title: The quality factor of a superconducting rf resonator in a magnetic field.
abstract: The quality factor of a superconducting NbTi resonator at 1.6 MHz in a magnetic field up to 1.2 T as well as its temperature dependence is investigated. A hysteresis effect in the superconducting surface resistance as a function of the magnetic field is observed. An unloaded Q-value of the resonator of 40,500 is achieved at 3.9 K. It is shown that this Q-value is limited by dielectric losses in the FORMVAR insulation of the coils wire. The details of the Q-value optimization are discussed. In the temperature dependence of the Q-value a steep decrease is observed above T approximately = 7.5 K. Finally, the implications of these measurements for real trap experiments are discussed in detail.
authors.affiliation: Institut für Physik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Ulmer
authors.forename: H
authors.initials: H
authors.lastname: Kracke
authors.forename: K
authors.initials: K
authors.lastname: Blaum
authors.forename: S
authors.initials: S
authors.lastname: Kreim
authors.forename: A
authors.initials: A
authors.lastname: Mooser
authors.forename: W
authors.initials: W
authors.lastname: Quint
authors.forename: C C
authors.initials: CC
authors.lastname: Rodegheri
authors.forename: J
authors.initials: J
authors.lastname: Walz