Fig. 3. Effect of ionizing radiation shielding on resonator performance.

a Quasiparticle burst rate Γ_B and b internal quality factor at single photon drive Q_i for all resonators and setups. When the sample is cleaned and tested in the R setup, the measured Γ_B and Q_i values are comparable to those obtained in K. Measurements in the G setup show a reduction in QP burst rate Γ_B (factor 30) and dissipation (up to a factor 4). In G, removing the lead shielding increases Γ_B by a factor two. Adding a ThO₂ radioactive source next to the cryostat body yields a Γ_B greater than the one measured above ground, and decreases the internal quality factor Q_i by 18 ± 3%. Error bars are $\sqrt{N}$ for Γ_B (Poissonian error) and standard deviations of all data points in the $\overline{n}=0.1-10$ range for Q_i when available, and are not shown when smaller than the marker size. The chronological order of measurements in the three different setups is indicated by the dotted gray arrows.