Title
| The Effect of Liner Induced Phase Fluctuations on the Gain of a Cerenkov FEL |
Author(s)
| De la Fuente, Isabel ; Boller, K ; Van der Slot, Peter |
Affiliation
| (UTWENTE, Enschede) |
Publication
| 2004 |
In:
| 26th International Free Electron Laser Conference and 11th FEL User Workshop 2004, Trieste, Italy, 29 Aug - 3 Sep 2004, pp.e-proc. MOPOS39 |
Subject category
| Accelerators and Storage Rings |
Abstract
| It is well known that wiggler errors can degrade the gain of a FEL. A similar process takes places in a Cerenkov FEL where the phase velocity of the amplified EM wave is determined by parameters of the dielectric liner. Thus deviations in the inner radius (R<sub>d</sub>) of the liner will result in fluctuations of the phase velocity of the EM wave. E.g., for a quartz liner (ε<sub>r</sub>=4.4) with R<sub>d</sub> = 1.5 mm and outer radius of 4 mm, the derivative of the longitudinal wavenumber with respect to R<sub>d</sub> is about 10<sup>5</sup> m<sup>-2</sup> for a frequency of 50 GHz. Thus fluctuations in the R<sub>d</sub> induce phase fluctuations that may degrade the gain of a Cerenkov FEL. In contrast to the undulator FEL, where the relative phase fluctuations are a result from deviations in the electron trajectories, the phase fluctuations are a result of pertubations in the radiation field for a Cerenkov FEL. As an example of the influence of pertubations in the inner radius of the liner on the gain we will present results of an analysis for a 100 kV Cerenkov FEL operating at a frequency of 50 GHz. |