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SRF2003 Show Abstract

Title Field emission related phenomena in a 3 GHz 20 cell cavity of the S-DALINAC
Type Poster operating experience
Abstract Investigations of field emission accompanied by emission of light in a superconducting niobium rf cavity of the S-DALINAC have been carried out by analysis of bremsstrahlung and optical  spectra. The spectral power density of the observed light spots could be interpreted as black body radiation emitted at a temperature of some 1500 K. From bremsstrahlung spectra measured at accelerating gradients from 6 to 7 MV/m the maximum energies gained by dark current electrons that were accelerated and able to leave the cavity were determined. In order to localize a possible position of an emission site, trajectories of dark current electrons in the cavity were numerically simulated by a simulation code based on the Leap-Frog method. The simulations have shown that the observed electron energies cannot be gained in a cavity with an ideal field flatness. Best agreement has resulted for a strongly deteriorated field profile with an end cell detuned by 5.4 MHz. Experimental evidence for this hypothesis is deduced from a comparison of the present eigenfrequencies of this particular cavity with both, the present eigenfrequencies of other  S-DALINAC cavities and the eigenfrequencies of the respective cavities after their initial tuning for field flatness in the pi-mode.

List of authors...

Principle author first.

Last (Family) Name First Name (Initials only) Affiliation or Organization (abbreviations if possible)
Gopych M. TUD
Graef H.-D. TUD
Laier U. TUD
Platz M. TUD
Richter A. TUD
Stascheck A. TUD
Watzlawik S. TUD
Setzter S. TEMF
Weiland T. TEMF

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