| Paper | Title | Page |
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| MOPPH036 | Influence of Linear Fluctuations on Low- and High-Gain Cherenkov FELs | 118 |
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In a previous study* it was shown that irregularities in the liner result in phase fluctuations of the ponderomotive potential which affects the gain of a low energy Cerenkov FEL. Here we investigate numerically how sensitive a Cerenkov FEL is to such fluctuations when operating in different gain regimes. For this study we considered an increased transverse dimensions of the liner and electron beam as compared to the study presented in*, while the resonance frequency and beam voltage are held constant around 50 GHz and 80 kV respectively. The different gain regimes then correspond to different electron beam currents ranging from 0.8 A to 20 A. Without liner fluctuations, these beam currents result in a single pass saturated output power of approx. 200 W to 25 kW respectively, where the laser output saturates in a much shorter distance for the higher beam current. We have found that the low gain system (I=0.8 A) shows a much higher sensitivity to liner fluctuations than the high gain system (I=20 A).
* I de la Fuente, PJM van der Slot and K-J Boller. Proceedings of the 26th International Free-Electron Laser Conference and the 11th FEL User-Workshop. Trieste, Italy, p53-56 (2004) |
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| TUPPH001 | A 3D Model of the 4GLS VUV-FEL Conceptual Design Including Improved Modelling of the Optical Cavity | 304 |
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The Conceptual Design Report for the 4th Generation Light Source (4GLS) at Daresbury Laboratory in the UK was published in Spring 2006. The proposal includes a low-Q cavity (also called a regenerative amplifier) FEL to generate variably-polarised, temporally-coherent radiation in the photon energy range 3-10eV. A new simulation code has been developed that incorporates the 3D FEL code Genesis 1.3 and which simulates in 3D the optical components and radiation propagation within the non-amplifying sections of an optical cavity*. This code is used to estimate the optimum low-Q cavity design and characterise the output from the 4GLS VUV-FEL.
* J. G. Karstenberg, P. J.M. van der Slot, J. W.J. Verschuur, I. V. Volohkin, K.-J. Boller (ibid) |
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| TUPPH037 | FEL-Oscillator Simulations with Genesis 1.3 | 407 |
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We present a paraxial optical propagation code (OPC) as an extension to Genesis 1.3* for the theoretical description of FELs with an optical resonator. The OPC receives the optical output from a Genesis simulation, propagates it once through the resonator, and applies the result as the optical input pulse for a next run of Genesis. The OPC allows both the description of time dependent and steady state FEL operation. The propagation algorithms available are the Spectral algorithm, the Fresnel algorithm and a modified Fresnel algorithm. The latter enables a fast modelling of feedback via complex resonator designs that may include hard-edge elements (apertures) or hole-coupled mirrors with arbitrary shapes. The code enables to predict the output at each of the various optical elements which is of advantage for beam diagnostics and for designing suitable optics for a further propagation of the output beam. Finally, the OPC can be used to determine the far field output in connection with any Genesis 1.3 simulation, be it an oscillator or an amplifier FEL. As a test of the combined OPC and Genesis 1.3 codes we found good agreement with experimental data available for FELIX**.
* http://pbpl.physics.ucla.edu/~reiche/index.html** B. Faatz, Ph. D. Thesis, Nieuwegein, The Netherlands 1992. |