to the electron bunch inside a waveguide, allowing for a sustained interaction in a magnetic undulator. The THz pulse is generated via optical rectification from the external laser source, with peak field of up to 4.6 MV/m. We present measurements of the THz waveform before and after a parallel plate waveguide with varying aperture size and estimate the group velocity. We also present results from a preliminary 1-D multi-frequency simulation code we are developing to model the guided broadband IFEL interaction. Given a 6 MeV, 100 fs electron bunch with an initial 10-3 energy spread, as can be readily produced at the UCLA Pegasus laboratory, the simulations predict a phase space rotation of the bunch distribution that will reduce the initial timing jitter and compress the electron bunch by nearly an order of magnitude. |
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WEB04 | Saturation Dynamics, Fine Spectrum, and Chirp Control in a CW FEL Oscillator | FEL, laser, electron, operation | 580 |
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As in conventional laser physics, the saturation dynamics of a long-pulse Electrostatic Accelerator FEL (EA-FEL) oscillator consists of oscillations build-up, resonator modes competition, and establishment of narrow linewidth single mode lasing. In EA-FEL the gain curve drifts to lower frequencies during the long laser pulse due to inevitable droop in the acceleration voltage. This post-saturation drift renders fine chirp of the single mode laser frequency due to the oscillator frequency pulling effect. We have integrated a voltage-ramping element into the electrostatic accelerator terminal that makes it possible to control the acceleration voltage throughout the lasing pulse. This allows us to keep the voltage constant throughout the e-beam pulse, and so increase the single mode lasing time, avoiding mode-hopping during the pulse due to the drift of the gain curve. Furthermore, by adjusting the voltage ramp rate and polarity we obtained controllable positive/negative laser frequency chirp that can be used in a single pulse sweep for fine spectral line (10-6) gas-spectroscopy. The study was conducted on the Israeli EA-FEL that operates at tunable frequencies between 95-110 GHz. | |||
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Slides WEB04 [2.310 MB] | ||
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