Optimization of infrared and magnetic shielding of superconducting TiN and Al coplanar microwave resonators

Abstract

We present a systematic study of the effects of shielding on the internal quality factors of Al and TiN microwave resonators designed for use in quantum coherent circuits. Measurements were performed in an adiabatic demagnetization refrigerator, where typical magnetic fields of 200 μT are present at the unshielded sample stage. Radiation shielding consisted of 100 and 500 mK Cu cans coated with infrared absorbing epoxy. Magnetic shields consisted of Cryoperm 10 and Sn plating of the Cu cans. A 2.7 K radiation can and coaxial thermalization filters were present in all measurements. TiN samples with at 100 mK exhibited no significant variation in quality factor when tested with limited shielding. In contrast, Al resonators showed improved with successive shielding, with the largest gains obtained from the addition of the first radiation and magnetic shields and saturating before the addition of Sn plating infrared absorbing epoxy.