Simulation study of the coupling between a Nearly Confocal Resonator pick-up and an electron beam
2007 (English)Report (Other academic)
In the framework of the CLIC/CTF3 studies, a numerical study of the couplingbetween an electron beam bunched at 12 GHz and a nearly confocal resonator(NCR) with spherical mirrors is presented in this paper. The geometry of theNCR pick-up was chosen to have a large quality factor for the diffraction lossesat 12 GHz, and thus a weak coupling to parasitic external TE and TM modesthat may propagate in the wake of the electron bunches. The simulated shuntimpedance shows the presence of undesired resonances at low frequencies, whichcan however be significantly damped, e.g. by placing bricks of absorbing materialalong the side walls of the beam pipe. The power spectrum induced by a singleelectron bunch in an extraction waveguide connected to the upper mirror of theNCR pick-up was computed. Another simulation was performed, this time withoutthe NCR cavity on the beam pipe. A comparison of the power induced by a bunchtrain at 12 GHz in these two cases shows that the presence of the NCR cavityreduces the available signal by at least three orders of magnitude, as a result ofthe transit time factor for the NCR eigen-mode at 12 GHz. Since this reduction isabout the same as for the parasitic modes propagating in the wake of the bunches,we conclude that no significant improvement of the signal-to-noise ratio can beobtained with the NCR pick-up.
Place, publisher, year, edition, pages
2007. , 18 p.
IdentifiersURN: urn:nbn:se:uu:diva-16872OAI: oai:DiVA.org:uu-16872DiVA: diva2:44643