The quality factor of a superconducting rf resonator in a magnetic field.
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.
Ulmer
S
S
Institut für Physik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
Kracke
H
H
Blaum
K
K
Kreim
S
S
Mooser
A
A
Quint
W
W
Rodegheri
C C
CC
Walz
J
J