# Abstracts

## XX International Linac Conference

## MOE06 (Poster)

**Presenter: **Wolfgang F.O. Mueller (U. Frankfurt)

** email: **peha@sunkist.physik.uni-frankfurt.
de

**Status: **Complete

**FullText: **
pdf

**Eprint:** physics/0008091
# The Diffraction Model And Its Applicability for
Wakefield Calculations*

P. HUELSMANN, W.F.O. MUELLER (U. Frankfurt)

The operation of a Free Electron Laser (FEL) in the ultraviolet or in the
X-ray regime requires the acceleration of electron bunches with an rms length of 25
to 50 micro meter. The wakefields generated by this sub picosecond bunches extend
into the frequency range well beyond the threshold for Cooper pair breakup (about 700
GHz) in superconductive Niobium at 2 K. It could be shown, that the superconducting
cavities could indeed be operated with 25 micro meter bunches without suffering a
breakdown of superconductivity (quench), however at the price of a reduced quality
factor and an increased heat transfer to the superfluid helium bath. This was first
shown [1,2] by wakefield calculations based on the diffraction model. In the meantime
a more conventional method of computing wake fields in the time domain by numerical
methods was developed and used for the wakefield calculations [2]. Both methods lead
to comparable results. With an analytical approach we will show the general
applicability of the diffraction model for wakefield calculations in the high
relativistic regime.

[1] P. Huelsmann, H. Klein, C. Peschke, W.F.O. Mueller: QThe Influence of
Wakefields on Superconducting TESLA-Cavities in FEL-Operationl, Proceedings of the
eighth Workshop on Superconductivity, Abano Terme, Italy, 06.10. -
10.10.1997

[2] R. Brinkmann, M. Dohlus, D. Trines, DESY: A. Novokhatski, M. Timm, T.
Weiland, TU Darmstadt: P. Huelsmann, Frankfurt University: C.T. Rieck, K. Scharnberg,
P. Schmueser, Hamburg University: QTerahertz Wakefileds in the Superconducting
Cavities of the TESLA-FEL Linacl: TESLA-Report, DESY, Hamburg, December
1999

*Work supported by DESY/Hamburg and BMBF under contract No.
06OF841

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